Last good Nixpkgs for Weston+nouveau? archive

I came this commit hash to terwiz[m] on IRC, who is trying to figure out
what the last version of Spectrum that worked on their NUC with Nvidia
graphics is.

110 files changed, 18027 insertions, 0 deletions

diff --git a/doc/.gitignore b/doc/.gitignore
new file mode 100644
index 00000000000..b5c58be03d1
--- /dev/null
+++ b/doc/.gitignore
@@ -0,0 +1,8 @@
+*.chapter.xml
+*.section.xml
+.version
+functions/library/generated
+functions/library/locations.xml
+highlightjs
+manual-full.xml
+out
diff --git a/doc/Makefile b/doc/Makefile
new file mode 100644
index 00000000000..f8d2d7248fa
--- /dev/null
+++ b/doc/Makefile
@@ -0,0 +1,116 @@
+MD_TARGETS=$(addsuffix .xml, $(basename $(shell find . -type f -regex '.*\.md$$' -not -name README.md)))
+
+PANDOC ?= pandoc
+
+pandoc_media_dir = media
+# NOTE: Keep in sync with NixOS manual (/nixos/doc/manual/md-to-db.sh) and conversion script (/maintainers/scripts/db-to-md.sh).
+# TODO: Remove raw-attribute when we can get rid of DocBook altogether.
+pandoc_commonmark_enabled_extensions = +attributes+fenced_divs+footnotes+bracketed_spans+definition_lists+pipe_tables+raw_attribute
+# Not needed:
+# - docbook-reader/citerefentry-to-rst-role.lua (only relevant for DocBook → MarkDown/rST/MyST)
+pandoc_flags = --extract-media=$(pandoc_media_dir) \
+	--lua-filter=$(PANDOC_LUA_FILTERS_DIR)/diagram-generator.lua \
+	--lua-filter=build-aux/pandoc-filters/myst-reader/roles.lua \
+	--lua-filter=build-aux/pandoc-filters/link-unix-man-references.lua \
+	--lua-filter=build-aux/pandoc-filters/docbook-writer/rst-roles.lua \
+	--lua-filter=build-aux/pandoc-filters/docbook-writer/labelless-link-is-xref.lua \
+	-f commonmark$(pandoc_commonmark_enabled_extensions)+smart
+
+.PHONY: all
+all: validate format out/html/index.html out/epub/manual.epub
+
+.PHONY: debug
+debug:
+	nix-shell --run "xmloscopy --docbook5 ./manual.xml ./manual-full.xml"
+
+.PHONY: format
+format: doc-support/result
+	find . -iname '*.xml' -type f | while read f; do \
+		echo $$f ;\
+		xmlformat --config-file "doc-support/result/xmlformat.conf" -i $$f ;\
+	done
+
+.PHONY: fix-misc-xml
+fix-misc-xml:
+	find . -iname '*.xml' -type f \
+		-exec ../nixos/doc/varlistentry-fixer.rb {} ';'
+
+.PHONY: clean
+clean:
+	rm -f ${MD_TARGETS} doc-support/result .version manual-full.xml functions/library/locations.xml functions/library/generated
+	rm -rf ./out/ ./highlightjs ./media
+
+.PHONY: validate
+validate: manual-full.xml doc-support/result
+	jing doc-support/result/docbook.rng manual-full.xml
+
+out/html/index.html: doc-support/result manual-full.xml style.css highlightjs
+	mkdir -p out/html
+	xsltproc \
+		--nonet --xinclude \
+		--output $@ \
+		doc-support/result/xhtml.xsl \
+		./manual-full.xml
+
+	mkdir -p out/html/highlightjs/
+	cp -r highlightjs out/html/
+
+	cp -r $(pandoc_media_dir) out/html/
+	cp ./overrides.css out/html/
+	cp ./style.css out/html/style.css
+
+	mkdir -p out/html/images/callouts
+	cp doc-support/result/xsl/docbook/images/callouts/*.svg out/html/images/callouts/
+	chmod u+w -R out/html/
+
+out/epub/manual.epub: manual-full.xml
+	mkdir -p out/epub/scratch
+	xsltproc --nonet \
+		--output out/epub/scratch/ \
+		doc-support/result/epub.xsl \
+		./manual-full.xml
+
+	cp -r $(pandoc_media_dir) out/epub/scratch/OEBPS
+	cp ./overrides.css out/epub/scratch/OEBPS
+	cp ./style.css out/epub/scratch/OEBPS
+	mkdir -p out/epub/scratch/OEBPS/images/callouts/
+	cp doc-support/result/xsl/docbook/images/callouts/*.svg out/epub/scratch/OEBPS/images/callouts/
+	echo "application/epub+zip" > mimetype
+	zip -0Xq "out/epub/manual.epub" mimetype
+	rm mimetype
+	cd "out/epub/scratch/" && zip -Xr9D "../manual.epub" *
+	rm -rf "out/epub/scratch/"
+
+highlightjs: doc-support/result
+	mkdir -p highlightjs
+	cp -r doc-support/result/highlightjs/highlight.pack.js highlightjs/
+	cp -r doc-support/result/highlightjs/LICENSE highlightjs/
+	cp -r doc-support/result/highlightjs/mono-blue.css highlightjs/
+	cp -r doc-support/result/highlightjs/loader.js highlightjs/
+
+
+manual-full.xml: ${MD_TARGETS} .version functions/library/locations.xml functions/library/generated *.xml **/*.xml **/**/*.xml
+	xmllint --nonet --xinclude --noxincludenode manual.xml --output manual-full.xml
+
+.version: doc-support/result
+	ln -rfs ./doc-support/result/version .version
+
+doc-support/result: doc-support/default.nix
+	(cd doc-support; nix-build)
+
+functions/library/locations.xml: doc-support/result
+	ln -rfs ./doc-support/result/function-locations.xml functions/library/locations.xml
+
+functions/library/generated: doc-support/result
+	ln -rfs ./doc-support/result/function-docs functions/library/generated
+
+%.section.xml: %.section.md
+	$(PANDOC) $^ -t docbook \
+		$(pandoc_flags) \
+		-o $@
+
+%.chapter.xml: %.chapter.md
+	$(PANDOC) $^ -t docbook \
+		--top-level-division=chapter \
+		$(pandoc_flags) \
+		-o $@
diff --git a/doc/README.md b/doc/README.md
new file mode 100644
index 00000000000..5395d7ca8f6
--- /dev/null
+++ b/doc/README.md
@@ -0,0 +1,12 @@
+
+# Nixpkgs/doc
+
+This directory houses the sources files for the Nixpkgs manual.
+
+You can find the [rendered documentation for Nixpkgs `unstable` on nixos.org](https://nixos.org/manual/nixpkgs/unstable/).
+
+[Docs for Nixpkgs stable](https://nixos.org/manual/nixpkgs/stable/) are also available.
+
+If you want to contribute to the documentation, [here's how to do it](https://nixos.org/manual/nixpkgs/unstable/#chap-contributing).
+
+If you're only getting started with Nix, go to [nixos.org/learn](https://nixos.org/learn).
diff --git a/doc/build-aux/pandoc-filters/docbook-reader/citerefentry-to-rst-role.lua b/doc/build-aux/pandoc-filters/docbook-reader/citerefentry-to-rst-role.lua
new file mode 100644
index 00000000000..281e85af271
--- /dev/null
+++ b/doc/build-aux/pandoc-filters/docbook-reader/citerefentry-to-rst-role.lua
@@ -0,0 +1,23 @@
+--[[
+Converts Code AST nodes produced by pandoc’s DocBook reader
+from citerefentry elements into AST for corresponding role
+for reStructuredText.
+
+We use subset of MyST syntax (CommonMark with features from rST)
+so let’s use the rST AST for rST features.
+
+Reference: https://www.sphinx-doc.org/en/master/usage/restructuredtext/roles.html#role-manpage
+]]
+
+function Code(elem)
+  elem.classes = elem.classes:map(function (x)
+    if x == 'citerefentry' then
+      elem.attributes['role'] = 'manpage'
+      return 'interpreted-text'
+    else
+      return x
+    end
+  end)
+
+  return elem
+end
diff --git a/doc/build-aux/pandoc-filters/docbook-writer/labelless-link-is-xref.lua b/doc/build-aux/pandoc-filters/docbook-writer/labelless-link-is-xref.lua
new file mode 100644
index 00000000000..fa97729a28b
--- /dev/null
+++ b/doc/build-aux/pandoc-filters/docbook-writer/labelless-link-is-xref.lua
@@ -0,0 +1,34 @@
+--[[
+Converts Link AST nodes with empty label to DocBook xref elements.
+
+This is a temporary script to be able use cross-references conveniently
+using syntax taken from MyST, while we still use docbook-xsl
+for generating the documentation.
+
+Reference: https://myst-parser.readthedocs.io/en/latest/using/syntax.html#targets-and-cross-referencing
+]]
+
+local function starts_with(start, str)
+  return str:sub(1, #start) == start
+end
+
+local function escape_xml_arg(arg)
+  amps = arg:gsub('&', '&')
+  amps_quotes = amps:gsub('"', '"')
+  amps_quotes_lt = amps_quotes:gsub('<', '&lt;')
+
+  return amps_quotes_lt
+end
+
+function Link(elem)
+  has_no_content = #elem.content == 0
+  targets_anchor = starts_with('#', elem.target)
+  has_no_attributes = elem.title == '' and elem.identifier == '' and #elem.classes == 0 and #elem.attributes == 0
+
+  if has_no_content and targets_anchor and has_no_attributes then
+    -- xref expects idref without the pound-sign
+    target_without_hash = elem.target:sub(2, #elem.target)
+
+    return pandoc.RawInline('docbook', '<xref linkend="' .. escape_xml_arg(target_without_hash) .. '" />')
+  end
+end
diff --git a/doc/build-aux/pandoc-filters/docbook-writer/rst-roles.lua b/doc/build-aux/pandoc-filters/docbook-writer/rst-roles.lua
new file mode 100644
index 00000000000..92dc6895750
--- /dev/null
+++ b/doc/build-aux/pandoc-filters/docbook-writer/rst-roles.lua
@@ -0,0 +1,36 @@
+--[[
+Converts AST for reStructuredText roles into corresponding
+DocBook elements.
+
+Currently, only a subset of roles is supported.
+
+Reference:
+  List of roles:
+    https://www.sphinx-doc.org/en/master/usage/restructuredtext/roles.html
+  manpage:
+    https://tdg.docbook.org/tdg/5.1/citerefentry.html
+  file:
+    https://tdg.docbook.org/tdg/5.1/filename.html
+]]
+
+function Code(elem)
+  if elem.classes:includes('interpreted-text') then
+    local tag = nil
+    local content = elem.text
+    if elem.attributes['role'] == 'manpage' then
+      tag = 'citerefentry'
+      local title, volnum = content:match('^(.+)%((%w+)%)$')
+      if title == nil then
+        -- No volnum in parentheses.
+        title = content
+      end
+      content = '<refentrytitle>' .. title .. '</refentrytitle>' .. (volnum ~= nil and ('<manvolnum>' .. volnum .. '</manvolnum>') or '')
+    elseif elem.attributes['role'] == 'file' then
+      tag = 'filename'
+    end
+
+    if tag ~= nil then
+      return pandoc.RawInline('docbook', '<' .. tag .. '>' .. content .. '</' .. tag .. '>')
+    end
+  end
+end
diff --git a/doc/build-aux/pandoc-filters/link-unix-man-references.lua b/doc/build-aux/pandoc-filters/link-unix-man-references.lua
new file mode 100644
index 00000000000..e437ac73a1c
--- /dev/null
+++ b/doc/build-aux/pandoc-filters/link-unix-man-references.lua
@@ -0,0 +1,17 @@
+--[[
+Turns a manpage reference into a link, when a mapping is defined below.
+]]
+
+local man_urls = {
+  ["tmpfiles.d(5)"] = "https://www.freedesktop.org/software/systemd/man/tmpfiles.d.html",
+  ["nix.conf(5)"] = "https://nixos.org/manual/nix/stable/#sec-conf-file",
+  ["systemd.time(7)"] = "https://www.freedesktop.org/software/systemd/man/systemd.time.html",
+  ["systemd.timer(5)"] = "https://www.freedesktop.org/software/systemd/man/systemd.timer.html",
+}
+
+function Code(elem)
+  local is_man_role = elem.classes:includes('interpreted-text') and elem.attributes['role'] == 'manpage'
+  if is_man_role and man_urls[elem.text] ~= nil then
+    return pandoc.Link(elem, man_urls[elem.text])
+  end
+end
diff --git a/doc/build-aux/pandoc-filters/myst-reader/roles.lua b/doc/build-aux/pandoc-filters/myst-reader/roles.lua
new file mode 100644
index 00000000000..c33a688eeba
--- /dev/null
+++ b/doc/build-aux/pandoc-filters/myst-reader/roles.lua
@@ -0,0 +1,29 @@
+--[[
+Replaces Str AST nodes containing {role}, followed by a Code node
+by a Code node with attrs that would be produced by rST reader
+from the role syntax.
+
+This is to emulate MyST syntax in Pandoc.
+(MyST is a CommonMark flavour with rST features mixed in.)
+
+Reference: https://myst-parser.readthedocs.io/en/latest/syntax/syntax.html#roles-an-in-line-extension-point
+]]
+
+function Inlines(inlines)
+  for i = #inlines-1,1,-1 do
+    local first = inlines[i]
+    local second = inlines[i+1]
+    local correct_tags = first.tag == 'Str' and second.tag == 'Code'
+    if correct_tags then
+      -- docutils supports alphanumeric strings separated by [-._:]
+      -- We are slightly more liberal for simplicity.
+      local role = first.text:match('^{([-._+:%w]+)}$')
+      if role ~= nil then
+        inlines:remove(i)
+        second.attributes['role'] = role
+        second.classes:insert('interpreted-text')
+      end
+    end
+  end
+  return inlines
+end
diff --git a/doc/build-aux/pandoc-filters/myst-writer/roles.lua b/doc/build-aux/pandoc-filters/myst-writer/roles.lua
new file mode 100644
index 00000000000..0136bc55065
--- /dev/null
+++ b/doc/build-aux/pandoc-filters/myst-writer/roles.lua
@@ -0,0 +1,25 @@
+--[[
+Replaces Code nodes with attrs that would be produced by rST reader
+from the role syntax by a Str AST node containing {role}, followed by a Code node.
+
+This is to emulate MyST syntax in Pandoc.
+(MyST is a CommonMark flavour with rST features mixed in.)
+
+Reference: https://myst-parser.readthedocs.io/en/latest/syntax/syntax.html#roles-an-in-line-extension-point
+]]
+
+function Code(elem)
+  local role = elem.attributes['role']
+
+  if elem.classes:includes('interpreted-text') and role ~= nil then
+    elem.classes = elem.classes:filter(function (c)
+      return c ~= 'interpreted-text'
+    end)
+    elem.attributes['role'] = nil
+
+    return {
+      pandoc.Str('{' .. role .. '}'),
+      elem,
+    }
+  end
+end
diff --git a/doc/builders/fetchers.chapter.md b/doc/builders/fetchers.chapter.md
new file mode 100644
index 00000000000..28388ba685d
--- /dev/null
+++ b/doc/builders/fetchers.chapter.md
@@ -0,0 +1,110 @@
+# Fetchers {#chap-pkgs-fetchers}
+
+When using Nix, you will frequently need to download source code and other files from the internet. For this purpose, Nix provides the [_fixed output derivation_](https://nixos.org/manual/nix/stable/#fixed-output-drvs) feature and Nixpkgs provides various functions that implement the actual fetching from various protocols and services.
+
+## Caveats
+
+Because fixed output derivations are _identified_ by their hash, a common mistake is to update a fetcher's URL or a version parameter, without updating the hash. **This will cause the old contents to be used.** So remember to always invalidate the hash argument.
+
+For those who develop and maintain fetchers, a similar problem arises with changes to the implementation of a fetcher. These may cause a fixed output derivation to fail, but won't normally be caught by tests because the supposed output is already in the store or cache. For the purpose of testing, you can use a trick that is embodied by the [`invalidateFetcherByDrvHash`](#sec-pkgs-invalidateFetcherByDrvHash) function. It uses the derivation `name` to create a unique output path per fetcher implementation, defeating the caching precisely where it would be harmful.
+
+## `fetchurl` and `fetchzip` {#fetchurl}
+
+Two basic fetchers are `fetchurl` and `fetchzip`. Both of these have two required arguments, a URL and a hash. The hash is typically `sha256`, although many more hash algorithms are supported. Nixpkgs contributors are currently recommended to use `sha256`. This hash will be used by Nix to identify your source. A typical usage of fetchurl is provided below.
+
+```nix
+{ stdenv, fetchurl }:
+
+stdenv.mkDerivation {
+  name = "hello";
+  src = fetchurl {
+    url = "http://www.example.org/hello.tar.gz";
+    sha256 = "1111111111111111111111111111111111111111111111111111";
+  };
+}
+```
+
+The main difference between `fetchurl` and `fetchzip` is in how they store the contents. `fetchurl` will store the unaltered contents of the URL within the Nix store. `fetchzip` on the other hand will decompress the archive for you, making files and directories directly accessible in the future. `fetchzip` can only be used with archives. Despite the name, `fetchzip` is not limited to .zip files and can also be used with any tarball.
+
+`fetchpatch` works very similarly to `fetchurl` with the same arguments expected. It expects patch files as a source and performs normalization on them before computing the checksum. For example it will remove comments or other unstable parts that are sometimes added by version control systems and can change over time.
+
+Most other fetchers return a directory rather than a single file.
+
+## `fetchsvn` {#fetchsvn}
+
+Used with Subversion. Expects `url` to a Subversion directory, `rev`, and `sha256`.
+
+## `fetchgit` {#fetchgit}
+
+Used with Git. Expects `url` to a Git repo, `rev`, and `sha256`. `rev` in this case can be full the git commit id (SHA1 hash) or a tag name like `refs/tags/v1.0`.
+
+Additionally the following optional arguments can be given: `fetchSubmodules = true` makes `fetchgit` also fetch the submodules of a repository. If `deepClone` is set to true, the entire repository is cloned as opposing to just creating a shallow clone. `deepClone = true` also implies `leaveDotGit = true` which means that the `.git` directory of the clone won't be removed after checkout.
+
+If only parts of the repository are needed, `sparseCheckout` can be used. This will prevent git from fetching unnecessary blobs from server, see [git sparse-checkout](https://git-scm.com/docs/git-sparse-checkout) and [git clone --filter](https://git-scm.com/docs/git-clone#Documentation/git-clone.txt---filterltfilter-specgt) for more infomation:
+
+```nix
+{ stdenv, fetchgit }:
+
+stdenv.mkDerivation {
+  name = "hello";
+  src = fetchgit {
+    url = "https://...";
+    sparseCheckout = ''
+      path/to/be/included
+      another/path
+    '';
+    sha256 = "0000000000000000000000000000000000000000000000000000";
+  };
+}
+```
+
+## `fetchfossil` {#fetchfossil}
+
+Used with Fossil. Expects `url` to a Fossil archive, `rev`, and `sha256`.
+
+## `fetchcvs` {#fetchcvs}
+
+Used with CVS. Expects `cvsRoot`, `tag`, and `sha256`.
+
+## `fetchhg` {#fetchhg}
+
+Used with Mercurial. Expects `url`, `rev`, and `sha256`.
+
+A number of fetcher functions wrap part of `fetchurl` and `fetchzip`. They are mainly convenience functions intended for commonly used destinations of source code in Nixpkgs. These wrapper fetchers are listed below.
+
+## `fetchFromGitHub` {#fetchfromgithub}
+
+`fetchFromGitHub` expects four arguments. `owner` is a string corresponding to the GitHub user or organization that controls this repository. `repo` corresponds to the name of the software repository. These are located at the top of every GitHub HTML page as `owner`/`repo`. `rev` corresponds to the Git commit hash or tag (e.g `v1.0`) that will be downloaded from Git. Finally, `sha256` corresponds to the hash of the extracted directory. Again, other hash algorithms are also available but `sha256` is currently preferred.
+
+`fetchFromGitHub` uses `fetchzip` to download the source archive generated by GitHub for the specified revision. If `leaveDotGit`, `deepClone` or `fetchSubmodules` are set to `true`, `fetchFromGitHub` will use `fetchgit` instead. Refer to its section for documentation of these options.
+
+## `fetchFromGitLab` {#fetchfromgitlab}
+
+This is used with GitLab repositories. The arguments expected are very similar to fetchFromGitHub above.
+
+## `fetchFromGitiles` {#fetchfromgitiles}
+
+This is used with Gitiles repositories. The arguments expected are similar to fetchgit.
+
+## `fetchFromBitbucket` {#fetchfrombitbucket}
+
+This is used with BitBucket repositories. The arguments expected are very similar to fetchFromGitHub above.
+
+## `fetchFromSavannah` {#fetchfromsavannah}
+
+This is used with Savannah repositories. The arguments expected are very similar to fetchFromGitHub above.
+
+## `fetchFromRepoOrCz` {#fetchfromrepoorcz}
+
+This is used with repo.or.cz repositories. The arguments expected are very similar to fetchFromGitHub above.
+
+## `fetchFromSourcehut` {#fetchfromsourcehut}
+
+This is used with sourcehut repositories. Similar to `fetchFromGitHub` above,
+it expects `owner`, `repo`, `rev` and `sha256`, but don't forget the tilde (~)
+in front of the username! Expected arguments also include `vc` ("git" (default)
+or "hg"), `domain` and `fetchSubmodules`.
+
+If `fetchSubmodules` is `true`, `fetchFromSourcehut` uses `fetchgit`
+or `fetchhg` with `fetchSubmodules` or `fetchSubrepos` set to `true`,
+respectively. Otherwise the fetcher uses `fetchzip`.
diff --git a/doc/builders/images.xml b/doc/builders/images.xml
new file mode 100644
index 00000000000..cd10d69a96d
--- /dev/null
+++ b/doc/builders/images.xml
@@ -0,0 +1,12 @@
+<chapter xmlns="http://docbook.org/ns/docbook"
+         xmlns:xi="http://www.w3.org/2001/XInclude"
+         xml:id="chap-images">
+ <title>Images</title>
+ <para>
+  This chapter describes tools for creating various types of images.
+ </para>
+ <xi:include href="images/appimagetools.section.xml" />
+ <xi:include href="images/dockertools.section.xml" />
+ <xi:include href="images/ocitools.section.xml" />
+ <xi:include href="images/snaptools.section.xml" />
+</chapter>
diff --git a/doc/builders/images/appimagetools.section.md b/doc/builders/images/appimagetools.section.md
new file mode 100644
index 00000000000..67e63dc5f61
--- /dev/null
+++ b/doc/builders/images/appimagetools.section.md
@@ -0,0 +1,48 @@
+# pkgs.appimageTools {#sec-pkgs-appimageTools}
+
+`pkgs.appimageTools` is a set of functions for extracting and wrapping [AppImage](https://appimage.org/) files. They are meant to be used if traditional packaging from source is infeasible, or it would take too long. To quickly run an AppImage file, `pkgs.appimage-run` can be used as well.
+
+::: {.warning}
+The `appimageTools` API is unstable and may be subject to backwards-incompatible changes in the future.
+:::
+
+## AppImage formats {#ssec-pkgs-appimageTools-formats}
+
+There are different formats for AppImages, see [the specification](https://github.com/AppImage/AppImageSpec/blob/74ad9ca2f94bf864a4a0dac1f369dd4f00bd1c28/draft.md#image-format) for details.
+
+- Type 1 images are ISO 9660 files that are also ELF executables.
+- Type 2 images are ELF executables with an appended filesystem.
+
+They can be told apart with `file -k`:
+
+```ShellSession
+$ file -k type1.AppImage
+type1.AppImage: ELF 64-bit LSB executable, x86-64, version 1 (SYSV) ISO 9660 CD-ROM filesystem data 'AppImage' (Lepton 3.x), scale 0-0,
+spot sensor temperature 0.000000, unit celsius, color scheme 0, calibration: offset 0.000000, slope 0.000000, dynamically linked, interpreter /lib64/ld-linux-x86-64.so.2, for GNU/Linux 2.6.18, BuildID[sha1]=d629f6099d2344ad82818172add1d38c5e11bc6d, stripped\012- data
+
+$ file -k type2.AppImage
+type2.AppImage: ELF 64-bit LSB executable, x86-64, version 1 (SYSV) (Lepton 3.x), scale 232-60668, spot sensor temperature -4.187500, color scheme 15, show scale bar, calibration: offset -0.000000, slope 0.000000 (Lepton 2.x), scale 4111-45000, spot sensor temperature 412442.250000, color scheme 3, minimum point enabled, calibration: offset -75402534979642766821519867692934234112.000000, slope 5815371847733706829839455140374904832.000000, dynamically linked, interpreter /lib64/ld-linux-x86-64.so.2, for GNU/Linux 2.6.18, BuildID[sha1]=79dcc4e55a61c293c5e19edbd8d65b202842579f, stripped\012- data
+```
+
+Note how the type 1 AppImage is described as an `ISO 9660 CD-ROM filesystem`, and the type 2 AppImage is not.
+
+## Wrapping {#ssec-pkgs-appimageTools-wrapping}
+
+Depending on the type of AppImage you're wrapping, you'll have to use `wrapType1` or `wrapType2`.
+
+```nix
+appimageTools.wrapType2 { # or wrapType1
+  name = "patchwork";
+  src = fetchurl {
+    url = "https://github.com/ssbc/patchwork/releases/download/v3.11.4/Patchwork-3.11.4-linux-x86_64.AppImage";
+    sha256 = "1blsprpkvm0ws9b96gb36f0rbf8f5jgmw4x6dsb1kswr4ysf591s";
+  };
+  extraPkgs = pkgs: with pkgs; [ ];
+}
+```
+
+- `name` specifies the name of the resulting image.
+- `src` specifies the AppImage file to extract.
+- `extraPkgs` allows you to pass a function to include additional packages inside the FHS environment your AppImage is going to run in. There are a few ways to learn which dependencies an application needs:
+  - Looking through the extracted AppImage files, reading its scripts and running `patchelf` and `ldd` on its executables. This can also be done in `appimage-run`, by setting `APPIMAGE_DEBUG_EXEC=bash`.
+  - Running `strace -vfefile` on the wrapped executable, looking for libraries that can't be found.
diff --git a/doc/builders/images/dockertools.section.md b/doc/builders/images/dockertools.section.md
new file mode 100644
index 00000000000..7ff4b2aeb36
--- /dev/null
+++ b/doc/builders/images/dockertools.section.md
@@ -0,0 +1,314 @@
+# pkgs.dockerTools {#sec-pkgs-dockerTools}
+
+`pkgs.dockerTools` is a set of functions for creating and manipulating Docker images according to the [Docker Image Specification v1.2.0](https://github.com/moby/moby/blob/master/image/spec/v1.2.md#docker-image-specification-v120). Docker itself is not used to perform any of the operations done by these functions.
+
+## buildImage {#ssec-pkgs-dockerTools-buildImage}
+
+This function is analogous to the `docker build` command, in that it can be used to build a Docker-compatible repository tarball containing a single image with one or multiple layers. As such, the result is suitable for being loaded in Docker with `docker load`.
+
+The parameters of `buildImage` with relative example values are described below:
+
+[]{#ex-dockerTools-buildImage}
+[]{#ex-dockerTools-buildImage-runAsRoot}
+
+```nix
+buildImage {
+  name = "redis";
+  tag = "latest";
+
+  fromImage = someBaseImage;
+  fromImageName = null;
+  fromImageTag = "latest";
+
+  contents = pkgs.redis;
+  runAsRoot = ''
+    #!${pkgs.runtimeShell}
+    mkdir -p /data
+  '';
+
+  config = {
+    Cmd = [ "/bin/redis-server" ];
+    WorkingDir = "/data";
+    Volumes = { "/data" = { }; };
+  };
+}
+```
+
+The above example will build a Docker image `redis/latest` from the given base image. Loading and running this image in Docker results in `redis-server` being started automatically.
+
+- `name` specifies the name of the resulting image. This is the only required argument for `buildImage`.
+
+- `tag` specifies the tag of the resulting image. By default it's `null`, which indicates that the nix output hash will be used as tag.
+
+- `fromImage` is the repository tarball containing the base image. It must be a valid Docker image, such as exported by `docker save`. By default it's `null`, which can be seen as equivalent to `FROM scratch` of a `Dockerfile`.
+
+- `fromImageName` can be used to further specify the base image within the repository, in case it contains multiple images. By default it's `null`, in which case `buildImage` will peek the first image available in the repository.
+
+- `fromImageTag` can be used to further specify the tag of the base image within the repository, in case an image contains multiple tags. By default it's `null`, in which case `buildImage` will peek the first tag available for the base image.
+
+- `contents` is a derivation that will be copied in the new layer of the resulting image. This can be similarly seen as `ADD contents/ /` in a `Dockerfile`. By default it's `null`.
+
+- `runAsRoot` is a bash script that will run as root in an environment that overlays the existing layers of the base image with the new resulting layer, including the previously copied `contents` derivation. This can be similarly seen as `RUN ...` in a `Dockerfile`.
+
+> **_NOTE:_** Using this parameter requires the `kvm` device to be available.
+
+- `config` is used to specify the configuration of the containers that will be started off the built image in Docker. The available options are listed in the [Docker Image Specification v1.2.0](https://github.com/moby/moby/blob/master/image/spec/v1.2.md#image-json-field-descriptions).
+
+After the new layer has been created, its closure (to which `contents`, `config` and `runAsRoot` contribute) will be copied in the layer itself. Only new dependencies that are not already in the existing layers will be copied.
+
+At the end of the process, only one new single layer will be produced and added to the resulting image.
+
+The resulting repository will only list the single image `image/tag`. In the case of [the `buildImage` example](#ex-dockerTools-buildImage) it would be `redis/latest`.
+
+It is possible to inspect the arguments with which an image was built using its `buildArgs` attribute.
+
+> **_NOTE:_** If you see errors similar to `getProtocolByName: does not exist (no such protocol name: tcp)` you may need to add `pkgs.iana-etc` to `contents`.
+
+> **_NOTE:_** If you see errors similar to `Error_Protocol ("certificate has unknown CA",True,UnknownCa)` you may need to add `pkgs.cacert` to `contents`.
+
+By default `buildImage` will use a static date of one second past the UNIX Epoch. This allows `buildImage` to produce binary reproducible images. When listing images with `docker images`, the newly created images will be listed like this:
+
+```ShellSession
+$ docker images
+REPOSITORY   TAG      IMAGE ID       CREATED        SIZE
+hello        latest   08c791c7846e   48 years ago   25.2MB
+```
+
+You can break binary reproducibility but have a sorted, meaningful `CREATED` column by setting `created` to `now`.
+
+```nix
+pkgs.dockerTools.buildImage {
+  name = "hello";
+  tag = "latest";
+  created = "now";
+  contents = pkgs.hello;
+
+  config.Cmd = [ "/bin/hello" ];
+}
+```
+
+and now the Docker CLI will display a reasonable date and sort the images as expected:
+
+```ShellSession
+$ docker images
+REPOSITORY   TAG      IMAGE ID       CREATED              SIZE
+hello        latest   de2bf4786de6   About a minute ago   25.2MB
+```
+
+however, the produced images will not be binary reproducible.
+
+## buildLayeredImage {#ssec-pkgs-dockerTools-buildLayeredImage}
+
+Create a Docker image with many of the store paths being on their own layer to improve sharing between images. The image is realized into the Nix store as a gzipped tarball. Depending on the intended usage, many users might prefer to use `streamLayeredImage` instead, which this function uses internally.
+
+`name`
+
+: The name of the resulting image.
+
+`tag` _optional_
+
+: Tag of the generated image.
+
+    *Default:* the output path's hash
+
+`fromImage` _optional_
+
+: The repository tarball containing the base image. It must be a valid Docker image, such as one exported by `docker save`.
+
+    *Default:* `null`, which can be seen as equivalent to `FROM scratch` of a `Dockerfile`.
+
+`contents` _optional_
+
+: Top level paths in the container. Either a single derivation, or a list of derivations.
+
+    *Default:* `[]`
+
+`config` _optional_
+
+: Run-time configuration of the container. A full list of the options are available at in the [ Docker Image Specification v1.2.0 ](https://github.com/moby/moby/blob/master/image/spec/v1.2.md#image-json-field-descriptions).
+
+    *Default:* `{}`
+
+`created` _optional_
+
+: Date and time the layers were created. Follows the same `now` exception supported by `buildImage`.
+
+    *Default:* `1970-01-01T00:00:01Z`
+
+`maxLayers` _optional_
+
+: Maximum number of layers to create.
+
+    *Default:* `100`
+
+    *Maximum:* `125`
+
+`extraCommands` _optional_
+
+: Shell commands to run while building the final layer, without access to most of the layer contents. Changes to this layer are "on top" of all the other layers, so can create additional directories and files.
+
+`fakeRootCommands` _optional_
+
+: Shell commands to run while creating the archive for the final layer in a fakeroot environment. Unlike `extraCommands`, you can run `chown` to change the owners of the files in the archive, changing fakeroot's state instead of the real filesystem. The latter would require privileges that the build user does not have. Static binaries do not interact with the fakeroot environment. By default all files in the archive will be owned by root.
+
+`enableFakechroot` _optional_
+
+: Whether to run in `fakeRootCommands` in `fakechroot`, making programs behave as though `/` is the root of the image being created, while files in the Nix store are available as usual. This allows scripts that perform installation in `/` to work as expected. Considering that `fakechroot` is implemented via the same mechanism as `fakeroot`, the same caveats apply.
+
+    *Default:* `false`
+
+### Behavior of `contents` in the final image {#dockerTools-buildLayeredImage-arg-contents}
+
+Each path directly listed in `contents` will have a symlink in the root of the image.
+
+For example:
+
+```nix
+pkgs.dockerTools.buildLayeredImage {
+  name = "hello";
+  contents = [ pkgs.hello ];
+}
+```
+
+will create symlinks for all the paths in the `hello` package:
+
+```ShellSession
+/bin/hello -> /nix/store/h1zb1padqbbb7jicsvkmrym3r6snphxg-hello-2.10/bin/hello
+/share/info/hello.info -> /nix/store/h1zb1padqbbb7jicsvkmrym3r6snphxg-hello-2.10/share/info/hello.info
+/share/locale/bg/LC_MESSAGES/hello.mo -> /nix/store/h1zb1padqbbb7jicsvkmrym3r6snphxg-hello-2.10/share/locale/bg/LC_MESSAGES/hello.mo
+```
+
+### Automatic inclusion of `config` references {#dockerTools-buildLayeredImage-arg-config}
+
+The closure of `config` is automatically included in the closure of the final image.
+
+This allows you to make very simple Docker images with very little code. This container will start up and run `hello`:
+
+```nix
+pkgs.dockerTools.buildLayeredImage {
+  name = "hello";
+  config.Cmd = [ "${pkgs.hello}/bin/hello" ];
+}
+```
+
+### Adjusting `maxLayers` {#dockerTools-buildLayeredImage-arg-maxLayers}
+
+Increasing the `maxLayers` increases the number of layers which have a chance to be shared between different images.
+
+Modern Docker installations support up to 128 layers, however older versions support as few as 42.
+
+If the produced image will not be extended by other Docker builds, it is safe to set `maxLayers` to `128`. However it will be impossible to extend the image further.
+
+The first (`maxLayers-2`) most "popular" paths will have their own individual layers, then layer \#`maxLayers-1` will contain all the remaining "unpopular" paths, and finally layer \#`maxLayers` will contain the Image configuration.
+
+Docker's Layers are not inherently ordered, they are content-addressable and are not explicitly layered until they are composed in to an Image.
+
+## streamLayeredImage {#ssec-pkgs-dockerTools-streamLayeredImage}
+
+Builds a script which, when run, will stream an uncompressed tarball of a Docker image to stdout. The arguments to this function are as for `buildLayeredImage`. This method of constructing an image does not realize the image into the Nix store, so it saves on IO and disk/cache space, particularly with large images.
+
+The image produced by running the output script can be piped directly into `docker load`, to load it into the local docker daemon:
+
+```ShellSession
+$(nix-build) | docker load
+```
+
+Alternatively, the image be piped via `gzip` into `skopeo`, e.g. to copy it into a registry:
+
+```ShellSession
+$(nix-build) | gzip --fast | skopeo copy docker-archive:/dev/stdin docker://some_docker_registry/myimage:tag
+```
+
+## pullImage {#ssec-pkgs-dockerTools-fetchFromRegistry}
+
+This function is analogous to the `docker pull` command, in that it can be used to pull a Docker image from a Docker registry. By default [Docker Hub](https://hub.docker.com/) is used to pull images.
+
+Its parameters are described in the example below:
+
+```nix
+pullImage {
+  imageName = "nixos/nix";
+  imageDigest =
+    "sha256:20d9485b25ecfd89204e843a962c1bd70e9cc6858d65d7f5fadc340246e2116b";
+  finalImageName = "nix";
+  finalImageTag = "1.11";
+  sha256 = "0mqjy3zq2v6rrhizgb9nvhczl87lcfphq9601wcprdika2jz7qh8";
+  os = "linux";
+  arch = "x86_64";
+}
+```
+
+- `imageName` specifies the name of the image to be downloaded, which can also include the registry namespace (e.g. `nixos`). This argument is required.
+
+- `imageDigest` specifies the digest of the image to be downloaded. This argument is required.
+
+- `finalImageName`, if specified, this is the name of the image to be created. Note it is never used to fetch the image since we prefer to rely on the immutable digest ID. By default it's equal to `imageName`.
+
+- `finalImageTag`, if specified, this is the tag of the image to be created. Note it is never used to fetch the image since we prefer to rely on the immutable digest ID. By default it's `latest`.
+
+- `sha256` is the checksum of the whole fetched image. This argument is required.
+
+- `os`, if specified, is the operating system of the fetched image. By default it's `linux`.
+
+- `arch`, if specified, is the cpu architecture of the fetched image. By default it's `x86_64`.
+
+`nix-prefetch-docker` command can be used to get required image parameters:
+
+```ShellSession
+$ nix run nixpkgs.nix-prefetch-docker -c nix-prefetch-docker --image-name mysql --image-tag 5
+```
+
+Since a given `imageName` may transparently refer to a manifest list of images which support multiple architectures and/or operating systems, you can supply the `--os` and `--arch` arguments to specify exactly which image you want. By default it will match the OS and architecture of the host the command is run on.
+
+```ShellSession
+$ nix-prefetch-docker --image-name mysql --image-tag 5 --arch x86_64 --os linux
+```
+
+Desired image name and tag can be set using `--final-image-name` and `--final-image-tag` arguments:
+
+```ShellSession
+$ nix-prefetch-docker --image-name mysql --image-tag 5 --final-image-name eu.gcr.io/my-project/mysql --final-image-tag prod
+```
+
+## exportImage {#ssec-pkgs-dockerTools-exportImage}
+
+This function is analogous to the `docker export` command, in that it can be used to flatten a Docker image that contains multiple layers. It is in fact the result of the merge of all the layers of the image. As such, the result is suitable for being imported in Docker with `docker import`.
+
+> **_NOTE:_** Using this function requires the `kvm` device to be available.
+
+The parameters of `exportImage` are the following:
+
+```nix
+exportImage {
+  fromImage = someLayeredImage;
+  fromImageName = null;
+  fromImageTag = null;
+
+  name = someLayeredImage.name;
+}
+```
+
+The parameters relative to the base image have the same synopsis as described in [buildImage](#ssec-pkgs-dockerTools-buildImage), except that `fromImage` is the only required argument in this case.
+
+The `name` argument is the name of the derivation output, which defaults to `fromImage.name`.
+
+## shadowSetup {#ssec-pkgs-dockerTools-shadowSetup}
+
+This constant string is a helper for setting up the base files for managing users and groups, only if such files don't exist already. It is suitable for being used in a [`buildImage` `runAsRoot`](#ex-dockerTools-buildImage-runAsRoot) script for cases like in the example below:
+
+```nix
+buildImage {
+  name = "shadow-basic";
+
+  runAsRoot = ''
+    #!${pkgs.runtimeShell}
+    ${shadowSetup}
+    groupadd -r redis
+    useradd -r -g redis redis
+    mkdir /data
+    chown redis:redis /data
+  '';
+}
+```
+
+Creating base files like `/etc/passwd` or `/etc/login.defs` is necessary for shadow-utils to manipulate users and groups.
diff --git a/doc/builders/images/ocitools.section.md b/doc/builders/images/ocitools.section.md
new file mode 100644
index 00000000000..d3dee57ebac
--- /dev/null
+++ b/doc/builders/images/ocitools.section.md
@@ -0,0 +1,37 @@
+# pkgs.ociTools {#sec-pkgs-ociTools}
+
+`pkgs.ociTools` is a set of functions for creating containers according to the [OCI container specification v1.0.0](https://github.com/opencontainers/runtime-spec). Beyond that it makes no assumptions about the container runner you choose to use to run the created container.
+
+## buildContainer {#ssec-pkgs-ociTools-buildContainer}
+
+This function creates a simple OCI container that runs a single command inside of it. An OCI container consists of a `config.json` and a rootfs directory.The nix store of the container will contain all referenced dependencies of the given command.
+
+The parameters of `buildContainer` with an example value are described below:
+
+```nix
+buildContainer {
+  args = [
+    (with pkgs;
+      writeScript "run.sh" ''
+        #!${bash}/bin/bash
+        exec ${bash}/bin/bash
+      '').outPath
+  ];
+
+  mounts = {
+    "/data" = {
+      type = "none";
+      source = "/var/lib/mydata";
+      options = [ "bind" ];
+    };
+  };
+
+  readonly = false;
+}
+```
+
+- `args` specifies a set of arguments to run inside the container. This is the only required argument for `buildContainer`. All referenced packages inside the derivation will be made available inside the container
+
+- `mounts` specifies additional mount points chosen by the user. By default only a minimal set of necessary filesystems are mounted into the container (e.g procfs, cgroupfs)
+
+- `readonly` makes the container\'s rootfs read-only if it is set to true. The default value is false `false`.
diff --git a/doc/builders/images/snaptools.section.md b/doc/builders/images/snaptools.section.md
new file mode 100644
index 00000000000..5f710d2de7f
--- /dev/null
+++ b/doc/builders/images/snaptools.section.md
@@ -0,0 +1,71 @@
+# pkgs.snapTools {#sec-pkgs-snapTools}
+
+`pkgs.snapTools` is a set of functions for creating Snapcraft images. Snap and Snapcraft is not used to perform these operations.
+
+## The makeSnap Function {#ssec-pkgs-snapTools-makeSnap-signature}
+
+`makeSnap` takes a single named argument, `meta`. This argument mirrors [the upstream `snap.yaml` format](https://docs.snapcraft.io/snap-format) exactly.
+
+The `base` should not be specified, as `makeSnap` will force set it.
+
+Currently, `makeSnap` does not support creating GUI stubs.
+
+## Build a Hello World Snap {#ssec-pkgs-snapTools-build-a-snap-hello}
+
+The following expression packages GNU Hello as a Snapcraft snap.
+
+``` {#ex-snapTools-buildSnap-hello .nix}
+let
+  inherit (import <nixpkgs> { }) snapTools hello;
+in snapTools.makeSnap {
+  meta = {
+    name = "hello";
+    summary = hello.meta.description;
+    description = hello.meta.longDescription;
+    architectures = [ "amd64" ];
+    confinement = "strict";
+    apps.hello.command = "${hello}/bin/hello";
+  };
+}
+```
+
+`nix-build` this expression and install it with `snap install ./result --dangerous`. `hello` will now be the Snapcraft version of the package.
+
+## Build a Graphical Snap {#ssec-pkgs-snapTools-build-a-snap-firefox}
+
+Graphical programs require many more integrations with the host. This example uses Firefox as an example, because it is one of the most complicated programs we could package.
+
+``` {#ex-snapTools-buildSnap-firefox .nix}
+let
+  inherit (import <nixpkgs> { }) snapTools firefox;
+in snapTools.makeSnap {
+  meta = {
+    name = "nix-example-firefox";
+    summary = firefox.meta.description;
+    architectures = [ "amd64" ];
+    apps.nix-example-firefox = {
+      command = "${firefox}/bin/firefox";
+      plugs = [
+        "pulseaudio"
+        "camera"
+        "browser-support"
+        "avahi-observe"
+        "cups-control"
+        "desktop"
+        "desktop-legacy"
+        "gsettings"
+        "home"
+        "network"
+        "mount-observe"
+        "removable-media"
+        "x11"
+      ];
+    };
+    confinement = "strict";
+  };
+}
+```
+
+`nix-build` this expression and install it with `snap install ./result --dangerous`. `nix-example-firefox` will now be the Snapcraft version of the Firefox package.
+
+The specific meaning behind plugs can be looked up in the [Snapcraft interface documentation](https://docs.snapcraft.io/supported-interfaces).
diff --git a/doc/builders/packages/cataclysm-dda.section.md b/doc/builders/packages/cataclysm-dda.section.md
new file mode 100644
index 00000000000..bfeacb47fef
--- /dev/null
+++ b/doc/builders/packages/cataclysm-dda.section.md
@@ -0,0 +1,129 @@
+# Cataclysm: Dark Days Ahead {#cataclysm-dark-days-ahead}
+
+## How to install Cataclysm DDA {#how-to-install-cataclysm-dda}
+
+To install the latest stable release of Cataclysm DDA to your profile, execute
+`nix-env -f "<nixpkgs>" -iA cataclysm-dda`. For the curses build (build
+without tiles), install `cataclysmDDA.stable.curses`. Note: `cataclysm-dda` is
+an alias to `cataclysmDDA.stable.tiles`.
+
+If you like access to a development build of your favorite git revision,
+override `cataclysm-dda-git` (or `cataclysmDDA.git.curses` if you like curses
+build):
+
+```nix
+cataclysm-dda-git.override {
+  version = "YYYY-MM-DD";
+  rev = "YOUR_FAVORITE_REVISION";
+  sha256 = "CHECKSUM_OF_THE_REVISION";
+}
+```
+
+The sha256 checksum can be obtained by
+
+```sh
+nix-prefetch-url --unpack "https://github.com/CleverRaven/Cataclysm-DDA/archive/${YOUR_FAVORITE_REVISION}.tar.gz"
+```
+
+The default configuration directory is `~/.cataclysm-dda`. If you prefer
+`$XDG_CONFIG_HOME/cataclysm-dda`, override the derivation:
+
+```nix
+cataclysm-dda.override {
+  useXdgDir = true;
+}
+```
+
+## Important note for overriding packages {#important-note-for-overriding-packages}
+
+After applying `overrideAttrs`, you need to fix `passthru.pkgs` and
+`passthru.withMods` attributes either manually or by using `attachPkgs`:
+
+```nix
+let
+  # You enabled parallel building.
+  myCDDA = cataclysm-dda-git.overrideAttrs (_: {
+    enableParallelBuilding = true;
+  });
+
+  # Unfortunately, this refers to the package before overriding and
+  # parallel building is still disabled.
+  badExample = myCDDA.withMods (_: []);
+
+  inherit (cataclysmDDA) attachPkgs pkgs wrapCDDA;
+
+  # You can fix it by hand
+  goodExample1 = myCDDA.overrideAttrs (old: {
+    passthru = old.passthru // {
+      pkgs = pkgs.override { build = goodExample1; };
+      withMods = wrapCDDA goodExample1;
+    };
+  });
+
+  # or by using a helper function `attachPkgs`.
+  goodExample2 = attachPkgs pkgs myCDDA;
+in
+
+# badExample                     # parallel building disabled
+# goodExample1.withMods (_: [])  # parallel building enabled
+goodExample2.withMods (_: [])    # parallel building enabled
+```
+
+## Customizing with mods {#customizing-with-mods}
+
+To install Cataclysm DDA with mods of your choice, you can use `withMods`
+attribute:
+
+```nix
+cataclysm-dda.withMods (mods: with mods; [
+  tileset.UndeadPeople
+])
+```
+
+All mods, soundpacks, and tilesets available in nixpkgs are found in
+`cataclysmDDA.pkgs`.
+
+Here is an example to modify existing mods and/or add more mods not available
+in nixpkgs:
+
+```nix
+let
+  customMods = self: super: lib.recursiveUpdate super {
+    # Modify existing mod
+    tileset.UndeadPeople = super.tileset.UndeadPeople.overrideAttrs (old: {
+      # If you like to apply a patch to the tileset for example
+      patches = [ ./path/to/your.patch ];
+    });
+
+    # Add another mod
+    mod.Awesome = cataclysmDDA.buildMod {
+      modName = "Awesome";
+      version = "0.x";
+      src = fetchFromGitHub {
+        owner = "Someone";
+        repo = "AwesomeMod";
+        rev = "...";
+        sha256 = "...";
+      };
+      # Path to be installed in the unpacked source (default: ".")
+      modRoot = "contents/under/this/path/will/be/installed";
+    };
+
+    # Add another soundpack
+    soundpack.Fantastic = cataclysmDDA.buildSoundPack {
+      # ditto
+    };
+
+    # Add another tileset
+    tileset.SuperDuper = cataclysmDDA.buildTileSet {
+      # ditto
+    };
+  };
+in
+cataclysm-dda.withMods (mods: with mods.extend customMods; [
+  tileset.UndeadPeople
+  mod.Awesome
+  soundpack.Fantastic
+  tileset.SuperDuper
+])
+```
diff --git a/doc/builders/packages/citrix.section.md b/doc/builders/packages/citrix.section.md
new file mode 100644
index 00000000000..b25ecb0bdef
--- /dev/null
+++ b/doc/builders/packages/citrix.section.md
@@ -0,0 +1,32 @@
+# Citrix Workspace {#sec-citrix}
+
+The [Citrix Workspace App](https://www.citrix.com/products/workspace-app/) is a remote desktop viewer which provides access to [XenDesktop](https://www.citrix.com/products/xenapp-xendesktop/) installations.
+
+## Basic usage {#sec-citrix-base}
+
+The tarball archive needs to be downloaded manually as the license agreements of the vendor for [Citrix Workspace](https://www.citrix.de/downloads/workspace-app/linux/workspace-app-for-linux-latest.html) needs to be accepted first. Then run `nix-prefetch-url file://$PWD/linuxx64-$version.tar.gz`. With the archive available in the store the package can be built and installed with Nix.
+
+## Citrix Selfservice {#sec-citrix-selfservice}
+
+The [selfservice](https://support.citrix.com/article/CTX200337) is an application managing Citrix desktops and applications. Please note that this feature only works with at least citrix_workspace_20_06_0 and later versions.
+
+In order to set this up, you first have to [download the `.cr` file from the Netscaler Gateway](https://its.uiowa.edu/support/article/102186). After that you can configure the `selfservice` like this:
+
+```ShellSession
+$ storebrowse -C ~/Downloads/receiverconfig.cr
+$ selfservice
+```
+
+## Custom certificates {#sec-citrix-custom-certs}
+
+The `Citrix Workspace App` in `nixpkgs` trusts several certificates [from the Mozilla database](https://curl.haxx.se/docs/caextract.html) by default. However several companies using Citrix might require their own corporate certificate. On distros with imperative packaging these certs can be stored easily in [`$ICAROOT`](https://developer-docs.citrix.com/projects/receiver-for-linux-command-reference/en/13.7/), however this directory is a store path in `nixpkgs`. In order to work around this issue the package provides a simple mechanism to add custom certificates without rebuilding the entire package using `symlinkJoin`:
+
+```nix
+with import <nixpkgs> { config.allowUnfree = true; };
+let
+  extraCerts = [
+    ./custom-cert-1.pem
+    ./custom-cert-2.pem # ...
+  ];
+in citrix_workspace.override { inherit extraCerts; }
+```
diff --git a/doc/builders/packages/dlib.section.md b/doc/builders/packages/dlib.section.md
new file mode 100644
index 00000000000..8f0aa861018
--- /dev/null
+++ b/doc/builders/packages/dlib.section.md
@@ -0,0 +1,13 @@
+# DLib {#dlib}
+
+[DLib](http://dlib.net/) is a modern, C++-based toolkit which provides several machine learning algorithms.
+
+## Compiling without AVX support {#compiling-without-avx-support}
+
+Especially older CPUs don\'t support [AVX](https://en.wikipedia.org/wiki/Advanced_Vector_Extensions) (Advanced Vector Extensions) instructions that are used by DLib to optimize their algorithms.
+
+On the affected hardware errors like `Illegal instruction` will occur. In those cases AVX support needs to be disabled:
+
+```nix
+self: super: { dlib = super.dlib.override { avxSupport = false; }; }
+```
diff --git a/doc/builders/packages/eclipse.section.md b/doc/builders/packages/eclipse.section.md
new file mode 100644
index 00000000000..faabb188450
--- /dev/null
+++ b/doc/builders/packages/eclipse.section.md
@@ -0,0 +1,64 @@
+# Eclipse {#sec-eclipse}
+
+The Nix expressions related to the Eclipse platform and IDE are in [`pkgs/applications/editors/eclipse`](https://github.com/NixOS/nixpkgs/blob/master/pkgs/applications/editors/eclipse).
+
+Nixpkgs provides a number of packages that will install Eclipse in its various forms. These range from the bare-bones Eclipse Platform to the more fully featured Eclipse SDK or Scala-IDE packages and multiple version are often available. It is possible to list available Eclipse packages by issuing the command:
+
+```ShellSession
+$ nix-env -f '<nixpkgs>' -qaP -A eclipses --description
+```
+
+Once an Eclipse variant is installed it can be run using the `eclipse` command, as expected. From within Eclipse it is then possible to install plugins in the usual manner by either manually specifying an Eclipse update site or by installing the Marketplace Client plugin and using it to discover and install other plugins. This installation method provides an Eclipse installation that closely resemble a manually installed Eclipse.
+
+If you prefer to install plugins in a more declarative manner then Nixpkgs also offer a number of Eclipse plugins that can be installed in an _Eclipse environment_. This type of environment is created using the function `eclipseWithPlugins` found inside the `nixpkgs.eclipses` attribute set. This function takes as argument `{ eclipse, plugins ? [], jvmArgs ? [] }` where `eclipse` is a one of the Eclipse packages described above, `plugins` is a list of plugin derivations, and `jvmArgs` is a list of arguments given to the JVM running the Eclipse. For example, say you wish to install the latest Eclipse Platform with the popular Eclipse Color Theme plugin and also allow Eclipse to use more RAM. You could then add
+
+```nix
+packageOverrides = pkgs: {
+  myEclipse = with pkgs.eclipses; eclipseWithPlugins {
+    eclipse = eclipse-platform;
+    jvmArgs = [ "-Xmx2048m" ];
+    plugins = [ plugins.color-theme ];
+  };
+}
+```
+
+to your Nixpkgs configuration (`~/.config/nixpkgs/config.nix`) and install it by running `nix-env -f '<nixpkgs>' -iA myEclipse` and afterward run Eclipse as usual. It is possible to find out which plugins are available for installation using `eclipseWithPlugins` by running
+
+```ShellSession
+$ nix-env -f '<nixpkgs>' -qaP -A eclipses.plugins --description
+```
+
+If there is a need to install plugins that are not available in Nixpkgs then it may be possible to define these plugins outside Nixpkgs using the `buildEclipseUpdateSite` and `buildEclipsePlugin` functions found in the `nixpkgs.eclipses.plugins` attribute set. Use the `buildEclipseUpdateSite` function to install a plugin distributed as an Eclipse update site. This function takes `{ name, src }` as argument where `src` indicates the Eclipse update site archive. All Eclipse features and plugins within the downloaded update site will be installed. When an update site archive is not available then the `buildEclipsePlugin` function can be used to install a plugin that consists of a pair of feature and plugin JARs. This function takes an argument `{ name, srcFeature, srcPlugin }` where `srcFeature` and `srcPlugin` are the feature and plugin JARs, respectively.
+
+Expanding the previous example with two plugins using the above functions we have
+
+```nix
+packageOverrides = pkgs: {
+  myEclipse = with pkgs.eclipses; eclipseWithPlugins {
+    eclipse = eclipse-platform;
+    jvmArgs = [ "-Xmx2048m" ];
+    plugins = [
+      plugins.color-theme
+      (plugins.buildEclipsePlugin {
+        name = "myplugin1-1.0";
+        srcFeature = fetchurl {
+          url = "http://…/features/myplugin1.jar";
+          sha256 = "123…";
+        };
+        srcPlugin = fetchurl {
+          url = "http://…/plugins/myplugin1.jar";
+          sha256 = "123…";
+        };
+      });
+      (plugins.buildEclipseUpdateSite {
+        name = "myplugin2-1.0";
+        src = fetchurl {
+          stripRoot = false;
+          url = "http://…/myplugin2.zip";
+          sha256 = "123…";
+        };
+      });
+    ];
+  };
+}
+```
diff --git a/doc/builders/packages/elm.section.md b/doc/builders/packages/elm.section.md
new file mode 100644
index 00000000000..ae223c802da
--- /dev/null
+++ b/doc/builders/packages/elm.section.md
@@ -0,0 +1,11 @@
+# Elm {#sec-elm}
+
+To start a development environment do
+
+```ShellSession
+nix-shell -p elmPackages.elm elmPackages.elm-format
+```
+
+To update the Elm compiler, see `nixpkgs/pkgs/development/compilers/elm/README.md`.
+
+To package Elm applications, [read about elm2nix](https://github.com/hercules-ci/elm2nix#elm2nix).
diff --git a/doc/builders/packages/emacs.section.md b/doc/builders/packages/emacs.section.md
new file mode 100644
index 00000000000..577f1a23ce0
--- /dev/null
+++ b/doc/builders/packages/emacs.section.md
@@ -0,0 +1,119 @@
+# Emacs {#sec-emacs}
+
+## Configuring Emacs {#sec-emacs-config}
+
+The Emacs package comes with some extra helpers to make it easier to configure. `emacs.pkgs.withPackages` allows you to manage packages from ELPA. This means that you will not have to install that packages from within Emacs. For instance, if you wanted to use `company` `counsel`, `flycheck`, `ivy`, `magit`, `projectile`, and `use-package` you could use this as a `~/.config/nixpkgs/config.nix` override:
+
+```nix
+{
+  packageOverrides = pkgs: with pkgs; {
+    myEmacs = emacs.pkgs.withPackages (epkgs: (with epkgs.melpaStablePackages; [
+      company
+      counsel
+      flycheck
+      ivy
+      magit
+      projectile
+      use-package
+    ]));
+  }
+}
+```
+
+You can install it like any other packages via `nix-env -iA myEmacs`. However, this will only install those packages. It will not `configure` them for us. To do this, we need to provide a configuration file. Luckily, it is possible to do this from within Nix! By modifying the above example, we can make Emacs load a custom config file. The key is to create a package that provide a `default.el` file in `/share/emacs/site-start/`. Emacs knows to load this file automatically when it starts.
+
+```nix
+{
+  packageOverrides = pkgs: with pkgs; rec {
+    myEmacsConfig = writeText "default.el" ''
+      ;; initialize package
+
+      (require 'package)
+      (package-initialize 'noactivate)
+      (eval-when-compile
+        (require 'use-package))
+
+      ;; load some packages
+
+      (use-package company
+        :bind ("<C-tab>" . company-complete)
+        :diminish company-mode
+        :commands (company-mode global-company-mode)
+        :defer 1
+        :config
+        (global-company-mode))
+
+      (use-package counsel
+        :commands (counsel-descbinds)
+        :bind (([remap execute-extended-command] . counsel-M-x)
+               ("C-x C-f" . counsel-find-file)
+               ("C-c g" . counsel-git)
+               ("C-c j" . counsel-git-grep)
+               ("C-c k" . counsel-ag)
+               ("C-x l" . counsel-locate)
+               ("M-y" . counsel-yank-pop)))
+
+      (use-package flycheck
+        :defer 2
+        :config (global-flycheck-mode))
+
+      (use-package ivy
+        :defer 1
+        :bind (("C-c C-r" . ivy-resume)
+               ("C-x C-b" . ivy-switch-buffer)
+               :map ivy-minibuffer-map
+               ("C-j" . ivy-call))
+        :diminish ivy-mode
+        :commands ivy-mode
+        :config
+        (ivy-mode 1))
+
+      (use-package magit
+        :defer
+        :if (executable-find "git")
+        :bind (("C-x g" . magit-status)
+               ("C-x G" . magit-dispatch-popup))
+        :init
+        (setq magit-completing-read-function 'ivy-completing-read))
+
+      (use-package projectile
+        :commands projectile-mode
+        :bind-keymap ("C-c p" . projectile-command-map)
+        :defer 5
+        :config
+        (projectile-global-mode))
+    '';
+
+    myEmacs = emacs.pkgs.withPackages (epkgs: (with epkgs.melpaStablePackages; [
+      (runCommand "default.el" {} ''
+         mkdir -p $out/share/emacs/site-lisp
+         cp ${myEmacsConfig} $out/share/emacs/site-lisp/default.el
+       '')
+      company
+      counsel
+      flycheck
+      ivy
+      magit
+      projectile
+      use-package
+    ]));
+  };
+}
+```
+
+This provides a fairly full Emacs start file. It will load in addition to the user's presonal config. You can always disable it by passing `-q` to the Emacs command.
+
+Sometimes `emacs.pkgs.withPackages` is not enough, as this package set has some priorities imposed on packages (with the lowest priority assigned to Melpa Unstable, and the highest for packages manually defined in `pkgs/top-level/emacs-packages.nix`). But you can't control this priorities when some package is installed as a dependency. You can override it on per-package-basis, providing all the required dependencies manually - but it's tedious and there is always a possibility that an unwanted dependency will sneak in through some other package. To completely override such a package you can use `overrideScope'`.
+
+```nix
+overrides = self: super: rec {
+  haskell-mode = self.melpaPackages.haskell-mode;
+  ...
+};
+((emacsPackagesFor emacs).overrideScope' overrides).withPackages
+  (p: with p; [
+    # here both these package will use haskell-mode of our own choice
+    ghc-mod
+    dante
+  ])
+```
diff --git a/doc/builders/packages/etc-files.section.md b/doc/builders/packages/etc-files.section.md
new file mode 100644
index 00000000000..2405a54634d
--- /dev/null
+++ b/doc/builders/packages/etc-files.section.md
@@ -0,0 +1,18 @@
+# /etc files {#etc}
+
+Certain calls in glibc require access to runtime files found in /etc such as `/etc/protocols` or `/etc/services` -- [getprotobyname](https://linux.die.net/man/3/getprotobyname) is one such function.
+
+On non-NixOS distributions these files are typically provided by packages (i.e. [netbase](https://packages.debian.org/sid/netbase)) if not already pre-installed in your distribution. This can cause non-reproducibility for code if they rely on these files being present.
+
+If [iana-etc](https://hydra.nixos.org/job/nixos/trunk-combined/nixpkgs.iana-etc.x86_64-linux) is part of your _buildInputs_ then it will set the environment varaibles `NIX_ETC_PROTOCOLS` and `NIX_ETC_SERVICES` to the corresponding files in the package through a _setup-hook_.
+
+
+```bash
+> nix-shell -p iana-etc
+
+[nix-shell:~]$ env | grep NIX_ETC
+NIX_ETC_SERVICES=/nix/store/aj866hr8fad8flnggwdhrldm0g799ccz-iana-etc-20210225/etc/services
+NIX_ETC_PROTOCOLS=/nix/store/aj866hr8fad8flnggwdhrldm0g799ccz-iana-etc-20210225/etc/protocols
+```
+
+Nixpkg's version of [glibc](https://github.com/NixOS/nixpkgs/blob/master/pkgs/development/libraries/glibc/default.nix) has been patched to check for the existence of these environment variables. If the environment variable are *not set*, then it will attempt to find the files at the default location within _/etc_.
diff --git a/doc/builders/packages/firefox.section.md b/doc/builders/packages/firefox.section.md
new file mode 100644
index 00000000000..d6426981da7
--- /dev/null
+++ b/doc/builders/packages/firefox.section.md
@@ -0,0 +1,52 @@
+# Firefox {#sec-firefox}
+
+## Build wrapped Firefox with extensions and policies {#build-wrapped-firefox-with-extensions-and-policies}
+
+The `wrapFirefox` function allows to pass policies, preferences and extension that are available to Firefox. With the help of `fetchFirefoxAddon` this allows build a Firefox version that already comes with addons pre-installed:
+
+```nix
+{
+  # Nix firefox addons only work with the firefox-esr package.
+  myFirefox = wrapFirefox firefox-esr-unwrapped {
+    nixExtensions = [
+      (fetchFirefoxAddon {
+        name = "ublock"; # Has to be unique!
+        url = "https://addons.mozilla.org/firefox/downloads/file/3679754/ublock_origin-1.31.0-an+fx.xpi";
+        sha256 = "1h768ljlh3pi23l27qp961v1hd0nbj2vasgy11bmcrlqp40zgvnr";
+      })
+    ];
+
+    extraPolicies = {
+      CaptivePortal = false;
+      DisableFirefoxStudies = true;
+      DisablePocket = true;
+      DisableTelemetry = true;
+      DisableFirefoxAccounts = true;
+      FirefoxHome = {
+        Pocket = false;
+        Snippets = false;
+      };
+       UserMessaging = {
+         ExtensionRecommendations = false;
+         SkipOnboarding = true;
+       };
+    };
+
+    extraPrefs = ''
+      // Show more ssl cert infos
+      lockPref("security.identityblock.show_extended_validation", true);
+    '';
+  };
+}
+```
+
+If `nixExtensions != null` then all manually installed addons will be uninstalled from your browser profile.
+To view available enterprise policies visit [enterprise policies](https://github.com/mozilla/policy-templates#enterprisepoliciesenabled)
+or type into the Firefox url bar: `about:policies#documentation`.
+Nix installed addons do not have a valid signature, which is why signature verification is disabled. This does not compromise security because downloaded addons are checksumed and manual addons can't be installed. Also make sure that the `name` field of fetchFirefoxAddon is unique. If you remove an addon from the nixExtensions array, rebuild and start Firefox the removed addon will be completly removed with all of its settings.
+
+## Troubleshooting {#sec-firefox-troubleshooting}
+If addons are marked as broken or the signature is invalid, make sure you have Firefox ESR installed. Normal Firefox does not provide the ability anymore to disable signature verification for addons thus nix addons get disabled by the normal Firefox binary.
+
+If addons do not appear installed although they have been defined in your nix configuration file reset the local addon state of your Firefox profile by clicking `help -> restart with addons disabled -> restart -> refresh firefox`. This can happen if you switch from manual addon mode to nix addon mode and then back to manual mode and then again to nix addon mode.
+
diff --git a/doc/builders/packages/fish.section.md b/doc/builders/packages/fish.section.md
new file mode 100644
index 00000000000..3086bd68348
--- /dev/null
+++ b/doc/builders/packages/fish.section.md
@@ -0,0 +1,50 @@
+# Fish {#sec-fish}
+
+Fish is a "smart and user-friendly command line shell" with support for plugins.
+
+
+## Vendor Fish scripts {#sec-fish-vendor}
+
+Any package may ship its own Fish completions, configuration snippets, and
+functions. Those should be installed to
+`$out/share/fish/vendor_{completions,conf,functions}.d` respectively.
+
+When the `programs.fish.enable` and
+`programs.fish.vendor.{completions,config,functions}.enable` options from the
+NixOS Fish module are set to true, those paths are symlinked in the current
+system environment and automatically loaded by Fish.
+
+
+## Packaging Fish plugins {#sec-fish-plugins-pkg}
+
+While packages providing standalone executables belong to the top level,
+packages which have the sole purpose of extending Fish belong to the
+`fishPlugins` scope and should be registered in
+`pkgs/shells/fish/plugins/default.nix`.
+
+The `buildFishPlugin` utility function can be used to automatically copy Fish
+scripts from `$src/{completions,conf,conf.d,functions}` to the standard vendor
+installation paths. It also sets up the test environment so that the optional
+`checkPhase` is executed in a Fish shell with other already packaged plugins
+and package-local Fish functions specified in `checkPlugins` and
+`checkFunctionDirs` respectively.
+
+See `pkgs/shells/fish/plugins/pure.nix` for an example of Fish plugin package
+using `buildFishPlugin` and running unit tests with the `fishtape` test runner.
+
+
+## Fish wrapper {#sec-fish-wrapper}
+
+The `wrapFish` package is a wrapper around Fish which can be used to create
+Fish shells initialised with some plugins as well as completions, configuration
+snippets and functions sourced from the given paths. This provides a convenient
+way to test Fish plugins and scripts without having to alter the environment.
+
+```nix
+wrapFish {
+  pluginPkgs = with fishPlugins; [ pure foreign-env ];
+  completionDirs = [];
+  functionDirs = [];
+  confDirs = [ "/path/to/some/fish/init/dir/" ];
+}
+```
diff --git a/doc/builders/packages/fuse.section.md b/doc/builders/packages/fuse.section.md
new file mode 100644
index 00000000000..eb0023fcbc3
--- /dev/null
+++ b/doc/builders/packages/fuse.section.md
@@ -0,0 +1,45 @@
+# FUSE {#sec-fuse}
+
+Some packages rely on
+[FUSE](https://www.kernel.org/doc/html/latest/filesystems/fuse.html) to provide
+support for additional filesystems not supported by the kernel.
+
+In general, FUSE software are primarily developed for Linux but many of them can
+also run on macOS. Nixpkgs supports FUSE packages on macOS, but it requires
+[macFUSE](https://osxfuse.github.io) to be installed outside of Nix. macFUSE
+currently isn't packaged in Nixpkgs mainly because it includes a kernel
+extension, which isn't supported by Nix outside of NixOS.
+
+If a package fails to run on macOS with an error message similar to the
+following, it's a likely sign that you need to have macFUSE installed.
+
+    dyld: Library not loaded: /usr/local/lib/libfuse.2.dylib
+    Referenced from: /nix/store/w8bi72bssv0bnxhwfw3xr1mvn7myf37x-sshfs-fuse-2.10/bin/sshfs
+    Reason: image not found
+    [1]    92299 abort      /nix/store/w8bi72bssv0bnxhwfw3xr1mvn7myf37x-sshfs-fuse-2.10/bin/sshfs
+
+Package maintainers may often encounter the following error when building FUSE
+packages on macOS:
+
+    checking for fuse.h... no
+    configure: error: No fuse.h found.
+
+This happens on autoconf based projects that uses `AC_CHECK_HEADERS` or
+`AC_CHECK_LIBS` to detect libfuse, and will occur even when the `fuse` package
+is included in `buildInputs`. It happens because libfuse headers throw an error
+on macOS if the `FUSE_USE_VERSION` macro is undefined. Many proejcts do define
+`FUSE_USE_VERSION`, but only inside C source files. This results in the above
+error at configure time because the configure script would attempt to compile
+sample FUSE programs without defining `FUSE_USE_VERSION`.
+
+There are two possible solutions for this problem in Nixpkgs:
+
+1. Pass `FUSE_USE_VERSION` to the configure script by adding
+   `CFLAGS=-DFUSE_USE_VERSION=25` in `configureFlags`. The actual value would
+   have to match the definition used in the upstream source code.
+2. Remove `AC_CHECK_HEADERS` / `AC_CHECK_LIBS` for libfuse.
+
+However, a better solution might be to fix the build script upstream to use
+`PKG_CHECK_MODULES` instead. This approach wouldn't suffer from the problem that
+`AC_CHECK_HEADERS`/`AC_CHECK_LIBS` has at the price of introducing a dependency
+on pkg-config.
diff --git a/doc/builders/packages/ibus.section.md b/doc/builders/packages/ibus.section.md
new file mode 100644
index 00000000000..2ce85467bb8
--- /dev/null
+++ b/doc/builders/packages/ibus.section.md
@@ -0,0 +1,38 @@
+# ibus-engines.typing-booster {#sec-ibus-typing-booster}
+
+This package is an ibus-based completion method to speed up typing.
+
+## Activating the engine {#sec-ibus-typing-booster-activate}
+
+IBus needs to be configured accordingly to activate `typing-booster`. The configuration depends on the desktop manager in use. For detailed instructions, please refer to the [upstream docs](https://mike-fabian.github.io/ibus-typing-booster/documentation.html).
+
+On NixOS you need to explicitly enable `ibus` with given engines before customizing your desktop to use `typing-booster`. This can be achieved using the `ibus` module:
+
+```nix
+{ pkgs, ... }: {
+  i18n.inputMethod = {
+    enabled = "ibus";
+    ibus.engines = with pkgs.ibus-engines; [ typing-booster ];
+  };
+}
+```
+
+## Using custom hunspell dictionaries {#sec-ibus-typing-booster-customize-hunspell}
+
+The IBus engine is based on `hunspell` to support completion in many languages. By default the dictionaries `de-de`, `en-us`, `fr-moderne` `es-es`, `it-it`, `sv-se` and `sv-fi` are in use. To add another dictionary, the package can be overridden like this:
+
+```nix
+ibus-engines.typing-booster.override { langs = [ "de-at" "en-gb" ]; }
+```
+
+_Note: each language passed to `langs` must be an attribute name in `pkgs.hunspellDicts`._
+
+## Built-in emoji picker {#sec-ibus-typing-booster-emoji-picker}
+
+The `ibus-engines.typing-booster` package contains a program named `emoji-picker`. To display all emojis correctly, a special font such as `noto-fonts-emoji` is needed:
+
+On NixOS it can be installed using the following expression:
+
+```nix
+{ pkgs, ... }: { fonts.fonts = with pkgs; [ noto-fonts-emoji ]; }
+```
diff --git a/doc/builders/packages/index.xml b/doc/builders/packages/index.xml
new file mode 100644
index 00000000000..206e1e49f1f
--- /dev/null
+++ b/doc/builders/packages/index.xml
@@ -0,0 +1,29 @@
+<chapter xmlns="http://docbook.org/ns/docbook"
+         xmlns:xi="http://www.w3.org/2001/XInclude"
+         xml:id="chap-packages">
+ <title>Packages</title>
+ <para>
+  This chapter contains information about how to use and maintain the Nix expressions for a number of specific packages, such as the Linux kernel or X.org.
+ </para>
+ <xi:include href="citrix.section.xml" />
+ <xi:include href="dlib.section.xml" />
+ <xi:include href="eclipse.section.xml" />
+ <xi:include href="elm.section.xml" />
+ <xi:include href="emacs.section.xml" />
+ <xi:include href="firefox.section.xml" />
+ <xi:include href="fish.section.xml" />
+ <xi:include href="fuse.section.xml" />
+ <xi:include href="ibus.section.xml" />
+ <xi:include href="kakoune.section.xml" />
+ <xi:include href="linux.section.xml" />
+ <xi:include href="locales.section.xml" />
+ <xi:include href="etc-files.section.xml" />
+ <xi:include href="nginx.section.xml" />
+ <xi:include href="opengl.section.xml" />
+ <xi:include href="shell-helpers.section.xml" />
+ <xi:include href="steam.section.xml" />
+ <xi:include href="cataclysm-dda.section.xml" />
+ <xi:include href="urxvt.section.xml" />
+ <xi:include href="weechat.section.xml" />
+ <xi:include href="xorg.section.xml" />
+</chapter>
diff --git a/doc/builders/packages/kakoune.section.md b/doc/builders/packages/kakoune.section.md
new file mode 100644
index 00000000000..8e054777a75
--- /dev/null
+++ b/doc/builders/packages/kakoune.section.md
@@ -0,0 +1,9 @@
+# Kakoune {#sec-kakoune}
+
+Kakoune can be built to autoload plugins:
+
+```nix
+(kakoune.override {
+  plugins = with pkgs.kakounePlugins; [ parinfer-rust ];
+})
+```
diff --git a/doc/builders/packages/linux.section.md b/doc/builders/packages/linux.section.md
new file mode 100644
index 00000000000..f669c720710
--- /dev/null
+++ b/doc/builders/packages/linux.section.md
@@ -0,0 +1,41 @@
+# Linux kernel {#sec-linux-kernel}
+
+The Nix expressions to build the Linux kernel are in [`pkgs/os-specific/linux/kernel`](https://github.com/NixOS/nixpkgs/blob/master/pkgs/os-specific/linux/kernel).
+
+The function that builds the kernel has an argument `kernelPatches` which should be a list of `{name, patch, extraConfig}` attribute sets, where `name` is the name of the patch (which is included in the kernel’s `meta.description` attribute), `patch` is the patch itself (possibly compressed), and `extraConfig` (optional) is a string specifying extra options to be concatenated to the kernel configuration file (`.config`).
+
+The kernel derivation exports an attribute `features` specifying whether optional functionality is or isn’t enabled. This is used in NixOS to implement kernel-specific behaviour. For instance, if the kernel has the `iwlwifi` feature (i.e. has built-in support for Intel wireless chipsets), then NixOS doesn’t have to build the external `iwlwifi` package:
+
+```nix
+modulesTree = [kernel]
+  ++ pkgs.lib.optional (!kernel.features ? iwlwifi) kernelPackages.iwlwifi
+  ++ ...;
+```
+
+How to add a new (major) version of the Linux kernel to Nixpkgs:
+
+1.  Copy the old Nix expression (e.g. `linux-2.6.21.nix`) to the new one (e.g. `linux-2.6.22.nix`) and update it.
+
+2.  Add the new kernel to the `kernels` attribute set in `linux-kernels.nix` (e.g., create an attribute `kernel_2_6_22`).
+
+3.  Now we’re going to update the kernel configuration. First unpack the kernel. Then for each supported platform (`i686`, `x86_64`, `uml`) do the following:
+
+    1.  Make an copy from the old config (e.g. `config-2.6.21-i686-smp`) to the new one (e.g. `config-2.6.22-i686-smp`).
+
+    2.  Copy the config file for this platform (e.g. `config-2.6.22-i686-smp`) to `.config` in the kernel source tree.
+
+    3.  Run `make oldconfig ARCH={i386,x86_64,um}` and answer all questions. (For the uml configuration, also add `SHELL=bash`.) Make sure to keep the configuration consistent between platforms (i.e. don’t enable some feature on `i686` and disable it on `x86_64`).
+
+    4.  If needed you can also run `make menuconfig`:
+
+        ```ShellSession
+        $ nix-env -f "<nixpkgs>" -iA ncurses
+        $ export NIX_CFLAGS_LINK=-lncurses
+        $ make menuconfig ARCH=arch
+        ```
+
+    5.  Copy `.config` over the new config file (e.g. `config-2.6.22-i686-smp`).
+
+4.  Test building the kernel: `nix-build -A linuxKernel.kernels.kernel_2_6_22`. If it compiles, ship it! For extra credit, try booting NixOS with it.
+
+5.  It may be that the new kernel requires updating the external kernel modules and kernel-dependent packages listed in the `linuxPackagesFor` function in `linux-kernels.nix` (such as the NVIDIA drivers, AUFS, etc.). If the updated packages aren’t backwards compatible with older kernels, you may need to keep the older versions around.
diff --git a/doc/builders/packages/locales.section.md b/doc/builders/packages/locales.section.md
new file mode 100644
index 00000000000..e5a03700481
--- /dev/null
+++ b/doc/builders/packages/locales.section.md
@@ -0,0 +1,5 @@
+# Locales {#locales}
+
+To allow simultaneous use of packages linked against different versions of `glibc` with different locale archive formats Nixpkgs patches `glibc` to rely on `LOCALE_ARCHIVE` environment variable.
+
+On non-NixOS distributions this variable is obviously not set. This can cause regressions in language support or even crashes in some Nixpkgs-provided programs. The simplest way to mitigate this problem is exporting the `LOCALE_ARCHIVE` variable pointing to `${glibcLocales}/lib/locale/locale-archive`. The drawback (and the reason this is not the default) is the relatively large (a hundred MiB) size of the full set of locales. It is possible to build a custom set of locales by overriding parameters `allLocales` and `locales` of the package.
diff --git a/doc/builders/packages/nginx.section.md b/doc/builders/packages/nginx.section.md
new file mode 100644
index 00000000000..154c21f9b36
--- /dev/null
+++ b/doc/builders/packages/nginx.section.md
@@ -0,0 +1,11 @@
+# Nginx {#sec-nginx}
+
+[Nginx](https://nginx.org) is a reverse proxy and lightweight webserver.
+
+## ETags on static files served from the Nix store {#sec-nginx-etag}
+
+HTTP has a couple different mechanisms for caching to prevent clients from having to download the same content repeatedly if a resource has not changed since the last time it was requested. When nginx is used as a server for static files, it implements the caching mechanism based on the [`Last-Modified`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Last-Modified) response header automatically; unfortunately, it works by using filesystem timestamps to determine the value of the `Last-Modified` header. This doesn't give the desired behavior when the file is in the Nix store, because all file timestamps are set to 0 (for reasons related to build reproducibility).
+
+Fortunately, HTTP supports an alternative (and more effective) caching mechanism: the [`ETag`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/ETag) response header. The value of the `ETag` header specifies some identifier for the particular content that the server is sending (e.g. a hash). When a client makes a second request for the same resource, it sends that value back in an `If-None-Match` header. If the ETag value is unchanged, then the server does not need to resend the content.
+
+As of NixOS 19.09, the nginx package in Nixpkgs is patched such that when nginx serves a file out of `/nix/store`, the hash in the store path is used as the `ETag` header in the HTTP response, thus providing proper caching functionality. This happens automatically; you do not need to do modify any configuration to get this behavior.
diff --git a/doc/builders/packages/opengl.section.md b/doc/builders/packages/opengl.section.md
new file mode 100644
index 00000000000..ee7f3af98cf
--- /dev/null
+++ b/doc/builders/packages/opengl.section.md
@@ -0,0 +1,15 @@
+# OpenGL {#sec-opengl}
+
+OpenGL support varies depending on which hardware is used and which drivers are available and loaded.
+
+Broadly, we support both GL vendors: Mesa and NVIDIA.
+
+## NixOS Desktop {#nixos-desktop}
+
+The NixOS desktop or other non-headless configurations are the primary target for OpenGL libraries and applications. The current solution for discovering which drivers are available is based on [libglvnd](https://gitlab.freedesktop.org/glvnd/libglvnd). `libglvnd` performs "vendor-neutral dispatch", trying a variety of techniques to find the system's GL implementation. In practice, this will be either via standard GLX for X11 users or EGL for Wayland users, and supporting either NVIDIA or Mesa extensions.
+
+## Nix on GNU/Linux {#nix-on-gnulinux}
+
+If you are using a non-NixOS GNU/Linux/X11 desktop with free software video drivers, consider launching OpenGL-dependent programs from Nixpkgs with Nixpkgs versions of `libglvnd` and `mesa.drivers` in `LD_LIBRARY_PATH`. For Mesa drivers, the Linux kernel version doesn't have to match nixpkgs.
+
+For proprietary video drivers you might have luck with also adding the corresponding video driver package.
diff --git a/doc/builders/packages/shell-helpers.section.md b/doc/builders/packages/shell-helpers.section.md
new file mode 100644
index 00000000000..57b8619c500
--- /dev/null
+++ b/doc/builders/packages/shell-helpers.section.md
@@ -0,0 +1,12 @@
+# Interactive shell helpers {#sec-shell-helpers}
+
+Some packages provide the shell integration to be more useful. But unlike other systems, nix doesn't have a standard `share` directory location. This is why a bunch `PACKAGE-share` scripts are shipped that print the location of the corresponding shared folder. Current list of such packages is as following:
+
+- `fzf` : `fzf-share`
+
+E.g. `fzf` can then used in the `.bashrc` like this:
+
+```bash
+source "$(fzf-share)/completion.bash"
+source "$(fzf-share)/key-bindings.bash"
+```
diff --git a/doc/builders/packages/steam.section.md b/doc/builders/packages/steam.section.md
new file mode 100644
index 00000000000..3ce33c9b60e
--- /dev/null
+++ b/doc/builders/packages/steam.section.md
@@ -0,0 +1,63 @@
+# Steam {#sec-steam}
+
+## Steam in Nix {#sec-steam-nix}
+
+Steam is distributed as a `.deb` file, for now only as an i686 package (the amd64 package only has documentation). When unpacked, it has a script called `steam` that in Ubuntu (their target distro) would go to `/usr/bin`. When run for the first time, this script copies some files to the user's home, which include another script that is the ultimate responsible for launching the steam binary, which is also in \$HOME.
+
+Nix problems and constraints:
+
+- We don't have `/bin/bash` and many scripts point there. Similarly for `/usr/bin/python`.
+- We don't have the dynamic loader in `/lib`.
+- The `steam.sh` script in \$HOME can not be patched, as it is checked and rewritten by steam.
+- The steam binary cannot be patched, it's also checked.
+
+The current approach to deploy Steam in NixOS is composing a FHS-compatible chroot environment, as documented [here](http://sandervanderburg.blogspot.nl/2013/09/composing-fhs-compatible-chroot.html). This allows us to have binaries in the expected paths without disrupting the system, and to avoid patching them to work in a non FHS environment.
+
+## How to play {#sec-steam-play}
+
+Use `programs.steam.enable = true;` if you want to add steam to systemPackages and also enable a few workarrounds aswell as Steam controller support or other Steam supported controllers such as the DualShock 4 or Nintendo Switch Pr.
+
+## Troubleshooting {#sec-steam-troub}
+
+- **Steam fails to start. What do I do?**
+
+  Try to run
+
+  ```ShellSession
+  strace steam
+  ```
+
+  to see what is causing steam to fail.
+
+- **Using the FOSS Radeon or nouveau (nvidia) drivers**
+
+  - The `newStdcpp` parameter was removed since NixOS 17.09 and should not be needed anymore.
+  - Steam ships statically linked with a version of libcrypto that conflics with the one dynamically loaded by radeonsi_dri.so. If you get the error
+
+    ```
+    steam.sh: line 713: 7842 Segmentation fault (core dumped)
+    ```
+
+    have a look at [this pull request](https://github.com/NixOS/nixpkgs/pull/20269).
+
+- **Java**
+
+  1. There is no java in steam chrootenv by default. If you get a message like
+
+    ```
+    /home/foo/.local/share/Steam/SteamApps/common/towns/towns.sh: line 1: java: command not found
+    ```
+
+    you need to add
+
+    ```nix
+    steam.override { withJava = true; };
+    ```
+
+## steam-run {#sec-steam-run}
+
+The FHS-compatible chroot used for Steam can also be used to run other Linux games that expect a FHS environment. To use it, install the `steam-run` package and run the game with
+
+```
+steam-run ./foo
+```
diff --git a/doc/builders/packages/unfree.xml b/doc/builders/packages/unfree.xml
new file mode 100644
index 00000000000..3d4f199f8fb
--- /dev/null
+++ b/doc/builders/packages/unfree.xml
@@ -0,0 +1,13 @@
+<section xmlns="http://docbook.org/ns/docbook"
+         xmlns:xlink="http://www.w3.org/1999/xlink"
+         xml:id="unfree-software">
+ <title>Unfree software</title>
+
+ <para>
+  All users of Nixpkgs are free software users, and many users (and developers) of Nixpkgs want to limit and tightly control their exposure to unfree software. At the same time, many users need (or want) to run some specific pieces of proprietary software. Nixpkgs includes some expressions for unfree software packages. By default unfree software cannot be installed and doesn’t show up in searches. To allow installing unfree software in a single Nix invocation one can export <literal>NIXPKGS_ALLOW_UNFREE=1</literal>. For a persistent solution, users can set <literal>allowUnfree</literal> in the Nixpkgs configuration.
+ </para>
+
+ <para>
+  Fine-grained control is possible by defining <literal>allowUnfreePredicate</literal> function in config; it takes the <literal>mkDerivation</literal> parameter attrset and returns <literal>true</literal> for unfree packages that should be allowed.
+ </para>
+</section>
diff --git a/doc/builders/packages/urxvt.section.md b/doc/builders/packages/urxvt.section.md
new file mode 100644
index 00000000000..2d1196d9227
--- /dev/null
+++ b/doc/builders/packages/urxvt.section.md
@@ -0,0 +1,71 @@
+# Urxvt {#sec-urxvt}
+
+Urxvt, also known as rxvt-unicode, is a highly customizable terminal emulator.
+
+## Configuring urxvt {#sec-urxvt-conf}
+
+In `nixpkgs`, urxvt is provided by the package `rxvt-unicode`. It can be configured to include your choice of plugins, reducing its closure size from the default configuration which includes all available plugins. To make use of this functionality, use an overlay or directly install an expression that overrides its configuration, such as
+
+```nix
+rxvt-unicode.override {
+  configure = { availablePlugins, ... }: {
+    plugins = with availablePlugins; [ perls resize-font vtwheel ];
+  };
+}
+```
+
+If the `configure` function returns an attrset without the `plugins` attribute, `availablePlugins` will be used automatically.
+
+In order to add plugins but also keep all default plugins installed, it is possible to use the following method:
+
+```nix
+rxvt-unicode.override {
+  configure = { availablePlugins, ... }: {
+    plugins = (builtins.attrValues availablePlugins) ++ [ custom-plugin ];
+  };
+}
+```
+
+To get a list of all the plugins available, open the Nix REPL and run
+
+```ShellSession
+$ nix repl
+:l <nixpkgs>
+map (p: p.name) pkgs.rxvt-unicode.plugins
+```
+
+Alternatively, if your shell is bash or zsh and have completion enabled, simply type `nixpkgs.rxvt-unicode.plugins.<tab>`.
+
+In addition to `plugins` the options `extraDeps` and `perlDeps` can be used to install extra packages. `extraDeps` can be used, for example, to provide `xsel` (a clipboard manager) to the clipboard plugin, without installing it globally:
+
+```nix
+rxvt-unicode.override {
+  configure = { availablePlugins, ... }: {
+    pluginsDeps = [ xsel ];
+  };
+}
+```
+
+`perlDeps` is a handy way to provide Perl packages to your custom plugins (in `$HOME/.urxvt/ext`). For example, if you need `AnyEvent` you can do:
+
+```nix
+rxvt-unicode.override {
+  configure = { availablePlugins, ... }: {
+    perlDeps = with perlPackages; [ AnyEvent ];
+  };
+}
+```
+
+## Packaging urxvt plugins {#sec-urxvt-pkg}
+
+Urxvt plugins resides in `pkgs/applications/misc/rxvt-unicode-plugins`. To add a new plugin create an expression in a subdirectory and add the package to the set in `pkgs/applications/misc/rxvt-unicode-plugins/default.nix`.
+
+A plugin can be any kind of derivation, the only requirement is that it should always install perl scripts in `$out/lib/urxvt/perl`. Look for existing plugins for examples.
+
+If the plugin is itself a perl package that needs to be imported from other plugins or scripts, add the following passthrough:
+
+```nix
+passthru.perlPackages = [ "self" ];
+```
+
+This will make the urxvt wrapper pick up the dependency and set up the perl path accordingly.
diff --git a/doc/builders/packages/weechat.section.md b/doc/builders/packages/weechat.section.md
new file mode 100644
index 00000000000..e4e956b908e
--- /dev/null
+++ b/doc/builders/packages/weechat.section.md
@@ -0,0 +1,85 @@
+# Weechat {#sec-weechat}
+
+Weechat can be configured to include your choice of plugins, reducing its closure size from the default configuration which includes all available plugins. To make use of this functionality, install an expression that overrides its configuration such as
+
+```nix
+weechat.override {configure = {availablePlugins, ...}: {
+    plugins = with availablePlugins; [ python perl ];
+  }
+}
+```
+
+If the `configure` function returns an attrset without the `plugins` attribute, `availablePlugins` will be used automatically.
+
+The plugins currently available are `python`, `perl`, `ruby`, `guile`, `tcl` and `lua`.
+
+The python and perl plugins allows the addition of extra libraries. For instance, the `inotify.py` script in `weechat-scripts` requires D-Bus or libnotify, and the `fish.py` script requires `pycrypto`. To use these scripts, use the plugin's `withPackages` attribute:
+
+```nix
+weechat.override { configure = {availablePlugins, ...}: {
+    plugins = with availablePlugins; [
+            (python.withPackages (ps: with ps; [ pycrypto python-dbus ]))
+        ];
+    };
+}
+```
+
+In order to also keep all default plugins installed, it is possible to use the following method:
+
+```nix
+weechat.override { configure = { availablePlugins, ... }: {
+  plugins = builtins.attrValues (availablePlugins // {
+    python = availablePlugins.python.withPackages (ps: with ps; [ pycrypto python-dbus ]);
+  });
+}; }
+```
+
+WeeChat allows to set defaults on startup using the `--run-command`. The `configure` method can be used to pass commands to the program:
+
+```nix
+weechat.override {
+  configure = { availablePlugins, ... }: {
+    init = ''
+      /set foo bar
+      /server add libera irc.libera.chat
+    '';
+  };
+}
+```
+
+Further values can be added to the list of commands when running `weechat --run-command "your-commands"`.
+
+Additionally it's possible to specify scripts to be loaded when starting `weechat`. These will be loaded before the commands from `init`:
+
+```nix
+weechat.override {
+  configure = { availablePlugins, ... }: {
+    scripts = with pkgs.weechatScripts; [
+      weechat-xmpp weechat-matrix-bridge wee-slack
+    ];
+    init = ''
+      /set plugins.var.python.jabber.key "val"
+    '':
+  };
+}
+```
+
+In `nixpkgs` there's a subpackage which contains derivations for WeeChat scripts. Such derivations expect a `passthru.scripts` attribute which contains a list of all scripts inside the store path. Furthermore all scripts have to live in `$out/share`. An exemplary derivation looks like this:
+
+```nix
+{ stdenv, fetchurl }:
+
+stdenv.mkDerivation {
+  name = "exemplary-weechat-script";
+  src = fetchurl {
+    url = "https://scripts.tld/your-scripts.tar.gz";
+    sha256 = "...";
+  };
+  passthru.scripts = [ "foo.py" "bar.lua" ];
+  installPhase = ''
+    mkdir $out/share
+    cp foo.py $out/share
+    cp bar.lua $out/share
+  '';
+}
+```
diff --git a/doc/builders/packages/xorg.section.md b/doc/builders/packages/xorg.section.md
new file mode 100644
index 00000000000..ae885f92346
--- /dev/null
+++ b/doc/builders/packages/xorg.section.md
@@ -0,0 +1,34 @@
+# X.org {#sec-xorg}
+
+The Nix expressions for the X.org packages reside in `pkgs/servers/x11/xorg/default.nix`. This file is automatically generated from lists of tarballs in an X.org release. As such it should not be modified directly; rather, you should modify the lists, the generator script or the file `pkgs/servers/x11/xorg/overrides.nix`, in which you can override or add to the derivations produced by the generator.
+
+## Katamari Tarballs {#katamari-tarballs}
+
+X.org upstream releases used to include [katamari](https://en.wiktionary.org/wiki/%E3%81%8B%E3%81%9F%E3%81%BE%E3%82%8A) releases, which included a holistic recommended version for each tarball, up until 7.7. To create a list of tarballs in a katamari release:
+
+```ShellSession
+export release="X11R7.7"
+export url="mirror://xorg/$release/src/everything/"
+cat $(PRINT_PATH=1 nix-prefetch-url $url | tail -n 1) \
+  | perl -e 'while (<>) { if (/(href|HREF)="([^"]*.bz2)"/) { print "$ENV{'url'}$2\n"; }; }' \
+  | sort > "tarballs-$release.list"
+```
+
+## Individual Tarballs {#individual-tarballs}
+
+The upstream release process for [X11R7.8](https://x.org/wiki/Releases/7.8/) does not include a planned katamari. Instead, each component of X.org is released as its own tarball. We maintain `pkgs/servers/x11/xorg/tarballs.list` as a list of tarballs for each individual package. This list includes X.org core libraries and protocol descriptions, extra newer X11 interface libraries, like `xorg.libxcb`, and classic utilities which are largely unused but still available if needed, like `xorg.imake`.
+
+## Generating Nix Expressions {#generating-nix-expressions}
+
+The generator is invoked as follows:
+
+```ShellSession
+cd pkgs/servers/x11/xorg
+<tarballs.list perl ./generate-expr-from-tarballs.pl
+```
+
+For each of the tarballs in the `.list` files, the script downloads it, unpacks it, and searches its `configure.ac` and `*.pc.in` files for dependencies. This information is used to generate `default.nix`. The generator caches downloaded tarballs between runs. Pay close attention to the `NOT FOUND: $NAME` messages at the end of the run, since they may indicate missing dependencies. (Some might be optional dependencies, however.)
+
+## Overriding the Generator {#overriding-the-generator}
+
+If the expression for a package requires derivation attributes that the generator cannot figure out automatically (say, `patches` or a `postInstall` hook), you should modify `pkgs/servers/x11/xorg/overrides.nix`.
diff --git a/doc/builders/special.xml b/doc/builders/special.xml
new file mode 100644
index 00000000000..2f84599cdd4
--- /dev/null
+++ b/doc/builders/special.xml
@@ -0,0 +1,11 @@
+<chapter xmlns="http://docbook.org/ns/docbook"
+         xmlns:xi="http://www.w3.org/2001/XInclude"
+         xml:id="chap-special">
+ <title>Special builders</title>
+ <para>
+  This chapter describes several special builders.
+ </para>
+ <xi:include href="special/fhs-environments.section.xml" />
+ <xi:include href="special/mkshell.section.xml" />
+ <xi:include href="special/invalidateFetcherByDrvHash.section.xml" />
+</chapter>
diff --git a/doc/builders/special/fhs-environments.section.md b/doc/builders/special/fhs-environments.section.md
new file mode 100644
index 00000000000..cacad261e28
--- /dev/null
+++ b/doc/builders/special/fhs-environments.section.md
@@ -0,0 +1,49 @@
+# buildFHSUserEnv {#sec-fhs-environments}
+
+`buildFHSUserEnv` provides a way to build and run FHS-compatible lightweight sandboxes. It creates an isolated root with bound `/nix/store`, so its footprint in terms of disk space needed is quite small. This allows one to run software which is hard or unfeasible to patch for NixOS -- 3rd-party source trees with FHS assumptions, games distributed as tarballs, software with integrity checking and/or external self-updated binaries. It uses Linux namespaces feature to create temporary lightweight environments which are destroyed after all child processes exit, without root user rights requirement. Accepted arguments are:
+
+- `name`
+        Environment name.
+- `targetPkgs`
+        Packages to be installed for the main host's architecture (i.e. x86_64 on x86_64 installations). Along with libraries binaries are also installed.
+- `multiPkgs`
+        Packages to be installed for all architectures supported by a host (i.e. i686 and x86_64 on x86_64 installations). Only libraries are installed by default.
+- `extraBuildCommands`
+        Additional commands to be executed for finalizing the directory structure.
+- `extraBuildCommandsMulti`
+        Like `extraBuildCommands`, but executed only on multilib architectures.
+- `extraOutputsToInstall`
+        Additional derivation outputs to be linked for both target and multi-architecture packages.
+- `extraInstallCommands`
+        Additional commands to be executed for finalizing the derivation with runner script.
+- `runScript`
+        A command that would be executed inside the sandbox and passed all the command line arguments. It defaults to `bash`.
+- `profile`
+        Optional script for `/etc/profile` within the sandbox.
+
+One can create a simple environment using a `shell.nix` like that:
+
+```nix
+{ pkgs ? import <nixpkgs> {} }:
+
+(pkgs.buildFHSUserEnv {
+  name = "simple-x11-env";
+  targetPkgs = pkgs: (with pkgs;
+    [ udev
+      alsa-lib
+    ]) ++ (with pkgs.xorg;
+    [ libX11
+      libXcursor
+      libXrandr
+    ]);
+  multiPkgs = pkgs: (with pkgs;
+    [ udev
+      alsa-lib
+    ]);
+  runScript = "bash";
+}).env
+```
+
+Running `nix-shell` would then drop you into a shell with these libraries and binaries available. You can use this to run closed-source applications which expect FHS structure without hassles: simply change `runScript` to the application path, e.g. `./bin/start.sh` -- relative paths are supported.
+
+Additionally, the FHS builder links all relocated gsettings-schemas (the glib setup-hook moves them to `share/gsettings-schemas/${name}/glib-2.0/schemas`) to their standard FHS location. This means you don't need to wrap binaries with `wrapGAppsHook`.
diff --git a/doc/builders/special/invalidateFetcherByDrvHash.section.md b/doc/builders/special/invalidateFetcherByDrvHash.section.md
new file mode 100644
index 00000000000..7c2f03a64b7
--- /dev/null
+++ b/doc/builders/special/invalidateFetcherByDrvHash.section.md
@@ -0,0 +1,31 @@
+
+## `invalidateFetcherByDrvHash` {#sec-pkgs-invalidateFetcherByDrvHash}
+
+Use the derivation hash to invalidate the output via name, for testing.
+
+Type: `(a@{ name, ... } -> Derivation) -> a -> Derivation`
+
+Normally, fixed output derivations can and should be cached by their output
+hash only, but for testing we want to re-fetch everytime the fetcher changes.
+
+Changes to the fetcher become apparent in the drvPath, which is a hash of
+how to fetch, rather than a fixed store path.
+By inserting this hash into the name, we can make sure to re-run the fetcher
+every time the fetcher changes.
+
+This relies on the assumption that Nix isn't clever enough to reuse its
+database of local store contents to optimize fetching.
+
+You might notice that the "salted" name derives from the normal invocation,
+not the final derivation. `invalidateFetcherByDrvHash` has to invoke the fetcher
+function twice: once to get a derivation hash, and again to produce the final
+fixed output derivation.
+
+Example:
+
+    tests.fetchgit = invalidateFetcherByDrvHash fetchgit {
+      name = "nix-source";
+      url = "https://github.com/NixOS/nix";
+      rev = "9d9dbe6ed05854e03811c361a3380e09183f4f4a";
+      sha256 = "sha256-7DszvbCNTjpzGRmpIVAWXk20P0/XTrWZ79KSOGLrUWY=";
+    };
diff --git a/doc/builders/special/mkshell.section.md b/doc/builders/special/mkshell.section.md
new file mode 100644
index 00000000000..73cc57f485b
--- /dev/null
+++ b/doc/builders/special/mkshell.section.md
@@ -0,0 +1,37 @@
+# pkgs.mkShell {#sec-pkgs-mkShell}
+
+`pkgs.mkShell` is a specialized `stdenv.mkDerivation` that removes some
+repetition when using it with `nix-shell` (or `nix develop`).
+
+## Usage {#sec-pkgs-mkShell-usage}
+
+Here is a common usage example:
+
+```nix
+{ pkgs ? import <nixpkgs> {} }:
+pkgs.mkShell {
+  packages = [ pkgs.gnumake ];
+
+  inputsFrom = [ pkgs.hello pkgs.gnutar ];
+
+  shellHook = ''
+    export DEBUG=1
+  '';
+}
+```
+
+## Attributes
+
+* `name` (default: `nix-shell`). Set the name of the derivation.
+* `packages` (default: `[]`). Add executable packages to the `nix-shell` environment.
+* `inputsFrom` (default: `[]`). Add build dependencies of the listed derivations to the `nix-shell` environment.
+* `shellHook` (default: `""`). Bash statements that are executed by `nix-shell`.
+
+... all the attributes of `stdenv.mkDerivation`.
+
+## Building the shell
+
+This derivation output will contain a text file that contains a reference to
+all the build inputs. This is useful in CI where we want to make sure that
+every derivation, and its dependencies, build properly. Or when creating a GC
+root so that the build dependencies don't get garbage-collected.
diff --git a/doc/builders/trivial-builders.chapter.md b/doc/builders/trivial-builders.chapter.md
new file mode 100644
index 00000000000..779a0a801b4
--- /dev/null
+++ b/doc/builders/trivial-builders.chapter.md
@@ -0,0 +1,223 @@
+# Trivial builders {#chap-trivial-builders}
+
+Nixpkgs provides a couple of functions that help with building derivations. The most important one, `stdenv.mkDerivation`, has already been documented above. The following functions wrap `stdenv.mkDerivation`, making it easier to use in certain cases.
+
+## `runCommand` {#trivial-builder-runCommand}
+
+This takes three arguments, `name`, `env`, and `buildCommand`. `name` is just the name that Nix will append to the store path in the same way that `stdenv.mkDerivation` uses its `name` attribute. `env` is an attribute set specifying environment variables that will be set for this derivation. These attributes are then passed to the wrapped `stdenv.mkDerivation`. `buildCommand` specifies the commands that will be run to create this derivation. Note that you will need to create `$out` for Nix to register the command as successful.
+
+An example of using `runCommand` is provided below.
+
+```nix
+(import <nixpkgs> {}).runCommand "my-example" {} ''
+  echo My example command is running
+
+  mkdir $out
+
+  echo I can write data to the Nix store > $out/message
+
+  echo I can also run basic commands like:
+
+  echo ls
+  ls
+
+  echo whoami
+  whoami
+
+  echo date
+  date
+''
+```
+
+## `runCommandCC` {#trivial-builder-runCommandCC}
+
+This works just like `runCommand`. The only difference is that it also provides a C compiler in `buildCommand`'s environment. To minimize your dependencies, you should only use this if you are sure you will need a C compiler as part of running your command.
+
+## `runCommandLocal` {#trivial-builder-runCommandLocal}
+
+Variant of `runCommand` that forces the derivation to be built locally, it is not substituted. This is intended for very cheap commands (<1s execution time). It saves on the network roundrip and can speed up a build.
+
+::: {.note}
+This sets [`allowSubstitutes` to `false`](https://nixos.org/nix/manual/#adv-attr-allowSubstitutes), so only use `runCommandLocal` if you are certain the user will always have a builder for the `system` of the derivation. This should be true for most trivial use cases (e.g. just copying some files to a different location or adding symlinks), because there the `system` is usually the same as `builtins.currentSystem`.
+:::
+
+## `writeTextFile`, `writeText`, `writeTextDir`, `writeScript`, `writeScriptBin` {#trivial-builder-writeText}
+
+These functions write `text` to the Nix store. This is useful for creating scripts from Nix expressions. `writeTextFile` takes an attribute set and expects two arguments, `name` and `text`. `name` corresponds to the name used in the Nix store path. `text` will be the contents of the file. You can also set `executable` to true to make this file have the executable bit set.
+
+Many more commands wrap `writeTextFile` including `writeText`, `writeTextDir`, `writeScript`, and `writeScriptBin`. These are convenience functions over `writeTextFile`.
+
+Here are a few examples:
+```nix
+# Writes my-file to /nix/store/<store path>
+writeTextFile {
+  name = "my-file";
+  text = ''
+    Contents of File
+  '';
+}
+# See also the `writeText` helper function below.
+
+# Writes executable my-file to /nix/store/<store path>/bin/my-file
+writeTextFile {
+  name = "my-file";
+  text = ''
+    Contents of File
+  '';
+  executable = true;
+  destination = "/bin/my-file";
+}
+# Writes contents of file to /nix/store/<store path>
+writeText "my-file"
+  ''
+  Contents of File
+  '';
+# Writes contents of file to /nix/store/<store path>/share/my-file
+writeTextDir "share/my-file"
+  ''
+  Contents of File
+  '';
+# Writes my-file to /nix/store/<store path> and makes executable
+writeScript "my-file"
+  ''
+  Contents of File
+  '';
+# Writes my-file to /nix/store/<store path>/bin/my-file and makes executable.
+writeScriptBin "my-file"
+  ''
+  Contents of File
+  '';
+# Writes my-file to /nix/store/<store path> and makes executable.
+writeShellScript "my-file"
+  ''
+  Contents of File
+  '';
+# Writes my-file to /nix/store/<store path>/bin/my-file and makes executable.
+writeShellScriptBin "my-file"
+  ''
+  Contents of File
+  '';
+
+```
+
+## `concatTextFile`, `concatText`, `concatScript` {#trivial-builder-concatText}
+
+These functions concatenate `files` to the Nix store in a single file. This is useful for configuration files structured in lines of text. `concatTextFile` takes an attribute set and expects two arguments, `name` and `files`. `name` corresponds to the name used in the Nix store path. `files` will be the files to be concatenated. You can also set `executable` to true to make this file have the executable bit set.
+`concatText` and`concatScript` are simple wrappers over `concatTextFile`.
+
+Here are a few examples:
+```nix
+
+# Writes my-file to /nix/store/<store path>
+concatTextFile {
+  name = "my-file";
+  files = [ drv1 "${drv2}/path/to/file" ];
+}
+# See also the `concatText` helper function below.
+
+# Writes executable my-file to /nix/store/<store path>/bin/my-file
+concatTextFile {
+  name = "my-file";
+  files = [ drv1 "${drv2}/path/to/file" ];
+  executable = true;
+  destination = "/bin/my-file";
+}
+# Writes contents of files to /nix/store/<store path>
+concatText "my-file" [ file1 file2 ]
+
+# Writes contents of files to /nix/store/<store path>
+concatScript "my-file" [ file1 file2 ]
+```
+
+## `writeShellApplication` {#trivial-builder-writeShellApplication}
+
+This can be used to easily produce a shell script that has some dependencies (`runtimeInputs`). It automatically sets the `PATH` of the script to contain all of the listed inputs, sets some sanity shellopts (`errexit`, `nounset`, `pipefail`), and checks the resulting script with [`shellcheck`](https://github.com/koalaman/shellcheck).
+
+For example, look at the following code:
+
+```nix
+writeShellApplication {
+  name = "show-nixos-org";
+
+  runtimeInputs = [ curl w3m ];
+
+  text = ''
+    curl -s 'https://nixos.org' | w3m -dump -T text/html
+  '';
+}
+```
+
+Unlike with normal `writeShellScriptBin`, there is no need to manually write out `${curl}/bin/curl`, setting the PATH
+was handled by `writeShellApplication`. Moreover, the script is being checked with `shellcheck` for more strict
+validation.
+
+## `symlinkJoin` {#trivial-builder-symlinkJoin}
+
+This can be used to put many derivations into the same directory structure. It works by creating a new derivation and adding symlinks to each of the paths listed. It expects two arguments, `name`, and `paths`. `name` is the name used in the Nix store path for the created derivation. `paths` is a list of paths that will be symlinked. These paths can be to Nix store derivations or any other subdirectory contained within.
+Here is an example:
+```nix
+# adds symlinks of hello and stack to current build and prints "links added"
+symlinkJoin { name = "myexample"; paths = [ pkgs.hello pkgs.stack ]; postBuild = "echo links added"; }
+```
+This creates a derivation with a directory structure like the following:
+```
+/nix/store/sglsr5g079a5235hy29da3mq3hv8sjmm-myexample
+|-- bin
+|   |-- hello -> /nix/store/qy93dp4a3rqyn2mz63fbxjg228hffwyw-hello-2.10/bin/hello
+|   `-- stack -> /nix/store/6lzdpxshx78281vy056lbk553ijsdr44-stack-2.1.3.1/bin/stack
+`-- share
+    |-- bash-completion
+    |   `-- completions
+    |       `-- stack -> /nix/store/6lzdpxshx78281vy056lbk553ijsdr44-stack-2.1.3.1/share/bash-completion/completions/stack
+    |-- fish
+    |   `-- vendor_completions.d
+    |       `-- stack.fish -> /nix/store/6lzdpxshx78281vy056lbk553ijsdr44-stack-2.1.3.1/share/fish/vendor_completions.d/stack.fish
+...
+```
+
+## `writeReferencesToFile` {#trivial-builder-writeReferencesToFile}
+
+Writes the closure of transitive dependencies to a file.
+
+This produces the equivalent of `nix-store -q --requisites`.
+
+For example,
+
+```nix
+writeReferencesToFile (writeScriptBin "hi" ''${hello}/bin/hello'')
+```
+
+produces an output path `/nix/store/<hash>-runtime-deps` containing
+
+```nix
+/nix/store/<hash>-hello-2.10
+/nix/store/<hash>-hi
+/nix/store/<hash>-libidn2-2.3.0
+/nix/store/<hash>-libunistring-0.9.10
+/nix/store/<hash>-glibc-2.32-40
+```
+
+You can see that this includes `hi`, the original input path,
+`hello`, which is a direct reference, but also
+the other paths that are indirectly required to run `hello`.
+
+## `writeDirectReferencesToFile` {#trivial-builder-writeDirectReferencesToFile}
+
+Writes the set of references to the output file, that is, their immediate dependencies.
+
+This produces the equivalent of `nix-store -q --references`.
+
+For example,
+
+```nix
+writeDirectReferencesToFile (writeScriptBin "hi" ''${hello}/bin/hello'')
+```
+
+produces an output path `/nix/store/<hash>-runtime-references` containing
+
+```nix
+/nix/store/<hash>-hello-2.10
+```
+
+but none of `hello`'s dependencies, because those are not referenced directly
+by `hi`'s output.
diff --git a/doc/contributing/coding-conventions.chapter.md b/doc/contributing/coding-conventions.chapter.md
new file mode 100644
index 00000000000..cfe8582e514
--- /dev/null
+++ b/doc/contributing/coding-conventions.chapter.md
@@ -0,0 +1,664 @@
+# Coding conventions {#chap-conventions}
+
+## Syntax {#sec-syntax}
+
+- Use 2 spaces of indentation per indentation level in Nix expressions, 4 spaces in shell scripts.
+
+- Do not use tab characters, i.e. configure your editor to use soft tabs. For instance, use `(setq-default indent-tabs-mode nil)` in Emacs. Everybody has different tab settings so it’s asking for trouble.
+
+- Use `lowerCamelCase` for variable names, not `UpperCamelCase`. Note, this rule does not apply to package attribute names, which instead follow the rules in [](#sec-package-naming).
+
+- Function calls with attribute set arguments are written as
+
+  ```nix
+  foo {
+    arg = ...;
+  }
+  ```
+
+  not
+
+  ```nix
+  foo
+  {
+    arg = ...;
+  }
+  ```
+
+  Also fine is
+
+  ```nix
+  foo { arg = ...; }
+  ```
+
+  if it's a short call.
+
+- In attribute sets or lists that span multiple lines, the attribute names or list elements should be aligned:
+
+  ```nix
+  # A long list.
+  list = [
+    elem1
+    elem2
+    elem3
+  ];
+
+  # A long attribute set.
+  attrs = {
+    attr1 = short_expr;
+    attr2 =
+      if true then big_expr else big_expr;
+  };
+
+  # Combined
+  listOfAttrs = [
+    {
+      attr1 = 3;
+      attr2 = "fff";
+    }
+    {
+      attr1 = 5;
+      attr2 = "ggg";
+    }
+  ];
+  ```
+
+- Short lists or attribute sets can be written on one line:
+
+  ```nix
+  # A short list.
+  list = [ elem1 elem2 elem3 ];
+
+  # A short set.
+  attrs = { x = 1280; y = 1024; };
+  ```
+
+- Breaking in the middle of a function argument can give hard-to-read code, like
+
+  ```nix
+  someFunction { x = 1280;
+    y = 1024; } otherArg
+    yetAnotherArg
+  ```
+
+  (especially if the argument is very large, spanning multiple lines).
+
+  Better:
+
+  ```nix
+  someFunction
+    { x = 1280; y = 1024; }
+    otherArg
+    yetAnotherArg
+  ```
+
+  or
+
+  ```nix
+  let res = { x = 1280; y = 1024; };
+  in someFunction res otherArg yetAnotherArg
+  ```
+
+- The bodies of functions, asserts, and withs are not indented to prevent a lot of superfluous indentation levels, i.e.
+
+  ```nix
+  { arg1, arg2 }:
+  assert system == "i686-linux";
+  stdenv.mkDerivation { ...
+  ```
+
+  not
+
+  ```nix
+  { arg1, arg2 }:
+    assert system == "i686-linux";
+      stdenv.mkDerivation { ...
+  ```
+
+- Function formal arguments are written as:
+
+  ```nix
+  { arg1, arg2, arg3 }:
+  ```
+
+  but if they don't fit on one line they're written as:
+
+  ```nix
+  { arg1, arg2, arg3
+  , arg4, ...
+  , # Some comment...
+    argN
+  }:
+  ```
+
+- Functions should list their expected arguments as precisely as possible. That is, write
+
+  ```nix
+  { stdenv, fetchurl, perl }: ...
+  ```
+
+  instead of
+
+  ```nix
+  args: with args; ...
+  ```
+
+  or
+
+  ```nix
+  { stdenv, fetchurl, perl, ... }: ...
+  ```
+
+  For functions that are truly generic in the number of arguments (such as wrappers around `mkDerivation`) that have some required arguments, you should write them using an `@`-pattern:
+
+  ```nix
+  { stdenv, doCoverageAnalysis ? false, ... } @ args:
+
+  stdenv.mkDerivation (args // {
+    ... if doCoverageAnalysis then "bla" else "" ...
+  })
+  ```
+
+  instead of
+
+  ```nix
+  args:
+
+  args.stdenv.mkDerivation (args // {
+    ... if args ? doCoverageAnalysis && args.doCoverageAnalysis then "bla" else "" ...
+  })
+  ```
+
+- Unnecessary string conversions should be avoided. Do
+
+  ```nix
+  rev = version;
+  ```
+
+  instead of
+
+  ```nix
+  rev = "${version}";
+  ```
+
+- Building lists conditionally _should_ be done with `lib.optional(s)` instead of using `if cond then [ ... ] else null` or `if cond then [ ... ] else [ ]`.
+
+  ```nix
+  buildInputs = lib.optional stdenv.isDarwin iconv;
+  ```
+
+  instead of
+
+  ```nix
+  buildInputs = if stdenv.isDarwin then [ iconv ] else null;
+  ```
+
+  As an exception, an explicit conditional expression with null can be used when fixing a important bug without triggering a mass rebuild.
+  If this is done a follow up pull request _should_ be created to change the code to `lib.optional(s)`.
+
+- Arguments should be listed in the order they are used, with the exception of `lib`, which always goes first.
+
+## Package naming {#sec-package-naming}
+
+The key words _must_, _must not_, _required_, _shall_, _shall not_, _should_, _should not_, _recommended_, _may_, and _optional_ in this section are to be interpreted as described in [RFC 2119](https://tools.ietf.org/html/rfc2119). Only _emphasized_ words are to be interpreted in this way.
+
+In Nixpkgs, there are generally three different names associated with a package:
+
+- The `name` attribute of the derivation (excluding the version part). This is what most users see, in particular when using `nix-env`.
+
+- The variable name used for the instantiated package in `all-packages.nix`, and when passing it as a dependency to other functions. Typically this is called the _package attribute name_. This is what Nix expression authors see. It can also be used when installing using `nix-env -iA`.
+
+- The filename for (the directory containing) the Nix expression.
+
+Most of the time, these are the same. For instance, the package `e2fsprogs` has a `name` attribute `"e2fsprogs-version"`, is bound to the variable name `e2fsprogs` in `all-packages.nix`, and the Nix expression is in `pkgs/os-specific/linux/e2fsprogs/default.nix`.
+
+There are a few naming guidelines:
+
+- The `name` attribute _should_ be identical to the upstream package name.
+
+- The `name` attribute _must not_ contain uppercase letters — e.g., `"mplayer-1.0rc2"` instead of `"MPlayer-1.0rc2"`.
+
+- The version part of the `name` attribute _must_ start with a digit (following a dash) — e.g., `"hello-0.3.1rc2"`.
+
+- If a package is not a release but a commit from a repository, then the version part of the name _must_ be the date of that (fetched) commit. The date _must_ be in `"YYYY-MM-DD"` format. Also append `"unstable"` to the name - e.g., `"pkgname-unstable-2014-09-23"`.
+
+- Dashes in the package name _should_ be preserved in new variable names, rather than converted to underscores or camel cased — e.g., `http-parser` instead of `http_parser` or `httpParser`. The hyphenated style is preferred in all three package names.
+
+- If there are multiple versions of a package, this _should_ be reflected in the variable names in `all-packages.nix`, e.g. `json-c_0_9` and `json-c_0_11`. If there is an obvious “default” version, make an attribute like `json-c = json-c_0_9;`. See also [](#sec-versioning)
+
+## File naming and organisation {#sec-organisation}
+
+Names of files and directories should be in lowercase, with dashes between words — not in camel case. For instance, it should be `all-packages.nix`, not `allPackages.nix` or `AllPackages.nix`.
+
+### Hierarchy {#sec-hierarchy}
+
+Each package should be stored in its own directory somewhere in the `pkgs/` tree, i.e. in `pkgs/category/subcategory/.../pkgname`. Below are some rules for picking the right category for a package. Many packages fall under several categories; what matters is the _primary_ purpose of a package. For example, the `libxml2` package builds both a library and some tools; but it’s a library foremost, so it goes under `pkgs/development/libraries`.
+
+When in doubt, consider refactoring the `pkgs/` tree, e.g. creating new categories or splitting up an existing category.
+
+**If it’s used to support _software development_:**
+
+- **If it’s a _library_ used by other packages:**
+
+  - `development/libraries` (e.g. `libxml2`)
+
+- **If it’s a _compiler_:**
+
+  - `development/compilers` (e.g. `gcc`)
+
+- **If it’s an _interpreter_:**
+
+  - `development/interpreters` (e.g. `guile`)
+
+- **If it’s a (set of) development _tool(s)_:**
+
+  - **If it’s a _parser generator_ (including lexers):**
+
+    - `development/tools/parsing` (e.g. `bison`, `flex`)
+
+  - **If it’s a _build manager_:**
+
+    - `development/tools/build-managers` (e.g. `gnumake`)
+
+  - **Else:**
+
+    - `development/tools/misc` (e.g. `binutils`)
+
+- **Else:**
+
+  - `development/misc`
+
+**If it’s a (set of) _tool(s)_:**
+
+(A tool is a relatively small program, especially one intended to be used non-interactively.)
+
+- **If it’s for _networking_:**
+
+  - `tools/networking` (e.g. `wget`)
+
+- **If it’s for _text processing_:**
+
+  - `tools/text` (e.g. `diffutils`)
+
+- **If it’s a _system utility_, i.e., something related or essential to the operation of a system:**
+
+  - `tools/system` (e.g. `cron`)
+
+- **If it’s an _archiver_ (which may include a compression function):**
+
+  - `tools/archivers` (e.g. `zip`, `tar`)
+
+- **If it’s a _compression_ program:**
+
+  - `tools/compression` (e.g. `gzip`, `bzip2`)
+
+- **If it’s a _security_-related program:**
+
+  - `tools/security` (e.g. `nmap`, `gnupg`)
+
+- **Else:**
+
+  - `tools/misc`
+
+**If it’s a _shell_:**
+
+- `shells` (e.g. `bash`)
+
+**If it’s a _server_:**
+
+- **If it’s a web server:**
+
+  - `servers/http` (e.g. `apache-httpd`)
+
+- **If it’s an implementation of the X Windowing System:**
+
+  - `servers/x11` (e.g. `xorg` — this includes the client libraries and programs)
+
+- **Else:**
+
+  - `servers/misc`
+
+**If it’s a _desktop environment_:**
+
+- `desktops` (e.g. `kde`, `gnome`, `enlightenment`)
+
+**If it’s a _window manager_:**
+
+- `applications/window-managers` (e.g. `awesome`, `stumpwm`)
+
+**If it’s an _application_:**
+
+A (typically large) program with a distinct user interface, primarily used interactively.
+
+- **If it’s a _version management system_:**
+
+  - `applications/version-management` (e.g. `subversion`)
+
+- **If it’s a _terminal emulator_:**
+
+  - `applications/terminal-emulators` (e.g. `alacritty` or `rxvt` or `termite`)
+
+- **If it’s for _video playback / editing_:**
+
+  - `applications/video` (e.g. `vlc`)
+
+- **If it’s for _graphics viewing / editing_:**
+
+  - `applications/graphics` (e.g. `gimp`)
+
+- **If it’s for _networking_:**
+
+  - **If it’s a _mailreader_:**
+
+    - `applications/networking/mailreaders` (e.g. `thunderbird`)
+
+  - **If it’s a _newsreader_:**
+
+    - `applications/networking/newsreaders` (e.g. `pan`)
+
+  - **If it’s a _web browser_:**
+
+    - `applications/networking/browsers` (e.g. `firefox`)
+
+  - **Else:**
+
+    - `applications/networking/misc`
+
+- **Else:**
+
+  - `applications/misc`
+
+**If it’s _data_ (i.e., does not have a straight-forward executable semantics):**
+
+- **If it’s a _font_:**
+
+  - `data/fonts`
+
+- **If it’s an _icon theme_:**
+
+  - `data/icons`
+
+- **If it’s related to _SGML/XML processing_:**
+
+  - **If it’s an _XML DTD_:**
+
+    - `data/sgml+xml/schemas/xml-dtd` (e.g. `docbook`)
+
+  - **If it’s an _XSLT stylesheet_:**
+
+    (Okay, these are executable...)
+
+    - `data/sgml+xml/stylesheets/xslt` (e.g. `docbook-xsl`)
+
+- **If it’s a _theme_ for a _desktop environment_, a _window manager_ or a _display manager_:**
+
+  - `data/themes`
+
+**If it’s a _game_:**
+
+- `games`
+
+**Else:**
+
+- `misc`
+
+### Versioning {#sec-versioning}
+
+Because every version of a package in Nixpkgs creates a potential maintenance burden, old versions of a package should not be kept unless there is a good reason to do so. For instance, Nixpkgs contains several versions of GCC because other packages don’t build with the latest version of GCC. Other examples are having both the latest stable and latest pre-release version of a package, or to keep several major releases of an application that differ significantly in functionality.
+
+If there is only one version of a package, its Nix expression should be named `e2fsprogs/default.nix`. If there are multiple versions, this should be reflected in the filename, e.g. `e2fsprogs/1.41.8.nix` and `e2fsprogs/1.41.9.nix`. The version in the filename should leave out unnecessary detail. For instance, if we keep the latest Firefox 2.0.x and 3.5.x versions in Nixpkgs, they should be named `firefox/2.0.nix` and `firefox/3.5.nix`, respectively (which, at a given point, might contain versions `2.0.0.20` and `3.5.4`). If a version requires many auxiliary files, you can use a subdirectory for each version, e.g. `firefox/2.0/default.nix` and `firefox/3.5/default.nix`.
+
+All versions of a package _must_ be included in `all-packages.nix` to make sure that they evaluate correctly.
+
+## Fetching Sources {#sec-sources}
+
+There are multiple ways to fetch a package source in nixpkgs. The general guideline is that you should package reproducible sources with a high degree of availability. Right now there is only one fetcher which has mirroring support and that is `fetchurl`. Note that you should also prefer protocols which have a corresponding proxy environment variable.
+
+You can find many source fetch helpers in `pkgs/build-support/fetch*`.
+
+In the file `pkgs/top-level/all-packages.nix` you can find fetch helpers, these have names on the form `fetchFrom*`. The intention of these are to provide snapshot fetches but using the same api as some of the version controlled fetchers from `pkgs/build-support/`. As an example going from bad to good:
+
+- Bad: Uses `git://` which won't be proxied.
+
+  ```nix
+  src = fetchgit {
+    url = "git://github.com/NixOS/nix.git";
+    rev = "1f795f9f44607cc5bec70d1300150bfefcef2aae";
+    sha256 = "1cw5fszffl5pkpa6s6wjnkiv6lm5k618s32sp60kvmvpy7a2v9kg";
+  }
+  ```
+
+- Better: This is ok, but an archive fetch will still be faster.
+
+  ```nix
+  src = fetchgit {
+    url = "https://github.com/NixOS/nix.git";
+    rev = "1f795f9f44607cc5bec70d1300150bfefcef2aae";
+    sha256 = "1cw5fszffl5pkpa6s6wjnkiv6lm5k618s32sp60kvmvpy7a2v9kg";
+  }
+  ```
+
+- Best: Fetches a snapshot archive and you get the rev you want.
+
+  ```nix
+  src = fetchFromGitHub {
+    owner = "NixOS";
+    repo = "nix";
+    rev = "1f795f9f44607cc5bec70d1300150bfefcef2aae";
+    sha256 = "1i2yxndxb6yc9l6c99pypbd92lfq5aac4klq7y2v93c9qvx2cgpc";
+  }
+  ```
+
+  Find the value to put as `sha256` by running `nix run -f '<nixpkgs>' nix-prefetch-github -c nix-prefetch-github --rev 1f795f9f44607cc5bec70d1300150bfefcef2aae NixOS nix` or `nix-prefetch-url --unpack https://github.com/NixOS/nix/archive/1f795f9f44607cc5bec70d1300150bfefcef2aae.tar.gz`.
+
+## Obtaining source hash {#sec-source-hashes}
+
+Preferred source hash type is sha256. There are several ways to get it.
+
+1. Prefetch URL (with `nix-prefetch-XXX URL`, where `XXX` is one of `url`, `git`, `hg`, `cvs`, `bzr`, `svn`). Hash is printed to stdout.
+
+2. Prefetch by package source (with `nix-prefetch-url '<nixpkgs>' -A PACKAGE.src`, where `PACKAGE` is package attribute name). Hash is printed to stdout.
+
+    This works well when you've upgraded existing package version and want to find out new hash, but is useless if package can't be accessed by attribute or package has multiple sources (`.srcs`, architecture-dependent sources, etc).
+
+3. Upstream provided hash: use it when upstream provides `sha256` or `sha512` (when upstream provides `md5`, don't use it, compute `sha256` instead).
+
+    A little nuance is that `nix-prefetch-*` tools produce hash encoded with `base32`, but upstream usually provides hexadecimal (`base16`) encoding. Fetchers understand both formats. Nixpkgs does not standardize on any one format.
+
+    You can convert between formats with nix-hash, for example:
+
+    ```ShellSession
+    $ nix-hash --type sha256 --to-base32 HASH
+    ```
+
+4. Extracting hash from local source tarball can be done with `sha256sum`. Use `nix-prefetch-url file:///path/to/tarball` if you want base32 hash.
+
+5. Fake hash: set fake hash in package expression, perform build and extract correct hash from error Nix prints.
+
+    For package updates it is enough to change one symbol to make hash fake. For new packages, you can use `lib.fakeSha256`, `lib.fakeSha512` or any other fake hash.
+
+    This is last resort method when reconstructing source URL is non-trivial and `nix-prefetch-url -A` isn’t applicable (for example, [one of `kodi` dependencies](https://github.com/NixOS/nixpkgs/blob/d2ab091dd308b99e4912b805a5eb088dd536adb9/pkgs/applications/video/kodi/default.nix#L73)). The easiest way then would be replace hash with a fake one and rebuild. Nix build will fail and error message will contain desired hash.
+
+::: {.warning}
+This method has security problems. Check below for details.
+:::
+
+### Obtaining hashes securely {#sec-source-hashes-security}
+
+Let's say Man-in-the-Middle (MITM) sits close to your network. Then instead of fetching source you can fetch malware, and instead of source hash you get hash of malware. Here are security considerations for this scenario:
+
+- `http://` URLs are not secure to prefetch hash from;
+
+- hashes from upstream (in method 3) should be obtained via secure protocol;
+
+- `https://` URLs are secure in methods 1, 2, 3;
+
+- `https://` URLs are not secure in method 5. When obtaining hashes with fake hash method, TLS checks are disabled. So refetch source hash from several different networks to exclude MITM scenario. Alternatively, use fake hash method to make Nix error, but instead of extracting hash from error, extract `https://` URL and prefetch it with method 1.
+
+## Patches {#sec-patches}
+
+Patches available online should be retrieved using `fetchpatch`.
+
+```nix
+patches = [
+  (fetchpatch {
+    name = "fix-check-for-using-shared-freetype-lib.patch";
+    url = "http://git.ghostscript.com/?p=ghostpdl.git;a=patch;h=8f5d285";
+    sha256 = "1f0k043rng7f0rfl9hhb89qzvvksqmkrikmm38p61yfx51l325xr";
+  })
+];
+```
+
+Otherwise, you can add a `.patch` file to the `nixpkgs` repository. In the interest of keeping our maintenance burden to a minimum, only patches that are unique to `nixpkgs` should be added in this way.
+
+```nix
+patches = [ ./0001-changes.patch ];
+```
+
+If you do need to do create this sort of patch file, one way to do so is with git:
+
+1. Move to the root directory of the source code you're patching.
+
+    ```ShellSession
+    $ cd the/program/source
+    ```
+
+2. If a git repository is not already present, create one and stage all of the source files.
+
+    ```ShellSession
+    $ git init
+    $ git add .
+    ```
+
+3. Edit some files to make whatever changes need to be included in the patch.
+
+4. Use git to create a diff, and pipe the output to a patch file:
+
+    ```ShellSession
+    $ git diff -a > nixpkgs/pkgs/the/package/0001-changes.patch
+    ```
+
+If a patch is available online but does not cleanly apply, it can be modified in some fixed ways by using additional optional arguments for `fetchpatch`:
+
+- `stripLen`: Remove the first `stripLen` components of pathnames in the patch.
+- `extraPrefix`: Prefix pathnames by this string.
+- `excludes`: Exclude files matching this pattern.
+- `includes`: Include only files matching this pattern.
+- `revert`: Revert the patch.
+
+Note that because the checksum is computed after applying these effects, using or modifying these arguments will have no effect unless the `sha256` argument is changed as well.
+
+## Package tests {#sec-package-tests}
+
+Tests are important to ensure quality and make reviews and automatic updates easy.
+
+The following types of tests exists:
+
+* [NixOS **module tests**](https://nixos.org/manual/nixos/stable/#sec-nixos-tests), which spawn one or more NixOS VMs. They exercise both NixOS modules and the packaged programs used within them. For example, a NixOS module test can start a web server VM running the `nginx` module, and a client VM running `curl` or a graphical `firefox`, and test that they can talk to each other and display the correct content.
+* Nix **package tests** are a lightweight alternative to NixOS module tests. They should be used to create simple integration tests for packages, but cannot test NixOS services, and some programs with graphical user interfaces may also be difficult to test with them.
+* The **`checkPhase` of a package**, which should execute the unit tests that are included in the source code of a package.
+
+Here in the nixpkgs manual we describe mostly _package tests_; for _module tests_ head over to the corresponding [section in the NixOS manual](https://nixos.org/manual/nixos/stable/#sec-nixos-tests).
+
+### Writing inline package tests {#ssec-inline-package-tests-writing}
+
+For very simple tests, they can be written inline:
+
+```nix
+{ …, yq-go }:
+
+buildGoModule rec {
+  …
+
+  passthru.tests = {
+    simple = runCommand "${pname}-test" {} ''
+      echo "test: 1" | ${yq-go}/bin/yq eval -j > $out
+      [ "$(cat $out | tr -d $'\n ')" = '{"test":1}' ]
+    '';
+  };
+}
+```
+
+### Writing larger package tests {#ssec-package-tests-writing}
+
+This is an example using the `phoronix-test-suite` package with the current best practices.
+
+Add the tests in `passthru.tests` to the package definition like this:
+
+```nix
+{ stdenv, lib, fetchurl, callPackage }:
+
+stdenv.mkDerivation {
+  …
+
+  passthru.tests = {
+    simple-execution = callPackage ./tests.nix { };
+  };
+
+  meta = { … };
+}
+```
+
+Create `tests.nix` in the package directory:
+
+```nix
+{ runCommand, phoronix-test-suite }:
+
+let
+  inherit (phoronix-test-suite) pname version;
+in
+
+runCommand "${pname}-tests" { meta.timeout = 60; }
+  ''
+    # automatic initial setup to prevent interactive questions
+    ${phoronix-test-suite}/bin/phoronix-test-suite enterprise-setup >/dev/null
+    # get version of installed program and compare with package version
+    if [[ `${phoronix-test-suite}/bin/phoronix-test-suite version` != *"${version}"*  ]]; then
+      echo "Error: program version does not match package version"
+      exit 1
+    fi
+    # run dummy command
+    ${phoronix-test-suite}/bin/phoronix-test-suite dummy_module.dummy-command >/dev/null
+    # needed for Nix to register the command as successful
+    touch $out
+  ''
+```
+
+### Running package tests {#ssec-package-tests-running}
+
+You can run these tests with:
+
+```ShellSession
+$ cd path/to/nixpkgs
+$ nix-build -A phoronix-test-suite.tests
+```
+
+### Examples of package tests {#ssec-package-tests-examples}
+
+Here are examples of package tests:
+
+- [Jasmin compile test](https://github.com/NixOS/nixpkgs/blob/master/pkgs/development/compilers/jasmin/test-assemble-hello-world/default.nix)
+- [Lobster compile test](https://github.com/NixOS/nixpkgs/blob/master/pkgs/development/compilers/lobster/test-can-run-hello-world.nix)
+- [Spacy annotation test](https://github.com/NixOS/nixpkgs/blob/master/pkgs/development/python-modules/spacy/annotation-test/default.nix)
+- [Libtorch test](https://github.com/NixOS/nixpkgs/blob/master/pkgs/development/libraries/science/math/libtorch/test/default.nix)
+- [Multiple tests for nanopb](https://github.com/NixOS/nixpkgs/blob/master/pkgs/development/libraries/nanopb/default.nix)
+
+### Linking NixOS module tests to a package {#ssec-nixos-tests-linking}
+
+Like [package tests](#ssec-package-tests-writing) as shown above, [NixOS module tests](https://nixos.org/manual/nixos/stable/#sec-nixos-tests) can also be linked to a package, so that the tests can be easily run when changing the related package.
+
+For example, assuming we're packaging `nginx`, we can link its module test via `passthru.tests`:
+
+```nix
+{ stdenv, lib, nixosTests }:
+
+stdenv.mkDerivation {
+  ...
+
+  passthru.tests = {
+    nginx = nixosTests.nginx;
+  };
+
+  ...
+}
+```
diff --git a/doc/contributing/contributing-to-documentation.chapter.md b/doc/contributing/contributing-to-documentation.chapter.md
new file mode 100644
index 00000000000..1384772ebb2
--- /dev/null
+++ b/doc/contributing/contributing-to-documentation.chapter.md
@@ -0,0 +1,106 @@
+# Contributing to this documentation {#chap-contributing}
+
+The sources of the Nixpkgs manual are in the [doc](https://github.com/NixOS/nixpkgs/tree/master/doc) subdirectory of the Nixpkgs repository. The manual is still partially written in DocBook but it is progressively being converted to [Markdown](#sec-contributing-markup).
+
+You can quickly check your edits with `make`:
+
+```ShellSession
+$ cd /path/to/nixpkgs/doc
+$ nix-shell
+[nix-shell]$ make
+```
+
+If you experience problems, run `make debug` to help understand the docbook errors.
+
+After making modifications to the manual, it's important to build it before committing. You can do that as follows:
+
+```ShellSession
+$ cd /path/to/nixpkgs/doc
+$ nix-shell
+[nix-shell]$ make clean
+[nix-shell]$ nix-build .
+```
+
+If the build succeeds, the manual will be in `./result/share/doc/nixpkgs/manual.html`.
+
+## Syntax {#sec-contributing-markup}
+
+As per [RFC 0072](https://github.com/NixOS/rfcs/pull/72), all new documentation content should be written in [CommonMark](https://commonmark.org/) Markdown dialect.
+
+Additionally, the following syntax extensions are currently used:
+
+- []{#ssec-contributing-markup-anchors}
+  Explicitly defined **anchors** on headings, to allow linking to sections. These should be always used, to ensure the anchors can be linked even when the heading text changes, and to prevent conflicts between [automatically assigned identifiers](https://github.com/jgm/commonmark-hs/blob/master/commonmark-extensions/test/auto_identifiers.md).
+
+  It uses the widely compatible [header attributes](https://github.com/jgm/commonmark-hs/blob/master/commonmark-extensions/test/attributes.md) syntax:
+
+  ```markdown
+  ## Syntax {#sec-contributing-markup}
+  ```
+
+- []{#ssec-contributing-markup-anchors-inline}
+  **Inline anchors**, which allow linking arbitrary place in the text (e.g. individual list items, sentences…).
+
+  They are defined using a hybrid of the link syntax with the attributes syntax known from headings, called [bracketed spans](https://github.com/jgm/commonmark-hs/blob/master/commonmark-extensions/test/bracketed_spans.md):
+
+  ```markdown
+  - []{#ssec-gnome-hooks-glib} `glib` setup hook will populate `GSETTINGS_SCHEMAS_PATH` and then `wrapGAppsHook` will prepend it to `XDG_DATA_DIRS`.
+  ```
+
+- []{#ssec-contributing-markup-automatic-links}
+  If you **omit a link text** for a link pointing to a section, the text will be substituted automatically. For example, `[](#chap-contributing)` will result in [](#chap-contributing).
+
+  This syntax is taken from [MyST](https://myst-parser.readthedocs.io/en/latest/using/syntax.html#targets-and-cross-referencing).
+
+- []{#ssec-contributing-markup-inline-roles}
+  If you want to link to a man page, you can use `` {manpage}`nix.conf(5)` ``, which will turn into {manpage}`nix.conf(5)`.
+
+  The references will turn into links when a mapping exists in {file}`doc/build-aux/pandoc-filters/link-unix-man-references.lua`.
+
+  This syntax is taken from [MyST](https://myst-parser.readthedocs.io/en/latest/syntax/syntax.html#roles-an-in-line-extension-point). Though, the feature originates from [reStructuredText](https://www.sphinx-doc.org/en/master/usage/restructuredtext/roles.html#role-manpage) with slightly different syntax.
+
+- []{#ssec-contributing-markup-admonitions}
+  **Admonitions**, set off from the text to bring attention to something.
+
+  It uses pandoc’s [fenced `div`s syntax](https://github.com/jgm/commonmark-hs/blob/master/commonmark-extensions/test/fenced_divs.md):
+
+  ```markdown
+  ::: {.warning}
+  This is a warning
+  :::
+  ```
+
+  which renders as
+
+  > ::: {.warning}
+  > This is a warning.
+  > :::
+
+  The following are supported:
+
+    - [`caution`](https://tdg.docbook.org/tdg/5.0/caution.html)
+    - [`important`](https://tdg.docbook.org/tdg/5.0/important.html)
+    - [`note`](https://tdg.docbook.org/tdg/5.0/note.html)
+    - [`tip`](https://tdg.docbook.org/tdg/5.0/tip.html)
+    - [`warning`](https://tdg.docbook.org/tdg/5.0/warning.html)
+
+- []{#ssec-contributing-markup-definition-lists}
+  [**Definition lists**](https://github.com/jgm/commonmark-hs/blob/master/commonmark-extensions/test/definition_lists.md), for defining a group of terms:
+
+  ```markdown
+  pear
+  :   green or yellow bulbous fruit
+
+  watermelon
+  :   green fruit with red flesh
+  ```
+
+  which renders as
+
+  > pear
+  > :   green or yellow bulbous fruit
+  >
+  > watermelon
+  > :   green fruit with red flesh
+
+For contributing to the legacy parts, please see [DocBook: The Definitive Guide](https://tdg.docbook.org/) or the [DocBook rocks! primer](https://web.archive.org/web/20200816233747/https://docbook.rocks/).
diff --git a/doc/contributing/quick-start.chapter.md b/doc/contributing/quick-start.chapter.md
new file mode 100644
index 00000000000..96b30d3822c
--- /dev/null
+++ b/doc/contributing/quick-start.chapter.md
@@ -0,0 +1,77 @@
+# Quick Start to Adding a Package {#chap-quick-start}
+
+To add a package to Nixpkgs:
+
+1. Checkout the Nixpkgs source tree:
+
+   ```ShellSession
+   $ git clone https://github.com/NixOS/nixpkgs
+   $ cd nixpkgs
+   ```
+
+2. Find a good place in the Nixpkgs tree to add the Nix expression for your package. For instance, a library package typically goes into `pkgs/development/libraries/pkgname`, while a web browser goes into `pkgs/applications/networking/browsers/pkgname`. See [](#sec-organisation) for some hints on the tree organisation. Create a directory for your package, e.g.
+
+   ```ShellSession
+   $ mkdir pkgs/development/libraries/libfoo
+   ```
+
+3. In the package directory, create a Nix expression — a piece of code that describes how to build the package. In this case, it should be a _function_ that is called with the package dependencies as arguments, and returns a build of the package in the Nix store. The expression should usually be called `default.nix`.
+
+   ```ShellSession
+   $ emacs pkgs/development/libraries/libfoo/default.nix
+   $ git add pkgs/development/libraries/libfoo/default.nix
+   ```
+
+   You can have a look at the existing Nix expressions under `pkgs/` to see how it’s done. Here are some good ones:
+
+   - GNU Hello: [`pkgs/applications/misc/hello/default.nix`](https://github.com/NixOS/nixpkgs/blob/master/pkgs/applications/misc/hello/default.nix). Trivial package, which specifies some `meta` attributes which is good practice.
+
+   - GNU cpio: [`pkgs/tools/archivers/cpio/default.nix`](https://github.com/NixOS/nixpkgs/blob/master/pkgs/tools/archivers/cpio/default.nix). Also a simple package. The generic builder in `stdenv` does everything for you. It has no dependencies beyond `stdenv`.
+
+   - GNU Multiple Precision arithmetic library (GMP): [`pkgs/development/libraries/gmp/5.1.x.nix`](https://github.com/NixOS/nixpkgs/blob/master/pkgs/development/libraries/gmp/5.1.x.nix). Also done by the generic builder, but has a dependency on `m4`.
+
+   - Pan, a GTK-based newsreader: [`pkgs/applications/networking/newsreaders/pan/default.nix`](https://github.com/NixOS/nixpkgs/blob/master/pkgs/applications/networking/newsreaders/pan/default.nix). Has an optional dependency on `gtkspell`, which is only built if `spellCheck` is `true`.
+
+   - Apache HTTPD: [`pkgs/servers/http/apache-httpd/2.4.nix`](https://github.com/NixOS/nixpkgs/blob/master/pkgs/servers/http/apache-httpd/2.4.nix). A bunch of optional features, variable substitutions in the configure flags, a post-install hook, and miscellaneous hackery.
+
+   - Thunderbird: [`pkgs/applications/networking/mailreaders/thunderbird/default.nix`](https://github.com/NixOS/nixpkgs/blob/master/pkgs/applications/networking/mailreaders/thunderbird/default.nix). Lots of dependencies.
+
+   - JDiskReport, a Java utility: [`pkgs/tools/misc/jdiskreport/default.nix`](https://github.com/NixOS/nixpkgs/blob/master/pkgs/tools/misc/jdiskreport/default.nix). Nixpkgs doesn’t have a decent `stdenv` for Java yet so this is pretty ad-hoc.
+
+   - XML::Simple, a Perl module: [`pkgs/top-level/perl-packages.nix`](https://github.com/NixOS/nixpkgs/blob/master/pkgs/top-level/perl-packages.nix) (search for the `XMLSimple` attribute). Most Perl modules are so simple to build that they are defined directly in `perl-packages.nix`; no need to make a separate file for them.
+
+   - Adobe Reader: [`pkgs/applications/misc/adobe-reader/default.nix`](https://github.com/NixOS/nixpkgs/blob/master/pkgs/applications/misc/adobe-reader/default.nix). Shows how binary-only packages can be supported. In particular the [builder](https://github.com/NixOS/nixpkgs/blob/master/pkgs/applications/misc/adobe-reader/builder.sh) uses `patchelf` to set the RUNPATH and ELF interpreter of the executables so that the right libraries are found at runtime.
+
+   Some notes:
+
+   - All [`meta`](#chap-meta) attributes are optional, but it’s still a good idea to provide at least the `description`, `homepage` and [`license`](#sec-meta-license).
+
+   - You can use `nix-prefetch-url url` to get the SHA-256 hash of source distributions. There are similar commands as `nix-prefetch-git` and `nix-prefetch-hg` available in `nix-prefetch-scripts` package.
+
+   - A list of schemes for `mirror://` URLs can be found in [`pkgs/build-support/fetchurl/mirrors.nix`](https://github.com/NixOS/nixpkgs/blob/master/pkgs/build-support/fetchurl/mirrors.nix).
+
+   The exact syntax and semantics of the Nix expression language, including the built-in function, are described in the Nix manual in the [chapter on writing Nix expressions](https://hydra.nixos.org/job/nix/trunk/tarball/latest/download-by-type/doc/manual/#chap-writing-nix-expressions).
+
+4. Add a call to the function defined in the previous step to [`pkgs/top-level/all-packages.nix`](https://github.com/NixOS/nixpkgs/blob/master/pkgs/top-level/all-packages.nix) with some descriptive name for the variable, e.g. `libfoo`.
+
+   ```ShellSession
+   $ emacs pkgs/top-level/all-packages.nix
+   ```
+
+   The attributes in that file are sorted by category (like “Development / Libraries”) that more-or-less correspond to the directory structure of Nixpkgs, and then by attribute name.
+
+5. To test whether the package builds, run the following command from the root of the nixpkgs source tree:
+
+   ```ShellSession
+   $ nix-build -A libfoo
+   ```
+
+   where `libfoo` should be the variable name defined in the previous step. You may want to add the flag `-K` to keep the temporary build directory in case something fails. If the build succeeds, a symlink `./result` to the package in the Nix store is created.
+
+6. If you want to install the package into your profile (optional), do
+
+   ```ShellSession
+   $ nix-env -f . -iA libfoo
+   ```
+
+7. Optionally commit the new package and open a pull request [to nixpkgs](https://github.com/NixOS/nixpkgs/pulls), or use [the Patches category](https://discourse.nixos.org/t/about-the-patches-category/477) on Discourse for sending a patch without a GitHub account.
diff --git a/doc/contributing/reviewing-contributions.chapter.md b/doc/contributing/reviewing-contributions.chapter.md
new file mode 100644
index 00000000000..0a90781d0c5
--- /dev/null
+++ b/doc/contributing/reviewing-contributions.chapter.md
@@ -0,0 +1,208 @@
+# Reviewing contributions {#chap-reviewing-contributions}
+
+::: {.warning}
+The following section is a draft, and the policy for reviewing is still being discussed in issues such as [#11166](https://github.com/NixOS/nixpkgs/issues/11166) and [#20836](https://github.com/NixOS/nixpkgs/issues/20836).
+:::
+
+The Nixpkgs project receives a fairly high number of contributions via GitHub pull requests. Reviewing and approving these is an important task and a way to contribute to the project.
+
+The high change rate of Nixpkgs makes any pull request that remains open for too long subject to conflicts that will require extra work from the submitter or the merger. Reviewing pull requests in a timely manner and being responsive to the comments is the key to avoid this issue. GitHub provides sort filters that can be used to see the [most recently](https://github.com/NixOS/nixpkgs/pulls?q=is%3Apr+is%3Aopen+sort%3Aupdated-desc) and the [least recently](https://github.com/NixOS/nixpkgs/pulls?q=is%3Apr+is%3Aopen+sort%3Aupdated-asc) updated pull requests. We highly encourage looking at [this list of ready to merge, unreviewed pull requests](https://github.com/NixOS/nixpkgs/pulls?q=is%3Apr+is%3Aopen+review%3Anone+status%3Asuccess+-label%3A%222.status%3A+work-in-progress%22+no%3Aproject+no%3Aassignee+no%3Amilestone).
+
+When reviewing a pull request, please always be nice and polite. Controversial changes can lead to controversial opinions, but it is important to respect every community member and their work.
+
+GitHub provides reactions as a simple and quick way to provide feedback to pull requests or any comments. The thumb-down reaction should be used with care and if possible accompanied with some explanation so the submitter has directions to improve their contribution.
+
+pull request reviews should include a list of what has been reviewed in a comment, so other reviewers and mergers can know the state of the review.
+
+All the review template samples provided in this section are generic and meant as examples. Their usage is optional and the reviewer is free to adapt them to their liking.
+
+## Package updates {#reviewing-contributions-package-updates}
+
+A package update is the most trivial and common type of pull request. These pull requests mainly consist of updating the version part of the package name and the source hash.
+
+It can happen that non-trivial updates include patches or more complex changes.
+
+Reviewing process:
+
+- Ensure that the package versioning fits the guidelines.
+- Ensure that the commit text fits the guidelines.
+- Ensure that the package maintainers are notified.
+  - [CODEOWNERS](https://help.github.com/articles/about-codeowners) will make GitHub notify users based on the submitted changes, but it can happen that it misses some of the package maintainers.
+- Ensure that the meta field information is correct.
+  - License can change with version updates, so it should be checked to match the upstream license.
+  - If the package has no maintainer, a maintainer must be set. This can be the update submitter or a community member that accepts to take maintainership of the package.
+- Ensure that the code contains no typos.
+- Building the package locally.
+  - pull requests are often targeted to the master or staging branch, and building the pull request locally when it is submitted can trigger many source builds.
+  - It is possible to rebase the changes on nixos-unstable or nixpkgs-unstable for easier review by running the following commands from a nixpkgs clone.
+
+    ```ShellSession
+    $ git fetch origin nixos-unstable
+    $ git fetch origin pull/PRNUMBER/head
+    $ git rebase --onto nixos-unstable BASEBRANCH FETCH_HEAD
+    ```
+
+    - The first command fetches the nixos-unstable branch.
+    - The second command fetches the pull request changes, `PRNUMBER` is the number at the end of the pull request title and `BASEBRANCH` the base branch of the pull request.
+    - The third command rebases the pull request changes to the nixos-unstable branch.
+  - The [nixpkgs-review](https://github.com/Mic92/nixpkgs-review) tool can be used to review a pull request content in a single command. `PRNUMBER` should be replaced by the number at the end of the pull request title. You can also provide the full github pull request url.
+
+    ```ShellSession
+    $ nix-shell -p nixpkgs-review --run "nixpkgs-review pr PRNUMBER"
+    ```
+- Running every binary.
+
+Sample template for a package update review is provided below.
+
+```markdown
+##### Reviewed points
+
+- [ ] package name fits guidelines
+- [ ] package version fits guidelines
+- [ ] package build on ARCHITECTURE
+- [ ] executables tested on ARCHITECTURE
+- [ ] all depending packages build
+
+##### Possible improvements
+
+##### Comments
+```
+
+## New packages {#reviewing-contributions-new-packages}
+
+New packages are a common type of pull requests. These pull requests consists in adding a new nix-expression for a package.
+
+Review process:
+
+- Ensure that the package versioning fits the guidelines.
+- Ensure that the commit name fits the guidelines.
+- Ensure that the meta fields contain correct information.
+  - License must match the upstream license.
+  - Platforms should be set (or the package will not get binary substitutes).
+  - Maintainers must be set. This can be the package submitter or a community member that accepts taking up maintainership of the package.
+- Report detected typos.
+- Ensure the package source:
+  - Uses mirror URLs when available.
+  - Uses the most appropriate functions (e.g. packages from GitHub should use `fetchFromGitHub`).
+- Building the package locally.
+- Running every binary.
+
+Sample template for a new package review is provided below.
+
+```markdown
+##### Reviewed points
+
+- [ ] package path fits guidelines
+- [ ] package name fits guidelines
+- [ ] package version fits guidelines
+- [ ] package build on ARCHITECTURE
+- [ ] executables tested on ARCHITECTURE
+- [ ] `meta.description` is set and fits guidelines
+- [ ] `meta.license` fits upstream license
+- [ ] `meta.platforms` is set
+- [ ] `meta.maintainers` is set
+- [ ] build time only dependencies are declared in `nativeBuildInputs`
+- [ ] source is fetched using the appropriate function
+- [ ] the list of `phases` is not overridden
+- [ ] when a phase (like `installPhase`) is overridden it starts with `runHook preInstall` and ends with `runHook postInstall`.
+- [ ] patches that are remotely available are fetched with `fetchpatch`
+
+##### Possible improvements
+
+##### Comments
+```
+
+## Module updates {#reviewing-contributions-module-updates}
+
+Module updates are submissions changing modules in some ways. These often contains changes to the options or introduce new options.
+
+Reviewing process:
+
+- Ensure that the module maintainers are notified.
+  - [CODEOWNERS](https://help.github.com/articles/about-codeowners/) will make GitHub notify users based on the submitted changes, but it can happen that it misses some of the package maintainers.
+- Ensure that the module tests, if any, are succeeding.
+- Ensure that the introduced options are correct.
+  - Type should be appropriate (string related types differs in their merging capabilities, `optionSet` and `string` types are deprecated).
+  - Description, default and example should be provided.
+- Ensure that option changes are backward compatible.
+  - `mkRenamedOptionModule` and `mkAliasOptionModule` functions provide way to make option changes backward compatible.
+- Ensure that removed options are declared with `mkRemovedOptionModule`
+- Ensure that changes that are not backward compatible are mentioned in release notes.
+- Ensure that documentations affected by the change is updated.
+
+Sample template for a module update review is provided below.
+
+```markdown
+##### Reviewed points
+
+- [ ] changes are backward compatible
+- [ ] removed options are declared with `mkRemovedOptionModule`
+- [ ] changes that are not backward compatible are documented in release notes
+- [ ] module tests succeed on ARCHITECTURE
+- [ ] options types are appropriate
+- [ ] options description is set
+- [ ] options example is provided
+- [ ] documentation affected by the changes is updated
+
+##### Possible improvements
+
+##### Comments
+```
+
+## New modules {#reviewing-contributions-new-modules}
+
+New modules submissions introduce a new module to NixOS.
+
+Reviewing process:
+
+- Ensure that the module tests, if any, are succeeding.
+- Ensure that the introduced options are correct.
+  - Type should be appropriate (string related types differs in their merging capabilities, `optionSet` and `string` types are deprecated).
+  - Description, default and example should be provided.
+- Ensure that module `meta` field is present
+  - Maintainers should be declared in `meta.maintainers`.
+  - Module documentation should be declared with `meta.doc`.
+- Ensure that the module respect other modules functionality.
+  - For example, enabling a module should not open firewall ports by default.
+
+Sample template for a new module review is provided below.
+
+```markdown
+##### Reviewed points
+
+- [ ] module path fits the guidelines
+- [ ] module tests succeed on ARCHITECTURE
+- [ ] options have appropriate types
+- [ ] options have default
+- [ ] options have example
+- [ ] options have descriptions
+- [ ] No unneeded package is added to environment.systemPackages
+- [ ] meta.maintainers is set
+- [ ] module documentation is declared in meta.doc
+
+##### Possible improvements
+
+##### Comments
+```
+
+## Other submissions {#reviewing-contributions-other-submissions}
+
+Other type of submissions requires different reviewing steps.
+
+If you consider having enough knowledge and experience in a topic and would like to be a long-term reviewer for related submissions, please contact the current reviewers for that topic. They will give you information about the reviewing process. The main reviewers for a topic can be hard to find as there is no list, but checking past pull requests to see who reviewed or git-blaming the code to see who committed to that topic can give some hints.
+
+Container system, boot system and library changes are some examples of the pull requests fitting this category.
+
+## Merging pull requests {#reviewing-contributions--merging-pull-requests}
+
+It is possible for community members that have enough knowledge and experience on a special topic to contribute by merging pull requests.
+
+<!--
+The following paragraphs about how to deal with unactive contributors is just a proposition and should be modified to what the community agrees to be the right policy.
+
+Please note that contributors with commit rights unactive for more than three months will have their commit rights revoked.
+-->
+
+Please see the discussion in [GitHub nixpkgs issue #50105](https://github.com/NixOS/nixpkgs/issues/50105) for information on how to proceed to be granted this level of access.
+
+In a case a contributor definitively leaves the Nix community, they should create an issue or post on [Discourse](https://discourse.nixos.org) with references of packages and modules they maintain so the maintainership can be taken over by other contributors.
diff --git a/doc/contributing/submitting-changes.chapter.md b/doc/contributing/submitting-changes.chapter.md
new file mode 100644
index 00000000000..109d051c016
--- /dev/null
+++ b/doc/contributing/submitting-changes.chapter.md
@@ -0,0 +1,292 @@
+# Submitting changes {#chap-submitting-changes}
+
+## Making patches {#submitting-changes-making-patches}
+
+- Read [Manual (How to write packages for Nix)](https://nixos.org/nixpkgs/manual/).
+
+- Fork [the Nixpkgs repository](https://github.com/nixos/nixpkgs/) on GitHub.
+
+- Create a branch for your future fix.
+
+  - You can make branch from a commit of your local `nixos-version`. That will help you to avoid additional local compilations. Because you will receive packages from binary cache. For example
+
+    ```ShellSession
+    $ nixos-version --hash
+    0998212
+    $ git checkout 0998212
+    $ git checkout -b 'fix/pkg-name-update'
+    ```
+
+  - Please avoid working directly on the `master` branch.
+
+- Make commits of logical units.
+
+- If you removed pkgs or made some major NixOS changes, write about it in the release notes for the next stable release. For example `nixos/doc/manual/release-notes/rl-2003.xml`.
+
+- Check for unnecessary whitespace with `git diff --check` before committing.
+
+- Format the commit in a following way:
+
+  ```
+  (pkg-name | nixos/<module>): (from -> to | init at version | refactor | etc)
+  Additional information.
+  ```
+
+  - Examples:
+    - `nginx: init at 2.0.1`
+    - `firefox: 54.0.1 -> 55.0`
+    - `nixos/hydra: add bazBaz option`
+    - `nixos/nginx: refactor config generation`
+
+- Test your changes. If you work with
+
+  - nixpkgs:
+
+    - update pkg
+      - `nix-env -iA pkg-attribute-name -f <path to your local nixpkgs folder>`
+    - add pkg
+      - Make sure it’s in `pkgs/top-level/all-packages.nix`
+      - `nix-env -iA pkg-attribute-name -f <path to your local nixpkgs folder>`
+    - _If you don’t want to install pkg in you profile_.
+      - `nix-build -A pkg-attribute-name <path to your local nixpkgs folder>` and check results in the folder `result`. It will appear in the same directory where you did `nix-build`.
+    - If you installed your package with `nix-env`, you can run `nix-env -e pkg-name` where `pkg-name` is as reported by `nix-env -q` to uninstall it from your system.
+
+  - NixOS and its modules:
+    - You can add new module to your NixOS configuration file (usually it’s `/etc/nixos/configuration.nix`). And do `sudo nixos-rebuild test -I nixpkgs=<path to your local nixpkgs folder> --fast`.
+
+- If you have commits `pkg-name: oh, forgot to insert whitespace`: squash commits in this case. Use `git rebase -i`.
+
+- [Rebase](https://git-scm.com/book/en/v2/Git-Branching-Rebasing) your branch against current `master`.
+
+## Submitting changes {#submitting-changes-submitting-changes}
+
+- Push your changes to your fork of nixpkgs.
+- Create the pull request
+- Follow [the contribution guidelines](https://github.com/NixOS/nixpkgs/blob/master/CONTRIBUTING.md#submitting-changes).
+
+## Submitting security fixes {#submitting-changes-submitting-security-fixes}
+
+Security fixes are submitted in the same way as other changes and thus the same guidelines apply.
+
+- If a new version fixing the vulnerability has been released, update the package;
+- If the security fix comes in the form of a patch and a CVE is available, then add the patch to the Nixpkgs tree, and apply it to the package.
+  The name of the patch should be the CVE identifier, so e.g. `CVE-2019-13636.patch`; If a patch is fetched the name needs to be set as well, e.g.:
+
+  ```nix
+  (fetchpatch {
+    name = "CVE-2019-11068.patch";
+    url = "https://gitlab.gnome.org/GNOME/libxslt/commit/e03553605b45c88f0b4b2980adfbbb8f6fca2fd6.patch";
+    sha256 = "0pkpb4837km15zgg6h57bncp66d5lwrlvkr73h0lanywq7zrwhj8";
+  })
+  ```
+
+If a security fix applies to both master and a stable release then, similar to regular changes, they are preferably delivered via master first and cherry-picked to the release branch.
+
+Critical security fixes may by-pass the staging branches and be delivered directly to release branches such as `master` and `release-*`.
+
+## Deprecating/removing packages {#submitting-changes-deprecating-packages}
+
+There is currently no policy when to remove a package.
+
+Before removing a package, one should try to find a new maintainer or fix smaller issues first.
+
+### Steps to remove a package from Nixpkgs {#steps-to-remove-a-package-from-nixpkgs}
+
+We use jbidwatcher as an example for a discontinued project here.
+
+1. Have Nixpkgs checked out locally and up to date.
+1. Create a new branch for your change, e.g. `git checkout -b jbidwatcher`
+1. Remove the actual package including its directory, e.g. `rm -rf pkgs/applications/misc/jbidwatcher`
+1. Remove the package from the list of all packages (`pkgs/top-level/all-packages.nix`).
+1. Add an alias for the package name in `pkgs/top-level/aliases.nix` (There is also `pkgs/applications/editors/vim/plugins/aliases.nix`. Package sets typically do not have aliases, so we can't add them there.)
+
+    For example in this case:
+
+    ```
+    jbidwatcher = throw "jbidwatcher was discontinued in march 2021"; # added 2021-03-15
+    ```
+
+    The throw message should explain in short why the package was removed for users that still have it installed.
+
+1. Test if the changes introduced any issues by running `nix-env -qaP -f . --show-trace`. It should show the list of packages without errors.
+1. Commit the changes. Explain again why the package was removed. If it was declared discontinued upstream, add a link to the source.
+
+    ```ShellSession
+    $ git add pkgs/applications/misc/jbidwatcher/default.nix pkgs/top-level/all-packages.nix pkgs/top-level/aliases.nix
+    $ git commit
+    ```
+
+    Example commit message:
+
+    ```
+    jbidwatcher: remove
+
+    project was discontinued in march 2021. the program does not work anymore because ebay changed the login.
+
+    https://web.archive.org/web/20210315205723/http://www.jbidwatcher.com/
+    ```
+
+1. Push changes to your GitHub fork with `git push`
+1. Create a pull request against Nixpkgs. Mention the package maintainer.
+
+This is how the pull request looks like in this case: [https://github.com/NixOS/nixpkgs/pull/116470](https://github.com/NixOS/nixpkgs/pull/116470)
+
+## Pull Request Template {#submitting-changes-pull-request-template}
+
+The pull request template helps determine what steps have been made for a contribution so far, and will help guide maintainers on the status of a change. The motivation section of the PR should include any extra details the title does not address and link any existing issues related to the pull request.
+
+When a PR is created, it will be pre-populated with some checkboxes detailed below:
+
+### Tested using sandboxing {#submitting-changes-tested-with-sandbox}
+
+When sandbox builds are enabled, Nix will setup an isolated environment for each build process. It is used to remove further hidden dependencies set by the build environment to improve reproducibility. This includes access to the network during the build outside of `fetch*` functions and files outside the Nix store. Depending on the operating system access to other resources are blocked as well (ex. inter process communication is isolated on Linux); see [sandbox](https://nixos.org/nix/manual/#conf-sandbox) in Nix manual for details.
+
+Sandboxing is not enabled by default in Nix due to a small performance hit on each build. In pull requests for [nixpkgs](https://github.com/NixOS/nixpkgs/) people are asked to test builds with sandboxing enabled (see `Tested using sandboxing` in the pull request template) because in<https://nixos.org/hydra/> sandboxing is also used.
+
+Depending if you use NixOS or other platforms you can use one of the following methods to enable sandboxing **before** building the package:
+
+- **Globally enable sandboxing on NixOS**: add the following to `configuration.nix`
+
+  ```nix
+  nix.useSandbox = true;
+  ```
+
+- **Globally enable sandboxing on non-NixOS platforms**: add the following to: `/etc/nix/nix.conf`
+
+  ```ini
+  sandbox = true
+  ```
+
+### Built on platform(s) {#submitting-changes-platform-diversity}
+
+Many Nix packages are designed to run on multiple platforms. As such, it’s important to let the maintainer know which platforms your changes have been tested on. It’s not always practical to test a change on all platforms, and is not required for a pull request to be merged. Only check the systems you tested the build on in this section.
+
+### Tested via one or more NixOS test(s) if existing and applicable for the change (look inside nixos/tests) {#submitting-changes-nixos-tests}
+
+Packages with automated tests are much more likely to be merged in a timely fashion because it doesn’t require as much manual testing by the maintainer to verify the functionality of the package. If there are existing tests for the package, they should be run to verify your changes do not break the tests. Tests can only be run on Linux. For more details on writing and running tests, see the [section in the NixOS manual](https://nixos.org/nixos/manual/index.html#sec-nixos-tests).
+
+### Tested compilation of all pkgs that depend on this change using `nixpkgs-review` {#submitting-changes-tested-compilation}
+
+If you are updating a package’s version, you can use nixpkgs-review to make sure all packages that depend on the updated package still compile correctly. The `nixpkgs-review` utility can look for and build all dependencies either based on uncommited changes with the `wip` option or specifying a github pull request number.
+
+review changes from pull request number 12345:
+
+```ShellSession
+nix run nixpkgs.nixpkgs-review -c nixpkgs-review pr 12345
+```
+
+review uncommitted changes:
+
+```ShellSession
+nix run nixpkgs.nixpkgs-review -c nixpkgs-review wip
+```
+
+review changes from last commit:
+
+```ShellSession
+nix run nixpkgs.nixpkgs-review -c nixpkgs-review rev HEAD
+```
+
+### Tested execution of all binary files (usually in `./result/bin/`) {#submitting-changes-tested-execution}
+
+It’s important to test any executables generated by a build when you change or create a package in nixpkgs. This can be done by looking in `./result/bin` and running any files in there, or at a minimum, the main executable for the package. For example, if you make a change to texlive, you probably would only check the binaries associated with the change you made rather than testing all of them.
+
+### Meets Nixpkgs contribution standards {#submitting-changes-contribution-standards}
+
+The last checkbox is fits [CONTRIBUTING.md](https://github.com/NixOS/nixpkgs/blob/master/CONTRIBUTING.md). The contributing document has detailed information on standards the Nix community has for commit messages, reviews, licensing of contributions you make to the project, etc\... Everyone should read and understand the standards the community has for contributing before submitting a pull request.
+
+## Hotfixing pull requests {#submitting-changes-hotfixing-pull-requests}
+
+- Make the appropriate changes in you branch.
+- Don’t create additional commits, do
+  - `git rebase -i`
+  - `git push --force` to your branch.
+
+## Commit policy {#submitting-changes-commit-policy}
+
+- Commits must be sufficiently tested before being merged, both for the master and staging branches.
+- Hydra builds for master and staging should not be used as testing platform, it’s a build farm for changes that have been already tested.
+- When changing the bootloader installation process, extra care must be taken. Grub installations cannot be rolled back, hence changes may break people’s installations forever. For any non-trivial change to the bootloader please file a PR asking for review, especially from \@edolstra.
+
+```{.graphviz caption="Staging workflow"}
+digraph {
+    "small changes" [shape=none]
+    "mass-rebuilds and other large changes" [shape=none]
+    "critical security fixes" [shape=none]
+    "broken staging-next fixes" [shape=none]
+
+    "small changes" -> master
+    "mass-rebuilds and other large changes" -> staging
+    "critical security fixes" -> master
+    "broken staging-next fixes" -> "staging-next"
+
+    "staging-next" -> master [color="#E85EB0"] [label="stabilization ends"] [fontcolor="#E85EB0"]
+    "staging" -> "staging-next" [color="#E85EB0"] [label="stabilization starts"] [fontcolor="#E85EB0"]
+
+    master -> "staging-next" -> staging [color="#5F5EE8"] [label="every six hours (GitHub Action)"] [fontcolor="#5F5EE8"]
+}
+```
+
+[This GitHub Action](https://github.com/NixOS/nixpkgs/blob/master/.github/workflows/periodic-merge-6h.yml) brings changes from `master` to `staging-next` and from `staging-next` to `staging` every 6 hours.
+
+
+### Master branch {#submitting-changes-master-branch}
+
+The `master` branch is the main development branch. It should only see non-breaking commits that do not cause mass rebuilds.
+
+### Staging branch {#submitting-changes-staging-branch}
+
+The `staging` branch is a development branch where mass-rebuilds go. It should only see non-breaking mass-rebuild commits. That means it is not to be used for testing, and changes must have been well tested already. If the branch is already in a broken state, please refrain from adding extra new breakages.
+
+### Staging-next branch {#submitting-changes-staging-next-branch}
+
+The `staging-next` branch is for stabilizing mass-rebuilds submitted to the `staging` branch prior to merging them into `master`. Mass-rebuilds must go via the `staging` branch. It must only see non-breaking commits that are fixing issues blocking it from being merged into the `master ` branch.
+
+If the branch is already in a broken state, please refrain from adding extra new breakages. Stabilize it for a few days and then merge into master.
+
+### Stable release branches {#submitting-changes-stable-release-branches}
+
+The same staging workflow applies to stable release branches, but the main branch is called `release-*` instead of `master`.
+
+Example branch names: `release-21.11`, `staging-21.11`, `staging-next-21.11`.
+
+Most changes added to the stable release branches are cherry-picked (“backported”) from the `master` and staging branches.
+
+#### Automatically backporting a Pull Request {#submitting-changes-stable-release-branches-automatic-backports}
+
+Assign label `backport <branch>` (e.g. `backport release-21.11`) to the PR and a backport PR is automatically created after the PR is merged.
+
+#### Manually backporting changes {#submitting-changes-stable-release-branches-manual-backports}
+
+Cherry-pick changes via `git cherry-pick -x <original commit>` so that the original commit id is included in the commit message.
+
+Add a reason for the backport when it is not obvious from the original commit message. You can do this by cherry picking with `git cherry-pick -xe <original commit>`, which allows editing the commit message. This is not needed for minor version updates that include security and bug fixes but don't add new features or when the commit fixes an otherwise broken package.
+
+Here is an example of a cherry-picked commit message with good reason description:
+
+```
+zfs: Keep trying root import until it works
+
+Works around #11003.
+
+(cherry picked from commit 98b213a11041af39b39473906b595290e2a4e2f9)
+
+Reason: several people cannot boot with ZFS on NVMe
+```
+
+Other examples of reasons are:
+
+- Previously the build would fail due to, e.g., `getaddrinfo` not being defined
+- The previous download links were all broken
+- Crash when starting on some X11 systems
+
+#### Acceptable backport criteria
+
+The stable branch does have some changes which cannot be backported. Most notable are breaking changes. The desire is to have stable users be uninterrupted when updating packages.
+
+However, many changes are able to be backported, including:
+- New Packages / Modules
+- Security / Patch updates
+- Version updates which include new functionality (but no breaking changes)
+- Services which require a client to be up-to-date regardless. (E.g. `spotify`, `steam`, or `discord`)
+- Security critical applications (E.g. `firefox`)
diff --git a/doc/contributing/vulnerability-roundup.chapter.md b/doc/contributing/vulnerability-roundup.chapter.md
new file mode 100644
index 00000000000..d451420f981
--- /dev/null
+++ b/doc/contributing/vulnerability-roundup.chapter.md
@@ -0,0 +1,45 @@
+# Vulnerability Roundup {#chap-vulnerability-roundup}
+
+## Issues {#vulnerability-roundup-issues}
+
+Vulnerable packages in Nixpkgs are managed using issues.
+Currently opened ones can be found using the following:
+
+[github.com/NixOS/nixpkgs/issues?q=is:issue+is:open+"Vulnerability+roundup"](https://github.com/NixOS/nixpkgs/issues?q=is%3Aissue+is%3Aopen+%22Vulnerability+roundup%22)
+
+Each issue correspond to a vulnerable version of a package; As a consequence:
+
+- One issue can contain several CVEs;
+- One CVE can be shared across several issues;
+- A single package can be concerned by several issues.
+
+
+A "Vulnerability roundup" issue usually respects the following format:
+
+```txt
+<link to relevant package search on search.nix.gsc.io>, <link to relevant files in Nixpkgs on GitHub>
+
+<list of related CVEs, their CVSS score, and the impacted NixOS version>
+
+<list of the scanned Nixpkgs versions>
+
+<list of relevant contributors>
+```
+
+Note that there can be an extra comment containing links to previously reported (and still open) issues for the same package.
+
+
+## Triaging and Fixing {#vulnerability-roundup-triaging-and-fixing}
+
+**Note**: An issue can be a "false positive" (i.e. automatically opened, but without the package it refers to being actually vulnerable).
+If you find such a "false positive", comment on the issue an explanation of why it falls into this category, linking as much information as the necessary to help maintainers double check.
+
+If you are investigating a "true positive":
+
+- Find the earliest patched version or a code patch in the CVE details;
+- Is the issue already patched (version up-to-date or patch applied manually) in Nixpkgs's `master` branch?
+  - **No**:
+    - [Submit a security fix](#submitting-changes-submitting-security-fixes);
+    - Once the fix is merged into `master`, [submit the change to the vulnerable release branch(es)](https://nixos.org/manual/nixpkgs/stable/#submitting-changes-stable-release-branches);
+  - **Yes**: [Backport the change to the vulnerable release branch(es)](https://nixos.org/manual/nixpkgs/stable/#submitting-changes-stable-release-branches).
+- When the patch has made it into all the relevant branches (`master`, and the vulnerable releases), close the relevant issue(s).
diff --git a/doc/default.nix b/doc/default.nix
new file mode 100644
index 00000000000..ac382ec8519
--- /dev/null
+++ b/doc/default.nix
@@ -0,0 +1,39 @@
+{ pkgs ? (import ./.. { }), nixpkgs ? { }}:
+let
+  lib = pkgs.lib;
+  doc-support = import ./doc-support { inherit pkgs nixpkgs; };
+in pkgs.stdenv.mkDerivation {
+  name = "nixpkgs-manual";
+
+  nativeBuildInputs = with pkgs; [
+    pandoc
+    graphviz
+    libxml2
+    libxslt
+    zip
+    jing
+    xmlformat
+  ];
+
+  src = lib.cleanSource ./.;
+
+  postPatch = ''
+    ln -s ${doc-support} ./doc-support/result
+  '';
+
+  installPhase = ''
+    dest="$out/share/doc/nixpkgs"
+    mkdir -p "$(dirname "$dest")"
+    mv out/html "$dest"
+    mv "$dest/index.html" "$dest/manual.html"
+
+    mv out/epub/manual.epub "$dest/nixpkgs-manual.epub"
+
+    mkdir -p $out/nix-support/
+    echo "doc manual $dest manual.html" >> $out/nix-support/hydra-build-products
+    echo "doc manual $dest nixpkgs-manual.epub" >> $out/nix-support/hydra-build-products
+  '';
+
+  # Environment variables
+  PANDOC_LUA_FILTERS_DIR = "${pkgs.pandoc-lua-filters}/share/pandoc/filters";
+}
diff --git a/doc/doc-support/default.nix b/doc/doc-support/default.nix
new file mode 100644
index 00000000000..53990b67719
--- /dev/null
+++ b/doc/doc-support/default.nix
@@ -0,0 +1,45 @@
+{ pkgs ? (import ../.. {}), nixpkgs ? { }}:
+let
+  locationsXml = import ./lib-function-locations.nix { inherit pkgs nixpkgs; };
+  functionDocs = import ./lib-function-docs.nix { inherit locationsXml pkgs; };
+  version = pkgs.lib.version;
+
+  epub-xsl = pkgs.writeText "epub.xsl" ''
+    <?xml version='1.0'?>
+    <xsl:stylesheet
+      xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
+      version="1.0">
+      <xsl:import href="${pkgs.docbook_xsl_ns}/xml/xsl/docbook/epub/docbook.xsl" />
+      <xsl:import href="${./parameters.xml}"/>
+    </xsl:stylesheet>
+  '';
+
+  xhtml-xsl = pkgs.writeText "xhtml.xsl" ''
+    <?xml version='1.0'?>
+    <xsl:stylesheet
+      xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
+      version="1.0">
+      <xsl:import href="${pkgs.docbook_xsl_ns}/xml/xsl/docbook/xhtml/docbook.xsl" />
+      <xsl:import href="${./parameters.xml}"/>
+    </xsl:stylesheet>
+  '';
+in pkgs.runCommand "doc-support" {}
+''
+  mkdir result
+  (
+    cd result
+    ln -s ${locationsXml} ./function-locations.xml
+    ln -s ${functionDocs} ./function-docs
+
+    ln -s ${pkgs.docbook5}/xml/rng/docbook/docbook.rng ./docbook.rng
+    ln -s ${pkgs.docbook_xsl_ns}/xml/xsl ./xsl
+    ln -s ${epub-xsl} ./epub.xsl
+    ln -s ${xhtml-xsl} ./xhtml.xsl
+
+    ln -s ${../../nixos/doc/xmlformat.conf} ./xmlformat.conf
+    ln -s ${pkgs.documentation-highlighter} ./highlightjs
+
+    echo -n "${version}" > ./version
+  )
+  mv result $out
+''
diff --git a/doc/doc-support/lib-function-docs.nix b/doc/doc-support/lib-function-docs.nix
new file mode 100644
index 00000000000..f6d613cac0b
--- /dev/null
+++ b/doc/doc-support/lib-function-docs.nix
@@ -0,0 +1,27 @@
+# Generates the documentation for library functons via nixdoc. To add
+# another library function file to this list, the include list in the
+# file `doc/functions/library.xml` must also be updated.
+
+{ pkgs ? import ./.. {}, locationsXml }:
+
+with pkgs; stdenv.mkDerivation {
+  name = "nixpkgs-lib-docs";
+  src = ./../../lib;
+
+  buildInputs = [ nixdoc ];
+  installPhase = ''
+    function docgen {
+      nixdoc -c "$1" -d "$2" -f "../lib/$1.nix"  > "$out/$1.xml"
+    }
+
+    mkdir -p $out
+    ln -s ${locationsXml} $out/locations.xml
+
+    docgen strings 'String manipulation functions'
+    docgen trivial 'Miscellaneous functions'
+    docgen lists 'List manipulation functions'
+    docgen debug 'Debugging functions'
+    docgen options 'NixOS / nixpkgs option handling'
+    docgen sources 'Source filtering functions'
+  '';
+}
diff --git a/doc/doc-support/lib-function-locations.nix b/doc/doc-support/lib-function-locations.nix
new file mode 100644
index 00000000000..68edd270985
--- /dev/null
+++ b/doc/doc-support/lib-function-locations.nix
@@ -0,0 +1,85 @@
+{ pkgs ? (import ./.. { }), nixpkgs ? { }}:
+let
+  revision = pkgs.lib.trivial.revisionWithDefault (nixpkgs.revision or "master");
+
+  libDefPos = set:
+    builtins.map
+      (name: {
+        name = name;
+        location = builtins.unsafeGetAttrPos name set;
+      })
+      (builtins.attrNames set);
+
+  libset = toplib:
+    builtins.map
+      (subsetname: {
+        subsetname = subsetname;
+        functions = libDefPos toplib.${subsetname};
+      })
+      (builtins.filter
+        (name: builtins.isAttrs toplib.${name})
+        (builtins.attrNames toplib));
+
+  nixpkgsLib = pkgs.lib;
+
+  flattenedLibSubset = { subsetname, functions }:
+  builtins.map
+    (fn: {
+      name = "lib.${subsetname}.${fn.name}";
+      value = fn.location;
+    })
+    functions;
+
+  locatedlibsets = libs: builtins.map flattenedLibSubset (libset libs);
+  removeFilenamePrefix = prefix: filename:
+    let
+    prefixLen = (builtins.stringLength prefix) + 1; # +1 to remove the leading /
+      filenameLen = builtins.stringLength filename;
+      substr = builtins.substring prefixLen filenameLen filename;
+      in substr;
+
+  removeNixpkgs = removeFilenamePrefix (builtins.toString pkgs.path);
+
+  liblocations =
+    builtins.filter
+      (elem: elem.value != null)
+      (nixpkgsLib.lists.flatten
+        (locatedlibsets nixpkgsLib));
+
+  fnLocationRelative = { name, value }:
+    {
+      inherit name;
+      value = value // { file = removeNixpkgs value.file; };
+    };
+
+  relativeLocs = (builtins.map fnLocationRelative liblocations);
+  sanitizeId = builtins.replaceStrings
+    [ "'"      ]
+    [ "-prime" ];
+
+  urlPrefix = "https://github.com/NixOS/nixpkgs/blob/${revision}";
+  xmlstrings = (nixpkgsLib.strings.concatMapStrings
+      ({ name, value }:
+      ''
+      <section><title>${name}</title>
+        <para xml:id="${sanitizeId name}">
+        Located at
+        <link
+          xlink:href="${urlPrefix}/${value.file}#L${builtins.toString value.line}">${value.file}:${builtins.toString value.line}</link>
+        in  <literal>&lt;nixpkgs&gt;</literal>.
+        </para>
+        </section>
+      '')
+      relativeLocs);
+
+in pkgs.writeText
+    "locations.xml"
+    ''
+    <section xmlns="http://docbook.org/ns/docbook"
+         xmlns:xlink="http://www.w3.org/1999/xlink"
+         version="5">
+         <title>All the locations for every lib function</title>
+         <para>This file is only for inclusion by other files.</para>
+         ${xmlstrings}
+    </section>
+    ''
diff --git a/doc/doc-support/parameters.xml b/doc/doc-support/parameters.xml
new file mode 100644
index 00000000000..e4b33e66ee4
--- /dev/null
+++ b/doc/doc-support/parameters.xml
@@ -0,0 +1,14 @@
+<?xml version='1.0'?>
+<xsl:stylesheet
+    xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
+    version="1.0">
+ <xsl:param name="section.autolabel" select="1" />
+ <xsl:param name="section.label.includes.component.label" select="1" />
+ <xsl:param name="html.stylesheet" select="'style.css overrides.css highlightjs/mono-blue.css'" />
+ <xsl:param name="html.script" select="'./highlightjs/highlight.pack.js ./highlightjs/loader.js'" />
+ <xsl:param name="xref.with.number.and.title" select="1" />
+ <xsl:param name="use.id.as.filename" select="1" />
+ <xsl:param name="toc.section.depth" select="0" />
+ <xsl:param name="admon.style" select="''" />
+ <xsl:param name="callout.graphics.extension" select="'.svg'" />
+</xsl:stylesheet>
diff --git a/doc/functions.xml b/doc/functions.xml
new file mode 100644
index 00000000000..8ef530d307c
--- /dev/null
+++ b/doc/functions.xml
@@ -0,0 +1,14 @@
+<chapter xmlns="http://docbook.org/ns/docbook"
+         xmlns:xlink="http://www.w3.org/1999/xlink"
+         xmlns:xi="http://www.w3.org/2001/XInclude"
+         xml:id="chap-functions">
+ <title>Functions reference</title>
+ <para>
+  The nixpkgs repository has several utility functions to manipulate Nix expressions.
+ </para>
+ <xi:include href="functions/library.xml" />
+ <xi:include href="functions/generators.section.xml" />
+ <xi:include href="functions/debug.section.xml" />
+ <xi:include href="functions/prefer-remote-fetch.section.xml" />
+ <xi:include href="functions/nix-gitignore.section.xml" />
+</chapter>
diff --git a/doc/functions/debug.section.md b/doc/functions/debug.section.md
new file mode 100644
index 00000000000..b2d8589431a
--- /dev/null
+++ b/doc/functions/debug.section.md
@@ -0,0 +1,5 @@
+# Debugging Nix Expressions {#sec-debug}
+
+Nix is a unityped, dynamic language, this means every value can potentially appear anywhere. Since it is also non-strict, evaluation order and what ultimately is evaluated might surprise you. Therefore it is important to be able to debug nix expressions.
+
+In the `lib/debug.nix` file you will find a number of functions that help (pretty-)printing values while evaluation is running. You can even specify how deep these values should be printed recursively, and transform them on the fly. Please consult the docstrings in `lib/debug.nix` for usage information.
diff --git a/doc/functions/generators.section.md b/doc/functions/generators.section.md
new file mode 100644
index 00000000000..d54e5027c79
--- /dev/null
+++ b/doc/functions/generators.section.md
@@ -0,0 +1,56 @@
+# Generators {#sec-generators}
+Generators are functions that create file formats from nix data structures, e. g. for configuration files. There are generators available for: `INI`, `JSON` and `YAML`
+
+All generators follow a similar call interface: `generatorName configFunctions data`, where `configFunctions` is an attrset of user-defined functions that format nested parts of the content. They each have common defaults, so often they do not need to be set manually. An example is `mkSectionName ? (name: libStr.escape [ "[" "]" ] name)` from the `INI` generator. It receives the name of a section and sanitizes it. The default `mkSectionName` escapes `[` and `]` with a backslash.
+
+Generators can be fine-tuned to produce exactly the file format required by your application/service. One example is an INI-file format which uses `: ` as separator, the strings `"yes"`/`"no"` as boolean values and requires all string values to be quoted:
+
+```nix
+with lib;
+let
+  customToINI = generators.toINI {
+    # specifies how to format a key/value pair
+    mkKeyValue = generators.mkKeyValueDefault {
+      # specifies the generated string for a subset of nix values
+      mkValueString = v:
+             if v == true then ''"yes"''
+        else if v == false then ''"no"''
+        else if isString v then ''"${v}"''
+        # and delegats all other values to the default generator
+        else generators.mkValueStringDefault {} v;
+    } ":";
+  };
+
+# the INI file can now be given as plain old nix values
+in customToINI {
+  main = {
+    pushinfo = true;
+    autopush = false;
+    host = "localhost";
+    port = 42;
+  };
+  mergetool = {
+    merge = "diff3";
+  };
+}
+```
+
+This will produce the following INI file as nix string:
+
+```INI
+[main]
+autopush:"no"
+host:"localhost"
+port:42
+pushinfo:"yes"
+str\:ange:"very::strange"
+
+[mergetool]
+merge:"diff3"
+```
+
+::: {.note}
+Nix store paths can be converted to strings by enclosing a derivation attribute like so: `"${drv}"`.
+:::
+
+Detailed documentation for each generator can be found in `lib/generators.nix`.
diff --git a/doc/functions/library.xml b/doc/functions/library.xml
new file mode 100644
index 00000000000..21bcf5b88c9
--- /dev/null
+++ b/doc/functions/library.xml
@@ -0,0 +1,30 @@
+<section xmlns="http://docbook.org/ns/docbook"
+         xmlns:xlink="http://www.w3.org/1999/xlink"
+         xmlns:xi="http://www.w3.org/2001/XInclude"
+         xml:id="sec-functions-library">
+ <title>Nixpkgs Library Functions</title>
+
+ <para>
+  Nixpkgs provides a standard library at <varname>pkgs.lib</varname>, or through <code>import &lt;nixpkgs/lib&gt;</code>.
+ </para>
+
+ <xi:include href="./library/asserts.xml" />
+
+ <xi:include href="./library/attrsets.xml" />
+
+<!-- These docs are generated via nixdoc. To add another generated
+      library function file to this list, the file
+      `lib-function-docs.nix` must also be updated. -->
+
+ <xi:include href="./library/generated/strings.xml" />
+
+ <xi:include href="./library/generated/trivial.xml" />
+
+ <xi:include href="./library/generated/lists.xml" />
+
+ <xi:include href="./library/generated/debug.xml" />
+
+ <xi:include href="./library/generated/options.xml" />
+
+ <xi:include href="./library/generated/sources.xml" />
+</section>
diff --git a/doc/functions/library/asserts.xml b/doc/functions/library/asserts.xml
new file mode 100644
index 00000000000..7c94222ef13
--- /dev/null
+++ b/doc/functions/library/asserts.xml
@@ -0,0 +1,112 @@
+<section xmlns="http://docbook.org/ns/docbook"
+         xmlns:xlink="http://www.w3.org/1999/xlink"
+         xmlns:xi="http://www.w3.org/2001/XInclude"
+         xml:id="sec-functions-library-asserts">
+ <title>Assert functions</title>
+
+ <section xml:id="function-library-lib.asserts.assertMsg">
+  <title><function>lib.asserts.assertMsg</function></title>
+
+  <subtitle><literal>assertMsg :: Bool -> String -> Bool</literal>
+  </subtitle>
+
+  <xi:include href="./locations.xml" xpointer="lib.asserts.assertMsg" />
+
+  <para>
+   Print a trace message if <literal>pred</literal> is false.
+  </para>
+
+  <para>
+   Intended to be used to augment asserts with helpful error messages.
+  </para>
+
+  <variablelist>
+   <varlistentry>
+    <term>
+     <varname>pred</varname>
+    </term>
+    <listitem>
+     <para>
+      Condition under which the <varname>msg</varname> should <emphasis>not</emphasis> be printed.
+     </para>
+    </listitem>
+   </varlistentry>
+   <varlistentry>
+    <term>
+     <varname>msg</varname>
+    </term>
+    <listitem>
+     <para>
+      Message to print.
+     </para>
+    </listitem>
+   </varlistentry>
+  </variablelist>
+
+  <example xml:id="function-library-lib.asserts.assertMsg-example-false">
+   <title>Printing when the predicate is false</title>
+<programlisting><![CDATA[
+assert lib.asserts.assertMsg ("foo" == "bar") "foo is not bar, silly"
+stderr> trace: foo is not bar, silly
+stderr> assert failed
+]]></programlisting>
+  </example>
+ </section>
+
+ <section xml:id="function-library-lib.asserts.assertOneOf">
+  <title><function>lib.asserts.assertOneOf</function></title>
+
+  <subtitle><literal>assertOneOf :: String -> String ->
+      StringList -> Bool</literal>
+  </subtitle>
+
+  <xi:include href="./locations.xml" xpointer="lib.asserts.assertOneOf" />
+
+  <para>
+   Specialized <function>asserts.assertMsg</function> for checking if <varname>val</varname> is one of the elements of <varname>xs</varname>. Useful for checking enums.
+  </para>
+
+  <variablelist>
+   <varlistentry>
+    <term>
+     <varname>name</varname>
+    </term>
+    <listitem>
+     <para>
+      The name of the variable the user entered <varname>val</varname> into, for inclusion in the error message.
+     </para>
+    </listitem>
+   </varlistentry>
+   <varlistentry>
+    <term>
+     <varname>val</varname>
+    </term>
+    <listitem>
+     <para>
+      The value of what the user provided, to be compared against the values in <varname>xs</varname>.
+     </para>
+    </listitem>
+   </varlistentry>
+   <varlistentry>
+    <term>
+     <varname>xs</varname>
+    </term>
+    <listitem>
+     <para>
+      The list of valid values.
+     </para>
+    </listitem>
+   </varlistentry>
+  </variablelist>
+
+  <example xml:id="function-library-lib.asserts.assertOneOf-example">
+   <title>Ensuring a user provided a possible value</title>
+<programlisting><![CDATA[
+let sslLibrary = "bearssl";
+in lib.asserts.assertOneOf "sslLibrary" sslLibrary [ "openssl" "libressl" ];
+=> false
+stderr> trace: sslLibrary must be one of "openssl", "libressl", but is: "bearssl"
+        ]]></programlisting>
+  </example>
+ </section>
+</section>
diff --git a/doc/functions/library/attrsets.xml b/doc/functions/library/attrsets.xml
new file mode 100644
index 00000000000..052bfa1f6ae
--- /dev/null
+++ b/doc/functions/library/attrsets.xml
@@ -0,0 +1,1751 @@
+<section xmlns="http://docbook.org/ns/docbook"
+         xmlns:xlink="http://www.w3.org/1999/xlink"
+         xmlns:xi="http://www.w3.org/2001/XInclude"
+         xml:id="sec-functions-library-attrset">
+ <title>Attribute-Set Functions</title>
+
+ <section xml:id="function-library-lib.attrsets.attrByPath">
+  <title><function>lib.attrset.attrByPath</function></title>
+
+  <subtitle><literal>attrByPath :: [String] -> Any -> AttrSet -> Any</literal>
+  </subtitle>
+
+  <xi:include href="./locations.xml" xpointer="lib.attrsets.attrByPath" />
+
+  <para>
+   Return an attribute from within nested attribute sets.
+  </para>
+
+  <variablelist>
+   <varlistentry>
+    <term>
+     <varname>attrPath</varname>
+    </term>
+    <listitem>
+     <para>
+      A list of strings representing the path through the nested attribute set <varname>set</varname>.
+     </para>
+    </listitem>
+   </varlistentry>
+   <varlistentry>
+    <term>
+     <varname>default</varname>
+    </term>
+    <listitem>
+     <para>
+      Default value if <varname>attrPath</varname> does not resolve to an existing value.
+     </para>
+    </listitem>
+   </varlistentry>
+   <varlistentry>
+    <term>
+     <varname>set</varname>
+    </term>
+    <listitem>
+     <para>
+      The nested attributeset to select values from.
+     </para>
+    </listitem>
+   </varlistentry>
+  </variablelist>
+
+  <example xml:id="function-library-lib.attrset.attrByPath-example-value-exists">
+   <title>Extracting a value from a nested attribute set</title>
+<programlisting><![CDATA[
+let set = { a = { b = 3; }; };
+in lib.attrsets.attrByPath [ "a" "b" ] 0 set
+=> 3
+]]></programlisting>
+  </example>
+
+  <example xml:id="function-library-lib.attrset.attrByPath-example-default-value">
+   <title>No value at the path, instead using the default</title>
+<programlisting><![CDATA[
+lib.attrsets.attrByPath [ "a" "b" ] 0 {}
+=> 0
+]]></programlisting>
+  </example>
+ </section>
+
+ <section xml:id="function-library-lib.attrsets.hasAttrByPath">
+  <title><function>lib.attrsets.hasAttrByPath</function></title>
+
+  <subtitle><literal>hasAttrByPath :: [String] -> AttrSet -> Bool</literal>
+  </subtitle>
+
+  <xi:include href="./locations.xml" xpointer="lib.attrsets.hasAttrByPath" />
+
+  <para>
+   Determine if an attribute exists within a nested attribute set.
+  </para>
+
+  <variablelist>
+   <varlistentry>
+    <term>
+     <varname>attrPath</varname>
+    </term>
+    <listitem>
+     <para>
+      A list of strings representing the path through the nested attribute set <varname>set</varname>.
+     </para>
+    </listitem>
+   </varlistentry>
+   <varlistentry>
+    <term>
+     <varname>set</varname>
+    </term>
+    <listitem>
+     <para>
+      The nested attributeset to check.
+     </para>
+    </listitem>
+   </varlistentry>
+  </variablelist>
+
+  <example xml:id="function-library-lib.attrsets.hasAttrByPath-example">
+   <title>A nested value does exist inside a set</title>
+<programlisting><![CDATA[
+lib.attrsets.hasAttrByPath
+  [ "a" "b" "c" "d" ]
+  { a = { b = { c = { d = 123; }; }; }; }
+=> true
+]]></programlisting>
+  </example>
+ </section>
+
+ <section xml:id="function-library-lib.attrsets.setAttrByPath">
+  <title><function>lib.attrsets.setAttrByPath</function></title>
+
+  <subtitle><literal>setAttrByPath :: [String] -> Any -> AttrSet</literal>
+  </subtitle>
+
+  <xi:include href="./locations.xml" xpointer="lib.attrsets.setAttrByPath" />
+
+  <para>
+   Create a new attribute set with <varname>value</varname> set at the nested attribute location specified in <varname>attrPath</varname>.
+  </para>
+
+  <variablelist>
+   <varlistentry>
+    <term>
+     <varname>attrPath</varname>
+    </term>
+    <listitem>
+     <para>
+      A list of strings representing the path through the nested attribute set.
+     </para>
+    </listitem>
+   </varlistentry>
+   <varlistentry>
+    <term>
+     <varname>value</varname>
+    </term>
+    <listitem>
+     <para>
+      The value to set at the location described by <varname>attrPath</varname>.
+     </para>
+    </listitem>
+   </varlistentry>
+  </variablelist>
+
+  <example xml:id="function-library-lib.attrsets.setAttrByPath-example">
+   <title>Creating a new nested attribute set</title>
+<programlisting><![CDATA[
+lib.attrsets.setAttrByPath [ "a" "b" ] 3
+=> { a = { b = 3; }; }
+]]></programlisting>
+  </example>
+ </section>
+
+ <section xml:id="function-library-lib.attrsets.getAttrFromPath">
+  <title><function>lib.attrsets.getAttrFromPath</function></title>
+
+  <subtitle><literal>getAttrFromPath :: [String] -> AttrSet -> Value</literal>
+  </subtitle>
+
+  <xi:include href="./locations.xml" xpointer="lib.attrsets.getAttrFromPath" />
+
+  <para>
+   Like <xref linkend="function-library-lib.attrsets.attrByPath" /> except without a default, and it will throw if the value doesn't exist.
+  </para>
+
+  <variablelist>
+   <varlistentry>
+    <term>
+     <varname>attrPath</varname>
+    </term>
+    <listitem>
+     <para>
+      A list of strings representing the path through the nested attribute set <varname>set</varname>.
+     </para>
+    </listitem>
+   </varlistentry>
+   <varlistentry>
+    <term>
+     <varname>set</varname>
+    </term>
+    <listitem>
+     <para>
+      The nested attribute set to find the value in.
+     </para>
+    </listitem>
+   </varlistentry>
+  </variablelist>
+
+  <example xml:id="function-library-lib.attrsets.getAttrPath-example-success">
+   <title>Succesfully getting a value from an attribute set</title>
+<programlisting><![CDATA[
+lib.attrsets.getAttrFromPath [ "a" "b" ] { a = { b = 3; }; }
+=> 3
+]]></programlisting>
+  </example>
+
+  <example xml:id="function-library-lib.attrsets.getAttrPath-example-throw">
+   <title>Throwing after failing to get a value from an attribute set</title>
+<programlisting><![CDATA[
+lib.attrsets.getAttrFromPath [ "x" "y" ] { }
+=> error: cannot find attribute `x.y'
+]]></programlisting>
+  </example>
+ </section>
+
+ <section xml:id="function-library-lib.attrsets.attrVals">
+  <title><function>lib.attrsets.attrVals</function></title>
+
+  <subtitle><literal>attrVals :: [String] -> AttrSet -> [Any]</literal>
+  </subtitle>
+
+  <xi:include href="./locations.xml" xpointer="lib.attrsets.attrVals" />
+
+  <para>
+   Return the specified attributes from a set. All values must exist.
+  </para>
+
+  <variablelist>
+   <varlistentry>
+    <term>
+     <varname>nameList</varname>
+    </term>
+    <listitem>
+     <para>
+      The list of attributes to fetch from <varname>set</varname>. Each attribute name must exist on the attrbitue set.
+     </para>
+    </listitem>
+   </varlistentry>
+   <varlistentry>
+    <term>
+     <varname>set</varname>
+    </term>
+    <listitem>
+     <para>
+      The set to get attribute values from.
+     </para>
+    </listitem>
+   </varlistentry>
+  </variablelist>
+
+  <example xml:id="function-library-lib.attrsets.attrVals-example-success">
+   <title>Getting several values from an attribute set</title>
+<programlisting><![CDATA[
+lib.attrsets.attrVals [ "a" "b" "c" ] { a = 1; b = 2; c = 3; }
+=> [ 1 2 3 ]
+]]></programlisting>
+  </example>
+
+  <example xml:id="function-library-lib.attrsets.attrVals-failure">
+   <title>Getting missing values from an attribute set</title>
+<programlisting><![CDATA[
+lib.attrsets.attrVals [ "d" ] { }
+error: attribute 'd' missing
+]]></programlisting>
+  </example>
+ </section>
+
+ <section xml:id="function-library-lib.attrsets.attrValues">
+  <title><function>lib.attrsets.attrValues</function></title>
+
+  <subtitle><literal>attrValues :: AttrSet -> [Any]</literal>
+  </subtitle>
+
+  <xi:include href="./locations.xml" xpointer="lib.attrsets.attrValues" />
+
+  <para>
+   Get all the attribute values from an attribute set.
+  </para>
+
+  <para>
+   Provides a backwards-compatible interface of <function>builtins.attrValues</function> for Nix version older than 1.8.
+  </para>
+
+  <variablelist>
+   <varlistentry>
+    <term>
+     <varname>attrs</varname>
+    </term>
+    <listitem>
+     <para>
+      The attribute set.
+     </para>
+    </listitem>
+   </varlistentry>
+  </variablelist>
+
+  <example xml:id="function-library-lib.attrsets.attrValues-example">
+   <title></title>
+<programlisting><![CDATA[
+lib.attrsets.attrValues { a = 1; b = 2; c = 3; }
+=> [ 1 2 3 ]
+]]></programlisting>
+  </example>
+ </section>
+
+ <section xml:id="function-library-lib.attrsets.catAttrs">
+  <title><function>lib.attrsets.catAttrs</function></title>
+
+  <subtitle><literal>catAttrs :: String -> [AttrSet] -> [Any]</literal>
+  </subtitle>
+
+  <xi:include href="./locations.xml" xpointer="lib.attrsets.catAttrs" />
+
+  <para>
+   Collect each attribute named `attr' from the list of attribute sets, <varname>sets</varname>. Sets that don't contain the named attribute are ignored.
+  </para>
+
+  <para>
+   Provides a backwards-compatible interface of <function>builtins.catAttrs</function> for Nix version older than 1.9.
+  </para>
+
+  <variablelist>
+   <varlistentry>
+    <term>
+     <varname>attr</varname>
+    </term>
+    <listitem>
+     <para>
+      Attribute name to select from each attribute set in <varname>sets</varname>.
+     </para>
+    </listitem>
+   </varlistentry>
+   <varlistentry>
+    <term>
+     <varname>sets</varname>
+    </term>
+    <listitem>
+     <para>
+      The list of attribute sets to select <varname>attr</varname> from.
+     </para>
+    </listitem>
+   </varlistentry>
+  </variablelist>
+
+  <example xml:id="function-library-lib.attrsets.catAttrs-example">
+   <title>Collect an attribute from a list of attribute sets.</title>
+   <para>
+    Attribute sets which don't have the attribute are ignored.
+   </para>
+<programlisting><![CDATA[
+catAttrs "a" [{a = 1;} {b = 0;} {a = 2;}]
+=> [ 1 2 ]
+      ]]></programlisting>
+  </example>
+ </section>
+
+ <section xml:id="function-library-lib.attrsets.filterAttrs">
+  <title><function>lib.attrsets.filterAttrs</function></title>
+
+  <subtitle><literal>filterAttrs :: (String -> Any -> Bool) -> AttrSet -> AttrSet</literal>
+  </subtitle>
+
+  <xi:include href="./locations.xml" xpointer="lib.attrsets.filterAttrs" />
+
+  <para>
+   Filter an attribute set by removing all attributes for which the given predicate return false.
+  </para>
+
+  <variablelist>
+   <varlistentry>
+    <term>
+     <varname>pred</varname>
+    </term>
+    <listitem>
+     <para>
+      <literal>String -> Any -> Bool</literal>
+     </para>
+     <para>
+      Predicate which returns true to include an attribute, or returns false to exclude it.
+     </para>
+     <variablelist>
+      <varlistentry>
+       <term>
+        <varname>name</varname>
+       </term>
+       <listitem>
+        <para>
+         The attribute's name
+        </para>
+       </listitem>
+      </varlistentry>
+      <varlistentry>
+       <term>
+        <varname>value</varname>
+       </term>
+       <listitem>
+        <para>
+         The attribute's value
+        </para>
+       </listitem>
+      </varlistentry>
+     </variablelist>
+     <para>
+      Returns <literal>true</literal> to include the attribute, <literal>false</literal> to exclude the attribute.
+     </para>
+    </listitem>
+   </varlistentry>
+   <varlistentry>
+    <term>
+     <varname>set</varname>
+    </term>
+    <listitem>
+     <para>
+      The attribute set to filter
+     </para>
+    </listitem>
+   </varlistentry>
+  </variablelist>
+
+  <example xml:id="function-library-lib.attrsets.filterAttrs-example">
+   <title>Filtering an attributeset</title>
+<programlisting><![CDATA[
+filterAttrs (n: v: n == "foo") { foo = 1; bar = 2; }
+=> { foo = 1; }
+]]></programlisting>
+  </example>
+ </section>
+
+ <section xml:id="function-library-lib.attrsets.filterAttrsRecursive">
+  <title><function>lib.attrsets.filterAttrsRecursive</function></title>
+
+  <subtitle><literal>filterAttrsRecursive :: (String -> Any -> Bool) -> AttrSet -> AttrSet</literal>
+  </subtitle>
+
+  <xi:include href="./locations.xml" xpointer="lib.attrsets.filterAttrsRecursive" />
+
+  <para>
+   Filter an attribute set recursively by removing all attributes for which the given predicate return false.
+  </para>
+
+  <variablelist>
+   <varlistentry>
+    <term>
+     <varname>pred</varname>
+    </term>
+    <listitem>
+     <para>
+      <literal>String -> Any -> Bool</literal>
+     </para>
+     <para>
+      Predicate which returns true to include an attribute, or returns false to exclude it.
+     </para>
+     <variablelist>
+      <varlistentry>
+       <term>
+        <varname>name</varname>
+       </term>
+       <listitem>
+        <para>
+         The attribute's name
+        </para>
+       </listitem>
+      </varlistentry>
+      <varlistentry>
+       <term>
+        <varname>value</varname>
+       </term>
+       <listitem>
+        <para>
+         The attribute's value
+        </para>
+       </listitem>
+      </varlistentry>
+     </variablelist>
+     <para>
+      Returns <literal>true</literal> to include the attribute, <literal>false</literal> to exclude the attribute.
+     </para>
+    </listitem>
+   </varlistentry>
+   <varlistentry>
+    <term>
+     <varname>set</varname>
+    </term>
+    <listitem>
+     <para>
+      The attribute set to filter
+     </para>
+    </listitem>
+   </varlistentry>
+  </variablelist>
+
+  <example xml:id="function-library-lib.attrsets.filterAttrsRecursive-example">
+   <title>Recursively filtering an attribute set</title>
+<programlisting><![CDATA[
+lib.attrsets.filterAttrsRecursive
+  (n: v: v != null)
+  {
+    levelA = {
+      example = "hi";
+      levelB = {
+        hello = "there";
+        this-one-is-present = {
+          this-is-excluded = null;
+        };
+      };
+      this-one-is-also-excluded = null;
+    };
+    also-excluded = null;
+  }
+=> {
+     levelA = {
+       example = "hi";
+       levelB = {
+         hello = "there";
+         this-one-is-present = { };
+       };
+     };
+   }
+     ]]></programlisting>
+  </example>
+ </section>
+
+ <section xml:id="function-library-lib.attrsets.foldAttrs">
+  <title><function>lib.attrsets.foldAttrs</function></title>
+
+  <subtitle><literal>foldAttrs :: (Any -> Any -> Any) -> Any -> [AttrSets] -> Any</literal>
+  </subtitle>
+
+  <xi:include href="./locations.xml" xpointer="lib.attrsets.foldAttrs" />
+
+  <para>
+   Apply fold function to values grouped by key.
+  </para>
+
+  <variablelist>
+   <varlistentry>
+    <term>
+     <varname>op</varname>
+    </term>
+    <listitem>
+     <para>
+      <literal>Any -> Any -> Any</literal>
+     </para>
+     <para>
+      Given a value <varname>val</varname> and a collector <varname>col</varname>, combine the two.
+     </para>
+     <variablelist>
+      <varlistentry>
+       <term>
+        <varname>val</varname>
+       </term>
+       <listitem>
+        <para>
+         An attribute's value
+        </para>
+       </listitem>
+      </varlistentry>
+      <varlistentry>
+       <term>
+        <varname>col</varname>
+       </term>
+       <listitem>
+<!-- TODO: make this not bad, use more fold-ey terms -->
+        <para>
+         The result of previous <function>op</function> calls with other values and <function>nul</function>.
+        </para>
+       </listitem>
+      </varlistentry>
+     </variablelist>
+    </listitem>
+   </varlistentry>
+   <varlistentry>
+    <term>
+     <varname>nul</varname>
+    </term>
+    <listitem>
+     <para>
+      The null-value, the starting value.
+     </para>
+    </listitem>
+   </varlistentry>
+   <varlistentry>
+    <term>
+     <varname>list_of_attrs</varname>
+    </term>
+    <listitem>
+     <para>
+      A list of attribute sets to fold together by key.
+     </para>
+    </listitem>
+   </varlistentry>
+  </variablelist>
+
+  <example xml:id="function-library-lib.attrsets.foldAttrs-example">
+   <title>Combining an attribute of lists in to one attribute set</title>
+<programlisting><![CDATA[
+lib.attrsets.foldAttrs
+  (n: a: [n] ++ a) []
+  [
+    { a = 2; b = 7; }
+    { a = 3; }
+    { b = 6; }
+  ]
+=> { a = [ 2 3 ]; b = [ 7 6 ]; }
+]]></programlisting>
+  </example>
+ </section>
+
+ <section xml:id="function-library-lib.attrsets.collect">
+  <title><function>lib.attrsets.collect</function></title>
+
+  <subtitle><literal>collect :: (Any -> Bool) -> AttrSet -> [Any]</literal>
+  </subtitle>
+
+  <xi:include href="./locations.xml" xpointer="lib.attrsets.collect" />
+
+  <para>
+   Recursively collect sets that verify a given predicate named <varname>pred</varname> from the set <varname>attrs</varname>. The recursion stops when <varname>pred</varname> returns <literal>true</literal>.
+  </para>
+
+  <variablelist>
+   <varlistentry>
+    <term>
+     <varname>pred</varname>
+    </term>
+    <listitem>
+     <para>
+      <literal>Any -> Bool</literal>
+     </para>
+     <para>
+      Given an attribute's value, determine if recursion should stop.
+     </para>
+     <variablelist>
+      <varlistentry>
+       <term>
+        <varname>value</varname>
+       </term>
+       <listitem>
+        <para>
+         The attribute set value.
+        </para>
+       </listitem>
+      </varlistentry>
+     </variablelist>
+    </listitem>
+   </varlistentry>
+   <varlistentry>
+    <term>
+     <varname>attrs</varname>
+    </term>
+    <listitem>
+     <para>
+      The attribute set to recursively collect.
+     </para>
+    </listitem>
+   </varlistentry>
+  </variablelist>
+
+  <example xml:id="function-library-lib.attrsets.collect-example-lists">
+   <title>Collecting all lists from an attribute set</title>
+<programlisting><![CDATA[
+lib.attrsets.collect isList { a = { b = ["b"]; }; c = [1]; }
+=> [["b"] [1]]
+]]></programlisting>
+  </example>
+
+  <example xml:id="function-library-lib.attrsets.collect-example-outpath">
+   <title>Collecting all attribute-sets which contain the <literal>outPath</literal> attribute name.</title>
+<programlisting><![CDATA[
+collect (x: x ? outPath)
+  { a = { outPath = "a/"; }; b = { outPath = "b/"; }; }
+=> [{ outPath = "a/"; } { outPath = "b/"; }]
+]]></programlisting>
+  </example>
+ </section>
+
+ <section xml:id="function-library-lib.attrsets.nameValuePair">
+  <title><function>lib.attrsets.nameValuePair</function></title>
+
+  <subtitle><literal>nameValuePair :: String -> Any -> AttrSet</literal>
+  </subtitle>
+
+  <xi:include href="./locations.xml" xpointer="lib.attrsets.nameValuePair" />
+
+  <para>
+   Utility function that creates a <literal>{name, value}</literal> pair as expected by <function>builtins.listToAttrs</function>.
+  </para>
+
+  <variablelist>
+   <varlistentry>
+    <term>
+     <varname>name</varname>
+    </term>
+    <listitem>
+     <para>
+      The attribute name.
+     </para>
+    </listitem>
+   </varlistentry>
+   <varlistentry>
+    <term>
+     <varname>value</varname>
+    </term>
+    <listitem>
+     <para>
+      The attribute value.
+     </para>
+    </listitem>
+   </varlistentry>
+  </variablelist>
+
+  <example xml:id="function-library-lib.attrsets.nameValuePair-example">
+   <title>Creating a name value pair</title>
+<programlisting><![CDATA[
+nameValuePair "some" 6
+=> { name = "some"; value = 6; }
+]]></programlisting>
+  </example>
+ </section>
+
+ <section xml:id="function-library-lib.attrsets.mapAttrs">
+  <title><function>lib.attrsets.mapAttrs</function></title>
+
+  <subtitle><literal></literal>
+  </subtitle>
+
+  <xi:include href="./locations.xml" xpointer="lib.attrsets.mapAttrs" />
+
+  <para>
+   Apply a function to each element in an attribute set, creating a new attribute set.
+  </para>
+
+  <para>
+   Provides a backwards-compatible interface of <function>builtins.mapAttrs</function> for Nix version older than 2.1.
+  </para>
+
+  <variablelist>
+   <varlistentry>
+    <term>
+     <varname>fn</varname>
+    </term>
+    <listitem>
+     <para>
+      <literal>String -> Any -> Any</literal>
+     </para>
+     <para>
+      Given an attribute's name and value, return a new value.
+     </para>
+     <variablelist>
+      <varlistentry>
+       <term>
+        <varname>name</varname>
+       </term>
+       <listitem>
+        <para>
+         The name of the attribute.
+        </para>
+       </listitem>
+      </varlistentry>
+      <varlistentry>
+       <term>
+        <varname>value</varname>
+       </term>
+       <listitem>
+        <para>
+         The attribute's value.
+        </para>
+       </listitem>
+      </varlistentry>
+     </variablelist>
+    </listitem>
+   </varlistentry>
+  </variablelist>
+
+  <example xml:id="function-library-lib.attrsets.mapAttrs-example">
+   <title>Modifying each value of an attribute set</title>
+<programlisting><![CDATA[
+lib.attrsets.mapAttrs
+  (name: value: name + "-" + value)
+  { x = "foo"; y = "bar"; }
+=> { x = "x-foo"; y = "y-bar"; }
+]]></programlisting>
+  </example>
+ </section>
+
+ <section xml:id="function-library-lib.attrsets.mapAttrs-prime">
+  <title><function>lib.attrsets.mapAttrs&apos;</function></title>
+
+  <subtitle><literal>mapAttrs' :: (String -> Any -> { name = String; value = Any }) -> AttrSet -> AttrSet</literal>
+  </subtitle>
+
+  <xi:include href="./locations.xml" xpointer="lib.attrsets.mapAttrs-prime" />
+
+  <para>
+   Like <function>mapAttrs</function>, but allows the name of each attribute to be changed in addition to the value. The applied function should return both the new name and value as a <function>nameValuePair</function>.
+  </para>
+
+  <variablelist>
+   <varlistentry>
+    <term>
+     <varname>fn</varname>
+    </term>
+    <listitem>
+     <para>
+      <literal>String -> Any -> { name = String; value = Any }</literal>
+     </para>
+     <para>
+      Given an attribute's name and value, return a new <link
+       linkend="function-library-lib.attrsets.nameValuePair">name value pair</link>.
+     </para>
+     <variablelist>
+      <varlistentry>
+       <term>
+        <varname>name</varname>
+       </term>
+       <listitem>
+        <para>
+         The name of the attribute.
+        </para>
+       </listitem>
+      </varlistentry>
+      <varlistentry>
+       <term>
+        <varname>value</varname>
+       </term>
+       <listitem>
+        <para>
+         The attribute's value.
+        </para>
+       </listitem>
+      </varlistentry>
+     </variablelist>
+    </listitem>
+   </varlistentry>
+   <varlistentry>
+    <term>
+     <varname>set</varname>
+    </term>
+    <listitem>
+     <para>
+      The attribute set to map over.
+     </para>
+    </listitem>
+   </varlistentry>
+  </variablelist>
+
+  <example xml:id="function-library-lib.attrsets.mapAttrs-prime-example">
+   <title>Change the name and value of each attribute of an attribute set</title>
+<programlisting><![CDATA[
+lib.attrsets.mapAttrs' (name: value: lib.attrsets.nameValuePair ("foo_" + name) ("bar-" + value))
+   { x = "a"; y = "b"; }
+=> { foo_x = "bar-a"; foo_y = "bar-b"; }
+
+    ]]></programlisting>
+  </example>
+ </section>
+
+ <section xml:id="function-library-lib.attrsets.mapAttrsToList">
+  <title><function>lib.attrsets.mapAttrsToList</function></title>
+
+  <subtitle><literal>mapAttrsToList :: (String -> Any -> Any) ->
+   AttrSet -> [Any]</literal>
+  </subtitle>
+
+  <xi:include href="./locations.xml" xpointer="lib.attrsets.mapAttrsToList" />
+
+  <para>
+   Call <varname>fn</varname> for each attribute in the given <varname>set</varname> and return the result in a list.
+  </para>
+
+  <variablelist>
+   <varlistentry>
+    <term>
+     <varname>fn</varname>
+    </term>
+    <listitem>
+     <para>
+      <literal>String -> Any -> Any</literal>
+     </para>
+     <para>
+      Given an attribute's name and value, return a new value.
+     </para>
+     <variablelist>
+      <varlistentry>
+       <term>
+        <varname>name</varname>
+       </term>
+       <listitem>
+        <para>
+         The name of the attribute.
+        </para>
+       </listitem>
+      </varlistentry>
+      <varlistentry>
+       <term>
+        <varname>value</varname>
+       </term>
+       <listitem>
+        <para>
+         The attribute's value.
+        </para>
+       </listitem>
+      </varlistentry>
+     </variablelist>
+    </listitem>
+   </varlistentry>
+   <varlistentry>
+    <term>
+     <varname>set</varname>
+    </term>
+    <listitem>
+     <para>
+      The attribute set to map over.
+     </para>
+    </listitem>
+   </varlistentry>
+  </variablelist>
+
+  <example xml:id="function-library-lib.attrsets.mapAttrsToList-example">
+   <title>Combine attribute values and names in to a list</title>
+<programlisting><![CDATA[
+lib.attrsets.mapAttrsToList (name: value: "${name}=${value}")
+   { x = "a"; y = "b"; }
+=> [ "x=a" "y=b" ]
+]]></programlisting>
+  </example>
+ </section>
+
+ <section xml:id="function-library-lib.attrsets.mapAttrsRecursive">
+  <title><function>lib.attrsets.mapAttrsRecursive</function></title>
+
+  <subtitle><literal>mapAttrsRecursive :: ([String] > Any -> Any) -> AttrSet -> AttrSet</literal>
+  </subtitle>
+
+  <xi:include href="./locations.xml" xpointer="lib.attrsets.mapAttrsRecursive" />
+
+  <para>
+   Like <function>mapAttrs</function>, except that it recursively applies itself to attribute sets. Also, the first argument of the argument function is a <emphasis>list</emphasis> of the names of the containing attributes.
+  </para>
+
+  <variablelist>
+   <varlistentry>
+    <term>
+     <varname>f</varname>
+    </term>
+    <listitem>
+     <para>
+      <literal>[ String ] -> Any -> Any</literal>
+     </para>
+     <para>
+      Given a list of attribute names and value, return a new value.
+     </para>
+     <variablelist>
+      <varlistentry>
+       <term>
+        <varname>name_path</varname>
+       </term>
+       <listitem>
+        <para>
+         The list of attribute names to this value.
+        </para>
+        <para>
+         For example, the <varname>name_path</varname> for the <literal>example</literal> string in the attribute set <literal>{ foo = { bar = "example"; }; }</literal> is <literal>[ "foo" "bar" ]</literal>.
+        </para>
+       </listitem>
+      </varlistentry>
+      <varlistentry>
+       <term>
+        <varname>value</varname>
+       </term>
+       <listitem>
+        <para>
+         The attribute's value.
+        </para>
+       </listitem>
+      </varlistentry>
+     </variablelist>
+    </listitem>
+   </varlistentry>
+   <varlistentry>
+    <term>
+     <varname>set</varname>
+    </term>
+    <listitem>
+     <para>
+      The attribute set to recursively map over.
+     </para>
+    </listitem>
+   </varlistentry>
+  </variablelist>
+
+  <example xml:id="function-library-lib.attrsets.mapAttrsRecursive-example">
+   <title>A contrived example of using <function>lib.attrsets.mapAttrsRecursive</function></title>
+<programlisting><![CDATA[
+mapAttrsRecursive
+  (path: value: concatStringsSep "-" (path ++ [value]))
+  {
+    n = {
+      a = "A";
+      m = {
+        b = "B";
+        c = "C";
+      };
+    };
+    d = "D";
+  }
+=> {
+     n = {
+       a = "n-a-A";
+       m = {
+         b = "n-m-b-B";
+         c = "n-m-c-C";
+       };
+     };
+     d = "d-D";
+   }
+    ]]></programlisting>
+  </example>
+ </section>
+
+ <section xml:id="function-library-lib.attrsets.mapAttrsRecursiveCond">
+  <title><function>lib.attrsets.mapAttrsRecursiveCond</function></title>
+
+  <subtitle><literal>mapAttrsRecursiveCond :: (AttrSet -> Bool) -> ([ String ] -> Any -> Any) -> AttrSet -> AttrSet</literal>
+  </subtitle>
+
+  <xi:include href="./locations.xml" xpointer="lib.attrsets.mapAttrsRecursiveCond" />
+
+  <para>
+   Like <function>mapAttrsRecursive</function>, but it takes an additional predicate function that tells it whether to recursive into an attribute set. If it returns false, <function>mapAttrsRecursiveCond</function> does not recurse, but does apply the map function. It is returns true, it does recurse, and does not apply the map function.
+  </para>
+
+  <variablelist>
+   <varlistentry>
+    <term>
+     <varname>cond</varname>
+    </term>
+    <listitem>
+     <para>
+      <literal>(AttrSet -> Bool)</literal>
+     </para>
+     <para>
+      Determine if <function>mapAttrsRecursive</function> should recurse deeper in to the attribute set.
+     </para>
+     <variablelist>
+      <varlistentry>
+       <term>
+        <varname>attributeset</varname>
+       </term>
+       <listitem>
+        <para>
+         An attribute set.
+        </para>
+       </listitem>
+      </varlistentry>
+     </variablelist>
+    </listitem>
+   </varlistentry>
+   <varlistentry>
+    <term>
+     <varname>f</varname>
+    </term>
+    <listitem>
+     <para>
+      <literal>[ String ] -> Any -> Any</literal>
+     </para>
+     <para>
+      Given a list of attribute names and value, return a new value.
+     </para>
+     <variablelist>
+      <varlistentry>
+       <term>
+        <varname>name_path</varname>
+       </term>
+       <listitem>
+        <para>
+         The list of attribute names to this value.
+        </para>
+        <para>
+         For example, the <varname>name_path</varname> for the <literal>example</literal> string in the attribute set <literal>{ foo = { bar = "example"; }; }</literal> is <literal>[ "foo" "bar" ]</literal>.
+        </para>
+       </listitem>
+      </varlistentry>
+      <varlistentry>
+       <term>
+        <varname>value</varname>
+       </term>
+       <listitem>
+        <para>
+         The attribute's value.
+        </para>
+       </listitem>
+      </varlistentry>
+     </variablelist>
+    </listitem>
+   </varlistentry>
+   <varlistentry>
+    <term>
+     <varname>set</varname>
+    </term>
+    <listitem>
+     <para>
+      The attribute set to recursively map over.
+     </para>
+    </listitem>
+   </varlistentry>
+  </variablelist>
+
+  <example xml:id="function-library-lib.attrsets.mapAttrsRecursiveCond-example">
+   <title>Only convert attribute values to JSON if the containing attribute set is marked for recursion</title>
+<programlisting><![CDATA[
+lib.attrsets.mapAttrsRecursiveCond
+  ({ recurse ? false, ... }: recurse)
+  (name: value: builtins.toJSON value)
+  {
+    dorecur = {
+      recurse = true;
+      hello = "there";
+    };
+    dontrecur = {
+      converted-to- = "json";
+    };
+  }
+=> {
+     dorecur = {
+       hello = "\"there\"";
+       recurse = "true";
+     };
+     dontrecur = "{\"converted-to\":\"json\"}";
+   }
+    ]]></programlisting>
+  </example>
+ </section>
+
+ <section xml:id="function-library-lib.attrsets.genAttrs">
+  <title><function>lib.attrsets.genAttrs</function></title>
+
+  <subtitle><literal>genAttrs :: [ String ] -> (String -> Any) -> AttrSet</literal>
+  </subtitle>
+
+  <xi:include href="./locations.xml" xpointer="lib.attrsets.genAttrs" />
+
+  <para>
+   Generate an attribute set by mapping a function over a list of attribute names.
+  </para>
+
+  <variablelist>
+   <varlistentry>
+    <term>
+     <varname>names</varname>
+    </term>
+    <listitem>
+     <para>
+      Names of values in the resulting attribute set.
+     </para>
+    </listitem>
+   </varlistentry>
+   <varlistentry>
+    <term>
+     <varname>f</varname>
+    </term>
+    <listitem>
+     <para>
+      <literal>String -> Any</literal>
+     </para>
+     <para>
+      Takes the name of the attribute and return the attribute's value.
+     </para>
+     <variablelist>
+      <varlistentry>
+       <term>
+        <varname>name</varname>
+       </term>
+       <listitem>
+        <para>
+         The name of the attribute to generate a value for.
+        </para>
+       </listitem>
+      </varlistentry>
+     </variablelist>
+    </listitem>
+   </varlistentry>
+  </variablelist>
+
+  <example xml:id="function-library-lib.attrsets.genAttrs-example">
+   <title>Generate an attrset based on names only</title>
+<programlisting><![CDATA[
+lib.attrsets.genAttrs [ "foo" "bar" ] (name: "x_${name}")
+=> { foo = "x_foo"; bar = "x_bar"; }
+     ]]></programlisting>
+  </example>
+ </section>
+
+ <section xml:id="function-library-lib.attrsets.isDerivation">
+  <title><function>lib.attrsets.isDerivation</function></title>
+
+  <subtitle><literal>isDerivation :: Any -> Bool</literal>
+  </subtitle>
+
+  <xi:include href="./locations.xml" xpointer="lib.attrsets.isDerivation" />
+
+  <para>
+   Check whether the argument is a derivation. Any set with <code>{ type = "derivation"; }</code> counts as a derivation.
+  </para>
+
+  <variablelist>
+   <varlistentry>
+    <term>
+     <varname>value</varname>
+    </term>
+    <listitem>
+     <para>
+      The value which is possibly a derivation.
+     </para>
+    </listitem>
+   </varlistentry>
+  </variablelist>
+
+  <example xml:id="function-library-lib.attrsets.isDerivation-example-true">
+   <title>A package is a derivation</title>
+<programlisting><![CDATA[
+lib.attrsets.isDerivation (import <nixpkgs> {}).ruby
+=> true
+     ]]></programlisting>
+  </example>
+
+  <example xml:id="function-library-lib.attrsets.isDerivation-example-false">
+   <title>Anything else is not a derivation</title>
+<programlisting><![CDATA[
+lib.attrsets.isDerivation "foobar"
+=> false
+     ]]></programlisting>
+  </example>
+ </section>
+
+ <section xml:id="function-library-lib.attrsets.toDerivation">
+  <title><function>lib.attrsets.toDerivation</function></title>
+
+  <subtitle><literal>toDerivation :: Path -> Derivation</literal>
+  </subtitle>
+
+  <xi:include href="./locations.xml" xpointer="lib.attrsets.toDerivation" />
+
+  <para>
+   Converts a store path to a fake derivation.
+  </para>
+
+  <variablelist>
+   <varlistentry>
+    <term>
+     <varname>path</varname>
+    </term>
+    <listitem>
+     <para>
+      A store path to convert to a derivation.
+     </para>
+    </listitem>
+   </varlistentry>
+  </variablelist>
+ </section>
+
+ <section xml:id="function-library-lib.attrsets.optionalAttrs">
+  <title><function>lib.attrsets.optionalAttrs</function></title>
+
+  <subtitle><literal>optionalAttrs :: Bool -> AttrSet</literal>
+  </subtitle>
+
+  <xi:include href="./locations.xml" xpointer="lib.attrsets.optionalAttrs" />
+
+  <para>
+   Conditionally return an attribute set or an empty attribute set.
+  </para>
+
+  <variablelist>
+   <varlistentry>
+    <term>
+     <varname>cond</varname>
+    </term>
+    <listitem>
+     <para>
+      Condition under which the <varname>as</varname> attribute set is returned.
+     </para>
+    </listitem>
+   </varlistentry>
+   <varlistentry>
+    <term>
+     <varname>as</varname>
+    </term>
+    <listitem>
+     <para>
+      The attribute set to return if <varname>cond</varname> is true.
+     </para>
+    </listitem>
+   </varlistentry>
+  </variablelist>
+
+  <example xml:id="function-library-lib.attrsets.optionalAttrs-example-true">
+   <title>Return the provided attribute set when <varname>cond</varname> is true</title>
+<programlisting><![CDATA[
+lib.attrsets.optionalAttrs true { my = "set"; }
+=> { my = "set"; }
+     ]]></programlisting>
+  </example>
+
+  <example xml:id="function-library-lib.attrsets.optionalAttrs-example-false">
+   <title>Return an empty attribute set when <varname>cond</varname> is false</title>
+<programlisting><![CDATA[
+lib.attrsets.optionalAttrs false { my = "set"; }
+=> { }
+     ]]></programlisting>
+  </example>
+ </section>
+
+ <section xml:id="function-library-lib.attrsets.zipAttrsWithNames">
+  <title><function>lib.attrsets.zipAttrsWithNames</function></title>
+
+  <subtitle><literal>zipAttrsWithNames :: [ String ] -> (String -> [ Any ] -> Any) -> [ AttrSet ] -> AttrSet</literal>
+  </subtitle>
+
+  <xi:include href="./locations.xml" xpointer="lib.attrsets.zipAttrsWithNames" />
+
+  <para>
+   Merge sets of attributes and use the function <varname>f</varname> to merge attribute values where the attribute name is in <varname>names</varname>.
+  </para>
+
+  <variablelist>
+   <varlistentry>
+    <term>
+     <varname>names</varname>
+    </term>
+    <listitem>
+     <para>
+      A list of attribute names to zip.
+     </para>
+    </listitem>
+   </varlistentry>
+   <varlistentry>
+    <term>
+     <varname>f</varname>
+    </term>
+    <listitem>
+     <para>
+      <literal>(String -> [ Any ] -> Any</literal>
+     </para>
+     <para>
+      Accepts an attribute name, all the values, and returns a combined value.
+     </para>
+     <variablelist>
+      <varlistentry>
+       <term>
+        <varname>name</varname>
+       </term>
+       <listitem>
+        <para>
+         The name of the attribute each value came from.
+        </para>
+       </listitem>
+      </varlistentry>
+      <varlistentry>
+       <term>
+        <varname>vs</varname>
+       </term>
+       <listitem>
+        <para>
+         A list of values collected from the list of attribute sets.
+        </para>
+       </listitem>
+      </varlistentry>
+     </variablelist>
+    </listitem>
+   </varlistentry>
+   <varlistentry>
+    <term>
+     <varname>sets</varname>
+    </term>
+    <listitem>
+     <para>
+      A list of attribute sets to zip together.
+     </para>
+    </listitem>
+   </varlistentry>
+  </variablelist>
+
+  <example xml:id="function-library-lib.attrsets.zipAttrsWithNames-example">
+   <title>Summing a list of attribute sets of numbers</title>
+<programlisting><![CDATA[
+lib.attrsets.zipAttrsWithNames
+  [ "a" "b" ]
+  (name: vals: "${name} ${toString (builtins.foldl' (a: b: a + b) 0 vals)}")
+  [
+    { a = 1; b = 1; c = 1; }
+    { a = 10; }
+    { b = 100; }
+    { c = 1000; }
+  ]
+=> { a = "a 11"; b = "b 101"; }
+     ]]></programlisting>
+  </example>
+ </section>
+
+ <section xml:id="function-library-lib.attrsets.zipAttrsWith">
+  <title><function>lib.attrsets.zipAttrsWith</function></title>
+
+  <subtitle><literal>zipAttrsWith :: (String -> [ Any ] -> Any) -> [ AttrSet ] -> AttrSet</literal>
+  </subtitle>
+
+  <xi:include href="./locations.xml" xpointer="lib.attrsets.zipAttrsWith" />
+
+  <para>
+   Merge sets of attributes and use the function <varname>f</varname> to merge attribute values. Similar to <xref
+   linkend="function-library-lib.attrsets.zipAttrsWithNames" /> where all key names are passed for <varname>names</varname>.
+  </para>
+
+  <variablelist>
+   <varlistentry>
+    <term>
+     <varname>f</varname>
+    </term>
+    <listitem>
+     <para>
+      <literal>(String -> [ Any ] -> Any</literal>
+     </para>
+     <para>
+      Accepts an attribute name, all the values, and returns a combined value.
+     </para>
+     <variablelist>
+      <varlistentry>
+       <term>
+        <varname>name</varname>
+       </term>
+       <listitem>
+        <para>
+         The name of the attribute each value came from.
+        </para>
+       </listitem>
+      </varlistentry>
+      <varlistentry>
+       <term>
+        <varname>vs</varname>
+       </term>
+       <listitem>
+        <para>
+         A list of values collected from the list of attribute sets.
+        </para>
+       </listitem>
+      </varlistentry>
+     </variablelist>
+    </listitem>
+   </varlistentry>
+   <varlistentry>
+    <term>
+     <varname>sets</varname>
+    </term>
+    <listitem>
+     <para>
+      A list of attribute sets to zip together.
+     </para>
+    </listitem>
+   </varlistentry>
+  </variablelist>
+
+  <example xml:id="function-library-lib.attrsets.zipAttrsWith-example">
+   <title>Summing a list of attribute sets of numbers</title>
+<programlisting><![CDATA[
+lib.attrsets.zipAttrsWith
+  (name: vals: "${name} ${toString (builtins.foldl' (a: b: a + b) 0 vals)}")
+  [
+    { a = 1; b = 1; c = 1; }
+    { a = 10; }
+    { b = 100; }
+    { c = 1000; }
+  ]
+=> { a = "a 11"; b = "b 101"; c = "c 1001"; }
+     ]]></programlisting>
+  </example>
+ </section>
+
+ <section xml:id="function-library-lib.attrsets.zipAttrs">
+  <title><function>lib.attrsets.zipAttrs</function></title>
+
+  <subtitle><literal>zipAttrs :: [ AttrSet ] -> AttrSet</literal>
+  </subtitle>
+
+  <xi:include href="./locations.xml" xpointer="lib.attrsets.zipAttrs" />
+
+  <para>
+   Merge sets of attributes and combine each attribute value in to a list. Similar to <xref linkend="function-library-lib.attrsets.zipAttrsWith" /> where the merge function returns a list of all values.
+  </para>
+
+  <variablelist>
+   <varlistentry>
+    <term>
+     <varname>sets</varname>
+    </term>
+    <listitem>
+     <para>
+      A list of attribute sets to zip together.
+     </para>
+    </listitem>
+   </varlistentry>
+  </variablelist>
+
+  <example xml:id="function-library-lib.attrsets.zipAttrs-example">
+   <title>Combining a list of attribute sets</title>
+<programlisting><![CDATA[
+lib.attrsets.zipAttrs
+  [
+    { a = 1; b = 1; c = 1; }
+    { a = 10; }
+    { b = 100; }
+    { c = 1000; }
+  ]
+=> { a = [ 1 10 ]; b = [ 1 100 ]; c = [ 1 1000 ]; }
+     ]]></programlisting>
+  </example>
+ </section>
+
+ <section xml:id="function-library-lib.attrsets.recursiveUpdateUntil">
+  <title><function>lib.attrsets.recursiveUpdateUntil</function></title>
+
+  <subtitle><literal>recursiveUpdateUntil :: ( [ String ] -> AttrSet -> AttrSet -> Bool ) -> AttrSet -> AttrSet -> AttrSet</literal>
+  </subtitle>
+
+  <xi:include href="./locations.xml" xpointer="lib.attrsets.recursiveUpdateUntil" />
+
+  <para>
+   Does the same as the update operator <literal>//</literal> except that attributes are merged until the given predicate is verified. The predicate should accept 3 arguments which are the path to reach the attribute, a part of the first attribute set and a part of the second attribute set. When the predicate is verified, the value of the first attribute set is replaced by the value of the second attribute set.
+  </para>
+
+  <variablelist>
+   <varlistentry>
+    <term>
+     <varname>pred</varname>
+    </term>
+    <listitem>
+     <para>
+      <literal>[ String ] -> AttrSet -> AttrSet -> Bool</literal>
+     </para>
+     <variablelist>
+      <varlistentry>
+       <term>
+        <varname>path</varname>
+       </term>
+       <listitem>
+        <para>
+         The path to the values in the left and right hand sides.
+        </para>
+       </listitem>
+      </varlistentry>
+      <varlistentry>
+       <term>
+        <varname>l</varname>
+       </term>
+       <listitem>
+        <para>
+         The left hand side value.
+        </para>
+       </listitem>
+      </varlistentry>
+      <varlistentry>
+       <term>
+        <varname>r</varname>
+       </term>
+       <listitem>
+        <para>
+         The right hand side value.
+        </para>
+       </listitem>
+      </varlistentry>
+     </variablelist>
+    </listitem>
+   </varlistentry>
+   <varlistentry>
+    <term>
+     <varname>lhs</varname>
+    </term>
+    <listitem>
+     <para>
+      The left hand attribute set of the merge.
+     </para>
+    </listitem>
+   </varlistentry>
+   <varlistentry>
+    <term>
+     <varname>rhs</varname>
+    </term>
+    <listitem>
+     <para>
+      The right hand attribute set of the merge.
+     </para>
+    </listitem>
+   </varlistentry>
+  </variablelist>
+
+  <example xml:id="function-library-lib.attrsets.recursiveUpdateUntil-example">
+   <title>Recursively merging two attribute sets</title>
+<programlisting><![CDATA[
+lib.attrsets.recursiveUpdateUntil (path: l: r: path == ["foo"])
+  {
+    # first attribute set
+    foo.bar = 1;
+    foo.baz = 2;
+    bar = 3;
+  }
+  {
+    #second attribute set
+    foo.bar = 1;
+    foo.quz = 2;
+    baz = 4;
+  }
+=> {
+  foo.bar = 1; # 'foo.*' from the second set
+  foo.quz = 2; #
+  bar = 3;     # 'bar' from the first set
+  baz = 4;     # 'baz' from the second set
+}
+     ]]></programlisting>
+  </example>
+ </section>
+
+ <section xml:id="function-library-lib.attrsets.recursiveUpdate">
+  <title><function>lib.attrsets.recursiveUpdate</function></title>
+
+  <subtitle><literal>recursiveUpdate :: AttrSet -> AttrSet -> AttrSet</literal>
+  </subtitle>
+
+  <xi:include href="./locations.xml" xpointer="lib.attrsets.recursiveUpdate" />
+
+  <para>
+   A recursive variant of the update operator <literal>//</literal>. The recursion stops when one of the attribute values is not an attribute set, in which case the right hand side value takes precedence over the left hand side value.
+  </para>
+
+  <variablelist>
+   <varlistentry>
+    <term>
+     <varname>lhs</varname>
+    </term>
+    <listitem>
+     <para>
+      The left hand attribute set of the merge.
+     </para>
+    </listitem>
+   </varlistentry>
+   <varlistentry>
+    <term>
+     <varname>rhs</varname>
+    </term>
+    <listitem>
+     <para>
+      The right hand attribute set of the merge.
+     </para>
+    </listitem>
+   </varlistentry>
+  </variablelist>
+
+  <example xml:id="function-library-lib.attrsets.recursiveUpdate-example">
+   <title>Recursively merging two attribute sets</title>
+<programlisting><![CDATA[
+recursiveUpdate
+  {
+    boot.loader.grub.enable = true;
+    boot.loader.grub.device = "/dev/hda";
+  }
+  {
+    boot.loader.grub.device = "";
+  }
+=> {
+  boot.loader.grub.enable = true;
+  boot.loader.grub.device = "";
+}
+]]></programlisting>
+  </example>
+ </section>
+
+ <section xml:id="function-library-lib.attrsets.recurseIntoAttrs">
+  <title><function>lib.attrsets.recurseIntoAttrs</function></title>
+
+  <subtitle><literal>recurseIntoAttrs :: AttrSet -> AttrSet</literal>
+  </subtitle>
+
+  <xi:include href="./locations.xml" xpointer="lib.attrsets.recurseIntoAttrs" />
+
+  <para>
+   Make various Nix tools consider the contents of the resulting attribute set when looking for what to build, find, etc.
+  </para>
+
+  <para>
+   This function only affects a single attribute set; it does not apply itself recursively for nested attribute sets.
+  </para>
+
+  <variablelist>
+   <varlistentry>
+    <term>
+     <varname>attrs</varname>
+    </term>
+    <listitem>
+     <para>
+      An attribute set to scan for derivations.
+     </para>
+    </listitem>
+   </varlistentry>
+  </variablelist>
+
+  <example xml:id="function-library-lib.attrsets.recurseIntoAttrs-example">
+   <title>Making Nix look inside an attribute set</title>
+<programlisting><![CDATA[
+{ pkgs ? import <nixpkgs> {} }:
+{
+  myTools = pkgs.lib.recurseIntoAttrs {
+    inherit (pkgs) hello figlet;
+  };
+}
+]]></programlisting>
+  </example>
+ </section>
+
+ <section xml:id="function-library-lib.attrsets.cartesianProductOfSets">
+  <title><function>lib.attrsets.cartesianProductOfSets</function></title>
+
+  <subtitle><literal>cartesianProductOfSets :: AttrSet -> [ AttrSet ]</literal>
+  </subtitle>
+
+  <xi:include href="./locations.xml" xpointer="lib.attrsets.cartesianProductOfSets" />
+
+  <para>
+   Return the cartesian product of attribute set value combinations.
+  </para>
+
+  <variablelist>
+   <varlistentry>
+    <term>
+     <varname>set</varname>
+    </term>
+    <listitem>
+     <para>
+      An attribute set with attributes that carry lists of values.
+     </para>
+    </listitem>
+   </varlistentry>
+  </variablelist>
+
+  <example xml:id="function-library-lib.attrsets.cartesianProductOfSets-example">
+   <title>Creating the cartesian product of a list of attribute values</title>
+<programlisting><![CDATA[
+cartesianProductOfSets { a = [ 1 2 ]; b = [ 10 20 ]; }
+=> [
+     { a = 1; b = 10; }
+     { a = 1; b = 20; }
+     { a = 2; b = 10; }
+     { a = 2; b = 20; }
+   ]
+]]></programlisting>
+  </example>
+ </section>
+</section>
diff --git a/doc/functions/nix-gitignore.section.md b/doc/functions/nix-gitignore.section.md
new file mode 100644
index 00000000000..2fb833b2300
--- /dev/null
+++ b/doc/functions/nix-gitignore.section.md
@@ -0,0 +1,49 @@
+# pkgs.nix-gitignore {#sec-pkgs-nix-gitignore}
+
+`pkgs.nix-gitignore` is a function that acts similarly to `builtins.filterSource` but also allows filtering with the help of the gitignore format.
+
+## Usage {#sec-pkgs-nix-gitignore-usage}
+
+`pkgs.nix-gitignore` exports a number of functions, but you\'ll most likely need either `gitignoreSource` or `gitignoreSourcePure`. As their first argument, they both accept either 1. a file with gitignore lines or 2. a string with gitignore lines, or 3. a list of either of the two. They will be concatenated into a single big string.
+
+```nix
+{ pkgs ? import <nixpkgs> {} }:
+
+ nix-gitignore.gitignoreSource [] ./source
+     # Simplest version
+
+ nix-gitignore.gitignoreSource "supplemental-ignores\n" ./source
+     # This one reads the ./source/.gitignore and concats the auxiliary ignores
+
+ nix-gitignore.gitignoreSourcePure "ignore-this\nignore-that\n" ./source
+     # Use this string as gitignore, don't read ./source/.gitignore.
+
+ nix-gitignore.gitignoreSourcePure ["ignore-this\nignore-that\n", ~/.gitignore] ./source
+     # It also accepts a list (of strings and paths) that will be concatenated
+     # once the paths are turned to strings via readFile.
+```
+
+These functions are derived from the `Filter` functions by setting the first filter argument to `(_: _: true)`:
+
+```nix
+gitignoreSourcePure = gitignoreFilterSourcePure (_: _: true);
+gitignoreSource = gitignoreFilterSource (_: _: true);
+```
+
+Those filter functions accept the same arguments the `builtins.filterSource` function would pass to its filters, thus `fn: gitignoreFilterSourcePure fn ""` should be extensionally equivalent to `filterSource`. The file is blacklisted if it\'s blacklisted by either your filter or the gitignoreFilter.
+
+If you want to make your own filter from scratch, you may use
+
+```nix
+gitignoreFilter = ign: root: filterPattern (gitignoreToPatterns ign) root;
+```
+
+## gitignore files in subdirectories {#sec-pkgs-nix-gitignore-usage-recursive}
+
+If you wish to use a filter that would search for .gitignore files in subdirectories, just like git does by default, use this function:
+
+```nix
+gitignoreFilterRecursiveSource = filter: patterns: root:
+# OR
+gitignoreRecursiveSource = gitignoreFilterSourcePure (_: _: true);
+```
diff --git a/doc/functions/prefer-remote-fetch.section.md b/doc/functions/prefer-remote-fetch.section.md
new file mode 100644
index 00000000000..8760c100224
--- /dev/null
+++ b/doc/functions/prefer-remote-fetch.section.md
@@ -0,0 +1,17 @@
+# prefer-remote-fetch overlay {#sec-prefer-remote-fetch}
+
+`prefer-remote-fetch` is an overlay that download sources on remote builder. This is useful when the evaluating machine has a slow upload while the builder can fetch faster directly from the source. To use it, put the following snippet as a new overlay:
+
+```nix
+self: super:
+  (super.prefer-remote-fetch self super)
+```
+
+A full configuration example for that sets the overlay up for your own account, could look like this
+
+```ShellSession
+$ mkdir ~/.config/nixpkgs/overlays/
+$ cat > ~/.config/nixpkgs/overlays/prefer-remote-fetch.nix <<EOF
+  self: super: super.prefer-remote-fetch self super
+EOF
+```
diff --git a/doc/languages-frameworks/agda.section.md b/doc/languages-frameworks/agda.section.md
new file mode 100644
index 00000000000..775a7a1a642
--- /dev/null
+++ b/doc/languages-frameworks/agda.section.md
@@ -0,0 +1,256 @@
+# Agda {#agda}
+
+## How to use Agda {#how-to-use-agda}
+
+Agda is available as the [agda](https://search.nixos.org/packages?channel=unstable&show=agda&from=0&size=30&sort=relevance&query=agda)
+package.
+
+The `agda` package installs an Agda-wrapper, which calls `agda` with `--library-file`
+set to a generated library-file within the nix store, this means your library-file in
+`$HOME/.agda/libraries` will be ignored. By default the agda package installs Agda
+with no libraries, i.e. the generated library-file is empty. To use Agda with libraries,
+the `agda.withPackages` function can be used. This function either takes:
+
+* A list of packages,
+* or a function which returns a list of packages when given the `agdaPackages` attribute set,
+* or an attribute set containing a list of packages and a GHC derivation for compilation (see below).
+* or an attribute set containing a function which returns a list of packages when given the `agdaPackages` attribute set and a GHC derivation for compilation (see below).
+
+For example, suppose we wanted a version of Agda which has access to the standard library. This can be obtained with the expressions:
+
+```nix
+agda.withPackages [ agdaPackages.standard-library ]
+```
+
+or
+
+```nix
+agda.withPackages (p: [ p.standard-library ])
+```
+
+or can be called as in the [Compiling Agda](#compiling-agda) section.
+
+If you want to use a different version of a library (for instance a development version)
+override the `src` attribute of the package to point to your local repository
+
+```nix
+agda.withPackages (p: [
+  (p.standard-library.overrideAttrs (oldAttrs: {
+    version = "local version";
+    src = /path/to/local/repo/agda-stdlib;
+  }))
+])
+```
+
+You can also reference a GitHub repository
+
+```nix
+agda.withPackages (p: [
+  (p.standard-library.overrideAttrs (oldAttrs: {
+    version = "1.5";
+    src =  fetchFromGitHub {
+      repo = "agda-stdlib";
+      owner = "agda";
+      rev = "v1.5";
+      sha256 = "16fcb7ssj6kj687a042afaa2gq48rc8abihpm14k684ncihb2k4w";
+    };
+  }))
+])
+```
+
+If you want to use a library not added to Nixpkgs, you can add a
+dependency to a local library by calling `agdaPackages.mkDerivation`.
+
+```nix
+agda.withPackages (p: [
+  (p.mkDerivation {
+    pname = "your-agda-lib";
+    version = "1.0.0";
+    src = /path/to/your-agda-lib;
+  })
+])
+```
+
+Again you can reference GitHub
+
+```nix
+agda.withPackages (p: [
+  (p.mkDerivation {
+    pname = "your-agda-lib";
+    version = "1.0.0";
+    src = fetchFromGitHub {
+      repo = "repo";
+      owner = "owner";
+      version = "...";
+      rev = "...";
+      sha256 = "...";
+    };
+  })
+])
+```
+
+See [Building Agda Packages](#building-agda-packages) for more information on `mkDerivation`.
+
+Agda will not by default use these libraries. To tell Agda to use a library we have some options:
+
+* Call `agda` with the library flag:
+  ```ShellSession
+  $ agda -l standard-library -i . MyFile.agda
+  ```
+* Write a `my-library.agda-lib` file for the project you are working on which may look like:
+  ```
+  name: my-library
+  include: .
+  depend: standard-library
+  ```
+* Create the file `~/.agda/defaults` and add any libraries you want to use by default.
+
+More information can be found in the [official Agda documentation on library management](https://agda.readthedocs.io/en/v2.6.1/tools/package-system.html).
+
+## Compiling Agda {#compiling-agda}
+
+Agda modules can be compiled using the GHC backend with the `--compile` flag. A version of `ghc` with `ieee754` is made available to the Agda program via the `--with-compiler` flag.
+This can be overridden by a different version of `ghc` as follows:
+
+```nix
+agda.withPackages {
+  pkgs = [ ... ];
+  ghc = haskell.compiler.ghcHEAD;
+}
+```
+
+## Writing Agda packages {#writing-agda-packages}
+
+To write a nix derivation for an Agda library, first check that the library has a `*.agda-lib` file.
+
+A derivation can then be written using `agdaPackages.mkDerivation`. This has similar arguments to `stdenv.mkDerivation` with the following additions:
+
+* `everythingFile` can be used to specify the location of the `Everything.agda` file, defaulting to `./Everything.agda`. If this file does not exist then either it should be patched in or the `buildPhase` should be overridden (see below).
+* `libraryName` should be the name that appears in the `*.agda-lib` file, defaulting to `pname`.
+* `libraryFile` should be the file name of the `*.agda-lib` file, defaulting to `${libraryName}.agda-lib`.
+
+Here is an example `default.nix`
+
+```nix
+{ nixpkgs ?  <nixpkgs> }:
+with (import nixpkgs {});
+agdaPackages.mkDerivation {
+  version = "1.0";
+  pname = "my-agda-lib";
+  src = ./.;
+  buildInputs = [
+    agdaPackages.standard-library
+  ];
+}
+```
+
+### Building Agda packages {#building-agda-packages}
+
+The default build phase for `agdaPackages.mkDerivation` simply runs `agda` on the `Everything.agda` file.
+If something else is needed to build the package (e.g. `make`) then the `buildPhase` should be overridden.
+Additionally, a `preBuild` or `configurePhase` can be used if there are steps that need to be done prior to checking the `Everything.agda` file.
+`agda` and the Agda libraries contained in `buildInputs` are made available during the build phase.
+
+### Installing Agda packages {#installing-agda-packages}
+
+The default install phase copies Agda source files, Agda interface files (`*.agdai`) and `*.agda-lib` files to the output directory.
+This can be overridden.
+
+By default, Agda sources are files ending on `.agda`, or literate Agda files ending on `.lagda`, `.lagda.tex`, `.lagda.org`, `.lagda.md`, `.lagda.rst`. The list of recognised Agda source extensions can be extended by setting the `extraExtensions` config variable.
+
+## Maintaining the Agda package set on Nixpkgs {#maintaining-the-agda-package-set-on-nixpkgs}
+
+We are aiming at providing all common Agda libraries as packages on `nixpkgs`,
+and keeping them up to date.
+Contributions and maintenance help is always appreciated,
+but the maintenance effort is typically low since the Agda ecosystem is quite small.
+
+The `nixpkgs` Agda package set tries to take up a role similar to that of [Stackage](https://www.stackage.org/) in the Haskell world.
+It is a curated set of libraries that:
+
+1. Always work together.
+2. Are as up-to-date as possible.
+
+While the Haskell ecosystem is huge, and Stackage is highly automatised,
+the Agda package set is small and can (still) be maintained by hand.
+
+### Adding Agda packages to Nixpkgs {#adding-agda-packages-to-nixpkgs}
+
+To add an Agda package to `nixpkgs`, the derivation should be written to `pkgs/development/libraries/agda/${library-name}/` and an entry should be added to `pkgs/top-level/agda-packages.nix`. Here it is called in a scope with access to all other Agda libraries, so the top line of the `default.nix` can look like:
+
+```nix
+{ mkDerivation, standard-library, fetchFromGitHub }:
+```
+
+Note that the derivation function is called with `mkDerivation` set to `agdaPackages.mkDerivation`, therefore you
+could use a similar set as in your `default.nix` from [Writing Agda Packages](#writing-agda-packages) with
+`agdaPackages.mkDerivation` replaced with `mkDerivation`.
+
+Here is an example skeleton derivation for iowa-stdlib:
+
+```nix
+mkDerivation {
+  version = "1.5.0";
+  pname = "iowa-stdlib";
+
+  src = ...
+
+  libraryFile = "";
+  libraryName = "IAL-1.3";
+
+  buildPhase = ''
+    patchShebangs find-deps.sh
+    make
+  '';
+}
+```
+
+This library has a file called `.agda-lib`, and so we give an empty string to `libraryFile` as nothing precedes `.agda-lib` in the filename. This file contains `name: IAL-1.3`, and so we let `libraryName =  "IAL-1.3"`. This library does not use an `Everything.agda` file and instead has a Makefile, so there is no need to set `everythingFile` and we set a custom `buildPhase`.
+
+When writing an Agda package it is essential to make sure that no `.agda-lib` file gets added to the store as a single file (for example by using `writeText`). This causes Agda to think that the nix store is a Agda library and it will attempt to write to it whenever it typechecks something. See [https://github.com/agda/agda/issues/4613](https://github.com/agda/agda/issues/4613).
+
+In the pull request adding this library,
+you can test whether it builds correctly by writing in a comment:
+
+```
+@ofborg build agdaPackages.iowa-stdlib
+```
+
+### Maintaining Agda packages
+
+As mentioned before, the aim is to have a compatible, and up-to-date package set.
+These two conditions sometimes exclude each other:
+For example, if we update `agdaPackages.standard-library` because there was an upstream release,
+this will typically break many reverse dependencies,
+i.e. downstream Agda libraries that depend on the standard library.
+In `nixpkgs` we are typically among the first to notice this,
+since we have build tests in place to check this.
+
+In a pull request updating e.g. the standard library, you should write the following comment:
+
+```
+@ofborg build agdaPackages.standard-library.passthru.tests
+```
+
+This will build all reverse dependencies of the standard library,
+for example `agdaPackages.agda-categories`, or `agdaPackages.generic`.
+
+In some cases it is useful to build _all_ Agda packages.
+This can be done with the following Github comment:
+
+```
+@ofborg build agda.passthru.tests.allPackages
+```
+
+Sometimes, the builds of the reverse dependencies fail because they have not yet been updated and released.
+You should drop the maintainers a quick issue notifying them of the breakage,
+citing the build error (which you can get from the ofborg logs).
+If you are motivated, you might even send a pull request that fixes it.
+Usually, the maintainers will answer within a week or two with a new release.
+Bumping the version of that reverse dependency should be a further commit on your PR.
+
+In the rare case that a new release is not to be expected within an acceptable time,
+simply mark the broken package as broken by setting `meta.broken = true;`.
+This will exclude it from the build test.
+It can be added later when it is fixed,
+and does not hinder the advancement of the whole package set in the meantime.
diff --git a/doc/languages-frameworks/android.section.md b/doc/languages-frameworks/android.section.md
new file mode 100644
index 00000000000..28128ead663
--- /dev/null
+++ b/doc/languages-frameworks/android.section.md
@@ -0,0 +1,346 @@
+# Android {#android}
+
+The Android build environment provides three major features and a number of
+supporting features.
+
+## Deploying an Android SDK installation with plugins {#deploying-an-android-sdk-installation-with-plugins}
+
+The first use case is deploying the SDK with a desired set of plugins or subsets
+of an SDK.
+
+```nix
+with import <nixpkgs> {};
+
+let
+  androidComposition = androidenv.composeAndroidPackages {
+    toolsVersion = "26.1.1";
+    platformToolsVersion = "30.0.5";
+    buildToolsVersions = [ "30.0.3" ];
+    includeEmulator = false;
+    emulatorVersion = "30.3.4";
+    platformVersions = [ "28" "29" "30" ];
+    includeSources = false;
+    includeSystemImages = false;
+    systemImageTypes = [ "google_apis_playstore" ];
+    abiVersions = [ "armeabi-v7a" "arm64-v8a" ];
+    cmakeVersions = [ "3.10.2" ];
+    includeNDK = true;
+    ndkVersions = ["22.0.7026061"];
+    useGoogleAPIs = false;
+    useGoogleTVAddOns = false;
+    includeExtras = [
+      "extras;google;gcm"
+    ];
+  };
+in
+androidComposition.androidsdk
+```
+
+The above function invocation states that we want an Android SDK with the above
+specified plugin versions. By default, most plugins are disabled. Notable
+exceptions are the tools, platform-tools and build-tools sub packages.
+
+The following parameters are supported:
+
+* `toolsVersion`, specifies the version of the tools package to use
+* `platformsToolsVersion` specifies the version of the `platform-tools` plugin
+* `buildToolsVersions` specifies the versions of the `build-tools` plugins to
+  use.
+* `includeEmulator` specifies whether to deploy the emulator package (`false`
+  by default). When enabled, the version of the emulator to deploy can be
+  specified by setting the `emulatorVersion` parameter.
+* `cmakeVersions` specifies which CMake versions should be deployed.
+* `includeNDK` specifies that the Android NDK bundle should be included.
+  Defaults to: `false`.
+* `ndkVersions` specifies the NDK versions that we want to use. These are linked
+  under the `ndk` directory of the SDK root, and the first is linked under the
+  `ndk-bundle` directory.
+* `ndkVersion` is equivalent to specifying one entry in `ndkVersions`, and
+  `ndkVersions` overrides this parameter if provided.
+* `includeExtras` is an array of identifier strings referring to arbitrary
+  add-on packages that should be installed.
+* `platformVersions` specifies which platform SDK versions should be included.
+
+For each platform version that has been specified, we can apply the following
+options:
+
+* `includeSystemImages` specifies whether a system image for each platform SDK
+  should be included.
+* `includeSources` specifies whether the sources for each SDK version should be
+  included.
+* `useGoogleAPIs` specifies that for each selected platform version the
+  Google API should be included.
+* `useGoogleTVAddOns` specifies that for each selected platform version the
+  Google TV add-on should be included.
+
+For each requested system image we can specify the following options:
+
+* `systemImageTypes` specifies what kind of system images should be included.
+  Defaults to: `default`.
+* `abiVersions` specifies what kind of ABI version of each system image should
+  be included. Defaults to: `armeabi-v7a`.
+
+Most of the function arguments have reasonable default settings.
+
+You can specify license names:
+
+* `extraLicenses` is a list of license names.
+  You can get these names from repo.json or `querypackages.sh licenses`. The SDK
+  license (`android-sdk-license`) is accepted for you if you set accept_license
+  to true. If you are doing something like working with preview SDKs, you will
+  want to add `android-sdk-preview-license` or whichever license applies here.
+
+Additionally, you can override the repositories that composeAndroidPackages will
+pull from:
+
+* `repoJson` specifies a path to a generated repo.json file. You can generate this
+  by running `generate.sh`, which in turn will call into `mkrepo.rb`.
+* `repoXmls` is an attribute set containing paths to repo XML files. If specified,
+  it takes priority over `repoJson`, and will trigger a local build writing out a
+  repo.json to the Nix store based on the given repository XMLs.
+
+```nix
+repoXmls = {
+  packages = [ ./xml/repository2-1.xml ];
+  images = [
+    ./xml/android-sys-img2-1.xml
+    ./xml/android-tv-sys-img2-1.xml
+    ./xml/android-wear-sys-img2-1.xml
+    ./xml/android-wear-cn-sys-img2-1.xml
+    ./xml/google_apis-sys-img2-1.xml
+    ./xml/google_apis_playstore-sys-img2-1.xml
+  ];
+  addons = [ ./xml/addon2-1.xml ];
+};
+```
+
+When building the above expression with:
+
+```bash
+$ nix-build
+```
+
+The Android SDK gets deployed with all desired plugin versions.
+
+We can also deploy subsets of the Android SDK. For example, to only the
+`platform-tools` package, you can evaluate the following expression:
+
+```nix
+with import <nixpkgs> {};
+
+let
+  androidComposition = androidenv.composeAndroidPackages {
+    # ...
+  };
+in
+androidComposition.platform-tools
+```
+
+## Using predefined Android package compositions {#using-predefined-android-package-compositions}
+
+In addition to composing an Android package set manually, it is also possible
+to use a predefined composition that contains all basic packages for a specific
+Android version, such as version 9.0 (API-level 28).
+
+The following Nix expression can be used to deploy the entire SDK with all basic
+plugins:
+
+```nix
+with import <nixpkgs> {};
+
+androidenv.androidPkgs_9_0.androidsdk
+```
+
+It is also possible to use one plugin only:
+
+```nix
+with import <nixpkgs> {};
+
+androidenv.androidPkgs_9_0.platform-tools
+```
+
+## Building an Android application {#building-an-android-application}
+
+In addition to the SDK, it is also possible to build an Ant-based Android
+project and automatically deploy all the Android plugins that a project
+requires.
+
+
+```nix
+with import <nixpkgs> {};
+
+androidenv.buildApp {
+  name = "MyAndroidApp";
+  src = ./myappsources;
+  release = true;
+
+  # If release is set to true, you need to specify the following parameters
+  keyStore = ./keystore;
+  keyAlias = "myfirstapp";
+  keyStorePassword = "mykeystore";
+  keyAliasPassword = "myfirstapp";
+
+  # Any Android SDK parameters that install all the relevant plugins that a
+  # build requires
+  platformVersions = [ "24" ];
+
+  # When we include the NDK, then ndk-build is invoked before Ant gets invoked
+  includeNDK = true;
+}
+```
+
+Aside from the app-specific build parameters (`name`, `src`, `release` and
+keystore parameters), the `buildApp {}` function supports all the function
+parameters that the SDK composition function (the function shown in the
+previous section) supports.
+
+This build function is particularly useful when it is desired to use
+[Hydra](https://nixos.org/hydra): the Nix-based continuous integration solution
+to build Android apps. An Android APK gets exposed as a build product and can be
+installed on any Android device with a web browser by navigating to the build
+result page.
+
+## Spawning emulator instances {#spawning-emulator-instances}
+
+For testing purposes, it can also be quite convenient to automatically generate
+scripts that spawn emulator instances with all desired configuration settings.
+
+An emulator spawn script can be configured by invoking the `emulateApp {}`
+function:
+
+```nix
+with import <nixpkgs> {};
+
+androidenv.emulateApp {
+  name = "emulate-MyAndroidApp";
+  platformVersion = "28";
+  abiVersion = "x86"; # armeabi-v7a, mips, x86_64
+  systemImageType = "google_apis_playstore";
+}
+```
+
+Additional flags may be applied to the Android SDK's emulator through the runtime environment variable `$NIX_ANDROID_EMULATOR_FLAGS`.
+
+It is also possible to specify an APK to deploy inside the emulator
+and the package and activity names to launch it:
+
+```nix
+with import <nixpkgs> {};
+
+androidenv.emulateApp {
+  name = "emulate-MyAndroidApp";
+  platformVersion = "24";
+  abiVersion = "armeabi-v7a"; # mips, x86, x86_64
+  systemImageType = "default";
+  useGoogleAPIs = false;
+  app = ./MyApp.apk;
+  package = "MyApp";
+  activity = "MainActivity";
+}
+```
+
+In addition to prebuilt APKs, you can also bind the APK parameter to a
+`buildApp {}` function invocation shown in the previous example.
+
+## Notes on environment variables in Android projects {#notes-on-environment-variables-in-android-projects}
+
+* `ANDROID_SDK_ROOT` should point to the Android SDK. In your Nix expressions, this should be
+  `${androidComposition.androidsdk}/libexec/android-sdk`. Note that `ANDROID_HOME` is deprecated,
+  but if you rely on tools that need it, you can export it too.
+* `ANDROID_NDK_ROOT` should point to the Android NDK, if you're doing NDK development.
+  In your Nix expressions, this should be `${ANDROID_SDK_ROOT}/ndk-bundle`.
+
+If you are running the Android Gradle plugin, you need to export GRADLE_OPTS to override aapt2
+to point to the aapt2 binary in the Nix store as well, or use a FHS environment so the packaged
+aapt2 can run. If you don't want to use a FHS environment, something like this should work:
+
+```nix
+let
+  buildToolsVersion = "30.0.3";
+
+  # Use buildToolsVersion when you define androidComposition
+  androidComposition = <...>;
+in
+pkgs.mkShell rec {
+  ANDROID_SDK_ROOT = "${androidComposition.androidsdk}/libexec/android-sdk";
+  ANDROID_NDK_ROOT = "${ANDROID_SDK_ROOT}/ndk-bundle";
+
+  # Use the same buildToolsVersion here
+  GRADLE_OPTS = "-Dorg.gradle.project.android.aapt2FromMavenOverride=${ANDROID_SDK_ROOT}/build-tools/${buildToolsVersion}/aapt2";
+}
+```
+
+If you are using cmake, you need to add it to PATH in a shell hook or FHS env profile.
+The path is suffixed with a build number, but properly prefixed with the version.
+So, something like this should suffice:
+
+```nix
+let
+  cmakeVersion = "3.10.2";
+
+  # Use cmakeVersion when you define androidComposition
+  androidComposition = <...>;
+in
+pkgs.mkShell rec {
+  ANDROID_SDK_ROOT = "${androidComposition.androidsdk}/libexec/android-sdk";
+  ANDROID_NDK_ROOT = "${ANDROID_SDK_ROOT}/ndk-bundle";
+
+  # Use the same cmakeVersion here
+  shellHook = ''
+    export PATH="$(echo "$ANDROID_SDK_ROOT/cmake/${cmakeVersion}".*/bin):$PATH"
+  '';
+}
+```
+
+Note that running Android Studio with ANDROID_SDK_ROOT set will automatically write a
+`local.properties` file with `sdk.dir` set to $ANDROID_SDK_ROOT if one does not already
+exist. If you are using the NDK as well, you may have to add `ndk.dir` to this file.
+
+An example shell.nix that does all this for you is provided in examples/shell.nix.
+This shell.nix includes a shell hook that overwrites local.properties with the correct
+sdk.dir and ndk.dir values. This will ensure that the SDK and NDK directories will
+both be correct when you run Android Studio inside nix-shell.
+
+## Notes on improving build.gradle compatibility {#notes-on-improving-build.gradle-compatibility}
+
+Ensure that your buildToolsVersion and ndkVersion match what is declared in androidenv.
+If you are using cmake, make sure its declared version is correct too.
+
+Otherwise, you may get cryptic errors from aapt2 and the Android Gradle plugin warning
+that it cannot install the build tools because the SDK directory is not writeable.
+
+```gradle
+android {
+    buildToolsVersion "30.0.3"
+    ndkVersion = "22.0.7026061"
+    externalNativeBuild {
+        cmake {
+            version "3.10.2"
+        }
+    }
+}
+
+```
+
+## Querying the available versions of each plugin {#querying-the-available-versions-of-each-plugin}
+
+repo.json provides all the options in one file now.
+
+A shell script in the `pkgs/development/mobile/androidenv/` subdirectory can be used to retrieve all
+possible options:
+
+```bash
+./querypackages.sh packages
+```
+
+The above command-line instruction queries all package versions in repo.json.
+
+## Updating the generated expressions {#updating-the-generated-expressions}
+
+repo.json is generated from XML files that the Android Studio package manager uses.
+To update the expressions run the `generate.sh` script that is stored in the
+`pkgs/development/mobile/androidenv/` subdirectory:
+
+```bash
+./generate.sh
+```
diff --git a/doc/languages-frameworks/beam.section.md b/doc/languages-frameworks/beam.section.md
new file mode 100644
index 00000000000..f6c74cb01e4
--- /dev/null
+++ b/doc/languages-frameworks/beam.section.md
@@ -0,0 +1,373 @@
+# BEAM Languages (Erlang, Elixir & LFE) {#sec-beam}
+
+## Introduction {#beam-introduction}
+
+In this document and related Nix expressions, we use the term, _BEAM_, to describe the environment. BEAM is the name of the Erlang Virtual Machine and, as far as we're concerned, from a packaging perspective, all languages that run on the BEAM are interchangeable. That which varies, like the build system, is transparent to users of any given BEAM package, so we make no distinction.
+
+## Available versions and deprecations schedule {#available-versions-and-deprecations-schedule}
+
+### Elixir {#elixir}
+
+nixpkgs follows the [official elixir deprecation schedule](https://hexdocs.pm/elixir/compatibility-and-deprecations.html) and keeps the last 5 released versions of Elixir available.
+
+## Structure {#beam-structure}
+
+All BEAM-related expressions are available via the top-level `beam` attribute, which includes:
+
+- `interpreters`: a set of compilers running on the BEAM, including multiple Erlang/OTP versions (`beam.interpreters.erlangR22`, etc), Elixir (`beam.interpreters.elixir`) and LFE (Lisp Flavoured Erlang) (`beam.interpreters.lfe`).
+
+- `packages`: a set of package builders (Mix and rebar3), each compiled with a specific Erlang/OTP version, e.g. `beam.packages.erlang22`.
+
+The default Erlang compiler, defined by `beam.interpreters.erlang`, is aliased as `erlang`. The default BEAM package set is defined by `beam.packages.erlang` and aliased at the top level as `beamPackages`.
+
+To create a package builder built with a custom Erlang version, use the lambda, `beam.packagesWith`, which accepts an Erlang/OTP derivation and produces a package builder similar to `beam.packages.erlang`.
+
+Many Erlang/OTP distributions available in `beam.interpreters` have versions with ODBC and/or Java enabled or without wx (no observer support). For example, there's `beam.interpreters.erlangR22_odbc_javac`, which corresponds to `beam.interpreters.erlangR22` and `beam.interpreters.erlangR22_nox`, which corresponds to `beam.interpreters.erlangR22`.
+
+## Build Tools {#build-tools}
+
+### Rebar3 {#build-tools-rebar3}
+
+We provide a version of Rebar3, under `rebar3`. We also provide a helper to fetch Rebar3 dependencies from a lockfile under `fetchRebar3Deps`.
+
+We also provide a version on Rebar3 with plugins included, under `rebar3WithPlugins`. This package is a function which takes two arguments: `plugins`, a list of nix derivations to include as plugins (loaded only when specified in `rebar.config`), and `globalPlugins`, which should always be loaded by rebar3. Example: `rebar3WithPlugins { globalPlugins = [beamPackages.pc]; }`.
+
+When adding a new plugin it is important that the `packageName` attribute is the same as the atom used by rebar3 to refer to the plugin.
+
+### Mix & Erlang.mk {#build-tools-other}
+
+Erlang.mk works exactly as expected. There is a bootstrap process that needs to be run, which is supported by the `buildErlangMk` derivation.
+
+For Elixir applications use `mixRelease` to make a release. See examples for more details.
+
+There is also a `buildMix` helper, whose behavior is closer to that of `buildErlangMk` and `buildRebar3`. The primary difference is that mixRelease makes a release, while buildMix only builds the package, making it useful for libraries and other dependencies.
+
+## How to Install BEAM Packages {#how-to-install-beam-packages}
+
+BEAM builders are not registered at the top level, simply because they are not relevant to the vast majority of Nix users. To install any of those builders into your profile, refer to them by their attribute path `beamPackages.rebar3`:
+
+```ShellSession
+$ nix-env -f "<nixpkgs>" -iA beamPackages.rebar3
+```
+
+## Packaging BEAM Applications {#packaging-beam-applications}
+
+### Erlang Applications {#packaging-erlang-applications}
+
+#### Rebar3 Packages {#rebar3-packages}
+
+The Nix function, `buildRebar3`, defined in `beam.packages.erlang.buildRebar3` and aliased at the top level, can be used to build a derivation that understands how to build a Rebar3 project.
+
+If a package needs to compile native code via Rebar3's port compilation mechanism, add `compilePort = true;` to the derivation.
+
+#### Erlang.mk Packages {#erlang-mk-packages}
+
+Erlang.mk functions similarly to Rebar3, except we use `buildErlangMk` instead of `buildRebar3`.
+
+#### Mix Packages {#mix-packages}
+
+`mixRelease` is used to make a release in the mix sense. Dependencies will need to be fetched with `fetchMixDeps` and passed to it.
+
+#### mixRelease - Elixir Phoenix example {#mix-release-elixir-phoenix-example}
+
+there are 3 steps, frontend dependencies (javascript), backend dependencies (elixir) and the final derivation that puts both of those together
+
+##### mixRelease - Frontend dependencies (javascript) {#mix-release-javascript-deps}
+
+For phoenix projects, inside of nixpkgs you can either use yarn2nix (mkYarnModule) or node2nix. An example with yarn2nix can be found [here](https://github.com/NixOS/nixpkgs/blob/master/pkgs/servers/web-apps/plausible/default.nix#L39). An example with node2nix will follow. To package something outside of nixpkgs, you have alternatives like [npmlock2nix](https://github.com/nix-community/npmlock2nix) or [nix-npm-buildpackage](https://github.com/serokell/nix-npm-buildpackage)
+
+##### mixRelease - backend dependencies (mix) {#mix-release-mix-deps}
+
+There are 2 ways to package backend dependencies. With mix2nix and with a fixed-output-derivation (FOD).
+
+###### mix2nix {#mix2nix}
+
+`mix2nix` is a cli tool available in nixpkgs. it will generate a nix expression from a mix.lock file. It is quite standard in the 2nix tool series.
+
+Note that currently mix2nix can't handle git dependencies inside the mix.lock file. If you have git dependencies, you can either add them manually (see [example](https://github.com/NixOS/nixpkgs/blob/master/pkgs/servers/pleroma/default.nix#L20)) or use the FOD method.
+
+The advantage of using mix2nix is that nix will know your whole dependency graph. On a dependency update, this won't trigger a full rebuild and download of all the dependencies, where FOD will do so.
+
+Practical steps:
+
+- run `mix2nix > mix_deps.nix` in the upstream repo.
+- pass `mixNixDeps = with pkgs; import ./mix_deps.nix { inherit lib beamPackages; };` as an argument to mixRelease.
+
+If there are git depencencies.
+
+- You'll need to fix the version artificially in mix.exs and regenerate the mix.lock with fixed version (on upstream). This will enable you to run `mix2nix > mix_deps.nix`.
+- From the mix_deps.nix file, remove the dependencies that had git versions and pass them as an override to the import function.
+
+```nix
+  mixNixDeps = import ./mix.nix {
+    inherit beamPackages lib;
+    overrides = (final: prev: {
+      # mix2nix does not support git dependencies yet,
+      # so we need to add them manually
+      prometheus_ex = beamPackages.buildMix rec {
+        name = "prometheus_ex";
+        version = "3.0.5";
+
+        # Change the argument src with the git src that you actually need
+        src = fetchFromGitLab {
+          domain = "git.pleroma.social";
+          group = "pleroma";
+          owner = "elixir-libraries";
+          repo = "prometheus.ex";
+          rev = "a4e9beb3c1c479d14b352fd9d6dd7b1f6d7deee5";
+          sha256 = "1v0q4bi7sb253i8q016l7gwlv5562wk5zy3l2sa446csvsacnpjk";
+        };
+        # you can re-use the same beamDeps argument as generated
+        beamDeps = with final; [ prometheus ];
+      };
+  });
+};
+```
+
+You will need to run the build process once to fix the sha256 to correspond to your new git src.
+
+###### FOD {#fixed-output-derivation}
+
+A fixed output derivation will download mix dependencies from the internet. To ensure reproducibility, a hash will be supplied. Note that mix is relatively reproducible. An FOD generating a different hash on each run hasn't been observed (as opposed to npm where the chances are relatively high). See [elixir_ls](https://github.com/NixOS/nixpkgs/blob/master/pkgs/development/beam-modules/elixir_ls.nix) for a usage example of FOD.
+
+Practical steps
+
+- start with the following argument to mixRelease
+
+```nix
+  mixFodDeps = fetchMixDeps {
+    pname = "mix-deps-${pname}";
+    inherit src version;
+    sha256 = lib.fakeSha256;
+  };
+```
+
+The first build will complain about the sha256 value, you can replace with the suggested value after that.
+
+Note that if after you've replaced the value, nix suggests another sha256, then mix is not fetching the dependencies reproducibly. An FOD will not work in that case and you will have to use mix2nix.
+
+##### mixRelease - example {#mix-release-example}
+
+Here is how your `default.nix` file would look for a phoenix project.
+
+```nix
+with import <nixpkgs> { };
+
+let
+  # beam.interpreters.erlangR23 is available if you need a particular version
+  packages = beam.packagesWith beam.interpreters.erlang;
+
+  pname = "your_project";
+  version = "0.0.1";
+
+  src = builtins.fetchgit {
+    url = "ssh://git@github.com/your_id/your_repo";
+    rev = "replace_with_your_commit";
+  };
+
+  # if using mix2nix you can use the mixNixDeps attribute
+  mixFodDeps = packages.fetchMixDeps {
+    pname = "mix-deps-${pname}";
+    inherit src version;
+    # nix will complain and tell you the right value to replace this with
+    sha256 = lib.fakeSha256;
+    # if you have build time environment variables add them here
+    MY_ENV_VAR="my_value";
+  };
+
+  nodeDependencies = (pkgs.callPackage ./assets/default.nix { }).shell.nodeDependencies;
+
+in packages.mixRelease {
+  inherit src pname version mixFodDeps;
+  # if you have build time environment variables add them here
+  MY_ENV_VAR="my_value";
+
+  postBuild = ''
+    ln -sf ${nodeDependencies}/lib/node_modules assets/node_modules
+    npm run deploy --prefix ./assets
+
+    # for external task you need a workaround for the no deps check flag
+    # https://github.com/phoenixframework/phoenix/issues/2690
+    mix do deps.loadpaths --no-deps-check, phx.digest
+    mix phx.digest --no-deps-check
+  '';
+}
+```
+
+Setup will require the following steps:
+
+- Move your secrets to runtime environment variables. For more information refer to the [runtime.exs docs](https://hexdocs.pm/mix/Mix.Tasks.Release.html#module-runtime-configuration). On a fresh Phoenix build that would mean that both `DATABASE_URL` and `SECRET_KEY` need to be moved to `runtime.exs`.
+- `cd assets` and `nix-shell -p node2nix --run node2nix --development` will generate a Nix expression containing your frontend dependencies
+- commit and push those changes
+- you can now `nix-build .`
+- To run the release, set the `RELEASE_TMP` environment variable to a directory that your program has write access to. It will be used to store the BEAM settings.
+
+#### Example of creating a service for an Elixir - Phoenix project {#example-of-creating-a-service-for-an-elixir---phoenix-project}
+
+In order to create a service with your release, you could add a `service.nix`
+in your project with the following
+
+```nix
+{config, pkgs, lib, ...}:
+
+let
+  release = pkgs.callPackage ./default.nix;
+  release_name = "app";
+  working_directory = "/home/app";
+in
+{
+  systemd.services.${release_name} = {
+    wantedBy = [ "multi-user.target" ];
+    after = [ "network.target" "postgresql.service" ];
+    # note that if you are connecting to a postgres instance on a different host
+    # postgresql.service should not be included in the requires.
+    requires = [ "network-online.target" "postgresql.service" ];
+    description = "my app";
+    environment = {
+      # RELEASE_TMP is used to write the state of the
+      # VM configuration when the system is running
+      # it needs to be a writable directory
+      RELEASE_TMP = working_directory;
+      # can be generated in an elixir console with
+      # Base.encode32(:crypto.strong_rand_bytes(32))
+      RELEASE_COOKIE = "my_cookie";
+      MY_VAR = "my_var";
+    };
+    serviceConfig = {
+      Type = "exec";
+      DynamicUser = true;
+      WorkingDirectory = working_directory;
+      # Implied by DynamicUser, but just to emphasize due to RELEASE_TMP
+      PrivateTmp = true;
+      ExecStart = ''
+        ${release}/bin/${release_name} start
+      '';
+      ExecStop = ''
+        ${release}/bin/${release_name} stop
+      '';
+      ExecReload = ''
+        ${release}/bin/${release_name} restart
+      '';
+      Restart = "on-failure";
+      RestartSec = 5;
+      StartLimitBurst = 3;
+      StartLimitInterval = 10;
+    };
+    # disksup requires bash
+    path = [ pkgs.bash ];
+  };
+
+  # in case you have migration scripts or you want to use a remote shell
+  environment.systemPackages = [ release ];
+}
+```
+
+## How to Develop {#how-to-develop}
+
+### Creating a Shell {#creating-a-shell}
+
+Usually, we need to create a `shell.nix` file and do our development inside of the environment specified therein. Just install your version of Erlang and any other interpreters, and then use your normal build tools. As an example with Elixir:
+
+```nix
+{ pkgs ? import <nixpkgs> {} }:
+
+with pkgs;
+let
+  elixir = beam.packages.erlangR24.elixir_1_12;
+in
+mkShell {
+  buildInputs = [ elixir ];
+}
+```
+
+### Using an overlay
+
+If you need to use an overlay to change some attributes of a derivation, e.g. if you need a bugfix from a version that is not yet available in nixpkgs, you can override attributes such as `version` (and the corresponding `sha256`) and then use this overlay in your development environment:
+
+#### `shell.nix`
+
+```nix
+let
+  elixir_1_13_1_overlay = (self: super: {
+      elixir_1_13 = super.elixir_1_13.override {
+        version = "1.13.1";
+        sha256 = "0z0b1w2vvw4vsnb99779c2jgn9bgslg7b1pmd9vlbv02nza9qj5p";
+      };
+    });
+  pkgs = import <nixpkgs> { overlays = [ elixir_1_13_1_overlay ]; };
+in
+with pkgs;
+mkShell {
+  buildInputs = [
+    elixir_1_13
+  ];
+}
+```
+
+#### Elixir - Phoenix project {#elixir---phoenix-project}
+
+Here is an example `shell.nix`.
+
+```nix
+with import <nixpkgs> { };
+
+let
+  # define packages to install
+  basePackages = [
+    git
+    # replace with beam.packages.erlang.elixir_1_13 if you need
+    beam.packages.erlang.elixir
+    nodejs
+    postgresql_14
+    # only used for frontend dependencies
+    # you are free to use yarn2nix as well
+    nodePackages.node2nix
+    # formatting js file
+    nodePackages.prettier
+  ];
+
+  inputs = basePackages ++ lib.optionals stdenv.isLinux [ inotify-tools ]
+    ++ lib.optionals stdenv.isDarwin
+    (with darwin.apple_sdk.frameworks; [ CoreFoundation CoreServices ]);
+
+  # define shell startup command
+  hooks = ''
+    # this allows mix to work on the local directory
+    mkdir -p .nix-mix .nix-hex
+    export MIX_HOME=$PWD/.nix-mix
+    export HEX_HOME=$PWD/.nix-mix
+    # make hex from Nixpkgs available
+    # `mix local.hex` will install hex into MIX_HOME and should take precedence
+    export MIX_PATH="${beam.packages.erlang.hex}/lib/erlang/lib/hex/ebin"
+    export PATH=$MIX_HOME/bin:$HEX_HOME/bin:$PATH
+    export LANG=C.UTF-8
+    # keep your shell history in iex
+    export ERL_AFLAGS="-kernel shell_history enabled"
+
+    # postges related
+    # keep all your db data in a folder inside the project
+    export PGDATA="$PWD/db"
+
+    # phoenix related env vars
+    export POOL_SIZE=15
+    export DB_URL="postgresql://postgres:postgres@localhost:5432/db"
+    export PORT=4000
+    export MIX_ENV=dev
+    # add your project env vars here, word readable in the nix store.
+    export ENV_VAR="your_env_var"
+  '';
+
+in mkShell {
+  buildInputs = inputs;
+  shellHook = hooks;
+}
+```
+
+Initializing the project will require the following steps:
+
+- create the db directory `initdb ./db` (inside your mix project folder)
+- create the postgres user `createuser postgres -ds`
+- create the db `createdb db`
+- start the postgres instance `pg_ctl -l "$PGDATA/server.log" start`
+- add the `/db` folder to your `.gitignore`
+- you can start your phoenix server and get a shell with `iex -S mix phx.server`
diff --git a/doc/languages-frameworks/bower.section.md b/doc/languages-frameworks/bower.section.md
new file mode 100644
index 00000000000..6226dc0702d
--- /dev/null
+++ b/doc/languages-frameworks/bower.section.md
@@ -0,0 +1,158 @@
+# Bower {#sec-bower}
+
+[Bower](https://bower.io) is a package manager for web site front-end components. Bower packages (comprising of build artefacts and sometimes sources) are stored in `git` repositories, typically on Github. The package registry is run by the Bower team with package metadata coming from the `bower.json` file within each package.
+
+The end result of running Bower is a `bower_components` directory which can be included in the web app's build process.
+
+Bower can be run interactively, by installing `nodePackages.bower`. More interestingly, the Bower components can be declared in a Nix derivation, with the help of `nodePackages.bower2nix`.
+
+## bower2nix usage {#ssec-bower2nix-usage}
+
+Suppose you have a `bower.json` with the following contents:
+
+### Example bower.json {#ex-bowerJson}
+
+```json
+  "name": "my-web-app",
+  "dependencies": {
+    "angular": "~1.5.0",
+    "bootstrap": "~3.3.6"
+  }
+```
+
+Running `bower2nix` will produce something like the following output:
+
+```nix
+{ fetchbower, buildEnv }:
+buildEnv { name = "bower-env"; ignoreCollisions = true; paths = [
+  (fetchbower "angular" "1.5.3" "~1.5.0" "1749xb0firxdra4rzadm4q9x90v6pzkbd7xmcyjk6qfza09ykk9y")
+  (fetchbower "bootstrap" "3.3.6" "~3.3.6" "1vvqlpbfcy0k5pncfjaiskj3y6scwifxygfqnw393sjfxiviwmbv")
+  (fetchbower "jquery" "2.2.2" "1.9.1 - 2" "10sp5h98sqwk90y4k6hbdviwqzvzwqf47r3r51pakch5ii2y7js1")
+];
+```
+
+Using the `bower2nix` command line arguments, the output can be redirected to a file. A name like `bower-packages.nix` would be fine.
+
+The resulting derivation is a union of all the downloaded Bower packages (and their dependencies). To use it, they still need to be linked together by Bower, which is where `buildBowerComponents` is useful.
+
+## buildBowerComponents function {#ssec-build-bower-components}
+
+The function is implemented in [pkgs/development/bower-modules/generic/default.nix](https://github.com/NixOS/nixpkgs/blob/master/pkgs/development/bower-modules/generic/default.nix).
+
+### Example buildBowerComponents {#ex-buildBowerComponents}
+
+```{=docbook}
+<programlisting language="nix">
+bowerComponents = buildBowerComponents {
+  name = "my-web-app";
+  generated = ./bower-packages.nix; <co xml:id="ex-buildBowerComponents-1" />
+  src = myWebApp; <co xml:id="ex-buildBowerComponents-2" />
+};
+</programlisting>
+```
+
+In ["buildBowerComponents" example](#ex-buildBowerComponents) the following arguments are of special significance to the function:
+
+```{=docbook}
+<calloutlist>
+  <callout arearefs="ex-buildBowerComponents-1">
+    <para>
+      <varname>generated</varname> specifies the file which was created by <command>bower2nix</command>.
+    </para>
+    </callout>
+      <callout arearefs="ex-buildBowerComponents-2">
+    <para>
+      <varname>src</varname> is your project's sources. It needs to contain a <filename>bower.json</filename> file.
+    </para>
+  </callout>
+</calloutlist>
+```
+
+`buildBowerComponents` will run Bower to link together the output of `bower2nix`, resulting in a `bower_components` directory which can be used.
+
+Here is an example of a web frontend build process using `gulp`. You might use `grunt`, or anything else.
+
+### Example build script (gulpfile.js) {#ex-bowerGulpFile}
+
+```javascript
+var gulp = require('gulp');
+
+gulp.task('default', [], function () {
+  gulp.start('build');
+});
+
+gulp.task('build', [], function () {
+  console.log("Just a dummy gulp build");
+  gulp
+    .src(["./bower_components/**/*"])
+    .pipe(gulp.dest("./gulpdist/"));
+});
+```
+
+### Example Full example — default.nix {#ex-buildBowerComponentsDefaultNix}
+
+```{=docbook}
+<programlisting language="nix">
+{ myWebApp ? { outPath = ./.; name = "myWebApp"; }
+, pkgs ? import &lt;nixpkgs&gt; {}
+}:
+
+pkgs.stdenv.mkDerivation {
+  name = "my-web-app-frontend";
+  src = myWebApp;
+
+  buildInputs = [ pkgs.nodePackages.gulp ];
+
+  bowerComponents = pkgs.buildBowerComponents { <co xml:id="ex-buildBowerComponentsDefault-1" />
+    name = "my-web-app";
+    generated = ./bower-packages.nix;
+    src = myWebApp;
+  };
+
+  buildPhase = ''
+    cp --reflink=auto --no-preserve=mode -R $bowerComponents/bower_components . <co xml:id="ex-buildBowerComponentsDefault-2" />
+    export HOME=$PWD <co xml:id="ex-buildBowerComponentsDefault-3" />
+    ${pkgs.nodePackages.gulp}/bin/gulp build <co xml:id="ex-buildBowerComponentsDefault-4" />
+  '';
+
+  installPhase = "mv gulpdist $out";
+}
+</programlisting>
+```
+
+A few notes about [Full example — `default.nix`](#ex-buildBowerComponentsDefaultNix):
+
+```{=docbook}
+<calloutlist>
+  <callout arearefs="ex-buildBowerComponentsDefault-1">
+    <para>
+      The result of <varname>buildBowerComponents</varname> is an input to the frontend build.
+    </para>
+  </callout>
+  <callout arearefs="ex-buildBowerComponentsDefault-2">
+    <para>
+      Whether to symlink or copy the <filename>bower_components</filename> directory depends on the build tool in use. In this case a copy is used to avoid <command>gulp</command> silliness with permissions.
+    </para>
+  </callout>
+  <callout arearefs="ex-buildBowerComponentsDefault-3">
+    <para>
+      <command>gulp</command> requires <varname>HOME</varname> to refer to a writeable directory.
+    </para>
+  </callout>
+  <callout arearefs="ex-buildBowerComponentsDefault-4">
+    <para>
+      The actual build command. Other tools could be used.
+    </para>
+  </callout>
+</calloutlist>
+```
+
+## Troubleshooting {#ssec-bower2nix-troubleshooting}
+
+### ENOCACHE errors from buildBowerComponents {#enocache-errors-from-buildbowercomponents}
+
+This means that Bower was looking for a package version which doesn't exist in the generated `bower-packages.nix`.
+
+If `bower.json` has been updated, then run `bower2nix` again.
+
+It could also be a bug in `bower2nix` or `fetchbower`. If possible, try reformulating the version specification in `bower.json`.
diff --git a/doc/languages-frameworks/coq.section.md b/doc/languages-frameworks/coq.section.md
new file mode 100644
index 00000000000..9a692104a04
--- /dev/null
+++ b/doc/languages-frameworks/coq.section.md
@@ -0,0 +1,83 @@
+# Coq and coq packages {#sec-language-coq}
+
+## Coq derivation: `coq` {#coq-derivation-coq}
+
+The Coq derivation is overridable through the `coq.override overrides`, where overrides is an attribute set which contains the arguments to override. We recommend overriding either of the following
+
+* `version` (optional, defaults to the latest version of Coq selected for nixpkgs, see `pkgs/top-level/coq-packages` to witness this choice), which follows the conventions explained in the `coqPackages` section below,
+* `customOCamlPackage` (optional, defaults to `null`, which lets Coq choose a version automatically), which can be set to any of the ocaml packages attribute of `ocaml-ng` (such as `ocaml-ng.ocamlPackages_4_10` which is the default for Coq 8.11 for example).
+* `coq-version` (optional, defaults to the short version e.g. "8.10"), is a version number of the form "x.y" that indicates which Coq's version build behavior to mimic when using a source which is not a release. E.g. `coq.override { version = "d370a9d1328a4e1cdb9d02ee032f605a9d94ec7a"; coq-version = "8.10"; }`.
+
+## Coq packages attribute sets: `coqPackages` {#coq-packages-attribute-sets-coqpackages}
+
+The recommended way of defining a derivation for a Coq library, is to use the `coqPackages.mkCoqDerivation` function, which is essentially a specialization of `mkDerivation` taking into account most of the specifics of Coq libraries. The following attributes are supported:
+
+* `pname` (required) is the name of the package,
+* `version` (optional, defaults to `null`), is the version to fetch and build,
+  this attribute is interpreted in several ways depending on its type and pattern:
+  * if it is a known released version string, i.e. from the `release` attribute below, the according release is picked, and the `version` attribute of the resulting derivation is set to this release string,
+  * if it is a majorMinor `"x.y"` prefix of a known released version (as defined above), then the latest `"x.y.z"` known released version is selected (for the ordering given by `versionAtLeast`),
+  * if it is a path or a string representing an absolute path (i.e. starting with `"/"`), the provided path is selected as a source, and the `version` attribute of the resulting derivation is set to `"dev"`,
+  * if it is a string of the form `owner:branch` then it tries to download the `branch` of owner `owner` for a project of the same name using the same vcs, and the `version` attribute of the resulting derivation is set to `"dev"`, additionally if the owner is not provided (i.e. if the `owner:` prefix is missing), it defaults to the original owner of the package (see below),
+  * if it is a string of the form `"#N"`, and the domain is github, then it tries to download the current head of the pull request `#N` from github,
+* `defaultVersion` (optional). Coq libraries may be compatible with some specific versions of Coq only. The `defaultVersion` attribute is used when no `version` is provided (or if `version = null`) to select the version of the library to use by default, depending on the context. This selection will mainly depend on a `coq` version number but also possibly on other packages versions (e.g. `mathcomp`). If its value ends up to be `null`, the package is marked for removal in end-user `coqPackages` attribute set.
+* `release` (optional, defaults to `{}`), lists all the known releases of the library and for each of them provides an attribute set with at least a `sha256` attribute (you may put the empty string `""` in order to automatically insert a fake sha256, this will trigger an error which will allow you to find the correct sha256), each attribute set of the list of releases also takes optional overloading arguments for the fetcher as below (i.e.`domain`, `owner`, `repo`, `rev` assuming the default fetcher is used) and optional overrides for the result of the fetcher (i.e. `version` and `src`).
+* `fetcher` (optional, defaults to a generic fetching mechanism supporting github or gitlab based infrastructures), is a function that takes at least an `owner`, a `repo`, a `rev`, and a `sha256` and returns an attribute set with a `version` and `src`.
+* `repo` (optional, defaults to the value of `pname`),
+* `owner` (optional, defaults to `"coq-community"`).
+* `domain` (optional, defaults to `"github.com"`), domains including the strings `"github"` or `"gitlab"` in their names are automatically supported, otherwise, one must change the `fetcher` argument to support them (cf `pkgs/development/coq-modules/heq/default.nix` for an example),
+* `releaseRev` (optional, defaults to `(v: v)`), provides a default mapping from release names to revision hashes/branch names/tags,
+* `displayVersion` (optional), provides a way to alter the computation of `name` from `pname`, by explaining how to display version numbers,
+* `namePrefix` (optional, defaults to `[ "coq" ]`), provides a way to alter the computation of `name` from `pname`, by explaining which dependencies must occur in `name`,
+* `extraNativeBuildInputs` (optional), by default `nativeBuildInputs` just contains `coq`, this allows to add more native build inputs, `nativeBuildInputs` are executables and `buildInputs` are libraries and dependencies,
+* `extraBuildInputs` (optional), this allows to add more build inputs,
+* `mlPlugin` (optional, defaults to `false`). Some extensions (plugins) might require OCaml and sometimes other OCaml packages. Standard dependencies can be added by setting the current option to `true`. For a finer grain control, the `coq.ocamlPackages` attribute can be used in `extraBuildInputs` to depend on the same package set Coq was built against.
+* `useDune2ifVersion` (optional, default to `(x: false)` uses Dune2 to build the package if the provided predicate evaluates to true on the version, e.g. `useDune2if = versions.isGe "1.1"`  will use dune if the version of the package is greater or equal to `"1.1"`,
+* `useDune2` (optional, defaults to `false`) uses Dune2 to build the package if set to true, the presence of this attribute overrides the behavior of the previous one.
+* `opam-name` (optional, defaults to concatenating with a dash separator the components of `namePrefix` and `pname`), name of the Dune package to build.
+* `enableParallelBuilding` (optional, defaults to `true`), since it is activated by default, we provide a way to disable it.
+* `extraInstallFlags` (optional), allows to extend `installFlags` which initializes the variable `COQMF_COQLIB` so as to install in the proper subdirectory. Indeed Coq libraries should be installed in `$(out)/lib/coq/${coq.coq-version}/user-contrib/`. Such directories are automatically added to the `$COQPATH` environment variable by the hook defined in the Coq derivation.
+* `setCOQBIN` (optional, defaults to `true`), by default, the environment variable `$COQBIN` is set to the current Coq's binary, but one can disable this behavior by setting it to `false`,
+* `useMelquiondRemake` (optional, default to `null`) is an attribute set, which, if given, overloads the `preConfigurePhases`, `configureFlags`, `buildPhase`, and `installPhase` attributes of the derivation for a specific use in libraries using `remake` as set up by Guillaume Melquiond for `flocq`, `gappalib`, `interval`, and `coquelicot` (see the corresponding derivation for concrete examples of use of this option). For backward compatibility, the attribute `useMelquiondRemake.logpath` must be set to the logical root of the library (otherwise, one can pass `useMelquiondRemake = {}` to activate this without backward compatibility).
+* `dropAttrs`, `keepAttrs`, `dropDerivationAttrs` are all optional and allow to tune which attribute is added or removed from the final call to `mkDerivation`.
+
+It also takes other standard `mkDerivation` attributes, they are added as such, except for `meta` which extends an automatically computed `meta` (where the `platform` is the same as `coq` and the homepage is automatically computed).
+
+Here is a simple package example. It is a pure Coq library, thus it depends on Coq. It builds on the Mathematical Components library, thus it also takes some `mathcomp` derivations as `extraBuildInputs`.
+
+```nix
+{ lib, mkCoqDerivation, version ? null
+, coq, mathcomp, mathcomp-finmap, mathcomp-bigenough }:
+with lib; mkCoqDerivation {
+  /* namePrefix leads to e.g. `name = coq8.11-mathcomp1.11-multinomials-1.5.2` */
+  namePrefix = [ "coq" "mathcomp" ];
+  pname = "multinomials";
+  owner = "math-comp";
+  inherit version;
+  defaultVersion =  with versions; switch [ coq.version mathcomp.version ] [
+      { cases = [ (range "8.7" "8.12")  "1.11.0" ];             out = "1.5.2"; }
+      { cases = [ (range "8.7" "8.11")  (range "1.8" "1.10") ]; out = "1.5.0"; }
+      { cases = [ (range "8.7" "8.10")  (range "1.8" "1.10") ]; out = "1.4"; }
+      { cases = [ "8.6"                 (range "1.6" "1.7") ];  out = "1.1"; }
+    ] null;
+  release = {
+    "1.5.2".sha256 = "15aspf3jfykp1xgsxf8knqkxv8aav2p39c2fyirw7pwsfbsv2c4s";
+    "1.5.1".sha256 = "13nlfm2wqripaq671gakz5mn4r0xwm0646araxv0nh455p9ndjs3";
+    "1.5.0".sha256 = "064rvc0x5g7y1a0nip6ic91vzmq52alf6in2bc2dmss6dmzv90hw";
+    "1.5.0".rev    = "1.5";
+    "1.4".sha256   = "0vnkirs8iqsv8s59yx1fvg1nkwnzydl42z3scya1xp1b48qkgn0p";
+    "1.3".sha256   = "0l3vi5n094nx3qmy66hsv867fnqm196r8v605kpk24gl0aa57wh4";
+    "1.2".sha256   = "1mh1w339dslgv4f810xr1b8v2w7rpx6fgk9pz96q0fyq49fw2xcq";
+    "1.1".sha256   = "1q8alsm89wkc0lhcvxlyn0pd8rbl2nnxg81zyrabpz610qqjqc3s";
+    "1.0".sha256   = "1qmbxp1h81cy3imh627pznmng0kvv37k4hrwi2faa101s6bcx55m";
+  };
+
+  propagatedBuildInputs =
+    [ mathcomp.ssreflect mathcomp.algebra mathcomp-finmap mathcomp-bigenough ];
+
+  meta = {
+    description = "A Coq/SSReflect Library for Monoidal Rings and Multinomials";
+    license = licenses.cecill-c;
+  };
+}
+```
diff --git a/doc/languages-frameworks/crystal.section.md b/doc/languages-frameworks/crystal.section.md
new file mode 100644
index 00000000000..cbabba24f0c
--- /dev/null
+++ b/doc/languages-frameworks/crystal.section.md
@@ -0,0 +1,73 @@
+# Crystal {#crystal}
+
+## Building a Crystal package {#building-a-crystal-package}
+
+This section uses [Mint](https://github.com/mint-lang/mint) as an example for how to build a Crystal package.
+
+If the Crystal project has any dependencies, the first step is to get a `shards.nix` file encoding those. Get a copy of the project and go to its root directory such that its `shard.lock` file is in the current directory. Executable projects should usually commit the `shard.lock` file, but sometimes that's not the case, which means you need to generate it yourself. With an existing `shard.lock` file, `crystal2nix` can be run.
+```bash
+$ git clone https://github.com/mint-lang/mint
+$ cd mint
+$ git checkout 0.5.0
+$ if [ ! -f shard.lock ]; then nix-shell -p shards --run "shards lock"; fi
+$ nix-shell -p crystal2nix --run crystal2nix
+```
+
+This should have generated a `shards.nix` file.
+
+Next create a Nix file for your derivation and use `pkgs.crystal.buildCrystalPackage` as follows:
+
+```nix
+with import <nixpkgs> {};
+crystal.buildCrystalPackage rec {
+  pname = "mint";
+  version = "0.5.0";
+
+  src = fetchFromGitHub {
+    owner = "mint-lang";
+    repo = "mint";
+    rev = version;
+    sha256 = "0vxbx38c390rd2ysvbwgh89v2232sh5rbsp3nk9wzb70jybpslvl";
+  };
+
+  # Insert the path to your shards.nix file here
+  shardsFile = ./shards.nix;
+
+  ...
+}
+```
+
+This won't build anything yet, because we haven't told it what files build. We can specify a mapping from binary names to source files with the `crystalBinaries` attribute. The project's compilation instructions should show this. For Mint, the binary is called "mint", which is compiled from the source file `src/mint.cr`, so we'll specify this as follows:
+
+```nix
+  crystalBinaries.mint.src = "src/mint.cr";
+
+  # ...
+```
+
+Additionally you can override the default `crystal build` options (which are currently `--release --progress --no-debug --verbose`) with
+
+```nix
+  crystalBinaries.mint.options = [ "--release" "--verbose" ];
+```
+
+Depending on the project, you might need additional steps to get it to compile successfully. In Mint's case, we need to link against openssl, so in the end the Nix file looks as follows:
+
+```nix
+with import <nixpkgs> {};
+crystal.buildCrystalPackage rec {
+  version = "0.5.0";
+  pname = "mint";
+  src = fetchFromGitHub {
+    owner = "mint-lang";
+    repo = "mint";
+    rev = version;
+    sha256 = "0vxbx38c390rd2ysvbwgh89v2232sh5rbsp3nk9wzb70jybpslvl";
+  };
+
+  shardsFile = ./shards.nix;
+  crystalBinaries.mint.src = "src/mint.cr";
+
+  buildInputs = [ openssl ];
+}
+```
diff --git a/doc/languages-frameworks/dhall.section.md b/doc/languages-frameworks/dhall.section.md
new file mode 100644
index 00000000000..4b49908b0b0
--- /dev/null
+++ b/doc/languages-frameworks/dhall.section.md
@@ -0,0 +1,463 @@
+# Dhall {#sec-language-dhall}
+
+The Nixpkgs support for Dhall assumes some familiarity with Dhall's language
+support for importing Dhall expressions, which is documented here:
+
+* [`dhall-lang.org` - Installing packages](https://docs.dhall-lang.org/tutorials/Language-Tour.html#installing-packages)
+
+## Remote imports {#ssec-dhall-remote-imports}
+
+Nixpkgs bypasses Dhall's support for remote imports using Dhall's
+semantic integrity checks.  Specifically, any Dhall import can be protected by
+an integrity check like:
+
+```dhall
+https://prelude.dhall-lang.org/v20.1.0/package.dhall
+  sha256:26b0ef498663d269e4dc6a82b0ee289ec565d683ef4c00d0ebdd25333a5a3c98
+```
+
+… and if the import is cached then the interpreter will load the import from
+cache instead of fetching the URL.
+
+Nixpkgs uses this trick to add all of a Dhall expression's dependencies into the
+cache so that the Dhall interpreter never needs to resolve any remote URLs.  In
+fact, Nixpkgs uses a Dhall interpreter with remote imports disabled when
+packaging Dhall expressions to enforce that the interpreter never resolves a
+remote import.  This means that Nixpkgs only supports building Dhall expressions
+if all of their remote imports are protected by semantic integrity checks.
+
+Instead of remote imports, Nixpkgs uses Nix to fetch remote Dhall code.  For
+example, the Prelude Dhall package uses `pkgs.fetchFromGitHub` to fetch the
+`dhall-lang` repository containing the Prelude.  Relying exclusively on Nix
+to fetch Dhall code ensures that Dhall packages built using Nix remain pure and
+also behave well when built within a sandbox.
+
+## Packaging a Dhall expression from scratch {#ssec-dhall-packaging-expression}
+
+We can illustrate how Nixpkgs integrates Dhall by beginning from the following
+trivial Dhall expression with one dependency (the Prelude):
+
+```dhall
+-- ./true.dhall
+
+let Prelude = https://prelude.dhall-lang.org/v20.1.0/package.dhall
+
+in  Prelude.Bool.not False
+```
+
+As written, this expression cannot be built using Nixpkgs because the
+expression does not protect the Prelude import with a semantic integrity
+check, so the first step is to freeze the expression using `dhall freeze`,
+like this:
+
+```ShellSession
+$ dhall freeze --inplace ./true.dhall
+```
+
+… which gives us:
+
+```dhall
+-- ./true.dhall
+
+let Prelude =
+      https://prelude.dhall-lang.org/v20.1.0/package.dhall
+        sha256:26b0ef498663d269e4dc6a82b0ee289ec565d683ef4c00d0ebdd25333a5a3c98
+
+in  Prelude.Bool.not False
+```
+
+To package that expression, we create a `./true.nix` file containing the
+following specification for the Dhall package:
+
+```nix
+# ./true.nix
+
+{ buildDhallPackage, Prelude }:
+
+buildDhallPackage {
+  name = "true";
+  code = ./true.dhall;
+  dependencies = [ Prelude ];
+  source = true;
+}
+```
+
+… and we complete the build by incorporating that Dhall package into the
+`pkgs.dhallPackages` hierarchy using an overlay, like this:
+
+```nix
+# ./example.nix
+
+let
+  nixpkgs = builtins.fetchTarball {
+    url    = "https://github.com/NixOS/nixpkgs/archive/94b2848559b12a8ed1fe433084686b2a81123c99.tar.gz";
+    sha256 = "1pbl4c2dsaz2lximgd31m96jwbps6apn3anx8cvvhk1gl9rkg107";
+  };
+
+  dhallOverlay = self: super: {
+    true = self.callPackage ./true.nix { };
+  };
+
+  overlay = self: super: {
+    dhallPackages = super.dhallPackages.override (old: {
+      overrides =
+        self.lib.composeExtensions (old.overrides or (_: _: {})) dhallOverlay;
+    });
+  };
+
+  pkgs = import nixpkgs { config = {}; overlays = [ overlay ]; };
+
+in
+  pkgs
+```
+
+… which we can then build using this command:
+
+```ShellSession
+$ nix build --file ./example.nix dhallPackages.true
+```
+
+## Contents of a Dhall package {#ssec-dhall-package-contents}
+
+The above package produces the following directory tree:
+
+```ShellSession
+$ tree -a ./result
+result
+├── .cache
+│   └── dhall
+│       └── 122027abdeddfe8503496adeb623466caa47da5f63abd2bc6fa19f6cfcb73ecfed70
+├── binary.dhall
+└── source.dhall
+```
+
+… where:
+
+* `source.dhall` contains the result of interpreting our Dhall package:
+
+  ```ShellSession
+  $ cat ./result/source.dhall
+  True
+  ```
+
+* The `.cache` subdirectory contains one binary cache product encoding the
+  same result as `source.dhall`:
+
+  ```ShellSession
+  $ dhall decode < ./result/.cache/dhall/122027abdeddfe8503496adeb623466caa47da5f63abd2bc6fa19f6cfcb73ecfed70
+  True
+  ```
+
+* `binary.dhall` contains a Dhall expression which handles fetching and decoding
+  the same cache product:
+
+  ```ShellSession
+  $ cat ./result/binary.dhall
+  missing sha256:27abdeddfe8503496adeb623466caa47da5f63abd2bc6fa19f6cfcb73ecfed70
+  $ cp -r ./result/.cache .cache
+
+  $ chmod -R u+w .cache
+
+  $ XDG_CACHE_HOME=.cache dhall --file ./result/binary.dhall
+  True
+  ```
+
+The `source.dhall` file is only present for packages that specify
+`source = true;`.  By default, Dhall packages omit the `source.dhall` in order
+to conserve disk space when they are used exclusively as dependencies.  For
+example, if we build the Prelude package it will only contain the binary
+encoding of the expression:
+
+```ShellSession
+$ nix build --file ./example.nix dhallPackages.Prelude
+
+$ tree -a result
+result
+├── .cache
+│   └── dhall
+│       └── 122026b0ef498663d269e4dc6a82b0ee289ec565d683ef4c00d0ebdd25333a5a3c98
+└── binary.dhall
+
+2 directories, 2 files
+```
+
+Typically, you only specify `source = true;` for the top-level Dhall expression
+of interest (such as our example `true.nix` Dhall package).  However, if you
+wish to specify `source = true` for all Dhall packages, then you can amend the
+Dhall overlay like this:
+
+```nix
+  dhallOverrides = self: super: {
+    # Enable source for all Dhall packages
+    buildDhallPackage =
+      args: super.buildDhallPackage (args // { source = true; });
+
+    true = self.callPackage ./true.nix { };
+  };
+```
+
+… and now the Prelude will contain the fully decoded result of interpreting
+the Prelude:
+
+```ShellSession
+$ nix build --file ./example.nix dhallPackages.Prelude
+
+$ tree -a result
+result
+├── .cache
+│   └── dhall
+│       └── 122026b0ef498663d269e4dc6a82b0ee289ec565d683ef4c00d0ebdd25333a5a3c98
+├── binary.dhall
+└── source.dhall
+
+$ cat ./result/source.dhall
+{ Bool =
+  { and =
+      \(_ : List Bool) ->
+        List/fold Bool _ Bool (\(_ : Bool) -> \(_ : Bool) -> _@1 && _) True
+  , build = \(_ : Type -> _ -> _@1 -> _@2) -> _ Bool True False
+  , even =
+      \(_ : List Bool) ->
+        List/fold Bool _ Bool (\(_ : Bool) -> \(_ : Bool) -> _@1 == _) True
+  , fold =
+      \(_ : Bool) ->
+…
+```
+
+## Packaging functions {#ssec-dhall-packaging-functions}
+
+We already saw an example of using `buildDhallPackage` to create a Dhall
+package from a single file, but most Dhall packages consist of more than one
+file and there are two derived utilities that you may find more useful when
+packaging multiple files:
+
+* `buildDhallDirectoryPackage` - build a Dhall package from a local directory
+
+* `buildDhallGitHubPackage` - build a Dhall package from a GitHub repository
+
+The `buildDhallPackage` is the lowest-level function and accepts the following
+arguments:
+
+* `name`: The name of the derivation
+
+* `dependencies`: Dhall dependencies to build and cache ahead of time
+
+* `code`: The top-level expression to build for this package
+
+  Note that the `code` field accepts an arbitrary Dhall expression.  You're
+  not limited to just a file.
+
+* `source`: Set to `true` to include the decoded result as `source.dhall` in the
+  build product, at the expense of requiring more disk space
+
+* `documentationRoot`: Set to the root directory of the package if you want
+  `dhall-docs` to generate documentation underneath the `docs` subdirectory of
+  the build product
+
+The `buildDhallDirectoryPackage` is a higher-level function implemented in terms
+of `buildDhallPackage` that accepts the following arguments:
+
+* `name`: Same as `buildDhallPackage`
+
+* `dependencies`: Same as `buildDhallPackage`
+
+* `source`: Same as `buildDhallPackage`
+
+* `src`: The directory containing Dhall code that you want to turn into a Dhall
+  package
+
+* `file`: The top-level file (`package.dhall` by default) that is the entrypoint
+  to the rest of the package
+
+* `document`: Set to `true` to generate documentation for the package
+
+The `buildDhallGitHubPackage` is another higher-level function implemented in
+terms of `buildDhallPackage` that accepts the following arguments:
+
+* `name`: Same as `buildDhallPackage`
+
+* `dependencies`: Same as `buildDhallPackage`
+
+* `source`: Same as `buildDhallPackage`
+
+* `owner`: The owner of the repository
+
+* `repo`: The repository name
+
+* `rev`: The desired revision (or branch, or tag)
+
+* `directory`: The subdirectory of the Git repository to package (if a
+  directory other than the root of the repository)
+
+* `file`: The top-level file (`${directory}/package.dhall` by default) that is
+  the entrypoint to the rest of the package
+
+* `document`: Set to `true` to generate documentation for the package
+
+Additionally, `buildDhallGitHubPackage` accepts the same arguments as
+`fetchFromGitHub`, such as `sha256` or `fetchSubmodules`.
+
+## `dhall-to-nixpkgs` {#ssec-dhall-dhall-to-nixpkgs}
+
+You can use the `dhall-to-nixpkgs` command-line utility to automate
+packaging Dhall code.  For example:
+
+```ShellSession
+$ nix-env --install --attr haskellPackages.dhall-nixpkgs
+
+$ nix-env --install --attr nix-prefetch-git  # Used by dhall-to-nixpkgs
+
+$ dhall-to-nixpkgs github https://github.com/Gabriel439/dhall-semver.git
+{ buildDhallGitHubPackage, Prelude }:
+  buildDhallGitHubPackage {
+    name = "dhall-semver";
+    githubBase = "github.com";
+    owner = "Gabriel439";
+    repo = "dhall-semver";
+    rev = "2d44ae605302ce5dc6c657a1216887fbb96392a4";
+    fetchSubmodules = false;
+    sha256 = "0y8shvp8srzbjjpmnsvz9c12ciihnx1szs0yzyi9ashmrjvd0jcz";
+    directory = "";
+    file = "package.dhall";
+    source = false;
+    document = false;
+    dependencies = [ (Prelude.overridePackage { file = "package.dhall"; }) ];
+    }
+```
+
+The utility takes care of automatically detecting remote imports and converting
+them to package dependencies.  You can also use the utility on local
+Dhall directories, too:
+
+```ShellSession
+$ dhall-to-nixpkgs directory ~/proj/dhall-semver
+{ buildDhallDirectoryPackage, Prelude }:
+  buildDhallDirectoryPackage {
+    name = "proj";
+    src = ~/proj/dhall-semver;
+    file = "package.dhall";
+    source = false;
+    document = false;
+    dependencies = [ (Prelude.overridePackage { file = "package.dhall"; }) ];
+    }
+```
+
+### Remote imports as fixed-output derivations {#ssec-dhall-remote-imports-as-fod}
+
+`dhall-to-nixpkgs` has the ability to fetch and build remote imports as
+fixed-output derivations by using their Dhall integrity check. This is
+sometimes easier than manually packaging all remote imports.
+
+This can be used like the following:
+
+```ShellSession
+$ dhall-to-nixpkgs directory --fixed-output-derivations ~/proj/dhall-semver
+{ buildDhallDirectoryPackage, buildDhallUrl }:
+  buildDhallDirectoryPackage {
+    name = "proj";
+    src = ~/proj/dhall-semver;
+    file = "package.dhall";
+    source = false;
+    document = false;
+    dependencies = [
+      (buildDhallUrl {
+        url = "https://prelude.dhall-lang.org/v17.0.0/package.dhall";
+        hash = "sha256-ENs8kZwl6QRoM9+Jeo/+JwHcOQ+giT2VjDQwUkvlpD4=";
+        dhallHash = "sha256:10db3c919c25e9046833df897a8ffe2701dc390fa0893d958c3430524be5a43e";
+        })
+      ];
+    }
+```
+
+Here, `dhall-semver`'s `Prelude` dependency is fetched and built with the
+`buildDhallUrl` helper function, instead of being passed in as a function
+argument.
+
+## Overriding dependency versions {#ssec-dhall-overriding-dependency-versions}
+
+Suppose that we change our `true.dhall` example expression to depend on an older
+version of the Prelude (19.0.0):
+
+```dhall
+-- ./true.dhall
+
+let Prelude =
+      https://prelude.dhall-lang.org/v19.0.0/package.dhall
+        sha256:eb693342eb769f782174157eba9b5924cf8ac6793897fc36a31ccbd6f56dafe2
+
+in  Prelude.Bool.not False
+```
+
+If we try to rebuild that expression the build will fail:
+
+```ShellSession
+$ nix build --file ./example.nix dhallPackages.true
+builder for '/nix/store/0f1hla7ff1wiaqyk1r2ky4wnhnw114fi-true.drv' failed with exit code 1; last 10 log lines:
+
+  Dhall was compiled without the 'with-http' flag.
+
+  The requested URL was: https://prelude.dhall-lang.org/v19.0.0/package.dhall
+
+
+  4│       https://prelude.dhall-lang.org/v19.0.0/package.dhall
+  5│         sha256:eb693342eb769f782174157eba9b5924cf8ac6793897fc36a31ccbd6f56dafe2
+
+  /nix/store/rsab4y99h14912h4zplqx2iizr5n4rc2-true.dhall:4:7
+[1 built (1 failed), 0.0 MiB DL]
+error: build of '/nix/store/0f1hla7ff1wiaqyk1r2ky4wnhnw114fi-true.drv' failed
+```
+
+… because the default Prelude selected by Nixpkgs revision
+`94b2848559b12a8ed1fe433084686b2a81123c99is` is version 20.1.0, which doesn't
+have the same integrity check as version 19.0.0.  This means that version
+19.0.0 is not cached and the interpreter is not allowed to fall back to
+importing the URL.
+
+However, we can override the default Prelude version by using `dhall-to-nixpkgs`
+to create a Dhall package for our desired Prelude:
+
+```ShellSession
+$ dhall-to-nixpkgs github https://github.com/dhall-lang/dhall-lang.git \
+    --name Prelude \
+    --directory Prelude \
+    --rev v19.0.0 \
+    > Prelude.nix
+```
+
+… and then referencing that package in our Dhall overlay, by either overriding
+the Prelude globally for all packages, like this:
+
+```nix
+  dhallOverrides = self: super: {
+    true = self.callPackage ./true.nix { };
+
+    Prelude = self.callPackage ./Prelude.nix { };
+  };
+```
+
+… or selectively overriding the Prelude dependency for just the `true` package,
+like this:
+
+```nix
+  dhallOverrides = self: super: {
+    true = self.callPackage ./true.nix {
+      Prelude = self.callPackage ./Prelude.nix { };
+    };
+  };
+```
+
+## Overrides {#ssec-dhall-overrides}
+
+You can override any of the arguments to `buildDhallGitHubPackage` or
+`buildDhallDirectoryPackage` using the `overridePackage` attribute of a package.
+For example, suppose we wanted to selectively enable `source = true` just for the Prelude.  We can do that like this:
+
+```nix
+  dhallOverrides = self: super: {
+    Prelude = super.Prelude.overridePackage { source = true; };
+
+    …
+  };
+```
+
+[semantic-integrity-checks]: https://docs.dhall-lang.org/tutorials/Language-Tour.html#installing-packages
diff --git a/doc/languages-frameworks/dotnet.section.md b/doc/languages-frameworks/dotnet.section.md
new file mode 100644
index 00000000000..f7af28a1677
--- /dev/null
+++ b/doc/languages-frameworks/dotnet.section.md
@@ -0,0 +1,132 @@
+# Dotnet {#dotnet}
+
+## Local Development Workflow {#local-development-workflow}
+
+For local development, it's recommended to use nix-shell to create a dotnet environment:
+
+```nix
+# shell.nix
+with import <nixpkgs> {};
+
+mkShell {
+  name = "dotnet-env";
+  packages = [
+    dotnet-sdk_3
+  ];
+}
+```
+
+### Using many sdks in a workflow {#using-many-sdks-in-a-workflow}
+
+It's very likely that more than one sdk will be needed on a given project. Dotnet provides several different frameworks (E.g dotnetcore, aspnetcore, etc.) as well as many versions for a given framework. Normally, dotnet is able to fetch a framework and install it relative to the executable. However, this would mean writing to the nix store in nixpkgs, which is read-only. To support the many-sdk use case, one can compose an environment using `dotnetCorePackages.combinePackages`:
+
+```nix
+with import <nixpkgs> {};
+
+mkShell {
+  name = "dotnet-env";
+  packages = [
+    (with dotnetCorePackages; combinePackages [
+      sdk_3_1
+      sdk_5_0
+    ])
+  ];
+}
+```
+
+This will produce a dotnet installation that has the dotnet 3.1, 3.0, and 2.1 sdk. The first sdk listed will have it's cli utility present in the resulting environment. Example info output:
+
+```ShellSession
+$ dotnet --info
+.NET Core SDK (reflecting any global.json):
+ Version:   3.1.101
+ Commit:    b377529961
+
+...
+
+.NET Core SDKs installed:
+  2.1.803 [/nix/store/iiv98i2jdi226dgh4jzkkj2ww7f8jgpd-dotnet-core-combined/sdk]
+  3.0.102 [/nix/store/iiv98i2jdi226dgh4jzkkj2ww7f8jgpd-dotnet-core-combined/sdk]
+  3.1.101 [/nix/store/iiv98i2jdi226dgh4jzkkj2ww7f8jgpd-dotnet-core-combined/sdk]
+
+.NET Core runtimes installed:
+  Microsoft.AspNetCore.All 2.1.15 [/nix/store/iiv98i2jdi226dgh4jzkkj2ww7f8jgpd-dotnet-core-combined/shared/Microsoft.AspNetCore.All]
+  Microsoft.AspNetCore.App 2.1.15 [/nix/store/iiv98i2jdi226dgh4jzkkj2ww7f8jgpd-dotnet-core-combined/shared/Microsoft.AspNetCore.App]
+  Microsoft.AspNetCore.App 3.0.2 [/nix/store/iiv98i2jdi226dgh4jzkkj2ww7f8jgpd-dotnet-core-combined/shared/Microsoft.AspNetCore.App]
+  Microsoft.AspNetCore.App 3.1.1 [/nix/store/iiv98i2jdi226dgh4jzkkj2ww7f8jgpd-dotnet-core-combined/shared/Microsoft.AspNetCore.App]
+  Microsoft.NETCore.App 2.1.15 [/nix/store/iiv98i2jdi226dgh4jzkkj2ww7f8jgpd-dotnet-core-combined/shared/Microsoft.NETCore.App]
+  Microsoft.NETCore.App 3.0.2 [/nix/store/iiv98i2jdi226dgh4jzkkj2ww7f8jgpd-dotnet-core-combined/shared/Microsoft.NETCore.App]
+  Microsoft.NETCore.App 3.1.1 [/nix/store/iiv98i2jdi226dgh4jzkkj2ww7f8jgpd-dotnet-core-combined/shared/Microsoft.NETCore.App]
+```
+
+## dotnet-sdk vs dotnetCorePackages.sdk {#dotnet-sdk-vs-dotnetcorepackages.sdk}
+
+The `dotnetCorePackages.sdk_X_Y` is preferred over the old dotnet-sdk as both major and minor version are very important for a dotnet environment. If a given minor version isn't present (or was changed), then this will likely break your ability to build a project.
+
+## dotnetCorePackages.sdk vs dotnetCorePackages.runtime vs dotnetCorePackages.aspnetcore {#dotnetcorepackages.sdk-vs-dotnetcorepackages.runtime-vs-dotnetcorepackages.aspnetcore}
+
+The `dotnetCorePackages.sdk` contains both a runtime and the full sdk of a given version. The `runtime` and `aspnetcore` packages are meant to serve as minimal runtimes to deploy alongside already built applications.
+
+## Packaging a Dotnet Application {#packaging-a-dotnet-application}
+
+To package Dotnet applications, you can use `buildDotnetModule`. This has similar arguments to `stdenv.mkDerivation`, with the following additions:
+
+* `projectFile` has to be used for specifying the dotnet project file relative to the source root. These usually have `.sln` or `.csproj` file extensions. This can be an array of multiple projects as well.
+* `nugetDeps` has to be used to specify the NuGet dependency file. Unfortunately, these cannot be deterministically fetched without a lockfile. A script to fetch these is available as `passthru.fetch-deps`. This file can also be generated manually using `nuget-to-nix` tool, which is available in nixpkgs.
+* `packNupkg` is used to pack project as a `nupkg`, and installs it to `$out/share`. If set to `true`, the derivation can be used as a dependency for another dotnet project by adding it to `projectReferences`.
+* `projectReferences` can be used to resolve `ProjectReference` project items. Referenced projects can be packed with `buildDotnetModule` by setting the `packNupkg = true` attribute and passing a list of derivations to `projectReferences`. Since we are sharing referenced projects as NuGets they must be added to csproj/fsproj files as `PackageReference` as well.
+ For example, your project has a local dependency:
+ ```xml
+     <ProjectReference Include="../foo/bar.fsproj" />
+ ```
+ To enable discovery through `projectReferences` you would need to add:
+ ```xml
+     <ProjectReference Include="../foo/bar.fsproj" />
+     <PackageReference Include="bar" Version="*" Condition=" '$(ContinuousIntegrationBuild)'=='true' "/>
+  ```
+* `executables` is used to specify which executables get wrapped to `$out/bin`, relative to `$out/lib/$pname`. If this is unset, all executables generated will get installed. If you do not want to install any, set this to `[]`. This gets done in the `preFixup` phase.
+* `runtimeDeps` is used to wrap libraries into `LD_LIBRARY_PATH`. This is how dotnet usually handles runtime dependencies.
+* `buildType` is used to change the type of build. Possible values are `Release`, `Debug`, etc. By default, this is set to `Release`.
+* `dotnet-sdk` is useful in cases where you need to change what dotnet SDK is being used.
+* `dotnet-runtime` is useful in cases where you need to change what dotnet runtime is being used. This can be either a regular dotnet runtime, or an aspnetcore.
+* `dotnet-test-sdk` is useful in cases where unit tests expect a different dotnet SDK. By default, this is set to the `dotnet-sdk` attribute.
+* `testProjectFile` is useful in cases where the regular project file does not contain the unit tests. It gets restored and build, but not installed. You may need to regenerate your nuget lockfile after setting this.
+* `disabledTests` is used to disable running specific unit tests. This gets passed as: `dotnet test --filter "FullyQualifiedName!={}"`, to ensure compatibility with all unit test frameworks.
+* `dotnetRestoreFlags` can be used to pass flags to `dotnet restore`.
+* `dotnetBuildFlags` can be used to pass flags to `dotnet build`.
+* `dotnetTestFlags` can be used to pass flags to `dotnet test`. Used only if `doCheck` is set to `true`.
+* `dotnetInstallFlags` can be used to pass flags to `dotnet install`.
+* `dotnetPackFlags` can be used to pass flags to `dotnet pack`. Used only if `packNupkg` is set to `true`.
+* `dotnetFlags` can be used to pass flags to all of the above phases.
+
+When packaging a new application, you need to fetch it's dependencies. You can set `nugetDeps` to an empty string to make the derivation temporarily evaluate, and then run `nix-build -A package.passthru.fetch-deps` to generate it's dependency fetching script. After running the script, you should have the location of the generated lockfile printed to the console. This can be copied to a stable directory. Note that if either `projectFile` or `nugetDeps` are unset, this script cannot be generated!
+
+Here is an example `default.nix`, using some of the previously discussed arguments:
+```nix
+{ lib, buildDotnetModule, dotnetCorePackages, ffmpeg }:
+
+let
+  referencedProject = import ../../bar { ... };
+in buildDotnetModule rec {
+  pname = "someDotnetApplication";
+  version = "0.1";
+
+  src = ./.;
+
+  projectFile = "src/project.sln";
+  nugetDeps = ./deps.nix; # File generated with `nix-build -A package.passthru.fetch-deps`.
+
+  projectReferences = [ referencedProject ]; # `referencedProject` must contain `nupkg` in the folder structure.
+
+  dotnet-sdk = dotnetCorePackages.sdk_3_1;
+  dotnet-runtime = dotnetCorePackages.net_5_0;
+  dotnetFlags = [ "--runtime linux-x64" ];
+
+  executables = [ "foo" ]; # This wraps "$out/lib/$pname/foo" to `$out/bin/foo`.
+  executables = []; # Don't install any executables.
+
+  packNupkg = true; # This packs the project as "foo-0.1.nupkg" at `$out/share`.
+
+  runtimeDeps = [ ffmpeg ]; # This will wrap ffmpeg's library path into `LD_LIBRARY_PATH`.
+}
+```
diff --git a/doc/languages-frameworks/emscripten.section.md b/doc/languages-frameworks/emscripten.section.md
new file mode 100644
index 00000000000..c96f689c4c0
--- /dev/null
+++ b/doc/languages-frameworks/emscripten.section.md
@@ -0,0 +1,182 @@
+# Emscripten {#emscripten}
+
+[Emscripten](https://github.com/kripken/emscripten): An LLVM-to-JavaScript Compiler
+
+This section of the manual covers how to use `emscripten` in nixpkgs.
+
+Minimal requirements:
+
+* nix
+* nixpkgs
+
+Modes of use of `emscripten`:
+
+* **Imperative usage** (on the command line):
+
+   If you want to work with `emcc`, `emconfigure` and `emmake` as you are used to from Ubuntu and similar distributions you can use these commands:
+
+    * `nix-env -f "<nixpkgs>" -iA emscripten`
+    * `nix-shell -p emscripten`
+
+* **Declarative usage**:
+
+    This mode is far more power full since this makes use of `nix` for dependency management of emscripten libraries and targets by using the `mkDerivation` which is implemented by `pkgs.emscriptenStdenv` and `pkgs.buildEmscriptenPackage`. The source for the packages is in `pkgs/top-level/emscripten-packages.nix` and the abstraction behind it in `pkgs/development/em-modules/generic/default.nix`. From the root of the nixpkgs repository:
+    * build and install all packages:
+        * `nix-env -iA emscriptenPackages`
+
+    * dev-shell for zlib implementation hacking:
+        * `nix-shell -A emscriptenPackages.zlib`
+
+## Imperative usage {#imperative-usage}
+
+A few things to note:
+
+* `export EMCC_DEBUG=2` is nice for debugging
+* `~/.emscripten`, the build artifact cache sometimes creates issues and needs to be removed from time to time
+
+## Declarative usage {#declarative-usage}
+
+Let's see two different examples from `pkgs/top-level/emscripten-packages.nix`:
+
+* `pkgs.zlib.override`
+* `pkgs.buildEmscriptenPackage`
+
+Both are interesting concepts.
+
+A special requirement of the `pkgs.buildEmscriptenPackage` is the `doCheck = true` is a default meaning that each emscriptenPackage requires a `checkPhase` implemented.
+
+* Use `export EMCC_DEBUG=2` from within a emscriptenPackage's `phase` to get more detailed debug output what is going wrong.
+* ~/.emscripten cache is requiring us to set `HOME=$TMPDIR` in individual phases. This makes compilation slower but also makes it more deterministic.
+
+### Usage 1: pkgs.zlib.override {#usage-1-pkgs.zlib.override}
+
+This example uses `zlib` from nixpkgs but instead of compiling **C** to **ELF** it compiles **C** to **JS** since we were using `pkgs.zlib.override` and changed stdenv to `pkgs.emscriptenStdenv`. A few adaptions and hacks were set in place to make it working. One advantage is that when `pkgs.zlib` is updated, it will automatically update this package as well. However, this can also be the downside...
+
+See the `zlib` example:
+
+    zlib = (pkgs.zlib.override {
+      stdenv = pkgs.emscriptenStdenv;
+    }).overrideDerivation
+    (old: rec {
+      buildInputs = old.buildInputs ++ [ pkg-config ];
+      # we need to reset this setting!
+      NIX_CFLAGS_COMPILE="";
+      configurePhase = ''
+        # FIXME: Some tests require writing at $HOME
+        HOME=$TMPDIR
+        runHook preConfigure
+
+        #export EMCC_DEBUG=2
+        emconfigure ./configure --prefix=$out --shared
+
+        runHook postConfigure
+      '';
+      dontStrip = true;
+      outputs = [ "out" ];
+      buildPhase = ''
+        emmake make
+      '';
+      installPhase = ''
+        emmake make install
+      '';
+      checkPhase = ''
+        echo "================= testing zlib using node ================="
+
+        echo "Compiling a custom test"
+        set -x
+        emcc -O2 -s EMULATE_FUNCTION_POINTER_CASTS=1 test/example.c -DZ_SOLO \
+        libz.so.${old.version} -I . -o example.js
+
+        echo "Using node to execute the test"
+        ${pkgs.nodejs}/bin/node ./example.js
+
+        set +x
+        if [ $? -ne 0 ]; then
+          echo "test failed for some reason"
+          exit 1;
+        else
+          echo "it seems to work! very good."
+        fi
+        echo "================= /testing zlib using node ================="
+      '';
+
+      postPatch = pkgs.lib.optionalString pkgs.stdenv.isDarwin ''
+        substituteInPlace configure \
+          --replace '/usr/bin/libtool' 'ar' \
+          --replace 'AR="libtool"' 'AR="ar"' \
+          --replace 'ARFLAGS="-o"' 'ARFLAGS="-r"'
+      '';
+    });
+
+### Usage 2: pkgs.buildEmscriptenPackage {#usage-2-pkgs.buildemscriptenpackage}
+
+This `xmlmirror` example features a emscriptenPackage which is defined completely from this context and no `pkgs.zlib.override` is used.
+
+    xmlmirror = pkgs.buildEmscriptenPackage rec {
+      name = "xmlmirror";
+
+      buildInputs = [ pkg-config autoconf automake libtool gnumake libxml2 nodejs openjdk json_c ];
+      nativeBuildInputs = [ pkg-config zlib ];
+
+      src = pkgs.fetchgit {
+        url = "https://gitlab.com/odfplugfest/xmlmirror.git";
+        rev = "4fd7e86f7c9526b8f4c1733e5c8b45175860a8fd";
+        sha256 = "1jasdqnbdnb83wbcnyrp32f36w3xwhwp0wq8lwwmhqagxrij1r4b";
+      };
+
+      configurePhase = ''
+        rm -f fastXmlLint.js*
+        # a fix for ERROR:root:For asm.js, TOTAL_MEMORY must be a multiple of 16MB, was 234217728
+        # https://gitlab.com/odfplugfest/xmlmirror/issues/8
+        sed -e "s/TOTAL_MEMORY=234217728/TOTAL_MEMORY=268435456/g" -i Makefile.emEnv
+        # https://github.com/kripken/emscripten/issues/6344
+        # https://gitlab.com/odfplugfest/xmlmirror/issues/9
+        sed -e "s/\$(JSONC_LDFLAGS) \$(ZLIB_LDFLAGS) \$(LIBXML20_LDFLAGS)/\$(JSONC_LDFLAGS) \$(LIBXML20_LDFLAGS) \$(ZLIB_LDFLAGS) /g" -i Makefile.emEnv
+        # https://gitlab.com/odfplugfest/xmlmirror/issues/11
+        sed -e "s/-o fastXmlLint.js/-s EXTRA_EXPORTED_RUNTIME_METHODS='[\"ccall\", \"cwrap\"]' -o fastXmlLint.js/g" -i Makefile.emEnv
+      '';
+
+      buildPhase = ''
+        HOME=$TMPDIR
+        make -f Makefile.emEnv
+      '';
+
+      outputs = [ "out" "doc" ];
+
+      installPhase = ''
+        mkdir -p $out/share
+        mkdir -p $doc/share/${name}
+
+        cp Demo* $out/share
+        cp -R codemirror-5.12 $out/share
+        cp fastXmlLint.js* $out/share
+        cp *.xsd $out/share
+        cp *.js $out/share
+        cp *.xhtml $out/share
+        cp *.html $out/share
+        cp *.json $out/share
+        cp *.rng $out/share
+        cp README.md $doc/share/${name}
+      '';
+      checkPhase = ''
+
+      '';
+    };
+
+### Declarative debugging {#declarative-debugging}
+
+Use `nix-shell -I nixpkgs=/some/dir/nixpkgs -A emscriptenPackages.libz` and from there you can go trough the individual steps. This makes it easy to build a good `unit test` or list the files of the project.
+
+1. `nix-shell -I nixpkgs=/some/dir/nixpkgs -A emscriptenPackages.libz`
+2. `cd /tmp/`
+3. `unpackPhase`
+4. cd libz-1.2.3
+5. `configurePhase`
+6. `buildPhase`
+7. ... happy hacking...
+
+## Summary {#summary}
+
+Using this toolchain makes it easy to leverage `nix` from NixOS, MacOSX or even Windows (WSL+ubuntu+nix). This toolchain is reproducible, behaves like the rest of the packages from nixpkgs and contains a set of well working examples to learn and adapt from.
+
+If in trouble, ask the maintainers.
diff --git a/doc/languages-frameworks/gnome.section.md b/doc/languages-frameworks/gnome.section.md
new file mode 100644
index 00000000000..29cb2e0e464
--- /dev/null
+++ b/doc/languages-frameworks/gnome.section.md
@@ -0,0 +1,204 @@
+# GNOME {#sec-language-gnome}
+
+## Packaging GNOME applications {#ssec-gnome-packaging}
+
+Programs in the GNOME universe are written in various languages but they all use GObject-based libraries like GLib, GTK or GStreamer. These libraries are often modular, relying on looking into certain directories to find their modules. However, due to Nix’s specific file system organization, this will fail without our intervention. Fortunately, the libraries usually allow overriding the directories through environment variables, either natively or thanks to a patch in nixpkgs. [Wrapping](#fun-wrapProgram) the executables to ensure correct paths are available to the application constitutes a significant part of packaging a modern desktop application. In this section, we will describe various modules needed by such applications, environment variables needed to make the modules load, and finally a script that will do the work for us.
+
+### Settings {#ssec-gnome-settings}
+
+[GSettings](https://developer.gnome.org/gio/stable/GSettings.html) API is often used for storing settings. GSettings schemas are required, to know the type and other metadata of the stored values. GLib looks for `glib-2.0/schemas/gschemas.compiled` files inside the directories of `XDG_DATA_DIRS`.
+
+On Linux, GSettings API is implemented using [dconf](https://wiki.gnome.org/Projects/dconf) backend. You will need to add `dconf` [GIO module](#ssec-gnome-gio-modules) to `GIO_EXTRA_MODULES` variable, otherwise the `memory` backend will be used and the saved settings will not be persistent.
+
+Last you will need the dconf database D-Bus service itself. You can enable it using `programs.dconf.enable`.
+
+Some applications will also require `gsettings-desktop-schemas` for things like reading proxy configuration or user interface customization. This dependency is often not mentioned by upstream, you should grep for `org.gnome.desktop` and `org.gnome.system` to see if the schemas are needed.
+
+### GIO modules {#ssec-gnome-gio-modules}
+
+GLib’s [GIO](https://developer.gnome.org/gio/stable/ch01.html) library supports several [extension points](https://developer.gnome.org/gio/stable/extending-gio.html). Notably, they allow:
+
+* implementing settings backends (already [mentioned](#ssec-gnome-settings))
+* adding TLS support
+* proxy settings
+* virtual file systems
+
+The modules are typically installed to `lib/gio/modules/` directory of a package and you need to add them to `GIO_EXTRA_MODULES` if you need any of those features.
+
+In particular, we recommend:
+
+* adding `dconf.lib` for any software on Linux that reads [GSettings](#ssec-gnome-settings) (even transitivily through e.g. GTK’s file manager)
+* adding `glib-networking` for any software that accesses network using GIO or libsoup – glib-networking contains a module that implements TLS support and loads system-wide proxy settings
+
+To allow software to use various virtual file systems, `gvfs` package can be also added. But that is usually an optional feature so we typically use `gvfs` from the system (e.g. installed globally using NixOS module).
+
+### GdkPixbuf loaders {#ssec-gnome-gdk-pixbuf-loaders}
+
+GTK applications typically use [GdkPixbuf](https://developer.gnome.org/gdk-pixbuf/stable/) to load images. But `gdk-pixbuf` package only supports basic bitmap formats like JPEG, PNG or TIFF, requiring to use third-party loader modules for other formats. This is especially painful since GTK itself includes SVG icons, which cannot be rendered without a loader provided by `librsvg`.
+
+Unlike other libraries mentioned in this section, GdkPixbuf only supports a single value in its controlling environment variable `GDK_PIXBUF_MODULE_FILE`. It is supposed to point to a cache file containing information about the available loaders. Each loader package will contain a `lib/gdk-pixbuf-2.0/2.10.0/loaders.cache` file describing the default loaders in `gdk-pixbuf` package plus the loader contained in the package itself. If you want to use multiple third-party loaders, you will need to create your own cache file manually. Fortunately, this is pretty rare as [not many loaders exist](https://gitlab.gnome.org/federico/gdk-pixbuf-survey/blob/master/src/modules.md).
+
+`gdk-pixbuf` contains [a setup hook](#ssec-gnome-hooks-gdk-pixbuf) that sets `GDK_PIXBUF_MODULE_FILE` from dependencies but as mentioned in further section, it is pretty limited. Loaders should propagate this setup hook.
+
+### Icons {#ssec-gnome-icons}
+
+When an application uses icons, an icon theme should be available in `XDG_DATA_DIRS` during runtime. The package for the default, icon-less [hicolor-icon-theme](https://www.freedesktop.org/wiki/Software/icon-theme/) (should be propagated by every icon theme) contains [a setup hook](#ssec-gnome-hooks-hicolor-icon-theme) that will pick up icon themes from `buildInputs` and pass it to our wrapper. Unfortunately, relying on that would mean every user has to download the theme included in the package expression no matter their preference. For that reason, we leave the installation of icon theme on the user. If you use one of the desktop environments, you probably already have an icon theme installed.
+
+To avoid costly file system access when locating icons, GTK, [as well as Qt](https://woboq.com/blog/qicon-reads-gtk-icon-cache-in-qt57.html), can rely on `icon-theme.cache` files from the themes' top-level directories. These files are generated using `gtk-update-icon-cache`, which is expected to be run whenever an icon is added or removed to an icon theme (typically an application icon into `hicolor` theme) and some programs do indeed run this after icon installation. However, since packages are installed into their own prefix by Nix, this would lead to conflicts. For that reason, `gtk3` provides a [setup hook](#ssec-gnome-hooks-gtk-drop-icon-theme-cache) that will clean the file from installation. Since most applications only ship their own icon that will be loaded on start-up, it should not affect them too much. On the other hand, icon themes are much larger and more widely used so we need to cache them. Because we recommend installing icon themes globally, we will generate the cache files from all packages in a profile using a NixOS module. You can enable the cache generation using `gtk.iconCache.enable` option if your desktop environment does not already do that.
+
+### Packaging icon themes {#ssec-icon-theme-packaging}
+
+Icon themes may inherit from other icon themes. The inheritance is specified using the `Inherits` key in the `index.theme` file distributed with the icon theme. According to the [icon theme specification](https://specifications.freedesktop.org/icon-theme-spec/icon-theme-spec-latest.html), icons not provided by the theme are looked for in its parent icon themes. Therefore the parent themes should be installed as dependencies for a more complete experience regarding the icon sets used.
+
+The package `hicolor-icon-theme` provides a setup hook which makes symbolic links for the parent themes into the directory `share/icons` of the current theme directory in the nix store, making sure they can be found at runtime. For that to work the packages providing parent icon themes should be listed as propagated build dependencies, together with `hicolor-icon-theme`.
+
+Also make sure that `icon-theme.cache` is installed for each theme provided by the package, and set `dontDropIconThemeCache` to `true` so that the cache file is not removed by the `gtk3` setup hook.
+
+### GTK Themes {#ssec-gnome-themes}
+
+Previously, a GTK theme needed to be in `XDG_DATA_DIRS`. This is no longer necessary for most programs since GTK incorporated Adwaita theme. Some programs (for example, those designed for [elementary HIG](https://elementary.io/docs/human-interface-guidelines#human-interface-guidelines)) might require a special theme like `pantheon.elementary-gtk-theme`.
+
+### GObject introspection typelibs {#ssec-gnome-typelibs}
+
+[GObject introspection](https://wiki.gnome.org/Projects/GObjectIntrospection) allows applications to use C libraries in other languages easily. It does this through `typelib` files searched in `GI_TYPELIB_PATH`.
+
+### Various plug-ins {#ssec-gnome-plugins}
+
+If your application uses [GStreamer](https://gstreamer.freedesktop.org/) or [Grilo](https://wiki.gnome.org/Projects/Grilo), you should set `GST_PLUGIN_SYSTEM_PATH_1_0` and `GRL_PLUGIN_PATH`, respectively.
+
+## Onto `wrapGAppsHook` {#ssec-gnome-hooks}
+
+Given the requirements above, the package expression would become messy quickly:
+
+```nix
+preFixup = ''
+  for f in $(find $out/bin/ $out/libexec/ -type f -executable); do
+    wrapProgram "$f" \
+      --prefix GIO_EXTRA_MODULES : "${getLib dconf}/lib/gio/modules" \
+      --prefix XDG_DATA_DIRS : "$out/share" \
+      --prefix XDG_DATA_DIRS : "$out/share/gsettings-schemas/${name}" \
+      --prefix XDG_DATA_DIRS : "${gsettings-desktop-schemas}/share/gsettings-schemas/${gsettings-desktop-schemas.name}" \
+      --prefix XDG_DATA_DIRS : "${hicolor-icon-theme}/share" \
+      --prefix GI_TYPELIB_PATH : "${lib.makeSearchPath "lib/girepository-1.0" [ pango json-glib ]}"
+  done
+'';
+```
+
+Fortunately, there is [`wrapGAppsHook`]{#ssec-gnome-hooks-wrapgappshook}. It works in conjunction with other setup hooks that populate environment variables, and it will then wrap all executables in `bin` and `libexec` directories using said variables.
+
+For convenience, it also adds `dconf.lib` for a GIO module implementing a GSettings backend using `dconf`, `gtk3` for GSettings schemas, and `librsvg` for GdkPixbuf loader to the closure. There is also [`wrapGAppsHook4`]{#ssec-gnome-hooks-wrapgappshook4}, which replaces GTK 3 with GTK 4. And in case you are packaging a program without a graphical interface, you might want to use [`wrapGAppsNoGuiHook`]{#ssec-gnome-hooks-wrapgappsnoguihook}, which runs the same script as `wrapGAppsHook` but does not bring `gtk3` and `librsvg` into the closure.
+
+- `wrapGAppsHook` itself will add the package’s `share` directory to `XDG_DATA_DIRS`.
+
+- []{#ssec-gnome-hooks-glib} `glib` setup hook will populate `GSETTINGS_SCHEMAS_PATH` and then `wrapGAppsHook` will prepend it to `XDG_DATA_DIRS`.
+
+- []{#ssec-gnome-hooks-gdk-pixbuf} `gdk-pixbuf` setup hook will populate `GDK_PIXBUF_MODULE_FILE` with the path to biggest `loaders.cache` file from the dependencies containing [GdkPixbuf loaders](#ssec-gnome-gdk-pixbuf-loaders). This works fine when there are only two packages containing loaders (`gdk-pixbuf` and e.g. `librsvg`) – it will choose the second one, reasonably expecting that it will be bigger since it describes extra loader in addition to the default ones. But when there are more than two loader packages, this logic will break. One possible solution would be constructing a custom cache file for each package containing a program like `services/x11/gdk-pixbuf.nix` NixOS module does. `wrapGAppsHook` copies the `GDK_PIXBUF_MODULE_FILE` environment variable into the produced wrapper.
+
+- []{#ssec-gnome-hooks-gtk-drop-icon-theme-cache} One of `gtk3`’s setup hooks will remove `icon-theme.cache` files from package’s icon theme directories to avoid conflicts. Icon theme packages should prevent this with `dontDropIconThemeCache = true;`.
+
+- []{#ssec-gnome-hooks-dconf} `dconf.lib` is a dependency of `wrapGAppsHook`, which then also adds it to the `GIO_EXTRA_MODULES` variable.
+
+- []{#ssec-gnome-hooks-hicolor-icon-theme} `hicolor-icon-theme`’s setup hook will add icon themes to `XDG_ICON_DIRS` which is prepended to `XDG_DATA_DIRS` by `wrapGAppsHook`.
+
+- []{#ssec-gnome-hooks-gobject-introspection} `gobject-introspection` setup hook populates `GI_TYPELIB_PATH` variable with `lib/girepository-1.0` directories of dependencies, which is then added to wrapper by `wrapGAppsHook`. It also adds `share` directories of dependencies to `XDG_DATA_DIRS`, which is intended to promote GIR files but it also [pollutes the closures](https://github.com/NixOS/nixpkgs/issues/32790) of packages using `wrapGAppsHook`.
+
+  ::: {.warning}
+  The setup hook [currently](https://github.com/NixOS/nixpkgs/issues/56943) does not work in expressions with `strictDeps` enabled, like Python packages. In those cases, you will need to disable it with `strictDeps = false;`.
+  :::
+
+- []{#ssec-gnome-hooks-gst-grl-plugins} Setup hooks of `gst_all_1.gstreamer` and `grilo` will populate the `GST_PLUGIN_SYSTEM_PATH_1_0` and `GRL_PLUGIN_PATH` variables, respectively, which will then be added to the wrapper by `wrapGAppsHook`.
+
+You can also pass additional arguments to `makeWrapper` using `gappsWrapperArgs` in `preFixup` hook:
+
+```nix
+preFixup = ''
+  gappsWrapperArgs+=(
+    # Thumbnailers
+    --prefix XDG_DATA_DIRS : "${gdk-pixbuf}/share"
+    --prefix XDG_DATA_DIRS : "${librsvg}/share"
+    --prefix XDG_DATA_DIRS : "${shared-mime-info}/share"
+  )
+'';
+```
+
+## Updating GNOME packages {#ssec-gnome-updating}
+
+Most GNOME package offer [`updateScript`](#var-passthru-updateScript), it is therefore possible to update to latest source tarball by running `nix-shell maintainers/scripts/update.nix --argstr package gnome.nautilus` or even en masse with `nix-shell maintainers/scripts/update.nix --argstr path gnome`. Read the package’s `NEWS` file to see what changed.
+
+## Frequently encountered issues {#ssec-gnome-common-issues}
+
+#### `GLib-GIO-ERROR **: 06:04:50.903: No GSettings schemas are installed on the system` {#ssec-gnome-common-issues-no-schemas}
+
+There are no schemas available in `XDG_DATA_DIRS`. Temporarily add a random package containing schemas like `gsettings-desktop-schemas` to `buildInputs`. [`glib`](#ssec-gnome-hooks-glib) and [`wrapGAppsHook`](#ssec-gnome-hooks-wrapgappshook) setup hooks will take care of making the schemas available to application and you will see the actual missing schemas with the [next error](#ssec-gnome-common-issues-missing-schema). Or you can try looking through the source code for the actual schemas used.
+
+#### `GLib-GIO-ERROR **: 06:04:50.903: Settings schema ‘org.gnome.foo’ is not installed` {#ssec-gnome-common-issues-missing-schema}
+
+Package is missing some GSettings schemas. You can find out the package containing the schema with `nix-locate org.gnome.foo.gschema.xml` and let the hooks handle the wrapping as [above](#ssec-gnome-common-issues-no-schemas).
+
+#### When using `wrapGAppsHook` with special derivers you can end up with double wrapped binaries. {#ssec-gnome-common-issues-double-wrapped}
+
+This is because derivers like `python.pkgs.buildPythonApplication` or `qt5.mkDerivation` have setup-hooks automatically added that produce wrappers with makeWrapper. The simplest way to workaround that is to disable the `wrapGAppsHook` automatic wrapping with `dontWrapGApps = true;` and pass the arguments it intended to pass to makeWrapper to another.
+
+In the case of a Python application it could look like:
+
+```nix
+python3.pkgs.buildPythonApplication {
+  pname = "gnome-music";
+  version = "3.32.2";
+
+  nativeBuildInputs = [
+    wrapGAppsHook
+    gobject-introspection
+    ...
+  ];
+
+  dontWrapGApps = true;
+
+  # Arguments to be passed to `makeWrapper`, only used by buildPython*
+  preFixup = ''
+    makeWrapperArgs+=("''${gappsWrapperArgs[@]}")
+  '';
+}
+```
+
+And for a QT app like:
+
+```nix
+mkDerivation {
+  pname = "calibre";
+  version = "3.47.0";
+
+  nativeBuildInputs = [
+    wrapGAppsHook
+    qmake
+    ...
+  ];
+
+  dontWrapGApps = true;
+
+  # Arguments to be passed to `makeWrapper`, only used by qt5’s mkDerivation
+  preFixup = ''
+    qtWrapperArgs+=("''${gappsWrapperArgs[@]}")
+  '';
+}
+```
+
+#### I am packaging a project that cannot be wrapped, like a library or GNOME Shell extension. {#ssec-gnome-common-issues-unwrappable-package}
+
+You can rely on applications depending on the library setting the necessary environment variables but that is often easy to miss. Instead we recommend to patch the paths in the source code whenever possible. Here are some examples:
+
+- []{#ssec-gnome-common-issues-unwrappable-package-gnome-shell-ext} [Replacing a `GI_TYPELIB_PATH` in GNOME Shell extension](https://github.com/NixOS/nixpkgs/blob/7bb8f05f12ca3cff9da72b56caa2f7472d5732bc/pkgs/desktops/gnome-3/core/gnome-shell-extensions/default.nix#L21-L24) – we are using `substituteAll` to include the path to a typelib into a patch.
+
+- []{#ssec-gnome-common-issues-unwrappable-package-gsettings} The following examples are hardcoding GSettings schema paths. To get the schema paths we use the functions
+
+  * `glib.getSchemaPath` Takes a nix package attribute as an argument.
+
+  * `glib.makeSchemaPath` Takes a package output like `$out` and a derivation name. You should use this if the schemas you need to hardcode are in the same derivation.
+
+  []{#ssec-gnome-common-issues-unwrappable-package-gsettings-vala} [Hard-coding GSettings schema path in Vala plug-in (dynamically loaded library)](https://github.com/NixOS/nixpkgs/blob/7bb8f05f12ca3cff9da72b56caa2f7472d5732bc/pkgs/desktops/pantheon/apps/elementary-files/default.nix#L78-L86) – here, `substituteAll` cannot be used since the schema comes from the same package preventing us from pass its path to the function, probably due to a [Nix bug](https://github.com/NixOS/nix/issues/1846).
+
+  []{#ssec-gnome-common-issues-unwrappable-package-gsettings-c} [Hard-coding GSettings schema path in C library](https://github.com/NixOS/nixpkgs/blob/29c120c065d03b000224872251bed93932d42412/pkgs/development/libraries/glib-networking/default.nix#L31-L34) – nothing special other than using [Coccinelle patch](https://github.com/NixOS/nixpkgs/pull/67957#issuecomment-527717467) to generate the patch itself.
+
+#### I need to wrap a binary outside `bin` and `libexec` directories. {#ssec-gnome-common-issues-weird-location}
+
+You can manually trigger the wrapping with `wrapGApp` in `preFixup` phase. It takes a path to a program as a first argument; the remaining arguments are passed directly to [`wrapProgram`](#fun-wrapProgram) function.
diff --git a/doc/languages-frameworks/go.section.md b/doc/languages-frameworks/go.section.md
new file mode 100644
index 00000000000..411205d08e4
--- /dev/null
+++ b/doc/languages-frameworks/go.section.md
@@ -0,0 +1,145 @@
+# Go {#sec-language-go}
+
+## Go modules {#ssec-language-go}
+
+The function `buildGoModule` builds Go programs managed with Go modules. It builds a [Go Modules](https://github.com/golang/go/wiki/Modules) through a two phase build:
+
+- An intermediate fetcher derivation. This derivation will be used to fetch all of the dependencies of the Go module.
+- A final derivation will use the output of the intermediate derivation to build the binaries and produce the final output.
+
+### Example for `buildGoModule` {#ex-buildGoModule}
+
+In the following is an example expression using `buildGoModule`, the following arguments are of special significance to the function:
+
+- `vendorSha256`: is the hash of the output of the intermediate fetcher derivation. `vendorSha256` can also take `null` as an input. When `null` is used as a value, rather than fetching the dependencies and vendoring them, we use the vendoring included within the source repo. If you'd like to not have to update this field on dependency changes, run `go mod vendor` in your source repo and set `vendorSha256 = null;`
+- `proxyVendor`: Fetches (go mod download) and proxies the vendor directory. This is useful if your code depends on c code and go mod tidy does not include the needed sources to build or if any dependency has case-insensitive conflicts which will produce platform dependant `vendorSha256` checksums.
+
+```nix
+pet = buildGoModule rec {
+  pname = "pet";
+  version = "0.3.4";
+
+  src = fetchFromGitHub {
+    owner = "knqyf263";
+    repo = "pet";
+    rev = "v${version}";
+    sha256 = "0m2fzpqxk7hrbxsgqplkg7h2p7gv6s1miymv3gvw0cz039skag0s";
+  };
+
+  vendorSha256 = "1879j77k96684wi554rkjxydrj8g3hpp0kvxz03sd8dmwr3lh83j";
+
+  meta = with lib; {
+    description = "Simple command-line snippet manager, written in Go";
+    homepage = "https://github.com/knqyf263/pet";
+    license = licenses.mit;
+    maintainers = with maintainers; [ kalbasit ];
+  };
+}
+```
+
+## `buildGoPackage` (legacy) {#ssec-go-legacy}
+
+The function `buildGoPackage` builds legacy Go programs, not supporting Go modules.
+
+### Example for `buildGoPackage` {#example-for-buildgopackage}
+
+In the following is an example expression using buildGoPackage, the following arguments are of special significance to the function:
+
+- `goPackagePath` specifies the package's canonical Go import path.
+- `goDeps` is where the Go dependencies of a Go program are listed as a list of package source identified by Go import path. It could be imported as a separate `deps.nix` file for readability. The dependency data structure is described below.
+
+```nix
+deis = buildGoPackage rec {
+  pname = "deis";
+  version = "1.13.0";
+
+  goPackagePath = "github.com/deis/deis";
+
+  src = fetchFromGitHub {
+    owner = "deis";
+    repo = "deis";
+    rev = "v${version}";
+    sha256 = "1qv9lxqx7m18029lj8cw3k7jngvxs4iciwrypdy0gd2nnghc68sw";
+  };
+
+  goDeps = ./deps.nix;
+}
+```
+
+The `goDeps` attribute can be imported from a separate `nix` file that defines which Go libraries are needed and should be included in `GOPATH` for `buildPhase`:
+
+```nix
+# deps.nix
+[ # goDeps is a list of Go dependencies.
+  {
+    # goPackagePath specifies Go package import path.
+    goPackagePath = "gopkg.in/yaml.v2";
+    fetch = {
+      # `fetch type` that needs to be used to get package source.
+      # If `git` is used there should be `url`, `rev` and `sha256` defined next to it.
+      type = "git";
+      url = "https://gopkg.in/yaml.v2";
+      rev = "a83829b6f1293c91addabc89d0571c246397bbf4";
+      sha256 = "1m4dsmk90sbi17571h6pld44zxz7jc4lrnl4f27dpd1l8g5xvjhh";
+    };
+  }
+  {
+    goPackagePath = "github.com/docopt/docopt-go";
+    fetch = {
+      type = "git";
+      url = "https://github.com/docopt/docopt-go";
+      rev = "784ddc588536785e7299f7272f39101f7faccc3f";
+      sha256 = "0wwz48jl9fvl1iknvn9dqr4gfy1qs03gxaikrxxp9gry6773v3sj";
+    };
+  }
+]
+```
+
+To extract dependency information from a Go package in automated way use [go2nix](https://github.com/kamilchm/go2nix). It can produce complete derivation and `goDeps` file for Go programs.
+
+You may use Go packages installed into the active Nix profiles by adding the following to your ~/.bashrc:
+
+```bash
+for p in $NIX_PROFILES; do
+    GOPATH="$p/share/go:$GOPATH"
+done
+```
+
+## Attributes used by the builders {#ssec-go-common-attributes}
+
+Both `buildGoModule` and `buildGoPackage` can be tweaked to behave slightly differently, if the following attributes are used:
+
+### `ldflags` {#var-go-ldflags}
+
+Arguments to pass to the Go linker tool via the `-ldflags` argument of `go build`. The most common use case for this argument is to make the resulting executable aware of its own version. For example:
+
+```nix
+  ldflags = [
+    "-s" "-w"
+    "-X main.Version=${version}"
+    "-X main.Commit=${version}"
+  ];
+```
+
+### `tags` {#var-go-tags}
+
+Arguments to pass to the Go via the `-tags` argument of `go build`. For example:
+
+```nix
+  tags = [
+    "production"
+    "sqlite"
+  ];
+```
+
+```nix
+  tags = [ "production" ] ++ lib.optionals withSqlite [ "sqlite" ];
+```
+
+### `deleteVendor` {#var-go-deleteVendor}
+
+Removes the pre-existing vendor directory. This should only be used if the dependencies included in the vendor folder are broken or incomplete.
+
+### `subPackages` {#var-go-subPackages}
+
+Limits the builder from building child packages that have not been listed. If `subPackages` is not specified, all child packages will be built.
diff --git a/doc/languages-frameworks/haskell.section.md b/doc/languages-frameworks/haskell.section.md
new file mode 100644
index 00000000000..1fda505a225
--- /dev/null
+++ b/doc/languages-frameworks/haskell.section.md
@@ -0,0 +1,7 @@
+# Haskell {#haskell}
+
+The documentation for the Haskell infrastructure is published at
+<https://haskell4nix.readthedocs.io/>. The source code for that
+site lives in the `doc/` sub-directory of the
+[`cabal2nix` Git repository](https://github.com/NixOS/cabal2nix)
+and changes can be submitted there.
diff --git a/doc/languages-frameworks/hy.section.md b/doc/languages-frameworks/hy.section.md
new file mode 100644
index 00000000000..a851ff24dfc
--- /dev/null
+++ b/doc/languages-frameworks/hy.section.md
@@ -0,0 +1,31 @@
+# Hy {#sec-language-hy}
+
+## Installation {#ssec-hy-installation}
+
+### Installation without packages {#installation-without-packages}
+
+You can install `hy` via nix-env or by adding it to `configuration.nix` by reffering to it as a `hy` attribute. This kind of installation adds `hy` to your environment and it succesfully works with `python3`.
+
+::: {.caution}
+Packages that are installed with your python derivation, are not accesible by `hy` this way.
+:::
+
+### Installation with packages {#installation-with-packages}
+
+Creating `hy` derivation with custom `python` packages is really simple and similar to the way that python does it. Attribute `hy` provides function `withPackages` that creates custom `hy` derivation with specified packages.
+
+For example if you want to create shell with `matplotlib` and `numpy`, you can do it like so:
+
+```ShellSession
+$ nix-shell -p "hy.withPackages (ps: with ps; [ numpy matplotlib ])"
+```
+
+Or if you want to extend your `configuration.nix`:
+```nix
+{ # ...
+
+  environment.systemPackages = with pkgs; [
+    (hy.withPackages (py-packages: with py-packages; [ numpy matplotlib ]))
+  ];
+}
+```
diff --git a/doc/languages-frameworks/idris.section.md b/doc/languages-frameworks/idris.section.md
new file mode 100644
index 00000000000..19146844cff
--- /dev/null
+++ b/doc/languages-frameworks/idris.section.md
@@ -0,0 +1,143 @@
+# Idris {#idris}
+
+## Installing Idris {#installing-idris}
+
+The easiest way to get a working idris version is to install the `idris` attribute:
+
+```ShellSession
+$ nix-env -f "<nixpkgs>" -iA idris
+```
+
+This however only provides the `prelude` and `base` libraries. To install idris with additional libraries, you can use the `idrisPackages.with-packages` function, e.g. in an overlay in `~/.config/nixpkgs/overlays/my-idris.nix`:
+
+```nix
+self: super: {
+  myIdris = with self.idrisPackages; with-packages [ contrib pruviloj ];
+}
+```
+
+And then:
+
+```ShellSession
+$ # On NixOS
+$ nix-env -iA nixos.myIdris
+$ # On non-NixOS
+$ nix-env -iA nixpkgs.myIdris
+```
+
+To see all available Idris packages:
+
+```ShellSession
+$ # On NixOS
+$ nix-env -qaPA nixos.idrisPackages
+$ # On non-NixOS
+$ nix-env -qaPA nixpkgs.idrisPackages
+```
+
+Similarly, entering a `nix-shell`:
+
+```ShellSession
+$ nix-shell -p 'idrisPackages.with-packages (with idrisPackages; [ contrib pruviloj ])'
+```
+
+## Starting Idris with library support {#starting-idris-with-library-support}
+
+To have access to these libraries in idris, call it with an argument `-p <library name>` for each library:
+
+```ShellSession
+$ nix-shell -p 'idrisPackages.with-packages (with idrisPackages; [ contrib pruviloj ])'
+[nix-shell:~]$ idris -p contrib -p pruviloj
+```
+
+A listing of all available packages the Idris binary has access to is available via `--listlibs`:
+
+```ShellSession
+$ idris --listlibs
+00prelude-idx.ibc
+pruviloj
+base
+contrib
+prelude
+00pruviloj-idx.ibc
+00base-idx.ibc
+00contrib-idx.ibc
+```
+
+## Building an Idris project with Nix {#building-an-idris-project-with-nix}
+
+As an example of how a Nix expression for an Idris package can be created, here is the one for `idrisPackages.yaml`:
+
+```nix
+{ lib
+, build-idris-package
+, fetchFromGitHub
+, contrib
+, lightyear
+}:
+build-idris-package  {
+  name = "yaml";
+  version = "2018-01-25";
+
+  # This is the .ipkg file that should be built, defaults to the package name
+  # In this case it should build `Yaml.ipkg` instead of `yaml.ipkg`
+  # This is only necessary because the yaml packages ipkg file is
+  # different from its package name here.
+  ipkgName = "Yaml";
+  # Idris dependencies to provide for the build
+  idrisDeps = [ contrib lightyear ];
+
+  src = fetchFromGitHub {
+    owner = "Heather";
+    repo = "Idris.Yaml";
+    rev = "5afa51ffc839844862b8316faba3bafa15656db4";
+    sha256 = "1g4pi0swmg214kndj85hj50ccmckni7piprsxfdzdfhg87s0avw7";
+  };
+
+  meta = with lib; {
+    description = "Idris YAML lib";
+    homepage = "https://github.com/Heather/Idris.Yaml";
+    license = licenses.mit;
+    maintainers = [ maintainers.brainrape ];
+  };
+}
+```
+
+Assuming this file is saved as `yaml.nix`, it's buildable using
+
+```ShellSession
+$ nix-build -E '(import <nixpkgs> {}).idrisPackages.callPackage ./yaml.nix {}'
+```
+
+Or it's possible to use
+
+```nix
+with import <nixpkgs> {};
+
+{
+  yaml = idrisPackages.callPackage ./yaml.nix {};
+}
+```
+
+in another file (say `default.nix`) to be able to build it with
+
+```ShellSession
+$ nix-build -A yaml
+```
+
+## Passing options to `idris` commands {#passing-options-to-idris-commands}
+
+The `build-idris-package` function provides also optional input values to set additional options for the used `idris` commands.
+
+Specifically, you can set `idrisBuildOptions`, `idrisTestOptions`, `idrisInstallOptions` and `idrisDocOptions` to provide additional options to the `idris` command respectively when building, testing, installing and generating docs for your package.
+
+For example you could set
+
+```nix
+build-idris-package {
+  idrisBuildOptions = [ "--log" "1" "--verbose" ]
+
+  ...
+}
+```
+
+to require verbose output during `idris` build phase.
diff --git a/doc/languages-frameworks/index.xml b/doc/languages-frameworks/index.xml
new file mode 100644
index 00000000000..f221693e764
--- /dev/null
+++ b/doc/languages-frameworks/index.xml
@@ -0,0 +1,40 @@
+<chapter xmlns="http://docbook.org/ns/docbook"
+         xmlns:xi="http://www.w3.org/2001/XInclude"
+         xml:id="chap-language-support">
+ <title>Languages and frameworks</title>
+ <para>
+  The <link linkend="chap-stdenv">standard build environment</link> makes it easy to build typical Autotools-based packages with very little code. Any other kind of package can be accomodated by overriding the appropriate phases of <literal>stdenv</literal>. However, there are specialised functions in Nixpkgs to easily build packages for other programming languages, such as Perl or Haskell. These are described in this chapter.
+ </para>
+ <xi:include href="agda.section.xml" />
+ <xi:include href="android.section.xml" />
+ <xi:include href="beam.section.xml" />
+ <xi:include href="bower.section.xml" />
+ <xi:include href="coq.section.xml" />
+ <xi:include href="crystal.section.xml" />
+ <xi:include href="dhall.section.xml" />
+ <xi:include href="dotnet.section.xml" />
+ <xi:include href="emscripten.section.xml" />
+ <xi:include href="gnome.section.xml" />
+ <xi:include href="go.section.xml" />
+ <xi:include href="haskell.section.xml" />
+ <xi:include href="hy.section.xml" />
+ <xi:include href="idris.section.xml" />
+ <xi:include href="ios.section.xml" />
+ <xi:include href="java.section.xml" />
+ <xi:include href="javascript.section.xml" />
+ <xi:include href="lua.section.xml" />
+ <xi:include href="maven.section.xml" />
+ <xi:include href="nim.section.xml" />
+ <xi:include href="ocaml.section.xml" />
+ <xi:include href="octave.section.xml" />
+ <xi:include href="perl.section.xml" />
+ <xi:include href="php.section.xml" />
+ <xi:include href="python.section.xml" />
+ <xi:include href="qt.section.xml" />
+ <xi:include href="r.section.xml" />
+ <xi:include href="ruby.section.xml" />
+ <xi:include href="rust.section.xml" />
+ <xi:include href="texlive.section.xml" />
+ <xi:include href="titanium.section.xml" />
+ <xi:include href="vim.section.xml" />
+</chapter>
diff --git a/doc/languages-frameworks/ios.section.md b/doc/languages-frameworks/ios.section.md
new file mode 100644
index 00000000000..04b013be12e
--- /dev/null
+++ b/doc/languages-frameworks/ios.section.md
@@ -0,0 +1,225 @@
+# iOS {#ios}
+
+This component is basically a wrapper/workaround that makes it possible to
+expose an Xcode installation as a Nix package by means of symlinking to the
+relevant executables on the host system.
+
+Since Xcode can't be packaged with Nix, nor we can publish it as a Nix package
+(because of its license) this is basically the only integration strategy
+making it possible to do iOS application builds that integrate with other
+components of the Nix ecosystem
+
+The primary objective of this project is to use the Nix expression language to
+specify how iOS apps can be built from source code, and to automatically spawn
+iOS simulator instances for testing.
+
+This component also makes it possible to use [Hydra](https://nixos.org/hydra),
+the Nix-based continuous integration server to regularly build iOS apps and to
+do wireless ad-hoc installations of enterprise IPAs on iOS devices through
+Hydra.
+
+The Xcode build environment implements a number of features.
+
+## Deploying a proxy component wrapper exposing Xcode {#deploying-a-proxy-component-wrapper-exposing-xcode}
+
+The first use case is deploying a Nix package that provides symlinks to the Xcode
+installation on the host system. This package can be used as a build input to
+any build function implemented in the Nix expression language that requires
+Xcode.
+
+```nix
+let
+  pkgs = import <nixpkgs> {};
+
+  xcodeenv = import ./xcodeenv {
+    inherit (pkgs) stdenv;
+  };
+in
+xcodeenv.composeXcodeWrapper {
+  version = "9.2";
+  xcodeBaseDir = "/Applications/Xcode.app";
+}
+```
+
+By deploying the above expression with `nix-build` and inspecting its content
+you will notice that several Xcode-related executables are exposed as a Nix
+package:
+
+```bash
+$ ls result/bin
+lrwxr-xr-x  1 sander  staff  94  1 jan  1970 Simulator -> /Applications/Xcode.app/Contents/Developer/Applications/Simulator.app/Contents/MacOS/Simulator
+lrwxr-xr-x  1 sander  staff  17  1 jan  1970 codesign -> /usr/bin/codesign
+lrwxr-xr-x  1 sander  staff  17  1 jan  1970 security -> /usr/bin/security
+lrwxr-xr-x  1 sander  staff  21  1 jan  1970 xcode-select -> /usr/bin/xcode-select
+lrwxr-xr-x  1 sander  staff  61  1 jan  1970 xcodebuild -> /Applications/Xcode.app/Contents/Developer/usr/bin/xcodebuild
+lrwxr-xr-x  1 sander  staff  14  1 jan  1970 xcrun -> /usr/bin/xcrun
+```
+
+## Building an iOS application {#building-an-ios-application}
+
+We can build an iOS app executable for the simulator, or an IPA/xcarchive file
+for release purposes, e.g. ad-hoc, enterprise or store installations, by
+executing the `xcodeenv.buildApp {}` function:
+
+```nix
+let
+  pkgs = import <nixpkgs> {};
+
+  xcodeenv = import ./xcodeenv {
+    inherit (pkgs) stdenv;
+  };
+in
+xcodeenv.buildApp {
+  name = "MyApp";
+  src = ./myappsources;
+  sdkVersion = "11.2";
+
+  target = null; # Corresponds to the name of the app by default
+  configuration = null; # Release for release builds, Debug for debug builds
+  scheme = null; # -scheme will correspond to the app name by default
+  sdk = null; # null will set it to 'iphonesimulator` for simulator builds or `iphoneos` to real builds
+  xcodeFlags = "";
+
+  release = true;
+  certificateFile = ./mycertificate.p12;
+  certificatePassword = "secret";
+  provisioningProfile = ./myprovisioning.profile;
+  signMethod = "ad-hoc"; # 'enterprise' or 'store'
+  generateIPA = true;
+  generateXCArchive = false;
+
+  enableWirelessDistribution = true;
+  installURL = "/installipa.php";
+  bundleId = "mycompany.myapp";
+  appVersion = "1.0";
+
+  # Supports all xcodewrapper parameters as well
+  xcodeBaseDir = "/Applications/Xcode.app";
+}
+```
+
+The above function takes a variety of parameters:
+
+* The `name` and `src` parameters are mandatory and specify the name of the app
+  and the location where the source code resides
+* `sdkVersion` specifies which version of the iOS SDK to use.
+
+It also possile to adjust the `xcodebuild` parameters. This is only needed in
+rare circumstances. In most cases the default values should suffice:
+
+* Specifies which `xcodebuild` target to build. By default it takes the target
+  that has the same name as the app.
+* The `configuration` parameter can be overridden if desired. By default, it
+  will do a debug build for the simulator and a release build for real devices.
+* The `scheme` parameter specifies which `-scheme` parameter to propagate to
+  `xcodebuild`. By default, it corresponds to the app name.
+* The `sdk` parameter specifies which SDK to use. By default, it picks
+  `iphonesimulator` for simulator builds and `iphoneos` for release builds.
+* The `xcodeFlags` parameter specifies arbitrary command line parameters that
+  should be propagated to `xcodebuild`.
+
+By default, builds are carried out for the iOS simulator. To do release builds
+(builds for real iOS devices), you must set the `release` parameter to `true`.
+In addition, you need to set the following parameters:
+
+* `certificateFile` refers to a P12 certificate file.
+* `certificatePassword` specifies the password of the P12 certificate.
+* `provisioningProfile` refers to the provision profile needed to sign the app
+* `signMethod` should refer to `ad-hoc` for signing the app with an ad-hoc
+  certificate, `enterprise` for enterprise certificates and `app-store` for App
+  store certificates.
+* `generateIPA` specifies that we want to produce an IPA file (this is probably
+  what you want)
+* `generateXCArchive` specifies thet we want to produce an xcarchive file.
+
+When building IPA files on Hydra and when it is desired to allow iOS devices to
+install IPAs by browsing to the Hydra build products page, you can enable the
+`enableWirelessDistribution` parameter.
+
+When enabled, you need to configure the following options:
+
+* The `installURL` parameter refers to the URL of a PHP script that composes the
+  `itms-services://` URL allowing iOS devices to install the IPA file.
+* `bundleId` refers to the bundle ID value of the app
+* `appVersion` refers to the app's version number
+
+To use wireless adhoc distributions, you must also install the corresponding
+PHP script on a web server (see section: 'Installing the PHP script for wireless
+ad hoc installations from Hydra' for more information).
+
+In addition to the build parameters, you can also specify any parameters that
+the `xcodeenv.composeXcodeWrapper {}` function takes. For example, the
+`xcodeBaseDir` parameter can be overridden to refer to a different Xcode
+version.
+
+## Spawning simulator instances {#spawning-simulator-instances}
+
+In addition to building iOS apps, we can also automatically spawn simulator
+instances:
+
+```nix
+let
+  pkgs = import <nixpkgs> {};
+
+  xcodeenv = import ./xcodeenv {
+    inherit (pkgs) stdenv;
+  };
+in
+xcode.simulateApp {
+  name = "simulate";
+
+  # Supports all xcodewrapper parameters as well
+  xcodeBaseDir = "/Applications/Xcode.app";
+}
+```
+
+The above expression produces a script that starts the simulator from the
+provided Xcode installation. The script can be started as follows:
+
+```bash
+./result/bin/run-test-simulator
+```
+
+By default, the script will show an overview of UDID for all available simulator
+instances and asks you to pick one. You can also provide a UDID as a
+command-line parameter to launch an instance automatically:
+
+```bash
+./result/bin/run-test-simulator 5C93129D-CF39-4B1A-955F-15180C3BD4B8
+```
+
+You can also extend the simulator script to automatically deploy and launch an
+app in the requested simulator instance:
+
+```nix
+let
+  pkgs = import <nixpkgs> {};
+
+  xcodeenv = import ./xcodeenv {
+    inherit (pkgs) stdenv;
+  };
+in
+xcode.simulateApp {
+  name = "simulate";
+  bundleId = "mycompany.myapp";
+  app = xcode.buildApp {
+    # ...
+  };
+
+  # Supports all xcodewrapper parameters as well
+  xcodeBaseDir = "/Applications/Xcode.app";
+}
+```
+
+By providing the result of an `xcode.buildApp {}` function and configuring the
+app bundle id, the app gets deployed automatically and started.
+
+## Troubleshooting {#troubleshooting}
+
+In some rare cases, it may happen that after a failure, changes are not picked
+up. Most likely, this is caused by a derived data cache that Xcode maintains.
+To wipe it you can run:
+
+```bash
+$ rm -rf ~/Library/Developer/Xcode/DerivedData
+```
diff --git a/doc/languages-frameworks/java.section.md b/doc/languages-frameworks/java.section.md
new file mode 100644
index 00000000000..371bdf6323f
--- /dev/null
+++ b/doc/languages-frameworks/java.section.md
@@ -0,0 +1,100 @@
+# Java {#sec-language-java}
+
+Ant-based Java packages are typically built from source as follows:
+
+```nix
+stdenv.mkDerivation {
+  name = "...";
+  src = fetchurl { ... };
+
+  nativeBuildInputs = [ jdk ant ];
+
+  buildPhase = "ant";
+}
+```
+
+Note that `jdk` is an alias for the OpenJDK (self-built where available,
+or pre-built via Zulu). Platforms with OpenJDK not (yet) in Nixpkgs
+(`Aarch32`, `Aarch64`) point to the (unfree) `oraclejdk`.
+
+JAR files that are intended to be used by other packages should be
+installed in `$out/share/java`. JDKs have a stdenv setup hook that add
+any JARs in the `share/java` directories of the build inputs to the
+`CLASSPATH` environment variable. For instance, if the package `libfoo`
+installs a JAR named `foo.jar` in its `share/java` directory, and
+another package declares the attribute
+
+```nix
+buildInputs = [ libfoo ];
+nativeBuildInputs = [ jdk ];
+```
+
+then `CLASSPATH` will be set to
+`/nix/store/...-libfoo/share/java/foo.jar`.
+
+Private JARs should be installed in a location like
+`$out/share/package-name`.
+
+If your Java package provides a program, you need to generate a wrapper
+script to run it using a JRE. You can use `makeWrapper` for this:
+
+```nix
+nativeBuildInputs = [ makeWrapper ];
+
+installPhase = ''
+  mkdir -p $out/bin
+  makeWrapper ${jre}/bin/java $out/bin/foo \
+    --add-flags "-cp $out/share/java/foo.jar org.foo.Main"
+'';
+```
+
+Since the introduction of the Java Platform Module System in Java 9,
+Java distributions typically no longer ship with a general-purpose JRE:
+instead, they allow generating a JRE with only the modules required for
+your application(s). Because we can't predict what modules will be
+needed on a general-purpose system, the default jre package is the full
+JDK. When building a minimal system/image, you can override the
+`modules` parameter on `jre_minimal` to build a JRE with only the
+modules relevant for you:
+
+```nix
+let
+  my_jre = pkgs.jre_minimal.override {
+    modules = [
+      # The modules used by 'something' and 'other' combined:
+      "java.base"
+      "java.logging"
+    ];
+  };
+  something = (pkgs.something.override { jre = my_jre; });
+  other = (pkgs.other.override { jre = my_jre; });
+in
+  ...
+```
+
+You can also specify what JDK your JRE should be based on, for example
+selecting a 'headless' build to avoid including a link to GTK+:
+
+```nix
+my_jre = pkgs.jre_minimal.override {
+  jdk = jdk11_headless;
+};
+```
+
+Note all JDKs passthru `home`, so if your application requires
+environment variables like `JAVA_HOME` being set, that can be done in a
+generic fashion with the `--set` argument of `makeWrapper`:
+
+```bash
+--set JAVA_HOME ${jdk.home}
+```
+
+It is possible to use a different Java compiler than `javac` from the
+OpenJDK. For instance, to use the GNU Java Compiler:
+
+```nix
+nativeBuildInputs = [ gcj ant ];
+```
+
+Here, Ant will automatically use `gij` (the GNU Java Runtime) instead of
+the OpenJRE.
diff --git a/doc/languages-frameworks/javascript.section.md b/doc/languages-frameworks/javascript.section.md
new file mode 100644
index 00000000000..bf5742d6855
--- /dev/null
+++ b/doc/languages-frameworks/javascript.section.md
@@ -0,0 +1,256 @@
+# Javascript {#language-javascript}
+
+## Introduction {#javascript-introduction}
+
+This contains instructions on how to package javascript applications.
+
+The various tools available will be listed in the [tools-overview](#javascript-tools-overview). Some general principles for packaging will follow. Finally some tool specific instructions will be given.
+
+## Getting unstuck / finding code examples
+
+If you find you are lacking inspiration for packing javascript applications, the links below might prove useful.
+Searching online for prior art can be helpful if you are running into solved problems.
+
+### Github
+
+- Searching Nix files for `mkYarnPackage`: <https://github.com/search?q=mkYarnPackage+language%3ANix&type=code>
+
+- Searching just `flake.nix` files for `mkYarnPackage`: <https://github.com/search?q=mkYarnPackage+filename%3Aflake.nix&type=code>
+
+### Gitlab
+
+- Searching Nix files for `mkYarnPackage`: <https://gitlab.com/search?scope=blobs&search=mkYarnPackage+extension%3Anix>
+
+- Searching just `flake.nix` files for `mkYarnPackage`: <https://gitlab.com/search?scope=blobs&search=mkYarnPackage+filename%3Aflake.nix>
+
+## Tools overview {#javascript-tools-overview}
+
+## General principles {#javascript-general-principles}
+
+The following principles are given in order of importance with potential exceptions.
+
+### Try to use the same node version used upstream {#javascript-upstream-node-version}
+
+It is often not documented which node version is used upstream, but if it is, try to use the same version when packaging.
+
+This can be a problem if upstream is using the latest and greatest and you are trying to use an earlier version of node. Some cryptic errors regarding V8 may appear.
+
+An exception to this:
+
+### Try to respect the package manager originally used by upstream (and use the upstream lock file) {#javascript-upstream-package-manager}
+
+A lock file (package-lock.json, yarn.lock...) is supposed to make reproducible installations of node_modules for each tool.
+
+Guidelines of package managers, recommend to commit those lock files to the repos. If a particular lock file is present, it is a strong indication of which package manager is used upstream.
+
+It's better to try to use a nix tool that understand the lock file. Using a different tool might give you hard to understand error because different packages have been installed. An example of problems that could arise can be found [here](https://github.com/NixOS/nixpkgs/pull/126629). Upstream uses npm, but this is an attempt to package it with yarn2nix (that uses yarn.lock)
+
+Using a different tool forces to commit a lock file to the repository. Those files are fairly large, so when packaging for nixpkgs, this approach does not scale well.
+
+Exceptions to this rule are:
+
+- when you encounter one of the bugs from a nix tool. In each of the tool specific instructions, known problems will be detailed. If you have a problem with a particular tool, then it's best to try another tool, even if this means you will have to recreate a lock file and commit it to nixpkgs. In general yarn2nix has less known problems and so a simple search in nixpkgs will reveal many yarn.lock files committed
+- Some lock files contain particular version of a package that has been pulled off npm for some reason. In that case, you can recreate upstream lock (by removing the original and `npm install`, `yarn`, ...) and commit this to nixpkgs.
+- The only tool that supports workspaces (a feature of npm that helps manage sub-directories with different package.json from a single top level package.json) is yarn2nix. If upstream has workspaces you should try yarn2nix.
+
+### Try to use upstream package.json {#javascript-upstream-package-json}
+
+Exceptions to this rule are
+
+- Sometimes the upstream repo assumes some dependencies be installed globally. In that case you can add them manually to the upstream package.json (`yarn add xxx` or `npm install xxx`, ...). Dependencies that are installed locally can be executed with `npx` for cli tools. (e.g. `npx postcss ...`, this is how you can call those dependencies in the phases).
+- Sometimes there is a version conflict between some dependency requirements. In that case you can fix a version (by removing the `^`).
+- Sometimes the script defined in the package.json does not work as is. Some scripts for example use cli tools that might not be available, or cd in directory with a different package.json (for workspaces notably). In that case, it's perfectly fine to look at what the particular script is doing and break this down in the phases. In the build script you can see `build:*` calling in turns several other build scripts like `build:ui` or `build:server`. If one of those fails, you can try to separate those into:
+
+```Shell
+yarn build:ui
+yarn build:server
+# OR
+npm run build:ui
+npm run build:server
+```
+
+when you need to override a package.json. It's nice to use the one from the upstream src and do some explicit override. Here is an example.
+
+```nix
+patchedPackageJSON = final.runCommand "package.json" { } ''
+  ${jq}/bin/jq '.version = "0.4.0" |
+    .devDependencies."@jsdoc/cli" = "^0.2.5"
+    ${sonar-src}/package.json > $out
+'';
+```
+
+you will still need to commit the modified version of the lock files, but at least the overrides are explicit for everyone to see.
+
+### Using node_modules directly {#javascript-using-node_modules}
+
+each tool has an abstraction to just build the node_modules (dependencies) directory. you can always use the stdenv.mkDerivation with the node_modules to build the package (symlink the node_modules directory and then use the package build command). the node_modules abstraction can be also used to build some web framework frontends. For an example of this see how [plausible](https://github.com/NixOS/nixpkgs/blob/master/pkgs/servers/web-apps/plausible/default.nix) is built. mkYarnModules to make the derivation containing node_modules. Then when building the frontend you can just symlink the node_modules directory
+
+## javascript packages inside nixpkgs {#javascript-packages-nixpkgs}
+
+The `pkgs/development/node-packages` folder contains a generated collection of
+[NPM packages](https://npmjs.com/) that can be installed with the Nix package
+manager.
+
+As a rule of thumb, the package set should only provide _end user_ software
+packages, such as command-line utilities. Libraries should only be added to the
+package set if there is a non-NPM package that requires it.
+
+When it is desired to use NPM libraries in a development project, use the
+`node2nix` generator directly on the `package.json` configuration file of the
+project.
+
+The package set provides support for the official stable Node.js versions.
+The latest stable LTS release in `nodePackages`, as well as the latest stable
+Current release in `nodePackages_latest`.
+
+If your package uses native addons, you need to examine what kind of native
+build system it uses. Here are some examples:
+
+- `node-gyp`
+- `node-gyp-builder`
+- `node-pre-gyp`
+
+After you have identified the correct system, you need to override your package
+expression while adding in build system as a build input. For example, `dat`
+requires `node-gyp-build`, so [we override](https://github.com/NixOS/nixpkgs/blob/32f5e5da4a1b3f0595527f5195ac3a91451e9b56/pkgs/development/node-packages/default.nix#L37-L40) its expression in [`default.nix`](https://github.com/NixOS/nixpkgs/blob/master/pkgs/development/node-packages/default.nix):
+
+```nix
+    dat = super.dat.override {
+      buildInputs = [ self.node-gyp-build pkgs.libtool pkgs.autoconf pkgs.automake ];
+      meta.broken = since "12";
+    };
+```
+
+To add a package from NPM to nixpkgs:
+
+1. Modify `pkgs/development/node-packages/node-packages.json` to add, update
+    or remove package entries to have it included in `nodePackages` and
+    `nodePackages_latest`.
+2. Run the script: `cd pkgs/development/node-packages && ./generate.sh`.
+3. Build your new package to test your changes:
+    `cd /path/to/nixpkgs && nix-build -A nodePackages.<new-or-updated-package>`.
+    To build against the latest stable Current Node.js version (e.g. 14.x):
+    `nix-build -A nodePackages_latest.<new-or-updated-package>`
+4. Add and commit all modified and generated files.
+
+For more information about the generation process, consult the
+[README.md](https://github.com/svanderburg/node2nix) file of the `node2nix`
+tool.
+
+## Tool specific instructions {#javascript-tool-specific}
+
+### node2nix {#javascript-node2nix}
+
+#### Preparation {#javascript-node2nix-preparation}
+
+you will need to generate a nix expression for the dependencies
+
+- don't forget the `-l package-lock.json` if there is a lock file
+- Most probably you will need the `--development` to include the `devDependencies`
+
+so the command will most likely be
+`node2nix --development -l package-lock.json`
+
+[link to the doc in the repo](https://github.com/svanderburg/node2nix)
+
+#### Pitfalls {#javascript-node2nix-pitfalls}
+
+- if upstream package.json does not have a "version" attribute, node2nix will crash. You will need to add it like shown in [the package.json section](#javascript-upstream-package-json)
+- node2nix has some [bugs](https://github.com/svanderburg/node2nix/issues/238). related to working with lock files from npm distributed with nodejs-16_x
+- node2nix does not like missing packages from npm. If you see something like `Cannot resolve version: vue-loader-v16@undefined` then you might want to try another tool. The package might have been pulled off of npm.
+
+### yarn2nix {#javascript-yarn2nix}
+
+#### Preparation {#javascript-yarn2nix-preparation}
+
+you will need at least a yarn.lock and yarn.nix file
+
+- generate a yarn.lock in upstream if it is not already there
+- `yarn2nix > yarn.nix` will generate the dependencies in a nix format
+
+#### mkYarnPackage {#javascript-yarn2nix-mkYarnPackage}
+
+this will by default try to generate a binary. For package only generating static assets (Svelte, Vue, React...), you will need to explicitly override the build step with your instructions. It's important to use the `--offline` flag. For example if you script is `"build": "something"` in package.json use
+
+```nix
+buildPhase = ''
+  yarn build --offline
+'';
+```
+
+The dist phase is also trying to build a binary, the only way to override it is with
+
+```nix
+distPhase = "true";
+```
+
+the configure phase can sometimes fail because it tries to be too clever.
+One common override is
+
+```nix
+configurePhase = "ln -s $node_modules node_modules";
+```
+
+#### mkYarnModules {#javascript-yarn2nix-mkYarnModules}
+
+this will generate a derivation including the node_modules. If you have to build a derivation for an integrated web framework (rails, phoenix..), this is probably the easiest way. [Plausible](https://github.com/NixOS/nixpkgs/blob/master/pkgs/servers/web-apps/plausible/default.nix#L39) offers a good example of how to do this.
+
+#### Overriding dependency behavior
+
+In the `mkYarnPackage` record the property `pkgConfig` can be used to override packages when you encounter problems building.
+
+For instance, say your package is throwing errors when trying to invoke node-sass: `ENOENT: no such file or directory, scandir '/build/source/node_modules/node-sass/vendor'`
+
+To fix this we will specify different versions of build inputs to use, as well as some post install steps to get the software built the way we want:
+
+```nix
+mkYarnPackage rec {
+  pkgConfig = {
+    node-sass = {
+      buildInputs = with final;[ python libsass pkg-config ];
+      postInstall = ''
+        LIBSASS_EXT=auto yarn --offline run build
+        rm build/config.gypi
+      '';
+    };
+  };
+}
+```
+
+#### Pitfalls {#javascript-yarn2nix-pitfalls}
+
+- if version is missing from upstream package.json, yarn will silently install nothing. In that case, you will need to override package.json as shown in the [package.json section](#javascript-upstream-package-json)
+
+- having trouble with node-gyp? Try adding these lines to the `yarnPreBuild` steps:
+
+  ```nix
+  yarnPreBuild = ''
+    mkdir -p $HOME/.node-gyp/${nodejs.version}
+    echo 9 > $HOME/.node-gyp/${nodejs.version}/installVersion
+    ln -sfv ${nodejs}/include $HOME/.node-gyp/${nodejs.version}
+    export npm_config_nodedir=${nodejs}
+  '';
+  ```
+
+  - The `echo 9` steps comes from this answer: <https://stackoverflow.com/a/49139496>
+  - Exporting the headers in `npm_config_nodedir` comes from this issue: <https://github.com/nodejs/node-gyp/issues/1191#issuecomment-301243919>
+
+## Outside of nixpkgs {#javascript-outside-nixpkgs}
+
+There are some other options available that can't be used inside nixpkgs. Those other options are written in nix. Importing them in nixpkgs will require moving the source code into nixpkgs. Using [Import From Derivation](https://nixos.wiki/wiki/Import_From_Derivation) is not allowed in hydra at present. If you are packaging something outside nixpkgs, those can be considered
+
+### npmlock2nix {#javascript-npmlock2nix}
+
+[npmlock2nix](https://github.com/nix-community/npmlock2nix) aims at building node_modules without code generation. It hasn't reached v1 yet, the api might be subject to change.
+
+#### Pitfalls {#javascript-npmlock2nix-pitfalls}
+
+- there are some [problems with npm v7](https://github.com/tweag/npmlock2nix/issues/45).
+
+### nix-npm-buildpackage {#javascript-nix-npm-buildpackage}
+
+[nix-npm-buildpackage](https://github.com/serokell/nix-npm-buildpackage) aims at building node_modules without code generation. It hasn't reached v1 yet, the api might change. It supports both package-lock.json and yarn.lock.
+
+#### Pitfalls {#javascript-nix-npm-buildpackage-pitfalls}
+
+- there are some [problems with npm v7](https://github.com/serokell/nix-npm-buildpackage/issues/33).
diff --git a/doc/languages-frameworks/lua.section.md b/doc/languages-frameworks/lua.section.md
new file mode 100644
index 00000000000..17b80f07d3e
--- /dev/null
+++ b/doc/languages-frameworks/lua.section.md
@@ -0,0 +1,253 @@
+# User’s Guide to Lua Infrastructure {#users-guide-to-lua-infrastructure}
+
+## Using Lua {#using-lua}
+
+### Overview of Lua {#overview-of-lua}
+
+Several versions of the Lua interpreter are available: luajit, lua 5.1, 5.2, 5.3.
+The attribute `lua` refers to the default interpreter, it is also possible to refer to specific versions, e.g. `lua5_2` refers to Lua 5.2.
+
+Lua libraries are in separate sets, with one set per interpreter version.
+
+The interpreters have several common attributes. One of these attributes is
+`pkgs`, which is a package set of Lua libraries for this specific
+interpreter. E.g., the `busted` package corresponding to the default interpreter
+is `lua.pkgs.busted`, and the lua 5.2 version is `lua5_2.pkgs.busted`.
+The main package set contains aliases to these package sets, e.g.
+`luaPackages` refers to `lua5_1.pkgs` and `lua52Packages` to
+`lua5_2.pkgs`.
+
+### Installing Lua and packages {#installing-lua-and-packages}
+
+#### Lua environment defined in separate `.nix` file {#lua-environment-defined-in-separate-.nix-file}
+
+Create a file, e.g. `build.nix`, with the following expression
+
+```nix
+with import <nixpkgs> {};
+
+lua5_2.withPackages (ps: with ps; [ busted luafilesystem ])
+```
+
+and install it in your profile with
+
+```shell
+nix-env -if build.nix
+```
+Now you can use the Lua interpreter, as well as the extra packages (`busted`,
+`luafilesystem`) that you added to the environment.
+
+#### Lua environment defined in `~/.config/nixpkgs/config.nix` {#lua-environment-defined-in-.confignixpkgsconfig.nix}
+
+If you prefer to, you could also add the environment as a package override to the Nixpkgs set, e.g.
+using `config.nix`,
+
+```nix
+{ # ...
+
+  packageOverrides = pkgs: with pkgs; {
+    myLuaEnv = lua5_2.withPackages (ps: with ps; [ busted luafilesystem ]);
+  };
+}
+```
+
+and install it in your profile with
+
+```shell
+nix-env -iA nixpkgs.myLuaEnv
+```
+The environment is installed by referring to the attribute, and considering
+the `nixpkgs` channel was used.
+
+#### Lua environment defined in `/etc/nixos/configuration.nix` {#lua-environment-defined-in-etcnixosconfiguration.nix}
+
+For the sake of completeness, here's another example how to install the environment system-wide.
+
+```nix
+{ # ...
+
+  environment.systemPackages = with pkgs; [
+    (lua.withPackages(ps: with ps; [ busted luafilesystem ]))
+  ];
+}
+```
+
+### How to override a Lua package using overlays? {#how-to-override-a-lua-package-using-overlays}
+
+Use the following overlay template:
+
+```nix
+final: prev:
+{
+
+  lua = prev.lua.override {
+    packageOverrides = luaself: luaprev: {
+
+      luarocks-nix = luaprev.luarocks-nix.overrideAttrs(oa: {
+        pname = "luarocks-nix";
+        src = /home/my_luarocks/repository;
+      });
+  };
+
+  luaPackages = lua.pkgs;
+}
+```
+
+### Temporary Lua environment with `nix-shell` {#temporary-lua-environment-with-nix-shell}
+
+
+There are two methods for loading a shell with Lua packages. The first and recommended method
+is to create an environment with `lua.buildEnv` or `lua.withPackages` and load that. E.g.
+
+```sh
+$ nix-shell -p 'lua.withPackages(ps: with ps; [ busted luafilesystem ])'
+```
+
+opens a shell from which you can launch the interpreter
+
+```sh
+[nix-shell:~] lua
+```
+
+The other method, which is not recommended, does not create an environment and requires you to list the packages directly,
+
+```sh
+$ nix-shell -p lua.pkgs.busted lua.pkgs.luafilesystem
+```
+Again, it is possible to launch the interpreter from the shell.
+The Lua interpreter has the attribute `pkgs` which contains all Lua libraries for that specific interpreter.
+
+
+## Developing with Lua {#developing-with-lua}
+
+Now that you know how to get a working Lua environment with Nix, it is time
+to go forward and start actually developing with Lua. There are two ways to
+package lua software, either it is on luarocks and most of it can be taken care
+of by the luarocks2nix converter or the packaging has to be done manually.
+Let's present the luarocks way first and the manual one in a second time.
+
+### Packaging a library on luarocks {#packaging-a-library-on-luarocks}
+
+[Luarocks.org](https://luarocks.org/) is the main repository of lua packages.
+The site proposes two types of packages, the rockspec and the src.rock
+(equivalent of a [rockspec](https://github.com/luarocks/luarocks/wiki/Rockspec-format) but with the source).
+These packages can have different build types such as `cmake`, `builtin` etc .
+
+Luarocks-based packages are generated in pkgs/development/lua-modules/generated-packages.nix from
+the whitelist maintainers/scripts/luarocks-packages.csv and updated by running maintainers/scripts/update-luarocks-packages.
+
+[luarocks2nix](https://github.com/nix-community/luarocks) is a tool capable of generating nix derivations from both rockspec and src.rock (and favors the src.rock).
+The automation only goes so far though and some packages need to be customized.
+These customizations go in `pkgs/development/lua-modules/overrides.nix`.
+For instance if the rockspec defines `external_dependencies`, these need to be manually added to the overrides.nix.
+
+You can try converting luarocks packages to nix packages with the command `nix-shell -p luarocks-nix` and then `luarocks nix PKG_NAME`.
+
+#### Packaging a library manually {#packaging-a-library-manually}
+
+You can develop your package as you usually would, just don't forget to wrap it
+within a `toLuaModule` call, for instance
+
+```nix
+mynewlib = toLuaModule ( stdenv.mkDerivation { ... });
+```
+
+There is also the `buildLuaPackage` function that can be used when lua modules
+are not packaged for luarocks. You can see a few examples at `pkgs/top-level/lua-packages.nix`.
+
+## Lua Reference {#lua-reference}
+
+### Lua interpreters {#lua-interpreters}
+
+Versions 5.1, 5.2, 5.3 and 5.4 of the lua interpreter are available as
+respectively `lua5_1`, `lua5_2`, `lua5_3` and `lua5_4`. Luajit is available too.
+The Nix expressions for the interpreters can be found in `pkgs/development/interpreters/lua-5`.
+
+#### Attributes on lua interpreters packages {#attributes-on-lua-interpreters-packages}
+
+Each interpreter has the following attributes:
+
+- `interpreter`. Alias for `${pkgs.lua}/bin/lua`.
+- `buildEnv`. Function to build lua interpreter environments with extra packages bundled together. See section *lua.buildEnv function* for usage and documentation.
+- `withPackages`. Simpler interface to `buildEnv`.
+- `pkgs`. Set of Lua packages for that specific interpreter. The package set can be modified by overriding the interpreter and passing `packageOverrides`.
+
+#### `buildLuarocksPackage` function {#buildluarockspackage-function}
+
+The `buildLuarocksPackage` function is implemented in `pkgs/development/interpreters/lua-5/build-lua-package.nix`
+The following is an example:
+```nix
+luaposix = buildLuarocksPackage {
+  pname = "luaposix";
+  version = "34.0.4-1";
+
+  src = fetchurl {
+    url    = "https://raw.githubusercontent.com/rocks-moonscript-org/moonrocks-mirror/master/luaposix-34.0.4-1.src.rock";
+    sha256 = "0yrm5cn2iyd0zjd4liyj27srphvy0gjrjx572swar6zqr4dwjqp2";
+  };
+  disabled = (luaOlder "5.1") || (luaAtLeast "5.4");
+  propagatedBuildInputs = [ bit32 lua std_normalize ];
+
+  meta = with lib; {
+    homepage = "https://github.com/luaposix/luaposix/";
+    description = "Lua bindings for POSIX";
+    maintainers = with maintainers; [ vyp lblasc ];
+    license.fullName = "MIT/X11";
+  };
+};
+```
+
+The `buildLuarocksPackage` delegates most tasks to luarocks:
+
+* it adds `luarocks` as an unpacker for `src.rock` files (zip files really).
+* configurePhase` writes a temporary luarocks configuration file which location
+is exported via the environment variable `LUAROCKS_CONFIG`.
+* the `buildPhase` does nothing.
+* `installPhase` calls `luarocks make --deps-mode=none --tree $out` to build and
+install the package
+* In the `postFixup` phase, the `wrapLuaPrograms` bash function is called to
+  wrap all programs in the `$out/bin/*` directory to include `$PATH`
+  environment variable and add dependent libraries to script's `LUA_PATH` and
+  `LUA_CPATH`.
+
+By default `meta.platforms` is set to the same value as the interpreter unless overridden otherwise.
+
+#### `buildLuaApplication` function {#buildluaapplication-function}
+
+The `buildLuaApplication` function is practically the same as `buildLuaPackage`.
+The difference is that `buildLuaPackage` by default prefixes the names of the packages with the version of the interpreter.
+Because with an application we're not interested in multiple version the prefix is dropped.
+
+#### lua.withPackages function {#lua.withpackages-function}
+
+The `lua.withPackages` takes a function as an argument that is passed the set of lua packages and returns the list of packages to be included in the environment.
+Using the `withPackages` function, the previous example for the luafilesystem environment can be written like this:
+
+```nix
+with import <nixpkgs> {};
+
+lua.withPackages (ps: [ps.luafilesystem])
+```
+
+`withPackages` passes the correct package set for the specific interpreter version as an argument to the function. In the above example, `ps` equals `luaPackages`.
+But you can also easily switch to using `lua5_2`:
+
+```nix
+with import <nixpkgs> {};
+
+lua5_2.withPackages (ps: [ps.lua])
+```
+
+Now, `ps` is set to `lua52Packages`, matching the version of the interpreter.
+
+### Possible Todos {#possible-todos}
+
+* export/use version specific variables such as `LUA_PATH_5_2`/`LUAROCKS_CONFIG_5_2`
+* let luarocks check for dependencies via exporting the different rocktrees in temporary config
+
+### Lua Contributing guidelines {#lua-contributing-guidelines}
+
+Following rules should be respected:
+
+* Make sure libraries build for all Lua interpreters.
+* Commit names of Lua libraries should reflect that they are Lua libraries, so write for example `luaPackages.luafilesystem: 1.11 -> 1.12`.
diff --git a/doc/languages-frameworks/maven.section.md b/doc/languages-frameworks/maven.section.md
new file mode 100644
index 00000000000..f53a6fa8ac2
--- /dev/null
+++ b/doc/languages-frameworks/maven.section.md
@@ -0,0 +1,351 @@
+# Maven {#maven}
+
+Maven is a well-known build tool for the Java ecosystem however it has some challenges when integrating into the Nix build system.
+
+The following provides a list of common patterns with how to package a Maven project (or any JVM language that can export to Maven) as a Nix package.
+
+For the purposes of this example let's consider a very basic Maven project with the following `pom.xml` with a single dependency on [emoji-java](https://github.com/vdurmont/emoji-java).
+
+```xml
+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+        xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+  <modelVersion>4.0.0</modelVersion>
+  <groupId>io.github.fzakaria</groupId>
+  <artifactId>maven-demo</artifactId>
+  <version>1.0</version>
+  <packaging>jar</packaging>
+  <name>NixOS Maven Demo</name>
+
+  <dependencies>
+    <dependency>
+        <groupId>com.vdurmont</groupId>
+        <artifactId>emoji-java</artifactId>
+        <version>5.1.1</version>
+      </dependency>
+  </dependencies>
+</project>
+```
+
+Our main class file will be very simple:
+
+```java
+import com.vdurmont.emoji.EmojiParser;
+
+public class Main {
+  public static void main(String[] args) {
+    String str = "NixOS :grinning: is super cool :smiley:!";
+    String result = EmojiParser.parseToUnicode(str);
+    System.out.println(result);
+  }
+}
+```
+
+You find this demo project at https://github.com/fzakaria/nixos-maven-example
+
+## Solving for dependencies {#solving-for-dependencies}
+
+### buildMaven with NixOS/mvn2nix-maven-plugin {#buildmaven-with-nixosmvn2nix-maven-plugin}
+
+> ⚠️ Although `buildMaven` is the "blessed" way within nixpkgs, as of 2020, it hasn't seen much activity in quite a while.
+
+`buildMaven` is an alternative method that tries to follow similar patterns of other programming languages by generating a lock file. It relies on the maven plugin [mvn2nix-maven-plugin](https://github.com/NixOS/mvn2nix-maven-plugin).
+
+First you generate a `project-info.json` file using the maven plugin.
+
+> This should be executed in the project's source repository or be told which `pom.xml` to execute with.
+
+```bash
+# run this step within the project's source repository
+❯ mvn org.nixos.mvn2nix:mvn2nix-maven-plugin:mvn2nix
+
+❯ cat project-info.json | jq | head
+{
+  "project": {
+    "artifactId": "maven-demo",
+    "groupId": "org.nixos",
+    "version": "1.0",
+    "classifier": "",
+    "extension": "jar",
+    "dependencies": [
+      {
+        "artifactId": "maven-resources-plugin",
+```
+
+This file is then given to the `buildMaven` function, and it returns 2 attributes.
+
+**`repo`**:
+    A Maven repository that is a symlink farm of all the dependencies found in the `project-info.json`
+
+
+**`build`**:
+    A simple derivation that runs through `mvn compile` & `mvn package` to build the JAR. You may use this as inspiration for more complicated derivations.
+
+Here is an [example](https://github.com/fzakaria/nixos-maven-example/blob/main/build-maven-repository.nix) of building the Maven repository
+
+```nix
+{ pkgs ? import <nixpkgs> { } }:
+with pkgs;
+(buildMaven ./project-info.json).repo
+```
+
+The benefit over the _double invocation_ as we will see below, is that the _/nix/store_ entry is a _linkFarm_ of every package, so that changes to your dependency set doesn't involve downloading everything from scratch.
+
+```bash
+❯ tree $(nix-build --no-out-link build-maven-repository.nix) | head
+/nix/store/g87va52nkc8jzbmi1aqdcf2f109r4dvn-maven-repository
+├── antlr
+│   └── antlr
+│       └── 2.7.2
+│           ├── antlr-2.7.2.jar -> /nix/store/d027c8f2cnmj5yrynpbq2s6wmc9cb559-antlr-2.7.2.jar
+│           └── antlr-2.7.2.pom -> /nix/store/mv42fc5gizl8h5g5vpywz1nfiynmzgp2-antlr-2.7.2.pom
+├── avalon-framework
+│   └── avalon-framework
+│       └── 4.1.3
+│           ├── avalon-framework-4.1.3.jar -> /nix/store/iv5fp3955w3nq28ff9xfz86wvxbiw6n9-avalon-framework-4.1.3.jar
+```
+
+### Double Invocation {#double-invocation}
+
+> ⚠️ This pattern is the simplest but may cause unnecessary rebuilds due to the output hash changing.
+
+The double invocation is a _simple_ way to get around the problem that `nix-build` may be sandboxed and have no Internet connectivity.
+
+It treats the entire Maven repository as a single source to be downloaded, relying on Maven's dependency resolution to satisfy the output hash. This is similar to fetchers like `fetchgit`, except it has to run a Maven build to determine what to download.
+
+The first step will be to build the Maven project as a fixed-output derivation in order to collect the Maven repository -- below is an [example](https://github.com/fzakaria/nixos-maven-example/blob/main/double-invocation-repository.nix).
+
+> Traditionally the Maven repository is at `~/.m2/repository`. We will override this to be the `$out` directory.
+
+```nix
+{ lib, stdenv, maven }:
+stdenv.mkDerivation {
+  name = "maven-repository";
+  buildInputs = [ maven ];
+  src = ./.; # or fetchFromGitHub, cleanSourceWith, etc
+  buildPhase = ''
+    mvn package -Dmaven.repo.local=$out
+  '';
+
+  # keep only *.{pom,jar,sha1,nbm} and delete all ephemeral files with lastModified timestamps inside
+  installPhase = ''
+    find $out -type f \
+      -name \*.lastUpdated -or \
+      -name resolver-status.properties -or \
+      -name _remote.repositories \
+      -delete
+  '';
+
+  # don't do any fixup
+  dontFixup = true;
+  outputHashAlgo = "sha256";
+  outputHashMode = "recursive";
+  # replace this with the correct SHA256
+  outputHash = lib.fakeSha256;
+}
+```
+
+The build will fail, and tell you the expected `outputHash` to place. When you've set the hash, the build will return with a `/nix/store` entry whose contents are the full Maven repository.
+
+> Some additional files are deleted that would cause the output hash to change potentially on subsequent runs.
+
+```bash
+❯ tree $(nix-build --no-out-link double-invocation-repository.nix) | head
+/nix/store/8kicxzp98j68xyi9gl6jda67hp3c54fq-maven-repository
+├── backport-util-concurrent
+│   └── backport-util-concurrent
+│       └── 3.1
+│           ├── backport-util-concurrent-3.1.pom
+│           └── backport-util-concurrent-3.1.pom.sha1
+├── classworlds
+│   └── classworlds
+│       ├── 1.1
+│       │   ├── classworlds-1.1.jar
+```
+
+If your package uses _SNAPSHOT_ dependencies or _version ranges_; there is a strong likelihood that over-time your output hash will change since the resolved dependencies may change. Hence this method is less recommended then using `buildMaven`.
+
+## Building a JAR {#building-a-jar}
+
+Regardless of which strategy is chosen above, the step to build the derivation is the same.
+
+```nix
+{ stdenv, maven, callPackage }:
+# pick a repository derivation, here we will use buildMaven
+let repository = callPackage ./build-maven-repository.nix { };
+in stdenv.mkDerivation rec {
+  pname = "maven-demo";
+  version = "1.0";
+
+  src = builtins.fetchTarball "https://github.com/fzakaria/nixos-maven-example/archive/main.tar.gz";
+  buildInputs = [ maven ];
+
+  buildPhase = ''
+    echo "Using repository ${repository}"
+    mvn --offline -Dmaven.repo.local=${repository} package;
+  '';
+
+  installPhase = ''
+    install -Dm644 target/${pname}-${version}.jar $out/share/java
+  '';
+}
+```
+
+> We place the library in `$out/share/java` since JDK package has a _stdenv setup hook_ that adds any JARs in the `share/java` directories of the build inputs to the CLASSPATH environment.
+
+```bash
+❯ tree $(nix-build --no-out-link build-jar.nix)
+/nix/store/7jw3xdfagkc2vw8wrsdv68qpsnrxgvky-maven-demo-1.0
+└── share
+    └── java
+        └── maven-demo-1.0.jar
+
+2 directories, 1 file
+```
+
+## Runnable JAR {#runnable-jar}
+
+The previous example builds a `jar` file but that's not a file one can run.
+
+You need to use it with `java -jar $out/share/java/output.jar` and make sure to provide the required dependencies on the classpath.
+
+The following explains how to use `makeWrapper` in order to make the derivation produce an executable that will run the JAR file you created.
+
+We will use the same repository we built above (either _double invocation_ or _buildMaven_) to setup a CLASSPATH for our JAR.
+
+The following two methods are more suited to Nix then building an [UberJar](https://imagej.net/Uber-JAR) which may be the more traditional approach.
+
+### CLASSPATH {#classpath}
+
+> This is ideal if you are providing a derivation for _nixpkgs_ and don't want to patch the project's `pom.xml`.
+
+We will read the Maven repository and flatten it to a single list. This list will then be concatenated with the _CLASSPATH_ separator to create the full classpath.
+
+We make sure to provide this classpath to the `makeWrapper`.
+
+```nix
+{ stdenv, maven, callPackage, makeWrapper, jre }:
+let
+  repository = callPackage ./build-maven-repository.nix { };
+in stdenv.mkDerivation rec {
+  pname = "maven-demo";
+  version = "1.0";
+
+  src = builtins.fetchTarball
+    "https://github.com/fzakaria/nixos-maven-example/archive/main.tar.gz";
+  buildInputs = [ maven makeWrapper ];
+
+  buildPhase = ''
+    echo "Using repository ${repository}"
+    mvn --offline -Dmaven.repo.local=${repository} package;
+  '';
+
+  installPhase = ''
+    mkdir -p $out/bin
+
+    classpath=$(find ${repository} -name "*.jar" -printf ':%h/%f');
+    install -Dm644 target/${pname}-${version}.jar $out/share/java
+    # create a wrapper that will automatically set the classpath
+    # this should be the paths from the dependency derivation
+    makeWrapper ${jre}/bin/java $out/bin/${pname} \
+          --add-flags "-classpath $out/share/java/${pname}-${version}.jar:''${classpath#:}" \
+          --add-flags "Main"
+  '';
+}
+```
+
+### MANIFEST file via Maven Plugin {#manifest-file-via-maven-plugin}
+
+> This is ideal if you are the project owner and want to change your `pom.xml` to set the CLASSPATH within it.
+
+Augment the `pom.xml` to create a JAR with the following manifest:
+
+```xml
+<build>
+  <plugins>
+    <plugin>
+        <artifactId>maven-jar-plugin</artifactId>
+        <configuration>
+            <archive>
+                <manifest>
+                    <addClasspath>true</addClasspath>
+                    <classpathPrefix>../../repository/</classpathPrefix>
+                    <classpathLayoutType>repository</classpathLayoutType>
+                    <mainClass>Main</mainClass>
+                </manifest>
+                <manifestEntries>
+                    <Class-Path>.</Class-Path>
+                </manifestEntries>
+            </archive>
+        </configuration>
+    </plugin>
+  </plugins>
+</build>
+```
+
+The above plugin instructs the JAR to look for the necessary dependencies in the `lib/` relative folder. The layout of the folder is also in the _maven repository_ style.
+
+```bash
+❯ unzip -q -c $(nix-build --no-out-link runnable-jar.nix)/share/java/maven-demo-1.0.jar META-INF/MANIFEST.MF
+
+Manifest-Version: 1.0
+Archiver-Version: Plexus Archiver
+Built-By: nixbld
+Class-Path: . ../../repository/com/vdurmont/emoji-java/5.1.1/emoji-jav
+ a-5.1.1.jar ../../repository/org/json/json/20170516/json-20170516.jar
+Created-By: Apache Maven 3.6.3
+Build-Jdk: 1.8.0_265
+Main-Class: Main
+```
+
+We will modify the derivation above to add a symlink to our repository so that it's accessible to our JAR during the `installPhase`.
+
+```nix
+{ stdenv, maven, callPackage, makeWrapper, jre }:
+# pick a repository derivation, here we will use buildMaven
+let repository = callPackage ./build-maven-repository.nix { };
+in stdenv.mkDerivation rec {
+  pname = "maven-demo";
+  version = "1.0";
+
+  src = builtins.fetchTarball
+    "https://github.com/fzakaria/nixos-maven-example/archive/main.tar.gz";
+  buildInputs = [ maven makeWrapper ];
+
+  buildPhase = ''
+    echo "Using repository ${repository}"
+    mvn --offline -Dmaven.repo.local=${repository} package;
+  '';
+
+  installPhase = ''
+    mkdir -p $out/bin
+
+    # create a symbolic link for the repository directory
+    ln -s ${repository} $out/repository
+
+    install -Dm644 target/${pname}-${version}.jar $out/share/java
+    # create a wrapper that will automatically set the classpath
+    # this should be the paths from the dependency derivation
+    makeWrapper ${jre}/bin/java $out/bin/${pname} \
+          --add-flags "-jar $out/share/java/${pname}-${version}.jar"
+  '';
+}
+```
+
+> Our script produces a dependency on `jre` rather than `jdk` to restrict the runtime closure necessary to run the application.
+
+This will give you an executable shell-script that launches your JAR with all the dependencies available.
+
+```bash
+❯ tree $(nix-build --no-out-link runnable-jar.nix)
+/nix/store/8d4c3ibw8ynsn01ibhyqmc1zhzz75s26-maven-demo-1.0
+├── bin
+│   └── maven-demo
+├── repository -> /nix/store/g87va52nkc8jzbmi1aqdcf2f109r4dvn-maven-repository
+└── share
+    └── java
+        └── maven-demo-1.0.jar
+
+❯ $(nix-build --no-out-link --option tarball-ttl 1 runnable-jar.nix)/bin/maven-demo
+NixOS 😀 is super cool 😃!
+```
diff --git a/doc/languages-frameworks/nim.section.md b/doc/languages-frameworks/nim.section.md
new file mode 100644
index 00000000000..16dce61d71c
--- /dev/null
+++ b/doc/languages-frameworks/nim.section.md
@@ -0,0 +1,91 @@
+# Nim {#nim}
+
+## Overview {#nim-overview}
+
+The Nim compiler, a builder function, and some packaged libraries are available
+in Nixpkgs. Until now each compiler release has been effectively backwards
+compatible so only the latest version is available.
+
+## Nim program packages in Nixpkgs {#nim-program-packages-in-nixpkgs}
+
+Nim programs can be built using `nimPackages.buildNimPackage`. In the
+case of packages not containing exported library code the attribute
+`nimBinOnly` should be set to `true`.
+
+The following example shows a Nim program that depends only on Nim libraries:
+
+```nix
+{ lib, nimPackages, fetchurl }:
+
+nimPackages.buildNimPackage rec {
+  pname = "hottext";
+  version = "1.4";
+
+  nimBinOnly = true;
+
+  src = fetchurl {
+    url = "https://git.sr.ht/~ehmry/hottext/archive/v${version}.tar.gz";
+    sha256 = "sha256-hIUofi81zowSMbt1lUsxCnVzfJGN3FEiTtN8CEFpwzY=";
+  };
+
+  buildInputs = with nimPackages; [
+    bumpy
+    chroma
+    flatty
+    nimsimd
+    pixie
+    sdl2
+    typography
+    vmath
+    zippy
+  ];
+}
+
+```
+
+## Nim library packages in Nixpkgs {#nim-library-packages-in-nixpkgs}
+
+
+Nim libraries can also be built using `nimPackages.buildNimPackage`, but
+often the product of a fetcher is sufficient to satisfy a dependency.
+The `fetchgit`, `fetchFromGitHub`, and `fetchNimble` functions yield an
+output that can be discovered during the `configurePhase` of `buildNimPackage`.
+
+Nim library packages are listed in
+[pkgs/top-level/nim-packages.nix](https://github.com/NixOS/nixpkgs/blob/master/pkgs/top-level/nim-packages.nix) and implemented at
+[pkgs/development/nim-packages](https://github.com/NixOS/nixpkgs/tree/master/pkgs/development/nim-packages).
+
+The following example shows a Nim library that propagates a dependency on a
+non-Nim package:
+```nix
+{ lib, buildNimPackage, fetchNimble, SDL2 }:
+
+buildNimPackage rec {
+  pname = "sdl2";
+  version = "2.0.4";
+  src = fetchNimble {
+    inherit pname version;
+    hash = "sha256-Vtcj8goI4zZPQs2TbFoBFlcR5UqDtOldaXSH/+/xULk=";
+  };
+  propagatedBuildInputs = [ SDL2 ];
+}
+```
+
+## `buildNimPackage` parameters {#buildnimpackage-parameters}
+
+All parameters from `stdenv.mkDerivation` function are still supported. The
+following are specific to `buildNimPackage`:
+
+* `nimBinOnly ? false`: If `true` then build only the programs listed in
+  the Nimble file in the packages sources.
+* `nimbleFile`: Specify the Nimble file location of the package being built
+  rather than discover the file at build-time.
+* `nimRelease ? true`: Build the package in *release* mode.
+* `nimDefines ? []`: A list of Nim defines. Key-value tuples are not supported.
+* `nimFlags ? []`: A list of command line arguments to pass to the Nim compiler.
+  Use this to specify defines with arguments in the form of `-d:${name}=${value}`.
+* `nimDoc` ? false`: Build and install HTML documentation.
+
+* `buildInputs` ? []: The packages listed here will be searched for `*.nimble`
+  files which are used to populate the Nim library path. Otherwise the standard
+  behavior is in effect.
diff --git a/doc/languages-frameworks/ocaml.section.md b/doc/languages-frameworks/ocaml.section.md
new file mode 100644
index 00000000000..e4813d7dd2d
--- /dev/null
+++ b/doc/languages-frameworks/ocaml.section.md
@@ -0,0 +1,127 @@
+# OCaml {#sec-language-ocaml}
+
+## User guide {#sec-language-ocaml-user-guide}
+
+OCaml libraries are available in attribute sets of the form `ocaml-ng.ocamlPackages_X_XX` where X is to be replaced with the desired compiler version. For example, ocamlgraph compiled with OCaml 4.12 can be found in `ocaml-ng.ocamlPackages_4_12.ocamlgraph`. The compiler itself is also located in this set, under the name `ocaml`.
+
+If you don't care about the exact compiler version, `ocamlPackages` is a top-level alias pointing to a recent version of OCaml.
+
+OCaml applications are usually available top-level, and not inside `ocamlPackages`. Notable exceptions are build tools that must be built with the same compiler version as the compiler you intend to use like `dune` or `ocaml-lsp`.
+
+To open a shell able to build a typical OCaml project, put the dependencies in `buildInputs` and add `ocamlPackages.ocaml` and `ocamlPackages.findlib` to `nativeBuildInputs` at least.
+For example:
+```nix
+let
+ pkgs = import <nixpkgs> {};
+ # choose the ocaml version you want to use
+ ocamlPackages = pkgs.ocaml-ng.ocamlPackages_4_12;
+in
+pkgs.mkShell {
+  # build tools
+  nativeBuildInputs = with ocamlPackages; [ ocaml findlib dune_2 ocaml-lsp ];
+  # dependencies
+  buildInputs = with ocamlPackages; [ ocamlgraph ];
+}
+```
+
+## Packaging guide {#sec-language-ocaml-packaging}
+
+OCaml libraries should be installed in `$(out)/lib/ocaml/${ocaml.version}/site-lib/`. Such directories are automatically added to the `$OCAMLPATH` environment variable when building another package that depends on them or when opening a `nix-shell`.
+
+Given that most of the OCaml ecosystem is now built with dune, nixpkgs includes a convenience build support function called `buildDunePackage` that will build an OCaml package using dune, OCaml and findlib and any additional dependencies provided as `buildInputs` or `propagatedBuildInputs`.
+
+Here is a simple package example.
+
+- It defines an (optional) attribute `minimalOCamlVersion` (see note below)
+  that will be used to throw a descriptive evaluation error if building with
+  an older OCaml is attempted.
+
+- It uses the `fetchFromGitHub` fetcher to get its source.
+
+- `useDune2 = true` ensures that Dune version 2 is used for the
+  build (this is the default; set to `false` to use Dune version 1).
+
+- It sets the optional `doCheck` attribute such that tests will be run with
+  `dune runtest -p angstrom` after the build (`dune build -p angstrom`) is
+  complete, but only if the Ocaml version is at at least `"4.05"`.
+
+- It uses the package `ocaml-syntax-shims` as a build input, `alcotest` and
+  `ppx_let` as check inputs (because they are needed to run the tests), and
+  `bigstringaf` and `result` as propagated build inputs (thus they will also be
+  available to libraries depending on this library).
+
+- The library will be installed using the `angstrom.install` file that dune
+  generates.
+
+```nix
+{ lib,
+  fetchFromGitHub,
+  buildDunePackage,
+  ocaml,
+  ocaml-syntax-shims,
+  alcotest,
+  result,
+  bigstringaf,
+  ppx_let }:
+
+buildDunePackage rec {
+  pname = "angstrom";
+  version = "0.15.0";
+  useDune2 = true;
+
+  minimalOCamlVersion = "4.04";
+
+  src = fetchFromGitHub {
+    owner  = "inhabitedtype";
+    repo   = pname;
+    rev    = version;
+    sha256 = "1hmrkdcdlkwy7rxhngf3cv3sa61cznnd9p5lmqhx20664gx2ibrh";
+  };
+
+  checkInputs = [ alcotest ppx_let ];
+  buildInputs = [ ocaml-syntax-shims ];
+  propagatedBuildInputs = [ bigstringaf result ];
+  doCheck = lib.versionAtLeast ocaml.version "4.05";
+
+  meta = {
+    homepage = "https://github.com/inhabitedtype/angstrom";
+    description = "OCaml parser combinators built for speed and memory efficiency";
+    license = lib.licenses.bsd3;
+    maintainers = with lib.maintainers; [ sternenseemann ];
+  };
+```
+
+Here is a second example, this time using a source archive generated with `dune-release`. It is a good idea to use this archive when it is available as it will usually contain substituted variables such as a `%%VERSION%%` field. This library does not depend on any other OCaml library and no tests are run after building it.
+
+```nix
+{ lib, fetchurl, buildDunePackage }:
+
+buildDunePackage rec {
+  pname = "wtf8";
+  version = "1.0.2";
+
+  useDune2 = true;
+
+  minimalOCamlVersion = "4.02";
+
+  src = fetchurl {
+    url = "https://github.com/flowtype/ocaml-${pname}/releases/download/v${version}/${pname}-v${version}.tbz";
+    sha256 = "09ygcxxd5warkdzz17rgpidrd0pg14cy2svvnvy1hna080lzg7vp";
+  };
+
+  meta = with lib; {
+    homepage = "https://github.com/flowtype/ocaml-wtf8";
+    description = "WTF-8 is a superset of UTF-8 that allows unpaired surrogates.";
+    license = licenses.mit;
+    maintainers = [ maintainers.eqyiel ];
+  };
+}
+```
+
+Note about `minimalOCamlVersion`.  A deprecated version of this argument was
+spelled `minimumOCamlVersion`; setting the old attribute wrongly modifies the
+derivation hash and is therefore inappropriate. As a technical dept, currently
+packaged libraries may still use the old spelling: maintainers are invited to
+fix this when updating packages. Massive renaming is strongly discouraged as it
+would be challenging to review, difficult to test, and will cause unnecessary
+rebuild.
diff --git a/doc/languages-frameworks/octave.section.md b/doc/languages-frameworks/octave.section.md
new file mode 100644
index 00000000000..4ad2cb0d5fb
--- /dev/null
+++ b/doc/languages-frameworks/octave.section.md
@@ -0,0 +1,92 @@
+# Octave {#sec-octave}
+
+## Introduction {#ssec-octave-introduction}
+
+Octave is a modular scientific programming language and environment.
+A majority of the packages supported by Octave from their [website](https://octave.sourceforge.io/packages.php) are packaged in nixpkgs.
+
+## Structure {#ssec-octave-structure}
+
+All Octave add-on packages are available in two ways:
+1. Under the top-level `Octave` attribute, `octave.pkgs`.
+2. As a top-level attribute, `octavePackages`.
+
+## Packaging Octave Packages {#ssec-octave-packaging}
+
+Nixpkgs provides a function `buildOctavePackage`, a generic package builder function for any Octave package that complies with the Octave's current packaging format.
+
+All Octave packages are defined in [pkgs/top-level/octave-packages.nix](https://github.com/NixOS/nixpkgs/blob/master/pkgs/top-level/octave-packages.nix) rather than `pkgs/all-packages.nix`.
+Each package is defined in their own file in the [pkgs/development/octave-modules](https://github.com/NixOS/nixpkgs/blob/master/pkgs/development/octave-modules) directory.
+Octave packages are made available through `all-packages.nix` through both the attribute `octavePackages` and `octave.pkgs`.
+You can test building an Octave package as follows:
+
+```ShellSession
+$ nix-build -A octavePackages.symbolic
+```
+
+To install it into your user profile, run this command from the root of the repository:
+
+```ShellSession
+$ nix-env -f. -iA octavePackages.symbolic
+```
+
+You can build Octave with packages by using the `withPackages` passed-through function.
+
+```ShellSession
+$ nix-shell -p 'octave.withPackages (ps: with ps; [ symbolic ])'
+```
+
+This will also work in a `shell.nix` file.
+
+```nix
+{ pkgs ? import <nixpkgs> { }}:
+
+pkgs.mkShell {
+  nativeBuildInputs = with pkgs; [
+    (octave.withPackages (opkgs: with opkgs; [ symbolic ]))
+  ];
+}
+```
+
+### `buildOctavePackage` Steps {#sssec-buildOctavePackage-steps}
+
+The `buildOctavePackage` does several things to make sure things work properly.
+
+1. Sets the environment variable `OCTAVE_HISTFILE` to `/dev/null` during package compilation so that the commands run through the Octave interpreter directly are not logged.
+2. Skips the configuration step, because the packages are stored as gzipped tarballs, which Octave itself handles directly.
+3. Change the hierarchy of the tarball so that only a single directory is at the top-most level of the tarball.
+4. Use Octave itself to run the `pkg build` command, which unzips the tarball, extracts the necessary files written in Octave, and compiles any code written in C++ or Fortran, and places the fully compiled artifact in `$out`.
+
+`buildOctavePackage` is built on top of `stdenv` in a standard way, allowing most things to be customized.
+
+### Handling Dependencies {#sssec-octave-handling-dependencies}
+
+In Octave packages, there are four sets of dependencies that can be specified:
+
+`nativeBuildInputs`
+: Just like other packages, `nativeBuildInputs` is intended for architecture-dependent build-time-only dependencies.
+
+`buildInputs`
+: Like other packages, `buildInputs` is intended for architecture-independent build-time-only dependencies.
+
+`propagatedBuildInputs`
+: Similar to other packages, `propagatedBuildInputs` is intended for packages that are required for both building and running of the package.
+See [Symbolic](https://github.com/NixOS/nixpkgs/blob/master/pkgs/development/octave-modules/symbolic/default.nix) for how this works and why it is needed.
+
+`requiredOctavePackages`
+: This is a special dependency that ensures the specified Octave packages are dependent on others, and are made available simultaneously when loading them in Octave.
+
+### Installing Octave Packages {#sssec-installing-octave-packages}
+
+By default, the `buildOctavePackage` function does _not_ install the requested package into Octave for use.
+The function will only build the requested package.
+This is due to Octave maintaining an text-based database about which packages are installed where.
+To this end, when all the requested packages have been built, the Octave package and all its add-on packages are put together into an environment, similar to Python.
+
+1. First, all the Octave binaries are wrapped with the environment variable `OCTAVE_SITE_INITFILE` set to a file in `$out`, which is required for Octave to be able to find the non-standard package database location.
+2. Because of the way `buildEnv` works, all tarballs that are present (which should be all Octave packages to install) should be removed.
+3. The path down to the default install location of Octave packages is recreated so that Nix-operated Octave can install the packages.
+4. Install the packages into the `$out` environment while writing package entries to the database file.
+This database file is unique for each different (according to Nix) environment invocation.
+5. Rewrite the Octave-wide startup file to read from the list of packages installed in that particular environment.
+6. Wrap any programs that are required by the Octave packages so that they work with all the paths defined within the environment.
diff --git a/doc/languages-frameworks/perl.section.md b/doc/languages-frameworks/perl.section.md
new file mode 100644
index 00000000000..9bfd209fec5
--- /dev/null
+++ b/doc/languages-frameworks/perl.section.md
@@ -0,0 +1,159 @@
+# Perl {#sec-language-perl}
+
+## Running perl programs on the shell {#ssec-perl-running}
+
+When executing a Perl script, it is possible you get an error such as `./myscript.pl: bad interpreter: /usr/bin/perl: no such file or directory`. This happens when the script expects Perl to be installed at `/usr/bin/perl`, which is not the case when using Perl from nixpkgs. You can fix the script by changing the first line to:
+
+```perl
+#!/usr/bin/env perl
+```
+
+to take the Perl installation from the `PATH` environment variable, or invoke Perl directly with:
+
+```ShellSession
+$ perl ./myscript.pl
+```
+
+When the script is using a Perl library that is not installed globally, you might get an error such as `Can't locate DB_File.pm in @INC (you may need to install the DB_File module)`. In that case, you can use `nix-shell` to start an ad-hoc shell with that library installed, for instance:
+
+```ShellSession
+$ nix-shell -p perl perlPackages.DBFile --run ./myscript.pl
+```
+
+If you are always using the script in places where `nix-shell` is available, you can embed the `nix-shell` invocation in the shebang like this:
+
+```perl
+#!/usr/bin/env nix-shell
+#! nix-shell -i perl -p perl perlPackages.DBFile
+```
+
+## Packaging Perl programs {#ssec-perl-packaging}
+
+Nixpkgs provides a function `buildPerlPackage`, a generic package builder function for any Perl package that has a standard `Makefile.PL`. It’s implemented in [pkgs/development/perl-modules/generic](https://github.com/NixOS/nixpkgs/blob/master/pkgs/development/perl-modules/generic).
+
+Perl packages from CPAN are defined in [pkgs/top-level/perl-packages.nix](https://github.com/NixOS/nixpkgs/blob/master/pkgs/top-level/perl-packages.nix) rather than `pkgs/all-packages.nix`. Most Perl packages are so straight-forward to build that they are defined here directly, rather than having a separate function for each package called from `perl-packages.nix`. However, more complicated packages should be put in a separate file, typically in `pkgs/development/perl-modules`. Here is an example of the former:
+
+```nix
+ClassC3 = buildPerlPackage rec {
+  name = "Class-C3-0.21";
+  src = fetchurl {
+    url = "mirror://cpan/authors/id/F/FL/FLORA/${name}.tar.gz";
+    sha256 = "1bl8z095y4js66pwxnm7s853pi9czala4sqc743fdlnk27kq94gz";
+  };
+};
+```
+
+Note the use of `mirror://cpan/`, and the `${name}` in the URL definition to ensure that the name attribute is consistent with the source that we’re actually downloading. Perl packages are made available in `all-packages.nix` through the variable `perlPackages`. For instance, if you have a package that needs `ClassC3`, you would typically write
+
+```nix
+foo = import ../path/to/foo.nix {
+  inherit stdenv fetchurl ...;
+  inherit (perlPackages) ClassC3;
+};
+```
+
+in `all-packages.nix`. You can test building a Perl package as follows:
+
+```ShellSession
+$ nix-build -A perlPackages.ClassC3
+```
+
+To install it with `nix-env` instead: `nix-env -f. -iA perlPackages.ClassC3`.
+
+So what does `buildPerlPackage` do? It does the following:
+
+1. In the configure phase, it calls `perl Makefile.PL` to generate a Makefile. You can set the variable `makeMakerFlags` to pass flags to `Makefile.PL`
+2. It adds the contents of the `PERL5LIB` environment variable to `#! .../bin/perl` line of Perl scripts as `-Idir` flags. This ensures that a script can find its dependencies. (This can cause this shebang line to become too long for Darwin to handle; see the note below.)
+3. In the fixup phase, it writes the propagated build inputs (`propagatedBuildInputs`) to the file `$out/nix-support/propagated-user-env-packages`. `nix-env` recursively installs all packages listed in this file when you install a package that has it. This ensures that a Perl package can find its dependencies.
+
+`buildPerlPackage` is built on top of `stdenv`, so everything can be customised in the usual way. For instance, the `BerkeleyDB` module has a `preConfigure` hook to generate a configuration file used by `Makefile.PL`:
+
+```nix
+{ buildPerlPackage, fetchurl, db }:
+
+buildPerlPackage rec {
+  name = "BerkeleyDB-0.36";
+
+  src = fetchurl {
+    url = "mirror://cpan/authors/id/P/PM/PMQS/${name}.tar.gz";
+    sha256 = "07xf50riarb60l1h6m2dqmql8q5dij619712fsgw7ach04d8g3z1";
+  };
+
+  preConfigure = ''
+    echo "LIB = ${db.out}/lib" > config.in
+    echo "INCLUDE = ${db.dev}/include" >> config.in
+  '';
+}
+```
+
+Dependencies on other Perl packages can be specified in the `buildInputs` and `propagatedBuildInputs` attributes. If something is exclusively a build-time dependency, use `buildInputs`; if it’s (also) a runtime dependency, use `propagatedBuildInputs`. For instance, this builds a Perl module that has runtime dependencies on a bunch of other modules:
+
+```nix
+ClassC3Componentised = buildPerlPackage rec {
+  name = "Class-C3-Componentised-1.0004";
+  src = fetchurl {
+    url = "mirror://cpan/authors/id/A/AS/ASH/${name}.tar.gz";
+    sha256 = "0xql73jkcdbq4q9m0b0rnca6nrlvf5hyzy8is0crdk65bynvs8q1";
+  };
+  propagatedBuildInputs = [
+    ClassC3 ClassInspector TestException MROCompat
+  ];
+};
+```
+
+On Darwin, if a script has too many `-Idir` flags in its first line (its “shebang line”), it will not run. This can be worked around by calling the `shortenPerlShebang` function from the `postInstall` phase:
+
+```nix
+{ lib, stdenv, buildPerlPackage, fetchurl, shortenPerlShebang }:
+
+ImageExifTool = buildPerlPackage {
+  pname = "Image-ExifTool";
+  version = "11.50";
+
+  src = fetchurl {
+    url = "https://www.sno.phy.queensu.ca/~phil/exiftool/Image-ExifTool-11.50.tar.gz";
+    sha256 = "0d8v48y94z8maxkmw1rv7v9m0jg2dc8xbp581njb6yhr7abwqdv3";
+  };
+
+  buildInputs = lib.optional stdenv.isDarwin shortenPerlShebang;
+  postInstall = lib.optionalString stdenv.isDarwin ''
+    shortenPerlShebang $out/bin/exiftool
+  '';
+};
+```
+
+This will remove the `-I` flags from the shebang line, rewrite them in the `use lib` form, and put them on the next line instead. This function can be given any number of Perl scripts as arguments; it will modify them in-place.
+
+### Generation from CPAN {#ssec-generation-from-CPAN}
+
+Nix expressions for Perl packages can be generated (almost) automatically from CPAN. This is done by the program `nix-generate-from-cpan`, which can be installed as follows:
+
+```ShellSession
+$ nix-env -f "<nixpkgs>" -iA nix-generate-from-cpan
+```
+
+Substitute `<nixpkgs>` by the path of a nixpkgs clone to use the latest version.
+
+This program takes a Perl module name, looks it up on CPAN, fetches and unpacks the corresponding package, and prints a Nix expression on standard output. For example:
+
+```ShellSession
+$ nix-generate-from-cpan XML::Simple
+  XMLSimple = buildPerlPackage rec {
+    name = "XML-Simple-2.22";
+    src = fetchurl {
+      url = "mirror://cpan/authors/id/G/GR/GRANTM/${name}.tar.gz";
+      sha256 = "b9450ef22ea9644ae5d6ada086dc4300fa105be050a2030ebd4efd28c198eb49";
+    };
+    propagatedBuildInputs = [ XMLNamespaceSupport XMLSAX XMLSAXExpat ];
+    meta = {
+      description = "An API for simple XML files";
+      license = with lib.licenses; [ artistic1 gpl1Plus ];
+    };
+  };
+```
+
+The output can be pasted into `pkgs/top-level/perl-packages.nix` or wherever else you need it.
+
+### Cross-compiling modules {#ssec-perl-cross-compilation}
+
+Nixpkgs has experimental support for cross-compiling Perl modules. In many cases, it will just work out of the box, even for modules with native extensions. Sometimes, however, the Makefile.PL for a module may (indirectly) import a native module. In that case, you will need to make a stub for that module that will satisfy the Makefile.PL and install it into `lib/perl5/site_perl/cross_perl/${perl.version}`. See the `postInstall` for `DBI` for an example.
diff --git a/doc/languages-frameworks/php.section.md b/doc/languages-frameworks/php.section.md
new file mode 100644
index 00000000000..5977363323f
--- /dev/null
+++ b/doc/languages-frameworks/php.section.md
@@ -0,0 +1,155 @@
+# PHP {#sec-php}
+
+## User Guide {#ssec-php-user-guide}
+
+### Overview {#ssec-php-user-guide-overview}
+
+Several versions of PHP are available on Nix, each of which having a
+wide variety of extensions and libraries available.
+
+The different versions of PHP that nixpkgs provides are located under
+attributes named based on major and minor version number; e.g.,
+`php74` is PHP 7.4.
+
+Only versions of PHP that are supported by upstream for the entirety
+of a given NixOS release will be included in that release of
+NixOS. See [PHP Supported
+Versions](https://www.php.net/supported-versions.php).
+
+The attribute `php` refers to the version of PHP considered most
+stable and thoroughly tested in nixpkgs for any given release of
+NixOS - not necessarily the latest major release from upstream.
+
+All available PHP attributes are wrappers around their respective
+binary PHP package and provide commonly used extensions this way. The
+real PHP 7.4 package, i.e. the unwrapped one, is available as
+`php74.unwrapped`; see the next section for more details.
+
+Interactive tools built on PHP are put in `php.packages`; composer is
+for example available at `php.packages.composer`.
+
+Most extensions that come with PHP, as well as some popular
+third-party ones, are available in `php.extensions`; for example, the
+opcache extension shipped with PHP is available at
+`php.extensions.opcache` and the third-party ImageMagick extension at
+`php.extensions.imagick`.
+
+### Installing PHP with extensions {#ssec-php-user-guide-installing-with-extensions}
+
+A PHP package with specific extensions enabled can be built using
+`php.withExtensions`. This is a function which accepts an anonymous
+function as its only argument; the function should accept two named
+parameters: `enabled` - a list of currently enabled extensions and
+`all` - the set of all extensions, and return a list of wanted
+extensions. For example, a PHP package with all default extensions and
+ImageMagick enabled:
+
+```nix
+php.withExtensions ({ enabled, all }:
+  enabled ++ [ all.imagick ])
+```
+
+To exclude some, but not all, of the default extensions, you can
+filter the `enabled` list like this:
+
+```nix
+php.withExtensions ({ enabled, all }:
+  (lib.filter (e: e != php.extensions.opcache) enabled)
+  ++ [ all.imagick ])
+```
+
+To build your list of extensions from the ground up, you can simply
+ignore `enabled`:
+
+```nix
+php.withExtensions ({ all, ... }: with all; [ imagick opcache ])
+```
+
+`php.withExtensions` provides extensions by wrapping a minimal php
+base package, providing a `php.ini` file listing all extensions to be
+loaded. You can access this package through the `php.unwrapped`
+attribute; useful if you, for example, need access to the `dev`
+output. The generated `php.ini` file can be accessed through the
+`php.phpIni` attribute.
+
+If you want a PHP build with extra configuration in the `php.ini`
+file, you can use `php.buildEnv`. This function takes two named and
+optional parameters: `extensions` and `extraConfig`. `extensions`
+takes an extension specification equivalent to that of
+`php.withExtensions`, `extraConfig` a string of additional `php.ini`
+configuration parameters. For example, a PHP package with the opcache
+and ImageMagick extensions enabled, and `memory_limit` set to `256M`:
+
+```nix
+php.buildEnv {
+  extensions = { all, ... }: with all; [ imagick opcache ];
+  extraConfig = "memory_limit=256M";
+}
+```
+
+#### Example setup for `phpfpm` {#ssec-php-user-guide-installing-with-extensions-phpfpm}
+
+You can use the previous examples in a `phpfpm` pool called `foo` as
+follows:
+
+```nix
+let
+  myPhp = php.withExtensions ({ all, ... }: with all; [ imagick opcache ]);
+in {
+  services.phpfpm.pools."foo".phpPackage = myPhp;
+};
+```
+
+```nix
+let
+  myPhp = php.buildEnv {
+    extensions = { all, ... }: with all; [ imagick opcache ];
+    extraConfig = "memory_limit=256M";
+  };
+in {
+  services.phpfpm.pools."foo".phpPackage = myPhp;
+};
+```
+
+#### Example usage with `nix-shell` {#ssec-php-user-guide-installing-with-extensions-nix-shell}
+
+This brings up a temporary environment that contains a PHP interpreter
+with the extensions `imagick` and `opcache` enabled:
+
+```sh
+nix-shell -p 'php.withExtensions ({ all, ... }: with all; [ imagick opcache ])'
+```
+
+### Installing PHP packages with extensions {#ssec-php-user-guide-installing-packages-with-extensions}
+
+All interactive tools use the PHP package you get them from, so all
+packages at `php.packages.*` use the `php` package with its default
+extensions. Sometimes this default set of extensions isn't enough and
+you may want to extend it. A common case of this is the `composer`
+package: a project may depend on certain extensions and `composer`
+won't work with that project unless those extensions are loaded.
+
+Example of building `composer` with additional extensions:
+```nix
+(php.withExtensions ({ all, enabled }:
+  enabled ++ (with all; [ imagick redis ]))
+).packages.composer
+```
+
+### Overriding PHP packages {#ssec-php-user-guide-overriding-packages}
+
+`php-packages.nix` form a scope, allowing us to override the packages defined within. For example, to apply a patch to a `mysqlnd` extension, you can simply pass an overlay-style function to `php`’s `packageOverrides` argument:
+
+```nix
+php.override {
+  packageOverrides = final: prev: {
+    extensions = prev.extensions // {
+      mysqlnd = prev.extensions.mysqlnd.overrideAttrs (attrs: {
+        patches = attrs.patches or [] ++ [
+          …
+        ];
+      });
+    };
+  };
+}
+```
diff --git a/doc/languages-frameworks/python.section.md b/doc/languages-frameworks/python.section.md
new file mode 100644
index 00000000000..693ea016e0a
--- /dev/null
+++ b/doc/languages-frameworks/python.section.md
@@ -0,0 +1,1682 @@
+# Python {#python}
+
+## User Guide {#user-guide}
+
+### Using Python {#using-python}
+
+#### Overview {#overview}
+
+Several versions of the Python interpreter are available on Nix, as well as a
+high amount of packages. The attribute `python3` refers to the default
+interpreter, which is currently CPython 3.9. The attribute `python` refers to
+CPython 2.7 for backwards-compatibility. It is also possible to refer to
+specific versions, e.g. `python38` refers to CPython 3.8, and `pypy` refers to
+the default PyPy interpreter.
+
+Python is used a lot, and in different ways. This affects also how it is
+packaged. In the case of Python on Nix, an important distinction is made between
+whether the package is considered primarily an application, or whether it should
+be used as a library, i.e., of primary interest are the modules in
+`site-packages` that should be importable.
+
+In the Nixpkgs tree Python applications can be found throughout, depending on
+what they do, and are called from the main package set. Python libraries,
+however, are in separate sets, with one set per interpreter version.
+
+The interpreters have several common attributes. One of these attributes is
+`pkgs`, which is a package set of Python libraries for this specific
+interpreter. E.g., the `toolz` package corresponding to the default interpreter
+is `python.pkgs.toolz`, and the CPython 3.8 version is `python38.pkgs.toolz`.
+The main package set contains aliases to these package sets, e.g.
+`pythonPackages` refers to `python.pkgs` and `python38Packages` to
+`python38.pkgs`.
+
+#### Installing Python and packages {#installing-python-and-packages}
+
+The Nix and NixOS manuals explain how packages are generally installed. In the
+case of Python and Nix, it is important to make a distinction between whether the
+package is considered an application or a library.
+
+Applications on Nix are typically installed into your user profile imperatively
+using `nix-env -i`, and on NixOS declaratively by adding the package name to
+`environment.systemPackages` in `/etc/nixos/configuration.nix`. Dependencies
+such as libraries are automatically installed and should not be installed
+explicitly.
+
+The same goes for Python applications. Python applications can be installed in
+your profile, and will be wrapped to find their exact library dependencies,
+without impacting other applications or polluting your user environment.
+
+But Python libraries you would like to use for development cannot be installed,
+at least not individually, because they won't be able to find each other
+resulting in import errors. Instead, it is possible to create an environment
+with `python.buildEnv` or `python.withPackages` where the interpreter and other
+executables are wrapped to be able to find each other and all of the modules.
+
+In the following examples we will start by creating a simple, ad-hoc environment
+with a nix-shell that has `numpy` and `toolz` in Python 3.8; then we will create
+a re-usable environment in a single-file Python script; then we will create a
+full Python environment for development with this same environment.
+
+Philosphically, this should be familiar to users who are used to a `venv` style
+of development: individual projects create their own Python environments without
+impacting the global environment or each other.
+
+#### Ad-hoc temporary Python environment with `nix-shell` {#ad-hoc-temporary-python-environment-with-nix-shell}
+
+The simplest way to start playing with the way nix wraps and sets up Python
+environments is with `nix-shell` at the cmdline. These environments create a
+temporary shell session with a Python and a *precise* list of packages (plus
+their runtime dependencies), with no other Python packages in the Python
+interpreter's scope.
+
+To create a Python 3.8 session with `numpy` and `toolz` available, run:
+
+```sh
+$ nix-shell -p 'python38.withPackages(ps: with ps; [ numpy toolz ])'
+```
+
+By default `nix-shell` will start a `bash` session with this interpreter in our
+`PATH`, so if we then run:
+
+```Python console
+[nix-shell:~/src/nixpkgs]$ python3
+Python 3.8.1 (default, Dec 18 2019, 19:06:26)
+[GCC 9.2.0] on linux
+Type "help", "copyright", "credits" or "license" for more information.
+>>> import numpy; import toolz
+```
+
+Note that no other modules are in scope, even if they were imperatively
+installed into our user environment as a dependency of a Python application:
+
+```Python console
+>>> import requests
+Traceback (most recent call last):
+  File "<stdin>", line 1, in <module>
+ModuleNotFoundError: No module named 'requests'
+```
+
+We can add as many additional modules onto the `nix-shell` as we need, and we
+will still get 1 wrapped Python interpreter. We can start the interpreter
+directly like so:
+
+```sh
+$ nix-shell -p 'python38.withPackages(ps: with ps; [ numpy toolz requests ])' --run python3
+these derivations will be built:
+  /nix/store/xbdsrqrsfa1yva5s7pzsra8k08gxlbz1-python3-3.8.1-env.drv
+building '/nix/store/xbdsrqrsfa1yva5s7pzsra8k08gxlbz1-python3-3.8.1-env.drv'...
+created 277 symlinks in user environment
+Python 3.8.1 (default, Dec 18 2019, 19:06:26)
+[GCC 9.2.0] on linux
+Type "help", "copyright", "credits" or "license" for more information.
+>>> import requests
+>>>
+```
+
+Notice that this time it built a new Python environment, which now includes
+`requests`. Building an environment just creates wrapper scripts that expose the
+selected dependencies to the interpreter while re-using the actual modules. This
+means if any other env has installed `requests` or `numpy` in a different
+context, we don't need to recompile them -- we just recompile the wrapper script
+that sets up an interpreter pointing to them. This matters much more for "big"
+modules like `pytorch` or `tensorflow`.
+
+Module names usually match their names on [pypi.org](https://pypi.org/), but
+you can use the [Nixpkgs search website](https://nixos.org/nixos/packages.html)
+to find them as well (along with non-python packages).
+
+At this point we can create throwaway experimental Python environments with
+arbitrary dependencies. This is a good way to get a feel for how the Python
+interpreter and dependencies work in Nix and NixOS, but to do some actual
+development, we'll want to make it a bit more persistent.
+
+##### Running Python scripts and using `nix-shell` as shebang {#running-python-scripts-and-using-nix-shell-as-shebang}
+
+Sometimes, we have a script whose header looks like this:
+
+```python
+#!/usr/bin/env python3
+import numpy as np
+a = np.array([1,2])
+b = np.array([3,4])
+print(f"The dot product of {a} and {b} is: {np.dot(a, b)}")
+```
+
+Executing this script requires a `python3` that has `numpy`. Using what we learned
+in the previous section, we could startup a shell and just run it like so:
+
+```ShellSession
+$ nix-shell -p 'python38.withPackages(ps: with ps; [ numpy ])' --run 'python3 foo.py'
+The dot product of [1 2] and [3 4] is: 11
+```
+
+But if we maintain the script ourselves, and if there are more dependencies, it
+may be nice to encode those dependencies in source to make the script re-usable
+without that bit of knowledge. That can be done by using `nix-shell` as a
+[shebang](https://en.wikipedia.org/wiki/Shebang_(Unix)), like so:
+
+```python
+#!/usr/bin/env nix-shell
+#!nix-shell -i python3 -p "python3.withPackages(ps: [ ps.numpy ])"
+import numpy as np
+a = np.array([1,2])
+b = np.array([3,4])
+print(f"The dot product of {a} and {b} is: {np.dot(a, b)}")
+```
+
+Then we simply execute it, without requiring any environment setup at all!
+
+```sh
+$ ./foo.py
+The dot product of [1 2] and [3 4] is: 11
+```
+
+If the dependencies are not available on the host where `foo.py` is executed, it
+will build or download them from a Nix binary cache prior to starting up, prior
+that it is executed on a machine with a multi-user nix installation.
+
+This provides a way to ship a self bootstrapping Python script, akin to a
+statically linked binary, where it can be run on any machine (provided nix is
+installed) without having to assume that `numpy` is installed globally on the
+system.
+
+By default it is pulling the import checkout of Nixpkgs itself from our nix
+channel, which is nice as it cache aligns with our other package builds, but we
+can make it fully reproducible by pinning the `nixpkgs` import:
+
+```python
+#!/usr/bin/env nix-shell
+#!nix-shell -i python3 -p "python3.withPackages(ps: [ ps.numpy ])"
+#!nix-shell -I nixpkgs=https://github.com/NixOS/nixpkgs/archive/d373d80b1207d52621961b16aa4a3438e4f98167.tar.gz
+import numpy as np
+a = np.array([1,2])
+b = np.array([3,4])
+print(f"The dot product of {a} and {b} is: {np.dot(a, b)}")
+```
+
+This will execute with the exact same versions of Python 3.8, numpy, and system
+dependencies a year from now as it does today, because it will always use
+exactly git commit `d373d80b1207d52621961b16aa4a3438e4f98167` of Nixpkgs for all
+of the package versions.
+
+This is also a great way to ensure the script executes identically on different
+servers.
+
+##### Load environment from `.nix` expression {#load-environment-from-.nix-expression}
+
+We've now seen how to create an ad-hoc temporary shell session, and how to
+create a single script with Python dependencies, but in the course of normal
+development we're usually working in an entire package repository.
+
+As explained in the Nix manual, `nix-shell` can also load an expression from a
+`.nix` file. Say we want to have Python 3.8, `numpy` and `toolz`, like before,
+in an environment. We can add a `shell.nix` file describing our dependencies:
+
+```nix
+with import <nixpkgs> {};
+(python38.withPackages (ps: [ps.numpy ps.toolz])).env
+```
+
+And then at the command line, just typing `nix-shell` produces the same
+environment as before. In a normal project, we'll likely have many more
+dependencies; this can provide a way for developers to share the environments
+with each other and with CI builders.
+
+What's happening here?
+
+1. We begin with importing the Nix Packages collections. `import <nixpkgs>`
+   imports the `<nixpkgs>` function, `{}` calls it and the `with` statement
+   brings all attributes of `nixpkgs` in the local scope. These attributes form
+   the main package set.
+2. Then we create a Python 3.8 environment with the `withPackages` function, as before.
+3. The `withPackages` function expects us to provide a function as an argument
+   that takes the set of all Python packages and returns a list of packages to
+   include in the environment. Here, we select the packages `numpy` and `toolz`
+   from the package set.
+
+To combine this with `mkShell` you can:
+
+```nix
+with import <nixpkgs> {};
+let
+  pythonEnv = python38.withPackages (ps: [
+    ps.numpy
+    ps.toolz
+  ]);
+in mkShell {
+  packages = [
+    pythonEnv
+
+    black
+    mypy
+
+    libffi
+    openssl
+  ];
+}
+```
+
+This will create a unified environment that has not just our Python interpreter
+and its Python dependencies, but also tools like `black` or `mypy` and libraries
+like `libffi` the `openssl` in scope. This is generic and can span any number of
+tools or languages across the Nixpkgs ecosystem.
+
+##### Installing environments globally on the system {#installing-environments-globally-on-the-system}
+
+Up to now, we've been creating environments scoped to an ad-hoc shell session,
+or a single script, or a single project. This is generally advisable, as it
+avoids pollution across contexts.
+
+However, sometimes we know we will often want a Python with some basic packages,
+and want this available without having to enter into a shell or build context.
+This can be useful to have things like vim/emacs editors and plugins or shell
+tools "just work" without having to set them up, or when running other software
+that expects packages to be installed globally.
+
+To create your own custom environment, create a file in `~/.config/nixpkgs/overlays/`
+that looks like this:
+
+```nix
+# ~/.config/nixpkgs/overlays/myEnv.nix
+self: super: {
+  myEnv = super.buildEnv {
+    name = "myEnv";
+    paths = [
+      # A Python 3 interpreter with some packages
+      (self.python3.withPackages (
+        ps: with ps; [
+          pyflakes
+          pytest
+          python-language-server
+        ]
+      ))
+
+      # Some other packages we'd like as part of this env
+      self.mypy
+      self.black
+      self.ripgrep
+      self.tmux
+    ];
+  };
+}
+```
+
+You can then build and install this to your profile with:
+
+```sh
+nix-env -iA myEnv
+```
+
+One limitation of this is that you can only have 1 Python env installed
+globally, since they conflict on the `python` to load out of your `PATH`.
+
+If you get a conflict or prefer to keep the setup clean, you can have `nix-env`
+atomically *uninstall* all other imperatively installed packages and replace
+your profile with just `myEnv` by using the `--replace` flag.
+
+##### Environment defined in `/etc/nixos/configuration.nix` {#environment-defined-in-etcnixosconfiguration.nix}
+
+For the sake of completeness, here's how to install the environment system-wide
+on NixOS.
+
+```nix
+{ # ...
+
+  environment.systemPackages = with pkgs; [
+    (python38.withPackages(ps: with ps; [ numpy toolz ]))
+  ];
+}
+```
+
+### Developing with Python {#developing-with-python}
+
+Above, we were mostly just focused on use cases and what to do to get started
+creating working Python environments in nix.
+
+Now that you know the basics to be up and running, it is time to take a step
+back and take a deeper look at how Python packages are packaged on Nix. Then,
+we will look at how you can use development mode with your code.
+
+#### Python library packages in Nixpkgs {#python-library-packages-in-nixpkgs}
+
+With Nix all packages are built by functions. The main function in Nix for
+building Python libraries is `buildPythonPackage`. Let's see how we can build the
+`toolz` package.
+
+```nix
+{ lib, buildPythonPackage, fetchPypi }:
+
+buildPythonPackage rec {
+  pname = "toolz";
+  version = "0.10.0";
+
+  src = fetchPypi {
+    inherit pname version;
+    sha256 = "08fdd5ef7c96480ad11c12d472de21acd32359996f69a5259299b540feba4560";
+  };
+
+  doCheck = false;
+
+  meta = with lib; {
+    homepage = "https://github.com/pytoolz/toolz";
+    description = "List processing tools and functional utilities";
+    license = licenses.bsd3;
+    maintainers = with maintainers; [ fridh ];
+  };
+}
+```
+
+What happens here? The function `buildPythonPackage` is called and as argument
+it accepts a set. In this case the set is a recursive set, `rec`. One of the
+arguments is the name of the package, which consists of a basename (generally
+following the name on PyPi) and a version. Another argument, `src` specifies the
+source, which in this case is fetched from PyPI using the helper function
+`fetchPypi`. The argument `doCheck` is used to set whether tests should be run
+when building the package. Furthermore, we specify some (optional) meta
+information. The output of the function is a derivation.
+
+An expression for `toolz` can be found in the Nixpkgs repository. As explained
+in the introduction of this Python section, a derivation of `toolz` is available
+for each interpreter version, e.g. `python38.pkgs.toolz` refers to the `toolz`
+derivation corresponding to the CPython 3.8 interpreter.
+
+The above example works when you're directly working on
+`pkgs/top-level/python-packages.nix` in the Nixpkgs repository. Often though,
+you will want to test a Nix expression outside of the Nixpkgs tree.
+
+The following expression creates a derivation for the `toolz` package,
+and adds it along with a `numpy` package to a Python environment.
+
+```nix
+with import <nixpkgs> {};
+
+( let
+    my_toolz = python38.pkgs.buildPythonPackage rec {
+      pname = "toolz";
+      version = "0.10.0";
+
+      src = python38.pkgs.fetchPypi {
+        inherit pname version;
+        sha256 = "08fdd5ef7c96480ad11c12d472de21acd32359996f69a5259299b540feba4560";
+      };
+
+      doCheck = false;
+
+      meta = {
+        homepage = "https://github.com/pytoolz/toolz/";
+        description = "List processing tools and functional utilities";
+      };
+    };
+
+  in python38.withPackages (ps: [ps.numpy my_toolz])
+).env
+```
+
+Executing `nix-shell` will result in an environment in which you can use
+Python 3.8 and the `toolz` package. As you can see we had to explicitly mention
+for which Python version we want to build a package.
+
+So, what did we do here? Well, we took the Nix expression that we used earlier
+to build a Python environment, and said that we wanted to include our own
+version of `toolz`, named `my_toolz`. To introduce our own package in the scope
+of `withPackages` we used a `let` expression. You can see that we used
+`ps.numpy` to select numpy from the nixpkgs package set (`ps`). We did not take
+`toolz` from the Nixpkgs package set this time, but instead took our own version
+that we introduced with the `let` expression.
+
+#### Handling dependencies {#handling-dependencies}
+
+Our example, `toolz`, does not have any dependencies on other Python packages or
+system libraries. According to the manual, `buildPythonPackage` uses the
+arguments `buildInputs` and `propagatedBuildInputs` to specify dependencies. If
+something is exclusively a build-time dependency, then the dependency should be
+included in `buildInputs`, but if it is (also) a runtime dependency, then it
+should be added to `propagatedBuildInputs`. Test dependencies are considered
+build-time dependencies and passed to `checkInputs`.
+
+The following example shows which arguments are given to `buildPythonPackage` in
+order to build [`datashape`](https://github.com/blaze/datashape).
+
+```nix
+{ lib, buildPythonPackage, fetchPypi, numpy, multipledispatch, python-dateutil, pytest }:
+
+buildPythonPackage rec {
+  pname = "datashape";
+  version = "0.4.7";
+
+  src = fetchPypi {
+    inherit pname version;
+    sha256 = "14b2ef766d4c9652ab813182e866f493475e65e558bed0822e38bf07bba1a278";
+  };
+
+  checkInputs = [ pytest ];
+  propagatedBuildInputs = [ numpy multipledispatch python-dateutil ];
+
+  meta = with lib; {
+    homepage = "https://github.com/ContinuumIO/datashape";
+    description = "A data description language";
+    license = licenses.bsd2;
+    maintainers = with maintainers; [ fridh ];
+  };
+}
+```
+
+We can see several runtime dependencies, `numpy`, `multipledispatch`, and
+`python-dateutil`. Furthermore, we have one `checkInputs`, i.e. `pytest`. `pytest` is a
+test runner and is only used during the `checkPhase` and is therefore not added
+to `propagatedBuildInputs`.
+
+In the previous case we had only dependencies on other Python packages to consider.
+Occasionally you have also system libraries to consider. E.g., `lxml` provides
+Python bindings to `libxml2` and `libxslt`. These libraries are only required
+when building the bindings and are therefore added as `buildInputs`.
+
+```nix
+{ lib, pkgs, buildPythonPackage, fetchPypi }:
+
+buildPythonPackage rec {
+  pname = "lxml";
+  version = "3.4.4";
+
+  src = fetchPypi {
+    inherit pname version;
+    sha256 = "16a0fa97hym9ysdk3rmqz32xdjqmy4w34ld3rm3jf5viqjx65lxk";
+  };
+
+  buildInputs = [ pkgs.libxml2 pkgs.libxslt ];
+
+  meta = with lib; {
+    description = "Pythonic binding for the libxml2 and libxslt libraries";
+    homepage = "https://lxml.de";
+    license = licenses.bsd3;
+    maintainers = with maintainers; [ sjourdois ];
+  };
+}
+```
+
+In this example `lxml` and Nix are able to work out exactly where the relevant
+files of the dependencies are. This is not always the case.
+
+The example below shows bindings to The Fastest Fourier Transform in the West,
+commonly known as FFTW. On Nix we have separate packages of FFTW for the
+different types of floats (`"single"`, `"double"`, `"long-double"`). The
+bindings need all three types, and therefore we add all three as `buildInputs`.
+The bindings don't expect to find each of them in a different folder, and
+therefore we have to set `LDFLAGS` and `CFLAGS`.
+
+```nix
+{ lib, pkgs, buildPythonPackage, fetchPypi, numpy, scipy }:
+
+buildPythonPackage rec {
+  pname = "pyFFTW";
+  version = "0.9.2";
+
+  src = fetchPypi {
+    inherit pname version;
+    sha256 = "f6bbb6afa93085409ab24885a1a3cdb8909f095a142f4d49e346f2bd1b789074";
+  };
+
+  buildInputs = [ pkgs.fftw pkgs.fftwFloat pkgs.fftwLongDouble];
+
+  propagatedBuildInputs = [ numpy scipy ];
+
+  # Tests cannot import pyfftw. pyfftw works fine though.
+  doCheck = false;
+
+  preConfigure = ''
+    export LDFLAGS="-L${pkgs.fftw.dev}/lib -L${pkgs.fftwFloat.out}/lib -L${pkgs.fftwLongDouble.out}/lib"
+    export CFLAGS="-I${pkgs.fftw.dev}/include -I${pkgs.fftwFloat.dev}/include -I${pkgs.fftwLongDouble.dev}/include"
+  '';
+
+  meta = with lib; {
+    description = "A pythonic wrapper around FFTW, the FFT library, presenting a unified interface for all the supported transforms";
+    homepage = "http://hgomersall.github.com/pyFFTW";
+    license = with licenses; [ bsd2 bsd3 ];
+    maintainers = with maintainers; [ fridh ];
+  };
+}
+```
+
+Note also the line `doCheck = false;`, we explicitly disabled running the test-suite.
+
+#### Testing Python Packages {#testing-python-packages}
+
+It is highly encouraged to have testing as part of the package build. This
+helps to avoid situations where the package was able to build and install,
+but is not usable at runtime. Currently, all packages will use the `test`
+command provided by the setup.py (i.e. `python setup.py test`). However,
+this is currently deprecated https://github.com/pypa/setuptools/pull/1878
+and your package should provide its own checkPhase.
+
+*NOTE:* The `checkPhase` for python maps to the `installCheckPhase` on a
+normal derivation. This is due to many python packages not behaving well
+to the pre-installed version of the package. Version info, and natively
+compiled extensions generally only exist in the install directory, and
+thus can cause issues when a test suite asserts on that behavior.
+
+*NOTE:* Tests should only be disabled if they don't agree with nix
+(e.g. external dependencies, network access, flakey tests), however,
+as many tests should be enabled as possible. Failing tests can still be
+a good indication that the package is not in a valid state.
+
+#### Using pytest {#using-pytest}
+
+Pytest is the most common test runner for python repositories. A trivial
+test run would be:
+
+```
+  checkInputs = [ pytest ];
+  checkPhase = "pytest";
+```
+
+However, many repositories' test suites do not translate well to nix's build
+sandbox, and will generally need many tests to be disabled.
+
+To filter tests using pytest, one can do the following:
+
+```
+  checkInputs = [ pytest ];
+  # avoid tests which need additional data or touch network
+  checkPhase = ''
+    pytest tests/ --ignore=tests/integration -k 'not download and not update'
+  '';
+```
+
+`--ignore` will tell pytest to ignore that file or directory from being
+collected as part of a test run. This is useful is a file uses a package
+which is not available in nixpkgs, thus skipping that test file is much
+easier than having to create a new package.
+
+`-k` is used to define a predicate for test names. In this example, we are
+filtering out tests which contain `download` or `update` in their test case name.
+Only one `-k` argument is allowed, and thus a long predicate should be concatenated
+with “\\” and wrapped to the next line.
+
+*NOTE:* In pytest==6.0.1, the use of “\\” to continue a line (e.g. `-k 'not download \'`) has
+been removed, in this case, it's recommended to use `pytestCheckHook`.
+
+#### Using pytestCheckHook {#using-pytestcheckhook}
+
+`pytestCheckHook` is a convenient hook which will substitute the setuptools
+`test` command for a checkPhase which runs `pytest`. This is also beneficial
+when a package may need many items disabled to run the test suite.
+
+Using the example above, the analagous pytestCheckHook usage would be:
+
+```
+  checkInputs = [ pytestCheckHook ];
+
+  # requires additional data
+  pytestFlagsArray = [ "tests/" "--ignore=tests/integration" ];
+
+  disabledTests = [
+    # touches network
+    "download"
+    "update"
+  ];
+
+  disabledTestPaths = [
+    "tests/test_failing.py"
+  ];
+```
+
+This is expecially useful when tests need to be conditionallydisabled,
+for example:
+
+```
+  disabledTests = [
+    # touches network
+    "download"
+    "update"
+  ] ++ lib.optionals (pythonAtLeast "3.8") [
+    # broken due to python3.8 async changes
+    "async"
+  ] ++ lib.optionals stdenv.isDarwin [
+    # can fail when building with other packages
+    "socket"
+  ];
+```
+Trying to concatenate the related strings to disable tests in a regular checkPhase
+would be much harder to read. This also enables us to comment on why specific tests
+are disabled.
+
+#### Using pythonImportsCheck {#using-pythonimportscheck}
+
+Although unit tests are highly prefered to validate correctness of a package, not
+all packages have test suites that can be ran easily, and some have none at all.
+To help ensure the package still works, `pythonImportsCheck` can attempt to import
+the listed modules.
+
+```
+  pythonImportsCheck = [ "requests" "urllib" ];
+```
+roughly translates to:
+```
+  postCheck = ''
+    PYTHONPATH=$out/${python.sitePackages}:$PYTHONPATH
+    python -c "import requests; import urllib"
+  '';
+```
+However, this is done in it's own phase, and not dependent on whether `doCheck = true;`
+
+This can also be useful in verifying that the package doesn't assume commonly
+present packages (e.g. `setuptools`)
+
+### Develop local package {#develop-local-package}
+
+As a Python developer you're likely aware of [development mode](http://setuptools.readthedocs.io/en/latest/setuptools.html#development-mode)
+(`python setup.py develop`); instead of installing the package this command
+creates a special link to the project code. That way, you can run updated code
+without having to reinstall after each and every change you make. Development
+mode is also available. Let's see how you can use it.
+
+In the previous Nix expression the source was fetched from an url. We can also
+refer to a local source instead using `src = ./path/to/source/tree;`
+
+If we create a `shell.nix` file which calls `buildPythonPackage`, and if `src`
+is a local source, and if the local source has a `setup.py`, then development
+mode is activated.
+
+In the following example we create a simple environment that has a Python 3.8
+version of our package in it, as well as its dependencies and other packages we
+like to have in the environment, all specified with `propagatedBuildInputs`.
+Indeed, we can just add any package we like to have in our environment to
+`propagatedBuildInputs`.
+
+```nix
+with import <nixpkgs> {};
+with python38Packages;
+
+buildPythonPackage rec {
+  name = "mypackage";
+  src = ./path/to/package/source;
+  propagatedBuildInputs = [ pytest numpy pkgs.libsndfile ];
+}
+```
+
+It is important to note that due to how development mode is implemented on Nix
+it is not possible to have multiple packages simultaneously in development mode.
+
+### Organising your packages {#organising-your-packages}
+
+So far we discussed how you can use Python on Nix, and how you can develop with
+it. We've looked at how you write expressions to package Python packages, and we
+looked at how you can create environments in which specified packages are
+available.
+
+At some point you'll likely have multiple packages which you would
+like to be able to use in different projects. In order to minimise unnecessary
+duplication we now look at how you can maintain a repository with your
+own packages. The important functions here are `import` and `callPackage`.
+
+### Including a derivation using `callPackage` {#including-a-derivation-using-callpackage}
+
+Earlier we created a Python environment using `withPackages`, and included the
+`toolz` package via a `let` expression.
+Let's split the package definition from the environment definition.
+
+We first create a function that builds `toolz` in `~/path/to/toolz/release.nix`
+
+```nix
+{ lib, buildPythonPackage }:
+
+buildPythonPackage rec {
+  pname = "toolz";
+  version = "0.10.0";
+
+  src = fetchPypi {
+    inherit pname version;
+    sha256 = "08fdd5ef7c96480ad11c12d472de21acd32359996f69a5259299b540feba4560";
+  };
+
+  meta = with lib; {
+    homepage = "https://github.com/pytoolz/toolz/";
+    description = "List processing tools and functional utilities";
+    license = licenses.bsd3;
+    maintainers = with maintainers; [ fridh ];
+  };
+}
+```
+
+It takes an argument `buildPythonPackage`. We now call this function using
+`callPackage` in the definition of our environment
+
+```nix
+with import <nixpkgs> {};
+
+( let
+    toolz = callPackage /path/to/toolz/release.nix {
+      buildPythonPackage = python38Packages.buildPythonPackage;
+    };
+  in python38.withPackages (ps: [ ps.numpy toolz ])
+).env
+```
+
+Important to remember is that the Python version for which the package is made
+depends on the `python` derivation that is passed to `buildPythonPackage`. Nix
+tries to automatically pass arguments when possible, which is why generally you
+don't explicitly define which `python` derivation should be used. In the above
+example we use `buildPythonPackage` that is part of the set `python38Packages`,
+and in this case the `python38` interpreter is automatically used.
+
+## Reference {#reference}
+
+### Interpreters {#interpreters}
+
+Versions 2.7, 3.7, 3.8 and 3.9 of the CPython interpreter are available as
+respectively `python27`, `python37`, `python38` and `python39`. The
+aliases `python2` and `python3` correspond to respectively `python27` and
+`python39`. The attribute `python` maps to `python2`. The PyPy interpreters
+compatible with Python 2.7 and 3 are available as `pypy27` and `pypy3`, with
+aliases `pypy2` mapping to `pypy27` and `pypy` mapping to `pypy2`. The Nix
+expressions for the interpreters can be found in
+`pkgs/development/interpreters/python`.
+
+All packages depending on any Python interpreter get appended
+`out/{python.sitePackages}` to `$PYTHONPATH` if such directory
+exists.
+
+#### Missing `tkinter` module standard library {#missing-tkinter-module-standard-library}
+
+To reduce closure size the `Tkinter`/`tkinter` is available as a separate package, `pythonPackages.tkinter`.
+
+#### Attributes on interpreters packages {#attributes-on-interpreters-packages}
+
+Each interpreter has the following attributes:
+
+- `libPrefix`. Name of the folder in `${python}/lib/` for corresponding interpreter.
+- `interpreter`. Alias for `${python}/bin/${executable}`.
+- `buildEnv`. Function to build python interpreter environments with extra packages bundled together. See section *python.buildEnv function* for usage and documentation.
+- `withPackages`. Simpler interface to `buildEnv`. See section *python.withPackages function* for usage and documentation.
+- `sitePackages`. Alias for `lib/${libPrefix}/site-packages`.
+- `executable`. Name of the interpreter executable, e.g. `python3.8`.
+- `pkgs`. Set of Python packages for that specific interpreter. The package set can be modified by overriding the interpreter and passing `packageOverrides`.
+
+### Optimizations {#optimizations}
+
+The Python interpreters are by default not build with optimizations enabled, because
+the builds are in that case not reproducible. To enable optimizations, override the
+interpreter of interest, e.g using
+
+```
+let
+  pkgs = import ./. {};
+  mypython = pkgs.python3.override {
+    enableOptimizations = true;
+    reproducibleBuild = false;
+    self = mypython;
+  };
+in mypython
+```
+
+### Building packages and applications {#building-packages-and-applications}
+
+Python libraries and applications that use `setuptools` or
+`distutils` are typically built with respectively the `buildPythonPackage` and
+`buildPythonApplication` functions. These two functions also support installing a `wheel`.
+
+All Python packages reside in `pkgs/top-level/python-packages.nix` and all
+applications elsewhere. In case a package is used as both a library and an
+application, then the package should be in `pkgs/top-level/python-packages.nix`
+since only those packages are made available for all interpreter versions. The
+preferred location for library expressions is in
+`pkgs/development/python-modules`. It is important that these packages are
+called from `pkgs/top-level/python-packages.nix` and not elsewhere, to guarantee
+the right version of the package is built.
+
+Based on the packages defined in `pkgs/top-level/python-packages.nix` an
+attribute set is created for each available Python interpreter. The available
+sets are
+
+* `pkgs.python27Packages`
+* `pkgs.python37Packages`
+* `pkgs.python38Packages`
+* `pkgs.python39Packages`
+* `pkgs.python310Packages`
+* `pkgs.python311Packages`
+* `pkgs.pypyPackages`
+
+and the aliases
+
+* `pkgs.python2Packages` pointing to `pkgs.python27Packages`
+* `pkgs.python3Packages` pointing to `pkgs.python39Packages`
+* `pkgs.pythonPackages` pointing to `pkgs.python2Packages`
+
+#### `buildPythonPackage` function {#buildpythonpackage-function}
+
+The `buildPythonPackage` function is implemented in
+`pkgs/development/interpreters/python/mk-python-derivation`
+using setup hooks.
+
+The following is an example:
+
+```nix
+{ lib, buildPythonPackage, fetchPypi, hypothesis, setuptools-scm, attrs, py, setuptools, six, pluggy }:
+
+buildPythonPackage rec {
+  pname = "pytest";
+  version = "3.3.1";
+
+  src = fetchPypi {
+    inherit pname version;
+    sha256 = "cf8436dc59d8695346fcd3ab296de46425ecab00d64096cebe79fb51ecb2eb93";
+  };
+
+  postPatch = ''
+    # don't test bash builtins
+    rm testing/test_argcomplete.py
+  '';
+
+  checkInputs = [ hypothesis ];
+  nativeBuildInputs = [ setuptools-scm ];
+  propagatedBuildInputs = [ attrs py setuptools six pluggy ];
+
+  meta = with lib; {
+    maintainers = with maintainers; [ domenkozar lovek323 madjar lsix ];
+    description = "Framework for writing tests";
+  };
+}
+```
+
+The `buildPythonPackage` mainly does four things:
+
+* In the `buildPhase`, it calls `${python.interpreter} setup.py bdist_wheel` to
+  build a wheel binary zipfile.
+* In the `installPhase`, it installs the wheel file using `pip install *.whl`.
+* In the `postFixup` phase, the `wrapPythonPrograms` bash function is called to
+  wrap all programs in the `$out/bin/*` directory to include `$PATH`
+  environment variable and add dependent libraries to script's `sys.path`.
+* In the `installCheck` phase, `${python.interpreter} setup.py test` is ran.
+
+By default tests are run because `doCheck = true`. Test dependencies, like
+e.g. the test runner, should be added to `checkInputs`.
+
+By default `meta.platforms` is set to the same value
+as the interpreter unless overridden otherwise.
+
+##### `buildPythonPackage` parameters {#buildpythonpackage-parameters}
+
+All parameters from `stdenv.mkDerivation` function are still supported. The
+following are specific to `buildPythonPackage`:
+
+* `catchConflicts ? true`: If `true`, abort package build if a package name
+  appears more than once in dependency tree. Default is `true`.
+* `disabled` ? false: If `true`, package is not built for the particular Python
+  interpreter version.
+* `dontWrapPythonPrograms ? false`: Skip wrapping of Python programs.
+* `permitUserSite ? false`: Skip setting the `PYTHONNOUSERSITE` environment
+  variable in wrapped programs.
+* `format ? "setuptools"`: Format of the source. Valid options are
+  `"setuptools"`, `"pyproject"`, `"flit"`, `"wheel"`, and `"other"`.
+  `"setuptools"` is for when the source has a `setup.py` and `setuptools` is
+  used to build a wheel, `flit`, in case `flit` should be used to build a wheel,
+  and `wheel` in case a wheel is provided. Use `other` when a custom
+  `buildPhase` and/or `installPhase` is needed.
+* `makeWrapperArgs ? []`: A list of strings. Arguments to be passed to
+  `makeWrapper`, which wraps generated binaries. By default, the arguments to
+  `makeWrapper` set `PATH` and `PYTHONPATH` environment variables before calling
+  the binary. Additional arguments here can allow a developer to set environment
+  variables which will be available when the binary is run. For example,
+  `makeWrapperArgs = ["--set FOO BAR" "--set BAZ QUX"]`.
+* `namePrefix`: Prepends text to `${name}` parameter. In case of libraries, this
+  defaults to `"python3.8-"` for Python 3.8, etc., and in case of applications
+  to `""`.
+* `pipInstallFlags ? []`: A list of strings. Arguments to be passed to `pip
+  install`. To pass options to `python setup.py install`, use
+  `--install-option`. E.g., `pipInstallFlags=["--install-option='--cpp_implementation'"]`.
+* `pythonPath ? []`: List of packages to be added into `$PYTHONPATH`. Packages
+  in `pythonPath` are not propagated (contrary to `propagatedBuildInputs`).
+* `preShellHook`: Hook to execute commands before `shellHook`.
+* `postShellHook`: Hook to execute commands after `shellHook`.
+* `removeBinByteCode ? true`: Remove bytecode from `/bin`. Bytecode is only
+  created when the filenames end with `.py`.
+* `setupPyGlobalFlags ? []`: List of flags passed to `setup.py` command.
+* `setupPyBuildFlags ? []`: List of flags passed to `setup.py build_ext` command.
+
+The `stdenv.mkDerivation` function accepts various parameters for describing
+build inputs (see "Specifying dependencies"). The following are of special
+interest for Python packages, either because these are primarily used, or
+because their behaviour is different:
+
+* `nativeBuildInputs ? []`: Build-time only dependencies. Typically executables
+  as well as the items listed in `setup_requires`.
+* `buildInputs ? []`: Build and/or run-time dependencies that need to be
+  compiled for the host machine. Typically non-Python libraries which are being
+  linked.
+* `checkInputs ? []`: Dependencies needed for running the `checkPhase`. These
+  are added to `nativeBuildInputs` when `doCheck = true`. Items listed in
+  `tests_require` go here.
+* `propagatedBuildInputs ? []`: Aside from propagating dependencies,
+  `buildPythonPackage` also injects code into and wraps executables with the
+  paths included in this list. Items listed in `install_requires` go here.
+
+##### Overriding Python packages {#overriding-python-packages}
+
+The `buildPythonPackage` function has a `overridePythonAttrs` method that can be
+used to override the package. In the following example we create an environment
+where we have the `blaze` package using an older version of `pandas`. We
+override first the Python interpreter and pass `packageOverrides` which contains
+the overrides for packages in the package set.
+
+```nix
+with import <nixpkgs> {};
+
+(let
+  python = let
+    packageOverrides = self: super: {
+      pandas = super.pandas.overridePythonAttrs(old: rec {
+        version = "0.19.1";
+        src =  super.fetchPypi {
+          pname = "pandas";
+          inherit version;
+          sha256 = "08blshqj9zj1wyjhhw3kl2vas75vhhicvv72flvf1z3jvapgw295";
+        };
+      });
+    };
+  in pkgs.python3.override {inherit packageOverrides; self = python;};
+
+in python.withPackages(ps: [ps.blaze])).env
+```
+
+#### Optional extra dependencies
+
+Some packages define optional dependencies for additional features. With
+`setuptools` this is called `extras_require` and `flit` calls it `extras-require`. A
+method for supporting this is by declaring the extras of a package in its
+`passthru`, e.g. in case of the package `dask`
+
+```nix
+passthru.extras-require = {
+  complete = [ distributed ];
+};
+```
+
+and letting the package requiring the extra add the list to its dependencies
+
+```nix
+propagatedBuildInputs = [
+  ...
+] ++ dask.extras-require.complete;
+```
+
+Note this method is preferred over adding parameters to builders, as that can
+result in packages depending on different variants and thereby causing
+collisions.
+
+#### `buildPythonApplication` function {#buildpythonapplication-function}
+
+The `buildPythonApplication` function is practically the same as
+`buildPythonPackage`. The main purpose of this function is to build a Python
+package where one is interested only in the executables, and not importable
+modules. For that reason, when adding this package to a `python.buildEnv`, the
+modules won't be made available.
+
+Another difference is that `buildPythonPackage` by default prefixes the names of
+the packages with the version of the interpreter. Because this is irrelevant for
+applications, the prefix is omitted.
+
+When packaging a Python application with `buildPythonApplication`, it should be
+called with `callPackage` and passed `python` or `pythonPackages` (possibly
+specifying an interpreter version), like this:
+
+```nix
+{ lib, python3 }:
+
+python3.pkgs.buildPythonApplication rec {
+  pname = "luigi";
+  version = "2.7.9";
+
+  src = python3.pkgs.fetchPypi {
+    inherit pname version;
+    sha256 = "035w8gqql36zlan0xjrzz9j4lh9hs0qrsgnbyw07qs7lnkvbdv9x";
+  };
+
+  propagatedBuildInputs = with python3.pkgs; [ tornado python-daemon ];
+
+  meta = with lib; {
+    ...
+  };
+}
+```
+
+This is then added to `all-packages.nix` just as any other application would be.
+
+```nix
+luigi = callPackage ../applications/networking/cluster/luigi { };
+```
+
+Since the package is an application, a consumer doesn't need to care about
+Python versions or modules, which is why they don't go in `pythonPackages`.
+
+#### `toPythonApplication` function {#topythonapplication-function}
+
+A distinction is made between applications and libraries, however, sometimes a
+package is used as both. In this case the package is added as a library to
+`python-packages.nix` and as an application to `all-packages.nix`. To reduce
+duplication the `toPythonApplication` can be used to convert a library to an
+application.
+
+The Nix expression shall use `buildPythonPackage` and be called from
+`python-packages.nix`. A reference shall be created from `all-packages.nix` to
+the attribute in `python-packages.nix`, and the `toPythonApplication` shall be
+applied to the reference:
+
+```nix
+youtube-dl = with pythonPackages; toPythonApplication youtube-dl;
+```
+
+#### `toPythonModule` function {#topythonmodule-function}
+
+In some cases, such as bindings, a package is created using
+`stdenv.mkDerivation` and added as attribute in `all-packages.nix`. The Python
+bindings should be made available from `python-packages.nix`. The
+`toPythonModule` function takes a derivation and makes certain Python-specific
+modifications.
+
+```nix
+opencv = toPythonModule (pkgs.opencv.override {
+  enablePython = true;
+  pythonPackages = self;
+});
+```
+
+Do pay attention to passing in the right Python version!
+
+#### `python.buildEnv` function {#python.buildenv-function}
+
+Python environments can be created using the low-level `pkgs.buildEnv` function.
+This example shows how to create an environment that has the Pyramid Web Framework.
+Saving the following as `default.nix`
+
+```nix
+with import <nixpkgs> {};
+
+python.buildEnv.override {
+  extraLibs = [ pythonPackages.pyramid ];
+  ignoreCollisions = true;
+}
+```
+
+and running `nix-build` will create
+
+```
+/nix/store/cf1xhjwzmdki7fasgr4kz6di72ykicl5-python-2.7.8-env
+```
+
+with wrapped binaries in `bin/`.
+
+You can also use the `env` attribute to create local environments with needed
+packages installed. This is somewhat comparable to `virtualenv`. For example,
+running `nix-shell` with the following `shell.nix`
+
+```nix
+with import <nixpkgs> {};
+
+(python3.buildEnv.override {
+  extraLibs = with python3Packages; [ numpy requests ];
+}).env
+```
+
+will drop you into a shell where Python will have the
+specified packages in its path.
+
+##### `python.buildEnv` arguments {#python.buildenv-arguments}
+
+
+* `extraLibs`: List of packages installed inside the environment.
+* `postBuild`: Shell command executed after the build of environment.
+* `ignoreCollisions`: Ignore file collisions inside the environment (default is `false`).
+* `permitUserSite`: Skip setting the `PYTHONNOUSERSITE` environment variable in
+  wrapped binaries in the environment.
+
+#### `python.withPackages` function {#python.withpackages-function}
+
+The `python.withPackages` function provides a simpler interface to the `python.buildEnv` functionality.
+It takes a function as an argument that is passed the set of python packages and returns the list
+of the packages to be included in the environment. Using the `withPackages` function, the previous
+example for the Pyramid Web Framework environment can be written like this:
+
+```nix
+with import <nixpkgs> {};
+
+python.withPackages (ps: [ps.pyramid])
+```
+
+`withPackages` passes the correct package set for the specific interpreter
+version as an argument to the function. In the above example, `ps` equals
+`pythonPackages`. But you can also easily switch to using python3:
+
+```nix
+with import <nixpkgs> {};
+
+python3.withPackages (ps: [ps.pyramid])
+```
+
+Now, `ps` is set to `python3Packages`, matching the version of the interpreter.
+
+As `python.withPackages` simply uses `python.buildEnv` under the hood, it also
+supports the `env` attribute. The `shell.nix` file from the previous section can
+thus be also written like this:
+
+```nix
+with import <nixpkgs> {};
+
+(python38.withPackages (ps: [ps.numpy ps.requests])).env
+```
+
+In contrast to `python.buildEnv`, `python.withPackages` does not support the
+more advanced options such as `ignoreCollisions = true` or `postBuild`. If you
+need them, you have to use `python.buildEnv`.
+
+Python 2 namespace packages may provide `__init__.py` that collide. In that case
+`python.buildEnv` should be used with `ignoreCollisions = true`.
+
+#### Setup hooks {#setup-hooks}
+
+The following are setup hooks specifically for Python packages. Most of these
+are used in `buildPythonPackage`.
+
+- `eggUnpackhook` to move an egg to the correct folder so it can be installed
+  with the `eggInstallHook`
+- `eggBuildHook` to skip building for eggs.
+- `eggInstallHook` to install eggs.
+- `flitBuildHook` to build a wheel using `flit`.
+- `pipBuildHook` to build a wheel using `pip` and PEP 517. Note a build system
+  (e.g. `setuptools` or `flit`) should still be added as `nativeBuildInput`.
+- `pipInstallHook` to install wheels.
+- `pytestCheckHook` to run tests with `pytest`. See [example usage](#using-pytestcheckhook).
+- `pythonCatchConflictsHook` to check whether a Python package is not already existing.
+- `pythonImportsCheckHook` to check whether importing the listed modules works.
+- `pythonRemoveBinBytecode` to remove bytecode from the `/bin` folder.
+- `setuptoolsBuildHook` to build a wheel using `setuptools`.
+- `setuptoolsCheckHook` to run tests with `python setup.py test`.
+- `venvShellHook` to source a Python 3 `venv` at the `venvDir` location. A
+  `venv` is created if it does not yet exist. `postVenvCreation` can be used to
+  to run commands only after venv is first created.
+- `wheelUnpackHook` to move a wheel to the correct folder so it can be installed
+  with the `pipInstallHook`.
+
+### Development mode {#development-mode}
+
+Development or editable mode is supported. To develop Python packages
+`buildPythonPackage` has additional logic inside `shellPhase` to run `pip
+install -e . --prefix $TMPDIR/`for the package.
+
+Warning: `shellPhase` is executed only if `setup.py` exists.
+
+Given a `default.nix`:
+
+```nix
+with import <nixpkgs> {};
+
+pythonPackages.buildPythonPackage {
+  name = "myproject";
+  buildInputs = with pythonPackages; [ pyramid ];
+
+  src = ./.;
+}
+```
+
+Running `nix-shell` with no arguments should give you the environment in which
+the package would be built with `nix-build`.
+
+Shortcut to setup environments with C headers/libraries and Python packages:
+
+```shell
+nix-shell -p pythonPackages.pyramid zlib libjpeg git
+```
+
+Note: There is a boolean value `lib.inNixShell` set to `true` if nix-shell is invoked.
+
+### Tools {#tools}
+
+Packages inside nixpkgs are written by hand. However many tools exist in
+community to help save time. No tool is preferred at the moment.
+
+- [pypi2nix](https://github.com/nix-community/pypi2nix): Generate Nix
+  expressions for your Python project. Note that [sharing derivations from
+  pypi2nix with nixpkgs is possible but not
+  encouraged](https://github.com/nix-community/pypi2nix/issues/222#issuecomment-443497376).
+- [nixpkgs-pytools](https://github.com/nix-community/nixpkgs-pytools)
+- [poetry2nix](https://github.com/nix-community/poetry2nix)
+
+### Deterministic builds {#deterministic-builds}
+
+The Python interpreters are now built deterministically. Minor modifications had
+to be made to the interpreters in order to generate deterministic bytecode. This
+has security implications and is relevant for those using Python in a
+`nix-shell`.
+
+When the environment variable `DETERMINISTIC_BUILD` is set, all bytecode will
+have timestamp 1. The `buildPythonPackage` function sets `DETERMINISTIC_BUILD=1`
+and [PYTHONHASHSEED=0](https://docs.python.org/3.8/using/cmdline.html#envvar-PYTHONHASHSEED).
+Both are also exported in `nix-shell`.
+
+### Automatic tests {#automatic-tests}
+
+It is recommended to test packages as part of the build process.
+Source distributions (`sdist`) often include test files, but not always.
+
+By default the command `python setup.py test` is run as part of the
+`checkPhase`, but often it is necessary to pass a custom `checkPhase`. An
+example of such a situation is when `py.test` is used.
+
+#### Common issues {#common-issues}
+
+* Non-working tests can often be deselected. By default `buildPythonPackage`
+  runs `python setup.py test`. Most Python modules follows the standard test
+  protocol where the pytest runner can be used instead. `py.test` supports a
+  `-k` parameter to ignore test methods or classes:
+
+  ```nix
+  buildPythonPackage {
+    # ...
+    # assumes the tests are located in tests
+    checkInputs = [ pytest ];
+    checkPhase = ''
+      py.test -k 'not function_name and not other_function' tests
+    '';
+  }
+  ```
+
+* Tests that attempt to access `$HOME` can be fixed by using the following
+  work-around before running tests (e.g. `preCheck`): `export HOME=$(mktemp -d)`
+
+## FAQ {#faq}
+
+### How to solve circular dependencies? {#how-to-solve-circular-dependencies}
+
+Consider the packages `A` and `B` that depend on each other. When packaging `B`,
+a solution is to override package `A` not to depend on `B` as an input. The same
+should also be done when packaging `A`.
+
+### How to override a Python package? {#how-to-override-a-python-package}
+
+We can override the interpreter and pass `packageOverrides`. In the following
+example we rename the `pandas` package and build it.
+
+```nix
+with import <nixpkgs> {};
+
+(let
+  python = let
+    packageOverrides = self: super: {
+      pandas = super.pandas.overridePythonAttrs(old: {name="foo";});
+    };
+  in pkgs.python38.override {inherit packageOverrides;};
+
+in python.withPackages(ps: [ps.pandas])).env
+```
+
+Using `nix-build` on this expression will build an environment that contains the
+package `pandas` but with the new name `foo`.
+
+All packages in the package set will use the renamed package. A typical use case
+is to switch to another version of a certain package. For example, in the
+Nixpkgs repository we have multiple versions of `django` and `scipy`. In the
+following example we use a different version of `scipy` and create an
+environment that uses it. All packages in the Python package set will now use
+the updated `scipy` version.
+
+```nix
+with import <nixpkgs> {};
+
+( let
+    packageOverrides = self: super: {
+      scipy = super.scipy_0_17;
+    };
+  in (pkgs.python38.override {inherit packageOverrides;}).withPackages (ps: [ps.blaze])
+).env
+```
+
+The requested package `blaze` depends on `pandas` which itself depends on `scipy`.
+
+If you want the whole of Nixpkgs to use your modifications, then you can use
+`overlays` as explained in this manual. In the following example we build a
+`inkscape` using a different version of `numpy`.
+
+```nix
+let
+  pkgs = import <nixpkgs> {};
+  newpkgs = import pkgs.path { overlays = [ (self: super: {
+    python38 = let
+      packageOverrides = python-self: python-super: {
+        numpy = python-super.numpy_1_18;
+      };
+    in super.python38.override {inherit packageOverrides;};
+  } ) ]; };
+in newpkgs.inkscape
+```
+
+### `python setup.py bdist_wheel` cannot create .whl {#python-setup.py-bdist_wheel-cannot-create-.whl}
+
+Executing `python setup.py bdist_wheel` in a `nix-shell `fails with
+```
+ValueError: ZIP does not support timestamps before 1980
+```
+
+This is because files from the Nix store (which have a timestamp of the UNIX
+epoch of January 1, 1970) are included in the .ZIP, but .ZIP archives follow the
+DOS convention of counting timestamps from 1980.
+
+The command `bdist_wheel` reads the `SOURCE_DATE_EPOCH` environment variable,
+which `nix-shell` sets to 1. Unsetting this variable or giving it a value
+corresponding to 1980 or later enables building wheels.
+
+Use 1980 as timestamp:
+
+```shell
+nix-shell --run "SOURCE_DATE_EPOCH=315532800 python3 setup.py bdist_wheel"
+```
+
+or the current time:
+
+```shell
+nix-shell --run "SOURCE_DATE_EPOCH=$(date +%s) python3 setup.py bdist_wheel"
+```
+
+or unset `SOURCE_DATE_EPOCH`:
+
+```shell
+nix-shell --run "unset SOURCE_DATE_EPOCH; python3 setup.py bdist_wheel"
+```
+
+### `install_data` / `data_files` problems {#install_data-data_files-problems}
+
+If you get the following error:
+
+```
+could not create '/nix/store/6l1bvljpy8gazlsw2aw9skwwp4pmvyxw-python-2.7.8/etc':
+Permission denied
+```
+
+This is a [known bug](https://github.com/pypa/setuptools/issues/130) in
+`setuptools`. Setuptools `install_data` does not respect `--prefix`. An example
+of such package using the feature is `pkgs/tools/X11/xpra/default.nix`.
+
+As workaround install it as an extra `preInstall` step:
+
+```shell
+${python.interpreter} setup.py install_data --install-dir=$out --root=$out
+sed -i '/ = data\_files/d' setup.py
+```
+
+### Rationale of non-existent global site-packages {#rationale-of-non-existent-global-site-packages}
+
+On most operating systems a global `site-packages` is maintained. This however
+becomes problematic if you want to run multiple Python versions or have multiple
+versions of certain libraries for your projects. Generally, you would solve such
+issues by creating virtual environments using `virtualenv`.
+
+On Nix each package has an isolated dependency tree which, in the case of
+Python, guarantees the right versions of the interpreter and libraries or
+packages are available. There is therefore no need to maintain a global `site-packages`.
+
+If you want to create a Python environment for development, then the recommended
+method is to use `nix-shell`, either with or without the `python.buildEnv`
+function.
+
+### How to consume Python modules using pip in a virtual environment like I am used to on other Operating Systems? {#how-to-consume-python-modules-using-pip-in-a-virtual-environment-like-i-am-used-to-on-other-operating-systems}
+
+While this approach is not very idiomatic from Nix perspective, it can still be
+useful when dealing with pre-existing projects or in situations where it's not
+feasible or desired to write derivations for all required dependencies.
+
+This is an example of a `default.nix` for a `nix-shell`, which allows to consume
+a virtual environment created by `venv`, and install Python modules through
+`pip` the traditional way.
+
+Create this `default.nix` file, together with a `requirements.txt` and simply
+execute `nix-shell`.
+
+```nix
+with import <nixpkgs> { };
+
+let
+  pythonPackages = python3Packages;
+in pkgs.mkShell rec {
+  name = "impurePythonEnv";
+  venvDir = "./.venv";
+  buildInputs = [
+    # A Python interpreter including the 'venv' module is required to bootstrap
+    # the environment.
+    pythonPackages.python
+
+    # This execute some shell code to initialize a venv in $venvDir before
+    # dropping into the shell
+    pythonPackages.venvShellHook
+
+    # Those are dependencies that we would like to use from nixpkgs, which will
+    # add them to PYTHONPATH and thus make them accessible from within the venv.
+    pythonPackages.numpy
+    pythonPackages.requests
+
+    # In this particular example, in order to compile any binary extensions they may
+    # require, the Python modules listed in the hypothetical requirements.txt need
+    # the following packages to be installed locally:
+    taglib
+    openssl
+    git
+    libxml2
+    libxslt
+    libzip
+    zlib
+  ];
+
+  # Run this command, only after creating the virtual environment
+  postVenvCreation = ''
+    unset SOURCE_DATE_EPOCH
+    pip install -r requirements.txt
+  '';
+
+  # Now we can execute any commands within the virtual environment.
+  # This is optional and can be left out to run pip manually.
+  postShellHook = ''
+    # allow pip to install wheels
+    unset SOURCE_DATE_EPOCH
+  '';
+
+}
+```
+
+In case the supplied venvShellHook is insufficient, or when Python 2 support is
+needed, you can define your own shell hook and adapt to your needs like in the
+following example:
+
+```nix
+with import <nixpkgs> { };
+
+let
+  venvDir = "./.venv";
+  pythonPackages = python3Packages;
+in pkgs.mkShell rec {
+  name = "impurePythonEnv";
+  buildInputs = [
+    pythonPackages.python
+    # Needed when using python 2.7
+    # pythonPackages.virtualenv
+    # ...
+  ];
+
+  # This is very close to how venvShellHook is implemented, but
+  # adapted to use 'virtualenv'
+  shellHook = ''
+    SOURCE_DATE_EPOCH=$(date +%s)
+
+    if [ -d "${venvDir}" ]; then
+      echo "Skipping venv creation, '${venvDir}' already exists"
+    else
+      echo "Creating new venv environment in path: '${venvDir}'"
+      # Note that the module venv was only introduced in python 3, so for 2.7
+      # this needs to be replaced with a call to virtualenv
+      ${pythonPackages.python.interpreter} -m venv "${venvDir}"
+    fi
+
+    # Under some circumstances it might be necessary to add your virtual
+    # environment to PYTHONPATH, which you can do here too;
+    # PYTHONPATH=$PWD/${venvDir}/${pythonPackages.python.sitePackages}/:$PYTHONPATH
+
+    source "${venvDir}/bin/activate"
+
+    # As in the previous example, this is optional.
+    pip install -r requirements.txt
+  '';
+}
+```
+
+Note that the `pip install` is an imperative action. So every time `nix-shell`
+is executed it will attempt to download the Python modules listed in
+requirements.txt. However these will be cached locally within the `virtualenv`
+folder and not downloaded again.
+
+### How to override a Python package from `configuration.nix`? {#how-to-override-a-python-package-from-configuration.nix}
+
+If you need to change a package's attribute(s) from `configuration.nix` you could do:
+
+```nix
+  nixpkgs.config.packageOverrides = super: {
+    python = super.python.override {
+      packageOverrides = python-self: python-super: {
+        twisted = python-super.twisted.overrideAttrs (oldAttrs: {
+          src = super.fetchPypi {
+            pname = "twisted";
+            version = "19.10.0";
+            sha256 = "7394ba7f272ae722a74f3d969dcf599bc4ef093bc392038748a490f1724a515d";
+            extension = "tar.bz2";
+          };
+        });
+      };
+    };
+  };
+```
+
+`pythonPackages.twisted` is now globally overridden.
+All packages and also all NixOS services that reference `twisted`
+(such as `services.buildbot-worker`) now use the new definition.
+Note that `python-super` refers to the old package set and `python-self`
+to the new, overridden version.
+
+To modify only a Python package set instead of a whole Python derivation, use
+this snippet:
+
+```nix
+  myPythonPackages = pythonPackages.override {
+    overrides = self: super: {
+      twisted = ...;
+    };
+  }
+```
+
+### How to override a Python package using overlays? {#how-to-override-a-python-package-using-overlays}
+
+Use the following overlay template:
+
+```nix
+self: super: {
+  python = super.python.override {
+    packageOverrides = python-self: python-super: {
+      twisted = python-super.twisted.overrideAttrs (oldAttrs: {
+        src = super.fetchPypi {
+          pname = "twisted";
+          version = "19.10.0";
+          sha256 = "7394ba7f272ae722a74f3d969dcf599bc4ef093bc392038748a490f1724a515d";
+          extension = "tar.bz2";
+        };
+      });
+    };
+  };
+}
+```
+
+### How to use Intel’s MKL with numpy and scipy? {#how-to-use-intels-mkl-with-numpy-and-scipy}
+
+MKL can be configured using an overlay. See the section "[Using overlays to
+configure alternatives](#sec-overlays-alternatives-blas-lapack)".
+
+### What inputs do `setup_requires`, `install_requires` and `tests_require` map to? {#what-inputs-do-setup_requires-install_requires-and-tests_require-map-to}
+
+In a `setup.py` or `setup.cfg` it is common to declare dependencies:
+
+* `setup_requires` corresponds to `nativeBuildInputs`
+* `install_requires` corresponds to `propagatedBuildInputs`
+* `tests_require` corresponds to `checkInputs`
+
+## Contributing {#contributing}
+
+### Contributing guidelines {#contributing-guidelines}
+
+The following rules are desired to be respected:
+
+* Python libraries are called from `python-packages.nix` and packaged with
+  `buildPythonPackage`. The expression of a library should be in
+  `pkgs/development/python-modules/<name>/default.nix`.
+* Python applications live outside of `python-packages.nix` and are packaged
+  with `buildPythonApplication`.
+* Make sure libraries build for all Python interpreters.
+* By default we enable tests. Make sure the tests are found and, in the case of
+  libraries, are passing for all interpreters. If certain tests fail they can be
+  disabled individually. Try to avoid disabling the tests altogether. In any
+  case, when you disable tests, leave a comment explaining why.
+* Commit names of Python libraries should reflect that they are Python
+  libraries, so write for example `pythonPackages.numpy: 1.11 -> 1.12`.
+* Attribute names in `python-packages.nix` as well as `pname`s should match the
+  library's name on PyPI, but be normalized according to [PEP
+  0503](https://www.python.org/dev/peps/pep-0503/#normalized-names). This means
+  that characters should be converted to lowercase and `.` and `_` should be
+  replaced by a single `-` (foo-bar-baz instead of Foo__Bar.baz).
+  If necessary, `pname` has to be given a different value within `fetchPypi`.
+* Attribute names in `python-packages.nix` should be sorted alphanumerically to
+  avoid merge conflicts and ease locating attributes.
+
+## Package set maintenance
+
+The whole Python package set has a lot of packages that do not see regular
+updates, because they either are a very fragile component in the Python
+ecosystem, like for example the `hypothesis` package, or packages that have
+no maintainer, so maintenance falls back to the package set maintainers.
+
+### Updating packages in bulk
+
+There is a tool to update alot of python libraries in bulk, it exists at
+`maintainers/scripts/update-python-libraries` with this repository.
+
+It can quickly update minor or major versions for all packages selected
+and create update commits, and supports the `fetchPypi`, `fetchurl` and
+`fetchFromGitHub` fetchers. When updating lots of packages that are
+hosted on GitHub, exporting a `GITHUB_API_TOKEN` is highly recommended.
+
+Updating packages in bulk leads to lots of breakages, which is why a
+stabilization period on the `python-unstable` branch is required.
+
+Once the branch is sufficiently stable it should normally be merged
+into the `staging` branch.
+
+An exemplary call to update all python libraries between minor versions
+would be:
+
+```ShellSession
+$ maintainers/scripts/update-python-libraries --target minor --commit --use-pkgs-prefix pkgs/development/python-modules/**/default.nix
+```
+
+## CPython Update Schedule
+
+With [PEP 602](https://www.python.org/dev/peps/pep-0602/), CPython now
+follows a yearly release cadence. In nixpkgs, all supported interpreters
+are made available, but only the most recent two
+interpreters package sets are built; this is a compromise between being
+the latest interpreter, and what the majority of the Python packages support.
+
+New CPython interpreters are released in October. Generally, it takes some
+time for the majority of active Python projects to support the latest stable
+interpreter. To help ease the migration for Nixpkgs users
+between Python interpreters the schedule below will be used:
+
+| When | Event |
+| --- | --- |
+| After YY.11 Release | Bump CPython package set window. The latest and previous latest stable should now be built. |
+| After YY.05 Release | Bump default CPython interpreter to latest stable. |
+
+In practice, this means that the Python community will have had a stable interpreter
+for ~2 months before attempting to update the package set. And this will
+allow for ~7 months for Python applications to support the latest interpreter.
diff --git a/doc/languages-frameworks/qt.section.md b/doc/languages-frameworks/qt.section.md
new file mode 100644
index 00000000000..986deeb0d4b
--- /dev/null
+++ b/doc/languages-frameworks/qt.section.md
@@ -0,0 +1,160 @@
+# Qt {#sec-language-qt}
+
+Writing Nix expressions for Qt libraries and applications is largely similar as for other C++ software.
+This section assumes some knowledge of the latter.
+There are two problems that the Nixpkgs Qt infrastructure addresses,
+which are not shared by other C++ software:
+
+1.  There are usually multiple supported versions of Qt in Nixpkgs.
+    All of a package's dependencies must be built with the same version of Qt.
+    This is similar to the version constraints imposed on interpreted languages like Python.
+2.  Qt makes extensive use of runtime dependency detection.
+    Runtime dependencies are made into build dependencies through wrappers.
+
+## Nix expression for a Qt package (default.nix) {#qt-default-nix}
+
+```{=docbook}
+<programlisting>
+{ stdenv, lib, qtbase, wrapQtAppsHook }: <co xml:id='qt-default-nix-co-1' />
+
+stdenv.mkDerivation {
+  pname = "myapp";
+  version = "1.0";
+
+  buildInputs = [ qtbase ];
+  nativeBuildInputs = [ wrapQtAppsHook ]; <co xml:id='qt-default-nix-co-2' />
+}
+</programlisting>
+
+ <calloutlist>
+  <callout arearefs='qt-default-nix-co-1'>
+   <para>
+    Import Qt modules directly, that is: <literal>qtbase</literal>, <literal>qtdeclarative</literal>, etc.
+    <emphasis>Do not</emphasis> import Qt package sets such as <literal>qt5</literal>
+    because the Qt versions of dependencies may not be coherent, causing build and runtime failures.
+   </para>
+  </callout>
+  <callout arearefs='qt-default-nix-co-2'>
+    <para>
+      All Qt packages must include <literal>wrapQtAppsHook</literal> in
+      <literal>nativeBuildInputs</literal>, or you must explicitly set
+      <literal>dontWrapQtApps</literal>.
+    </para>
+  </callout>
+ </calloutlist>
+```
+
+## Locating runtime dependencies {#qt-runtime-dependencies}
+
+Qt applications must be wrapped to find runtime dependencies.
+Include `wrapQtAppsHook` in `nativeBuildInputs`:
+
+```nix
+{ stdenv, wrapQtAppsHook }:
+
+stdenv.mkDerivation {
+  # ...
+  nativeBuildInputs = [ wrapQtAppsHook ];
+}
+```
+
+Add entries to `qtWrapperArgs` are to modify the wrappers created by
+`wrapQtAppsHook`:
+
+```nix
+{ stdenv, wrapQtAppsHook }:
+
+stdenv.mkDerivation {
+  # ...
+  nativeBuildInputs = [ wrapQtAppsHook ];
+  qtWrapperArgs = [ ''--prefix PATH : /path/to/bin'' ];
+}
+```
+
+The entries are passed as arguments to [wrapProgram](#fun-wrapProgram).
+
+Set `dontWrapQtApps` to stop applications from being wrapped automatically.
+Wrap programs manually with `wrapQtApp`, using the syntax of
+[wrapProgram](#fun-wrapProgram):
+
+```nix
+{ stdenv, lib, wrapQtAppsHook }:
+
+stdenv.mkDerivation {
+  # ...
+  nativeBuildInputs = [ wrapQtAppsHook ];
+  dontWrapQtApps = true;
+  preFixup = ''
+      wrapQtApp "$out/bin/myapp" --prefix PATH : /path/to/bin
+  '';
+}
+```
+
+::: {.note}
+`wrapQtAppsHook` ignores files that are non-ELF executables.
+This means that scripts won't be automatically wrapped so you'll need to manually wrap them as previously mentioned.
+An example of when you'd always need to do this is with Python applications that use PyQt.
+:::
+
+## Adding a library to Nixpkgs {#adding-a-library-to-nixpkgs}
+
+Add Qt libraries to `qt5-packages.nix` to make them available for every
+supported Qt version.
+
+### Example adding a Qt library {#qt-library-all-packages-nix}
+
+The following represents the contents of `qt5-packages.nix`.
+
+```nix
+{
+  # ...
+
+  mylib = callPackage ../path/to/mylib {};
+
+  # ...
+}
+```
+
+Libraries are built with every available version of Qt.
+Use the `meta.broken` attribute to disable the package for unsupported Qt versions:
+
+```nix
+{ stdenv, lib, qtbase }:
+
+stdenv.mkDerivation {
+  # ...
+  # Disable this library with Qt < 5.9.0
+  meta.broken = lib.versionOlder qtbase.version "5.9.0";
+}
+```
+
+## Adding an application to Nixpkgs {#adding-an-application-to-nixpkgs}
+
+Add Qt applications to `qt5-packages.nix`. Add an alias to `all-packages.nix`
+to select the Qt 5 version used for the application.
+
+### Example adding a Qt application {#qt-application-all-packages-nix}
+
+The following represents the contents of `qt5-packages.nix`.
+
+```nix
+{
+  # ...
+
+  myapp = callPackage ../path/to/myapp {};
+
+  # ...
+}
+```
+
+The following represents the contents of `all-packages.nix`.
+
+```nix
+{
+  # ...
+
+  myapp = libsForQt5.myapp;
+
+  # ...
+}
+```
diff --git a/doc/languages-frameworks/r.section.md b/doc/languages-frameworks/r.section.md
new file mode 100644
index 00000000000..ad0fb10987c
--- /dev/null
+++ b/doc/languages-frameworks/r.section.md
@@ -0,0 +1,127 @@
+# R {#r}
+
+## Installation {#installation}
+
+Define an environment for R that contains all the libraries that you'd like to
+use by adding the following snippet to your $HOME/.config/nixpkgs/config.nix file:
+
+```nix
+{
+    packageOverrides = super: let self = super.pkgs; in
+    {
+
+        rEnv = super.rWrapper.override {
+            packages = with self.rPackages; [
+                devtools
+                ggplot2
+                reshape2
+                yaml
+                optparse
+                ];
+        };
+    };
+}
+```
+
+Then you can use `nix-env -f "<nixpkgs>" -iA rEnv` to install it into your user
+profile. The set of available libraries can be discovered by running the
+command `nix-env -f "<nixpkgs>" -qaP -A rPackages`. The first column from that
+output is the name that has to be passed to rWrapper in the code snipped above.
+
+However, if you'd like to add a file to your project source to make the
+environment available for other contributors, you can create a `default.nix`
+file like so:
+
+```nix
+with import <nixpkgs> {};
+{
+  myProject = stdenv.mkDerivation {
+    name = "myProject";
+    version = "1";
+    src = if lib.inNixShell then null else nix;
+
+    buildInputs = with rPackages; [
+      R
+      ggplot2
+      knitr
+    ];
+  };
+}
+```
+and then run `nix-shell .` to be dropped into a shell with those packages
+available.
+
+## RStudio {#rstudio}
+
+RStudio uses a standard set of packages and ignores any custom R
+environments or installed packages you may have.  To create a custom
+environment, see `rstudioWrapper`, which functions similarly to
+`rWrapper`:
+
+```nix
+{
+    packageOverrides = super: let self = super.pkgs; in
+    {
+
+        rstudioEnv = super.rstudioWrapper.override {
+            packages = with self.rPackages; [
+                dplyr
+                ggplot2
+                reshape2
+                ];
+        };
+    };
+}
+```
+
+Then like above, `nix-env -f "<nixpkgs>" -iA rstudioEnv` will install
+this into your user profile.
+
+Alternatively, you can create a self-contained `shell.nix` without the need to
+modify any configuration files:
+
+```nix
+{ pkgs ? import <nixpkgs> {}
+}:
+
+pkgs.rstudioWrapper.override {
+  packages = with pkgs.rPackages; [ dplyr ggplot2 reshape2 ];
+}
+
+```
+
+Executing `nix-shell` will then drop you into an environment equivalent to the
+one above. If you need additional packages just add them to the list and
+re-enter the shell.
+
+## Updating the package set {#updating-the-package-set}
+
+There is a script and associated environment for regenerating the package
+sets and synchronising the rPackages tree to the current CRAN and matching
+BIOC release. These scripts are found in the `pkgs/development/r-modules`
+directory and executed as follows:
+
+```bash
+nix-shell generate-shell.nix
+
+Rscript generate-r-packages.R cran  > cran-packages.nix.new
+mv cran-packages.nix.new cran-packages.nix
+
+Rscript generate-r-packages.R bioc  > bioc-packages.nix.new
+mv bioc-packages.nix.new bioc-packages.nix
+
+Rscript generate-r-packages.R bioc-annotation > bioc-annotation-packages.nix.new
+mv bioc-annotation-packages.nix.new bioc-annotation-packages.nix
+
+Rscript generate-r-packages.R bioc-experiment > bioc-experiment-packages.nix.new
+mv bioc-experiment-packages.nix.new bioc-experiment-packages.nix
+```
+
+`generate-r-packages.R <repo>` reads  `<repo>-packages.nix`, therefore
+the renaming.
+
+Some packages require overrides to specify external dependencies or other
+patches and special requirements. These overrides are specified in the
+`pkgs/development/r-modules/default.nix` file. As the `*-packages.nix`
+contents are automatically generated it should not be edited and broken
+builds should be addressed using overrides.
diff --git a/doc/languages-frameworks/ruby.section.md b/doc/languages-frameworks/ruby.section.md
new file mode 100644
index 00000000000..e29f97c566c
--- /dev/null
+++ b/doc/languages-frameworks/ruby.section.md
@@ -0,0 +1,283 @@
+# Ruby {#sec-language-ruby}
+
+## Using Ruby {#using-ruby}
+
+Several versions of Ruby interpreters are available on Nix, as well as over 250 gems and many applications written in Ruby. The attribute `ruby` refers to the default Ruby interpreter, which is currently MRI 2.6. It's also possible to refer to specific versions, e.g. `ruby_2_y`, `jruby`, or `mruby`.
+
+In the Nixpkgs tree, Ruby packages can be found throughout, depending on what they do, and are called from the main package set. Ruby gems, however are separate sets, and there's one default set for each interpreter (currently MRI only).
+
+There are two main approaches for using Ruby with gems. One is to use a specifically locked `Gemfile` for an application that has very strict dependencies. The other is to depend on the common gems, which we'll explain further down, and rely on them being updated regularly.
+
+The interpreters have common attributes, namely `gems`, and `withPackages`. So you can refer to `ruby.gems.nokogiri`, or `ruby_2_7.gems.nokogiri` to get the Nokogiri gem already compiled and ready to use.
+
+Since not all gems have executables like `nokogiri`, it's usually more convenient to use the `withPackages` function like this: `ruby.withPackages (p: with p; [ nokogiri ])`. This will also make sure that the Ruby in your environment will be able to find the gem and it can be used in your Ruby code (for example via `ruby` or `irb` executables) via `require "nokogiri"` as usual.
+
+### Temporary Ruby environment with `nix-shell` {#temporary-ruby-environment-with-nix-shell}
+
+Rather than having a single Ruby environment shared by all Ruby development projects on a system, Nix allows you to create separate environments per project. `nix-shell` gives you the possibility to temporarily load another environment akin to a combined `chruby` or `rvm` and `bundle exec`.
+
+There are two methods for loading a shell with Ruby packages. The first and recommended method is to create an environment with `ruby.withPackages` and load that.
+
+```ShellSession
+$ nix-shell -p "ruby.withPackages (ps: with ps; [ nokogiri pry ])"
+```
+
+The other method, which is not recommended, is to create an environment and list all the packages directly.
+
+```ShellSession
+$ nix-shell -p ruby.gems.nokogiri ruby.gems.pry
+```
+
+Again, it's possible to launch the interpreter from the shell. The Ruby interpreter has the attribute `gems` which contains all Ruby gems for that specific interpreter.
+
+#### Load Ruby environment from `.nix` expression {#load-ruby-environment-from-.nix-expression}
+
+As explained in the Nix manual, `nix-shell` can also load an expression from a `.nix` file. Say we want to have Ruby 2.6, `nokogori`, and `pry`. Consider a `shell.nix` file with:
+
+```nix
+with import <nixpkgs> {};
+ruby.withPackages (ps: with ps; [ nokogiri pry ])
+```
+
+What's happening here?
+
+1. We begin with importing the Nix Packages collections. `import <nixpkgs>` imports the `<nixpkgs>` function, `{}` calls it and the `with` statement brings all attributes of `nixpkgs` in the local scope. These attributes form the main package set.
+2. Then we create a Ruby environment with the `withPackages` function.
+3. The `withPackages` function expects us to provide a function as an argument that takes the set of all ruby gems and returns a list of packages to include in the environment. Here, we select the packages `nokogiri` and `pry` from the package set.
+
+#### Execute command with `--run` {#execute-command-with---run}
+
+A convenient flag for `nix-shell` is `--run`. It executes a command in the `nix-shell`. We can e.g. directly open a `pry` REPL:
+
+```ShellSession
+$ nix-shell -p "ruby.withPackages (ps: with ps; [ nokogiri pry ])" --run "pry"
+```
+
+Or immediately require `nokogiri` in pry:
+
+```ShellSession
+$ nix-shell -p "ruby.withPackages (ps: with ps; [ nokogiri pry ])" --run "pry -rnokogiri"
+```
+
+Or run a script using this environment:
+
+```ShellSession
+$ nix-shell -p "ruby.withPackages (ps: with ps; [ nokogiri pry ])" --run "ruby example.rb"
+```
+
+#### Using `nix-shell` as shebang {#using-nix-shell-as-shebang}
+
+In fact, for the last case, there is a more convenient method. You can add a [shebang](<https://en.wikipedia.org/wiki/Shebang_(Unix)>) to your script specifying which dependencies `nix-shell` needs. With the following shebang, you can just execute `./example.rb`, and it will run with all dependencies.
+
+```ruby
+#! /usr/bin/env nix-shell
+#! nix-shell -i ruby -p "ruby.withPackages (ps: with ps; [ nokogiri rest-client ])"
+
+require 'nokogiri'
+require 'rest-client'
+
+body = RestClient.get('http://example.com').body
+puts Nokogiri::HTML(body).at('h1').text
+```
+
+## Developing with Ruby {#developing-with-ruby}
+
+### Using an existing Gemfile {#using-an-existing-gemfile}
+
+In most cases, you'll already have a `Gemfile.lock` listing all your dependencies. This can be used to generate a `gemset.nix` which is used to fetch the gems and combine them into a single environment. The reason why you need to have a separate file for this, is that Nix requires you to have a checksum for each input to your build. Since the `Gemfile.lock` that `bundler` generates doesn't provide us with checksums, we have to first download each gem, calculate its SHA256, and store it in this separate file.
+
+So the steps from having just a `Gemfile` to a `gemset.nix` are:
+
+```ShellSession
+$ bundle lock
+$ bundix
+```
+
+If you already have a `Gemfile.lock`, you can simply run `bundix` and it will work the same.
+
+To update the gems in your `Gemfile.lock`, you may use the `bundix -l` flag, which will create a new `Gemfile.lock` in case the `Gemfile` has a more recent time of modification.
+
+Once the `gemset.nix` is generated, it can be used in a `bundlerEnv` derivation. Here is an example you could use for your `shell.nix`:
+
+```nix
+# ...
+let
+  gems = bundlerEnv {
+    name = "gems-for-some-project";
+    gemdir = ./.;
+  };
+in mkShell { packages = [ gems gems.wrappedRuby ]; }
+```
+
+With this file in your directory, you can run `nix-shell` to build and use the gems. The important parts here are `bundlerEnv` and `wrappedRuby`.
+
+The `bundlerEnv` is a wrapper over all the gems in your gemset. This means that all the `/lib` and `/bin` directories will be available, and the executables of all gems (even of indirect dependencies) will end up in your `$PATH`. The `wrappedRuby` provides you with all executables that come with Ruby itself, but wrapped so they can easily find the gems in your gemset.
+
+One common issue that you might have is that you have Ruby 2.6, but also `bundler` in your gemset. That leads to a conflict for `/bin/bundle` and `/bin/bundler`. You can resolve this by wrapping either your Ruby or your gems in a `lowPrio` call. So in order to give the `bundler` from your gemset priority, it would be used like this:
+
+```nix
+# ...
+mkShell { buildInputs = [ gems (lowPrio gems.wrappedRuby) ]; }
+```
+
+### Gem-specific configurations and workarounds {#gem-specific-configurations-and-workarounds}
+
+In some cases, especially if the gem has native extensions, you might need to modify the way the gem is built.
+
+This is done via a common configuration file that includes all of the workarounds for each gem.
+
+This file lives at `/pkgs/development/ruby-modules/gem-config/default.nix`, since it already contains a lot of entries, it should be pretty easy to add the modifications you need for your needs.
+
+In the meanwhile, or if the modification is for a private gem, you can also add the configuration to only your own environment.
+
+Two places that allow this modification are the `ruby` derivation, or `bundlerEnv`.
+
+Here's the `ruby` one:
+
+```nix
+{ pg_version ? "10", pkgs ? import <nixpkgs> { } }:
+let
+  myRuby = pkgs.ruby.override {
+    defaultGemConfig = pkgs.defaultGemConfig // {
+      pg = attrs: {
+        buildFlags =
+        [ "--with-pg-config=${pkgs."postgresql_${pg_version}"}/bin/pg_config" ];
+      };
+    };
+  };
+in myRuby.withPackages (ps: with ps; [ pg ])
+```
+
+And an example with `bundlerEnv`:
+
+```nix
+{ pg_version ? "10", pkgs ? import <nixpkgs> { } }:
+let
+  gems = pkgs.bundlerEnv {
+    name = "gems-for-some-project";
+    gemdir = ./.;
+    gemConfig = pkgs.defaultGemConfig // {
+      pg = attrs: {
+        buildFlags =
+        [ "--with-pg-config=${pkgs."postgresql_${pg_version}"}/bin/pg_config" ];
+      };
+    };
+  };
+in mkShell { buildInputs = [ gems gems.wrappedRuby ]; }
+```
+
+And finally via overlays:
+
+```nix
+{ pg_version ? "10" }:
+let
+  pkgs = import <nixpkgs> {
+    overlays = [
+      (self: super: {
+        defaultGemConfig = super.defaultGemConfig // {
+          pg = attrs: {
+            buildFlags = [
+              "--with-pg-config=${
+                pkgs."postgresql_${pg_version}"
+              }/bin/pg_config"
+            ];
+          };
+        };
+      })
+    ];
+  };
+in pkgs.ruby.withPackages (ps: with ps; [ pg ])
+```
+
+Then we can get whichever postgresql version we desire and the `pg` gem will always reference it correctly:
+
+```ShellSession
+$ nix-shell --argstr pg_version 9_4 --run 'ruby -rpg -e "puts PG.library_version"'
+90421
+
+$ nix-shell --run 'ruby -rpg -e "puts PG.library_version"'
+100007
+```
+
+Of course for this use-case one could also use overlays since the configuration for `pg` depends on the `postgresql` alias, but for demonstration purposes this has to suffice.
+
+### Platform-specific gems
+
+Right now, bundix has some issues with pre-built, platform-specific gems: [bundix PR #68](https://github.com/nix-community/bundix/pull/68).
+Until this is solved, you can tell bundler to not use platform-specific gems and instead build them from source each time:
+- globally (will be set in `~/.config/.bundle/config`):
+```shell
+$ bundle config set force_ruby_platform true
+```
+- locally (will be set in `<project-root>/.bundle/config`):
+```shell
+$ bundle config set --local force_ruby_platform true
+```
+
+### Adding a gem to the default gemset {#adding-a-gem-to-the-default-gemset}
+
+Now that you know how to get a working Ruby environment with Nix, it's time to go forward and start actually developing with Ruby. We will first have a look at how Ruby gems are packaged on Nix. Then, we will look at how you can use development mode with your code.
+
+All gems in the standard set are automatically generated from a single `Gemfile`. The dependency resolution is done with `bundler` and makes it more likely that all gems are compatible to each other.
+
+In order to add a new gem to nixpkgs, you can put it into the `/pkgs/development/ruby-modules/with-packages/Gemfile` and run `./maintainers/scripts/update-ruby-packages`.
+
+To test that it works, you can then try using the gem with:
+
+```shell
+NIX_PATH=nixpkgs=$PWD nix-shell -p "ruby.withPackages (ps: with ps; [ name-of-your-gem ])"
+```
+
+### Packaging applications {#packaging-applications}
+
+A common task is to add a ruby executable to nixpkgs, popular examples would be `chef`, `jekyll`, or `sass`. A good way to do that is to use the `bundlerApp` function, that allows you to make a package that only exposes the listed executables, otherwise the package may cause conflicts through common paths like `bin/rake` or `bin/bundler` that aren't meant to be used.
+
+The absolute easiest way to do that is to write a `Gemfile` along these lines:
+
+```ruby
+source 'https://rubygems.org' do
+  gem 'mdl'
+end
+```
+
+If you want to package a specific version, you can use the standard Gemfile syntax for that, e.g. `gem 'mdl', '0.5.0'`, but if you want the latest stable version anyway, it's easier to update by simply running the `bundle lock` and `bundix` steps again.
+
+Now you can also make a `default.nix` that looks like this:
+
+```nix
+{ bundlerApp }:
+
+bundlerApp {
+  pname = "mdl";
+  gemdir = ./.;
+  exes = [ "mdl" ];
+}
+```
+
+All that's left to do is to generate the corresponding `Gemfile.lock` and `gemset.nix` as described above in the `Using an existing Gemfile` section.
+
+#### Packaging executables that require wrapping {#packaging-executables-that-require-wrapping}
+
+Sometimes your app will depend on other executables at runtime, and tries to find it through the `PATH` environment variable.
+
+In this case, you can provide a `postBuild` hook to `bundlerApp` that wraps the gem in another script that prefixes the `PATH`.
+
+Of course you could also make a custom `gemConfig` if you know exactly how to patch it, but it's usually much easier to maintain with a simple wrapper so the patch doesn't have to be adjusted for each version.
+
+Here's another example:
+
+```nix
+{ lib, bundlerApp, makeWrapper, git, gnutar, gzip }:
+
+bundlerApp {
+  pname = "r10k";
+  gemdir = ./.;
+  exes = [ "r10k" ];
+
+  buildInputs = [ makeWrapper ];
+
+  postBuild = ''
+    wrapProgram $out/bin/r10k --prefix PATH : ${lib.makeBinPath [ git gnutar gzip ]}
+  '';
+}
+```
diff --git a/doc/languages-frameworks/rust.section.md b/doc/languages-frameworks/rust.section.md
new file mode 100644
index 00000000000..e19783e29e6
--- /dev/null
+++ b/doc/languages-frameworks/rust.section.md
@@ -0,0 +1,1008 @@
+# Rust {#rust}
+
+To install the rust compiler and cargo put
+
+```nix
+environment.systemPackages = [
+  rustc
+  cargo
+];
+```
+
+into your `configuration.nix` or bring them into scope with `nix-shell -p rustc cargo`.
+
+For other versions such as daily builds (beta and nightly),
+use either `rustup` from nixpkgs (which will manage the rust installation in your home directory),
+or use a community maintained [Rust overlay](#using-community-rust-overlays).
+
+## Compiling Rust applications with Cargo {#compiling-rust-applications-with-cargo}
+
+Rust applications are packaged by using the `buildRustPackage` helper from `rustPlatform`:
+
+```nix
+{ lib, fetchFromGitHub, rustPlatform }:
+
+rustPlatform.buildRustPackage rec {
+  pname = "ripgrep";
+  version = "12.1.1";
+
+  src = fetchFromGitHub {
+    owner = "BurntSushi";
+    repo = pname;
+    rev = version;
+    sha256 = "1hqps7l5qrjh9f914r5i6kmcz6f1yb951nv4lby0cjnp5l253kps";
+  };
+
+  cargoSha256 = "03wf9r2csi6jpa7v5sw5lpxkrk4wfzwmzx7k3991q3bdjzcwnnwp";
+
+  meta = with lib; {
+    description = "A fast line-oriented regex search tool, similar to ag and ack";
+    homepage = "https://github.com/BurntSushi/ripgrep";
+    license = licenses.unlicense;
+    maintainers = [ maintainers.tailhook ];
+  };
+}
+```
+
+`buildRustPackage` requires either the `cargoSha256` or the
+`cargoHash` attribute which is computed over all crate sources of this
+package. `cargoHash256` is used for traditional Nix SHA-256 hashes,
+such as the one in the example above. `cargoHash` should instead be
+used for [SRI](https://www.w3.org/TR/SRI/) hashes. For example:
+
+```nix
+  cargoHash = "sha256-l1vL2ZdtDRxSGvP0X/l3nMw8+6WF67KPutJEzUROjg8=";
+```
+
+Both types of hashes are permitted when contributing to nixpkgs. The
+Cargo hash is obtained by inserting a fake checksum into the
+expression and building the package once. The correct checksum can
+then be taken from the failed build. A fake hash can be used for
+`cargoSha256` as follows:
+
+```nix
+  cargoSha256 = lib.fakeSha256;
+```
+
+For `cargoHash` you can use:
+
+```nix
+  cargoHash = lib.fakeHash;
+```
+
+Per the instructions in the [Cargo Book](https://doc.rust-lang.org/cargo/guide/cargo-toml-vs-cargo-lock.html)
+best practices guide, Rust applications should always commit the `Cargo.lock`
+file in git to ensure a reproducible build. However, a few packages do not, and
+Nix depends on this file, so if it is missing you can use `cargoPatches` to
+apply it in the `patchPhase`. Consider sending a PR upstream with a note to the
+maintainer describing why it's important to include in the application.
+
+The fetcher will verify that the `Cargo.lock` file is in sync with the `src`
+attribute, and fail the build if not. It will also will compress the vendor
+directory into a tar.gz archive.
+
+The tarball with vendored dependencies contains a directory with the
+package's `name`, which is normally composed of `pname` and
+`version`. This means that the vendored dependencies hash
+(`cargoSha256`/`cargoHash`) is dependent on the package name and
+version. The `cargoDepsName` attribute can be used to use another name
+for the directory of vendored dependencies. For example, the hash can
+be made invariant to the version by setting `cargoDepsName` to
+`pname`:
+
+```nix
+rustPlatform.buildRustPackage rec {
+  pname = "broot";
+  version = "1.2.0";
+
+  src = fetchCrate {
+    inherit pname version;
+    sha256 = "1mqaynrqaas82f5957lx31x80v74zwmwmjxxlbywajb61vh00d38";
+  };
+
+  cargoHash = "sha256-JmBZcDVYJaK1cK05cxx5BrnGWp4t8ca6FLUbvIot67s=";
+  cargoDepsName = pname;
+
+  # ...
+}
+```
+
+### Importing a `Cargo.lock` file {#importing-a-cargo.lock-file}
+
+Using `cargoSha256` or `cargoHash` is tedious when using
+`buildRustPackage` within a project, since it requires that the hash
+is updated after every change to `Cargo.lock`. Therefore,
+`buildRustPackage` also supports vendoring dependencies directly from
+a `Cargo.lock` file using the `cargoLock` argument. For example:
+
+```nix
+rustPlatform.buildRustPackage {
+  pname = "myproject";
+  version = "1.0.0";
+
+  cargoLock = {
+    lockFile = ./Cargo.lock;
+  };
+
+  # ...
+}
+```
+
+This will retrieve the dependencies using fixed-output derivations from
+the specified lockfile.
+
+One caveat is that `Cargo.lock` cannot be patched in the `patchPhase`
+because it runs after the dependencies have already been fetched. If
+you need to patch or generate the lockfile you can alternatively set
+`cargoLock.lockFileContents` to a string of its contents:
+
+```nix
+rustPlatform.buildRustPackage {
+  pname = "myproject";
+  version = "1.0.0";
+
+  cargoLock = let
+    fixupLockFile = path: f (builtins.readFile path);
+  in {
+    lockFileContents = fixupLockFile ./Cargo.lock;
+  };
+
+  # ...
+}
+```
+
+Note that setting `cargoLock.lockFile` or `cargoLock.lockFileContents`
+doesn't add a `Cargo.lock` to your `src`, and a `Cargo.lock` is still
+required to build a rust package. A simple fix is to use:
+
+```nix
+postPatch = ''
+  cp ${./Cargo.lock} Cargo.lock
+'';
+```
+
+The output hash of each dependency that uses a git source must be
+specified in the `outputHashes` attribute. For example:
+
+```nix
+rustPlatform.buildRustPackage rec {
+  pname = "myproject";
+  version = "1.0.0";
+
+  cargoLock = {
+    lockFile = ./Cargo.lock;
+    outputHashes = {
+      "finalfusion-0.14.0" = "17f4bsdzpcshwh74w5z119xjy2if6l2wgyjy56v621skr2r8y904";
+    };
+  };
+
+  # ...
+}
+```
+
+If you do not specify an output hash for a git dependency, building
+the package will fail and inform you of which crate needs to be
+added. To find the correct hash, you can first use `lib.fakeSha256` or
+`lib.fakeHash` as a stub hash. Building the package (and thus the
+vendored dependencies) will then inform you of the correct hash.
+
+### Cargo features {#cargo-features}
+
+You can disable default features using `buildNoDefaultFeatures`, and
+extra features can be added with `buildFeatures`.
+
+If you want to use different features for check phase, you can use
+`checkNoDefaultFeatures` and `checkFeatures`. They are only passed to
+`cargo test` and not `cargo build`. If left unset, they default to
+`buildNoDefaultFeatures` and `buildFeatures`.
+
+For example:
+
+```nix
+rustPlatform.buildRustPackage rec {
+  pname = "myproject";
+  version = "1.0.0";
+
+  buildNoDefaultFeatures = true;
+  buildFeatures = [ "color" "net" ];
+
+  # disable network features in tests
+  checkFeatures = [ "color" ];
+
+  # ...
+}
+```
+
+### Cross compilation {#cross-compilation}
+
+By default, Rust packages are compiled for the host platform, just like any
+other package is.  The `--target` passed to rust tools is computed from this.
+By default, it takes the `stdenv.hostPlatform.config` and replaces components
+where they are known to differ. But there are ways to customize the argument:
+
+ - To choose a different target by name, define
+   `stdenv.hostPlatform.rustc.config` as that name (a string), and that
+   name will be used instead.
+
+   For example:
+
+   ```nix
+   import <nixpkgs> {
+     crossSystem = (import <nixpkgs/lib>).systems.examples.armhf-embedded // {
+       rustc.config = "thumbv7em-none-eabi";
+     };
+   }
+   ```
+
+   will result in:
+
+   ```shell
+   --target thumbv7em-none-eabi
+   ```
+
+ - To pass a completely custom target, define
+   `stdenv.hostPlatform.rustc.config` with its name, and
+   `stdenv.hostPlatform.rustc.platform` with the value.  The value will be
+   serialized to JSON in a file called
+   `${stdenv.hostPlatform.rustc.config}.json`, and the path of that file
+   will be used instead.
+
+   For example:
+
+   ```nix
+   import <nixpkgs> {
+     crossSystem = (import <nixpkgs/lib>).systems.examples.armhf-embedded // {
+       rustc.config = "thumb-crazy";
+       rustc.platform = { foo = ""; bar = ""; };
+     };
+   }
+   ```
+
+   will result in:
+
+   ```shell
+   --target /nix/store/asdfasdfsadf-thumb-crazy.json # contains {"foo":"","bar":""}
+   ```
+
+Note that currently custom targets aren't compiled with `std`, so `cargo test`
+will fail. This can be ignored by adding `doCheck = false;` to your derivation.
+
+### Running package tests {#running-package-tests}
+
+When using `buildRustPackage`, the `checkPhase` is enabled by default and runs
+`cargo test` on the package to build. To make sure that we don't compile the
+sources twice and to actually test the artifacts that will be used at runtime,
+the tests will be ran in the `release` mode by default.
+
+However, in some cases the test-suite of a package doesn't work properly in the
+`release` mode. For these situations, the mode for `checkPhase` can be changed like
+so:
+
+```nix
+rustPlatform.buildRustPackage {
+  /* ... */
+  checkType = "debug";
+}
+```
+
+Please note that the code will be compiled twice here: once in `release` mode
+for the `buildPhase`, and again in `debug` mode for the `checkPhase`.
+
+Test flags, e.g., `--package foo`, can be passed to `cargo test` via the
+`cargoTestFlags` attribute.
+
+Another attribute, called `checkFlags`, is used to pass arguments to the test
+binary itself, as stated
+[here](https://doc.rust-lang.org/cargo/commands/cargo-test.html).
+
+#### Tests relying on the structure of the `target/` directory {#tests-relying-on-the-structure-of-the-target-directory}
+
+Some tests may rely on the structure of the `target/` directory. Those tests
+are likely to fail because we use `cargo --target` during the build. This means that
+the artifacts
+[are stored in `target/<architecture>/release/`](https://doc.rust-lang.org/cargo/guide/build-cache.html),
+rather than in `target/release/`.
+
+This can only be worked around by patching the affected tests accordingly.
+
+#### Disabling package-tests {#disabling-package-tests}
+
+In some instances, it may be necessary to disable testing altogether (with `doCheck = false;`):
+
+* If no tests exist -- the `checkPhase` should be explicitly disabled to skip
+  unnecessary build steps to speed up the build.
+* If tests are highly impure (e.g. due to network usage).
+
+There will obviously be some corner-cases not listed above where it's sensible to disable tests.
+The above are just guidelines, and exceptions may be granted on a case-by-case basis.
+
+However, please check if it's possible to disable a problematic subset of the
+test suite and leave a comment explaining your reasoning.
+
+#### Setting `test-threads` {#setting-test-threads}
+
+`buildRustPackage` will use parallel test threads by default,
+sometimes it may be necessary to disable this so the tests run consecutively.
+
+```nix
+rustPlatform.buildRustPackage {
+  /* ... */
+  dontUseCargoParallelTests = true;
+}
+```
+
+### Building a package in `debug` mode {#building-a-package-in-debug-mode}
+
+By default, `buildRustPackage` will use `release` mode for builds. If a package
+should be built in `debug` mode, it can be configured like so:
+
+```nix
+rustPlatform.buildRustPackage {
+  /* ... */
+  buildType = "debug";
+}
+```
+
+In this scenario, the `checkPhase` will be ran in `debug` mode as well.
+
+### Custom `build`/`install`-procedures {#custom-buildinstall-procedures}
+
+Some packages may use custom scripts for building/installing, e.g. with a `Makefile`.
+In these cases, it's recommended to override the `buildPhase`/`installPhase`/`checkPhase`.
+
+Otherwise, some steps may fail because of the modified directory structure of `target/`.
+
+### Building a crate with an absent or out-of-date Cargo.lock file {#building-a-crate-with-an-absent-or-out-of-date-cargo.lock-file}
+
+`buildRustPackage` needs a `Cargo.lock` file to get all dependencies in the
+source code in a reproducible way. If it is missing or out-of-date one can use
+the `cargoPatches` attribute to update or add it.
+
+```nix
+rustPlatform.buildRustPackage rec {
+  (...)
+  cargoPatches = [
+    # a patch file to add/update Cargo.lock in the source code
+    ./add-Cargo.lock.patch
+  ];
+}
+```
+
+## Compiling non-Rust packages that include Rust code {#compiling-non-rust-packages-that-include-rust-code}
+
+Several non-Rust packages incorporate Rust code for performance- or
+security-sensitive parts. `rustPlatform` exposes several functions and
+hooks that can be used to integrate Cargo in non-Rust packages.
+
+### Vendoring of dependencies {#vendoring-of-dependencies}
+
+Since network access is not allowed in sandboxed builds, Rust crate
+dependencies need to be retrieved using a fetcher. `rustPlatform`
+provides the `fetchCargoTarball` fetcher, which vendors all
+dependencies of a crate. For example, given a source path `src`
+containing `Cargo.toml` and `Cargo.lock`, `fetchCargoTarball`
+can be used as follows:
+
+```nix
+cargoDeps = rustPlatform.fetchCargoTarball {
+  inherit src;
+  hash = "sha256-BoHIN/519Top1NUBjpB/oEMqi86Omt3zTQcXFWqrek0=";
+};
+```
+
+The `src` attribute is required, as well as a hash specified through
+one of the `sha256` or `hash` attributes. The following optional
+attributes can also be used:
+
+* `name`: the name that is used for the dependencies tarball.  If
+  `name` is not specified, then the name `cargo-deps` will be used.
+* `sourceRoot`: when the `Cargo.lock`/`Cargo.toml` are in a
+  subdirectory, `sourceRoot` specifies the relative path to these
+  files.
+* `patches`: patches to apply before vendoring. This is useful when
+  the `Cargo.lock`/`Cargo.toml` files need to be patched before
+  vendoring.
+
+If a `Cargo.lock` file is available, you can alternatively use the
+`importCargoLock` function. In contrast to `fetchCargoTarball`, this
+function does not require a hash (unless git dependencies are used)
+and fetches every dependency as a separate fixed-output derivation.
+`importCargoLock` can be used as follows:
+
+```
+cargoDeps = rustPlatform.importCargoLock {
+  lockFile = ./Cargo.lock;
+};
+```
+
+If the `Cargo.lock` file includes git dependencies, then their output
+hashes need to be specified since they are not available through the
+lock file. For example:
+
+```
+cargoDeps = rustPlatform.importCargoLock {
+  lockFile = ./Cargo.lock;
+  outputHashes = {
+    "rand-0.8.3" = "0ya2hia3cn31qa8894s3av2s8j5bjwb6yq92k0jsnlx7jid0jwqa";
+  };
+};
+```
+
+If you do not specify an output hash for a git dependency, building
+`cargoDeps` will fail and inform you of which crate needs to be
+added. To find the correct hash, you can first use `lib.fakeSha256` or
+`lib.fakeHash` as a stub hash. Building `cargoDeps` will then inform
+you of the correct hash.
+
+### Hooks {#hooks}
+
+`rustPlatform` provides the following hooks to automate Cargo builds:
+
+* `cargoSetupHook`: configure Cargo to use dependencies vendored
+  through `fetchCargoTarball`. This hook uses the `cargoDeps`
+  environment variable to find the vendored dependencies. If a project
+  already vendors its dependencies, the variable `cargoVendorDir` can
+  be used instead. When the `Cargo.toml`/`Cargo.lock` files are not in
+  `sourceRoot`, then the optional `cargoRoot` is used to specify the
+  Cargo root directory relative to `sourceRoot`.
+* `cargoBuildHook`: use Cargo to build a crate. If the crate to be
+  built is a crate in e.g. a Cargo workspace, the relative path to the
+  crate to build can be set through the optional `buildAndTestSubdir`
+  environment variable. Features can be specified with
+  `cargoBuildNoDefaultFeatures` and `cargoBuildFeatures`. Additional
+  Cargo build flags can be passed through `cargoBuildFlags`.
+* `maturinBuildHook`: use [Maturin](https://github.com/PyO3/maturin)
+  to build a Python wheel. Similar to `cargoBuildHook`, the optional
+  variable `buildAndTestSubdir` can be used to build a crate in a
+  Cargo workspace. Additional Maturin flags can be passed through
+  `maturinBuildFlags`.
+* `cargoCheckHook`: run tests using Cargo. The build type for checks
+  can be set using `cargoCheckType`. Features can be specified with
+  `cargoCheckNoDefaultFeaatures` and `cargoCheckFeatures`. Additional
+  flags can be passed to the tests using `checkFlags` and
+  `checkFlagsArray`. By default, tests are run in parallel. This can
+  be disabled by setting `dontUseCargoParallelTests`.
+* `cargoInstallHook`: install binaries and static/shared libraries
+  that were built using `cargoBuildHook`.
+* `bindgenHook`: for crates which use `bindgen` as a build dependency, lets
+  `bindgen` find `libclang` and `libclang` find the libraries in `buildInputs`.
+
+### Examples {#examples}
+
+#### Python package using `setuptools-rust` {#python-package-using-setuptools-rust}
+
+For Python packages using `setuptools-rust`, you can use
+`fetchCargoTarball` and `cargoSetupHook` to retrieve and set up Cargo
+dependencies. The build itself is then performed by
+`buildPythonPackage`.
+
+The following example outlines how the `tokenizers` Python package is
+built. Since the Python package is in the `source/bindings/python`
+directory of the `tokenizers` project's source archive, we use
+`sourceRoot` to point the tooling to this directory:
+
+```nix
+{ fetchFromGitHub
+, buildPythonPackage
+, rustPlatform
+, setuptools-rust
+}:
+
+buildPythonPackage rec {
+  pname = "tokenizers";
+  version = "0.10.0";
+
+  src = fetchFromGitHub {
+    owner = "huggingface";
+    repo = pname;
+    rev = "python-v${version}";
+    hash = "sha256-rQ2hRV52naEf6PvRsWVCTN7B1oXAQGmnpJw4iIdhamw=";
+  };
+
+  cargoDeps = rustPlatform.fetchCargoTarball {
+    inherit src sourceRoot;
+    name = "${pname}-${version}";
+    hash = "sha256-BoHIN/519Top1NUBjpB/oEMqi86Omt3zTQcXFWqrek0=";
+  };
+
+  sourceRoot = "source/bindings/python";
+
+  nativeBuildInputs = [ setuptools-rust ] ++ (with rustPlatform; [
+    cargoSetupHook
+    rust.cargo
+    rust.rustc
+  ]);
+
+  # ...
+}
+```
+
+In some projects, the Rust crate is not in the main Python source
+directory.  In such cases, the `cargoRoot` attribute can be used to
+specify the crate's directory relative to `sourceRoot`. In the
+following example, the crate is in `src/rust`, as specified in the
+`cargoRoot` attribute. Note that we also need to specify the correct
+path for `fetchCargoTarball`.
+
+```nix
+
+{ buildPythonPackage
+, fetchPypi
+, rustPlatform
+, setuptools-rust
+, openssl
+}:
+
+buildPythonPackage rec {
+  pname = "cryptography";
+  version = "3.4.2"; # Also update the hash in vectors.nix
+
+  src = fetchPypi {
+    inherit pname version;
+    sha256 = "1i1mx5y9hkyfi9jrrkcw804hmkcglxi6rmf7vin7jfnbr2bf4q64";
+  };
+
+  cargoDeps = rustPlatform.fetchCargoTarball {
+    inherit src;
+    sourceRoot = "${pname}-${version}/${cargoRoot}";
+    name = "${pname}-${version}";
+    hash = "sha256-PS562W4L1NimqDV2H0jl5vYhL08H9est/pbIxSdYVfo=";
+  };
+
+  cargoRoot = "src/rust";
+
+  # ...
+}
+```
+
+#### Python package using `maturin` {#python-package-using-maturin}
+
+Python packages that use [Maturin](https://github.com/PyO3/maturin)
+can be built with `fetchCargoTarball`, `cargoSetupHook`, and
+`maturinBuildHook`. For example, the following (partial) derivation
+builds the `retworkx` Python package. `fetchCargoTarball` and
+`cargoSetupHook` are used to fetch and set up the crate dependencies.
+`maturinBuildHook` is used to perform the build.
+
+```nix
+{ lib
+, buildPythonPackage
+, rustPlatform
+, fetchFromGitHub
+}:
+
+buildPythonPackage rec {
+  pname = "retworkx";
+  version = "0.6.0";
+
+  src = fetchFromGitHub {
+    owner = "Qiskit";
+    repo = "retworkx";
+    rev = version;
+    sha256 = "11n30ldg3y3y6qxg3hbj837pnbwjkqw3nxq6frds647mmmprrd20";
+  };
+
+  cargoDeps = rustPlatform.fetchCargoTarball {
+    inherit src;
+    name = "${pname}-${version}";
+    hash = "sha256-heOBK8qi2nuc/Ib+I/vLzZ1fUUD/G/KTw9d7M4Hz5O0=";
+  };
+
+  format = "pyproject";
+
+  nativeBuildInputs = with rustPlatform; [ cargoSetupHook maturinBuildHook ];
+
+  # ...
+}
+```
+
+## Compiling Rust crates using Nix instead of Cargo {#compiling-rust-crates-using-nix-instead-of-cargo}
+
+### Simple operation {#simple-operation}
+
+When run, `cargo build` produces a file called `Cargo.lock`,
+containing pinned versions of all dependencies. Nixpkgs contains a
+tool called `carnix` (`nix-env -iA nixos.carnix`), which can be used
+to turn a `Cargo.lock` into a Nix expression.
+
+That Nix expression calls `rustc` directly (hence bypassing Cargo),
+and can be used to compile a crate and all its dependencies. Here is
+an example for a minimal `hello` crate:
+
+```ShellSession
+$ cargo new hello
+$ cd hello
+$ cargo build
+     Compiling hello v0.1.0 (file:///tmp/hello)
+     Finished dev [unoptimized + debuginfo] target(s) in 0.20 secs
+$ carnix -o hello.nix --src ./. Cargo.lock --standalone
+$ nix-build hello.nix -A hello_0_1_0
+```
+
+Now, the file produced by the call to `carnix`, called `hello.nix`, looks like:
+
+```nix
+# Generated by carnix 0.6.5: carnix -o hello.nix --src ./. Cargo.lock --standalone
+{ stdenv, buildRustCrate, fetchgit }:
+let kernel = stdenv.buildPlatform.parsed.kernel.name;
+    # ... (content skipped)
+in
+rec {
+  hello = f: hello_0_1_0 { features = hello_0_1_0_features { hello_0_1_0 = f; }; };
+  hello_0_1_0_ = { dependencies?[], buildDependencies?[], features?[] }: buildRustCrate {
+    crateName = "hello";
+    version = "0.1.0";
+    authors = [ "pe@pijul.org <pe@pijul.org>" ];
+    src = ./.;
+    inherit dependencies buildDependencies features;
+  };
+  hello_0_1_0 = { features?(hello_0_1_0_features {}) }: hello_0_1_0_ {};
+  hello_0_1_0_features = f: updateFeatures f (rec {
+        hello_0_1_0.default = (f.hello_0_1_0.default or true);
+    }) [ ];
+}
+```
+
+In particular, note that the argument given as `--src` is copied
+verbatim to the source. If we look at a more complicated
+dependencies, for instance by adding a single line `libc="*"` to our
+`Cargo.toml`, we first need to run `cargo build` to update the
+`Cargo.lock`. Then, `carnix` needs to be run again, and produces the
+following nix file:
+
+```nix
+# Generated by carnix 0.6.5: carnix -o hello.nix --src ./. Cargo.lock --standalone
+{ stdenv, buildRustCrate, fetchgit }:
+let kernel = stdenv.buildPlatform.parsed.kernel.name;
+    # ... (content skipped)
+in
+rec {
+  hello = f: hello_0_1_0 { features = hello_0_1_0_features { hello_0_1_0 = f; }; };
+  hello_0_1_0_ = { dependencies?[], buildDependencies?[], features?[] }: buildRustCrate {
+    crateName = "hello";
+    version = "0.1.0";
+    authors = [ "pe@pijul.org <pe@pijul.org>" ];
+    src = ./.;
+    inherit dependencies buildDependencies features;
+  };
+  libc_0_2_36_ = { dependencies?[], buildDependencies?[], features?[] }: buildRustCrate {
+    crateName = "libc";
+    version = "0.2.36";
+    authors = [ "The Rust Project Developers" ];
+    sha256 = "01633h4yfqm0s302fm0dlba469bx8y6cs4nqc8bqrmjqxfxn515l";
+    inherit dependencies buildDependencies features;
+  };
+  hello_0_1_0 = { features?(hello_0_1_0_features {}) }: hello_0_1_0_ {
+    dependencies = mapFeatures features ([ libc_0_2_36 ]);
+  };
+  hello_0_1_0_features = f: updateFeatures f (rec {
+    hello_0_1_0.default = (f.hello_0_1_0.default or true);
+    libc_0_2_36.default = true;
+  }) [ libc_0_2_36_features ];
+  libc_0_2_36 = { features?(libc_0_2_36_features {}) }: libc_0_2_36_ {
+    features = mkFeatures (features.libc_0_2_36 or {});
+  };
+  libc_0_2_36_features = f: updateFeatures f (rec {
+    libc_0_2_36.default = (f.libc_0_2_36.default or true);
+    libc_0_2_36.use_std =
+      (f.libc_0_2_36.use_std or false) ||
+      (f.libc_0_2_36.default or false) ||
+      (libc_0_2_36.default or false);
+  }) [];
+}
+```
+
+Here, the `libc` crate has no `src` attribute, so `buildRustCrate`
+will fetch it from [crates.io](https://crates.io). A `sha256`
+attribute is still needed for Nix purity.
+
+### Handling external dependencies {#handling-external-dependencies}
+
+Some crates require external libraries. For crates from
+[crates.io](https://crates.io), such libraries can be specified in
+`defaultCrateOverrides` package in nixpkgs itself.
+
+Starting from that file, one can add more overrides, to add features
+or build inputs by overriding the hello crate in a separate file.
+
+```nix
+with import <nixpkgs> {};
+((import ./hello.nix).hello {}).override {
+  crateOverrides = defaultCrateOverrides // {
+    hello = attrs: { buildInputs = [ openssl ]; };
+  };
+}
+```
+
+Here, `crateOverrides` is expected to be a attribute set, where the
+key is the crate name without version number and the value a function.
+The function gets all attributes passed to `buildRustCrate` as first
+argument and returns a set that contains all attribute that should be
+overwritten.
+
+For more complicated cases, such as when parts of the crate's
+derivation depend on the crate's version, the `attrs` argument of
+the override above can be read, as in the following example, which
+patches the derivation:
+
+```nix
+with import <nixpkgs> {};
+((import ./hello.nix).hello {}).override {
+  crateOverrides = defaultCrateOverrides // {
+    hello = attrs: lib.optionalAttrs (lib.versionAtLeast attrs.version "1.0")  {
+      postPatch = ''
+        substituteInPlace lib/zoneinfo.rs \
+          --replace "/usr/share/zoneinfo" "${tzdata}/share/zoneinfo"
+      '';
+    };
+  };
+}
+```
+
+Another situation is when we want to override a nested
+dependency. This actually works in the exact same way, since the
+`crateOverrides` parameter is forwarded to the crate's
+dependencies. For instance, to override the build inputs for crate
+`libc` in the example above, where `libc` is a dependency of the main
+crate, we could do:
+
+```nix
+with import <nixpkgs> {};
+((import hello.nix).hello {}).override {
+  crateOverrides = defaultCrateOverrides // {
+    libc = attrs: { buildInputs = []; };
+  };
+}
+```
+
+### Options and phases configuration {#options-and-phases-configuration}
+
+Actually, the overrides introduced in the previous section are more
+general. A number of other parameters can be overridden:
+
+- The version of `rustc` used to compile the crate:
+
+  ```nix
+  (hello {}).override { rust = pkgs.rust; };
+  ```
+
+- Whether to build in release mode or debug mode (release mode by
+  default):
+
+  ```nix
+  (hello {}).override { release = false; };
+  ```
+
+- Whether to print the commands sent to `rustc` when building
+  (equivalent to `--verbose` in cargo:
+
+  ```nix
+  (hello {}).override { verbose = false; };
+  ```
+
+- Extra arguments to be passed to `rustc`:
+
+  ```nix
+  (hello {}).override { extraRustcOpts = "-Z debuginfo=2"; };
+  ```
+
+- Phases, just like in any other derivation, can be specified using
+  the following attributes: `preUnpack`, `postUnpack`, `prePatch`,
+  `patches`, `postPatch`, `preConfigure` (in the case of a Rust crate,
+  this is run before calling the "build" script), `postConfigure`
+  (after the "build" script),`preBuild`, `postBuild`, `preInstall` and
+  `postInstall`. As an example, here is how to create a new module
+  before running the build script:
+
+  ```nix
+  (hello {}).override {
+    preConfigure = ''
+       echo "pub const PATH=\"${hi.out}\";" >> src/path.rs"
+    '';
+  };
+  ```
+
+### Features {#features}
+
+One can also supply features switches. For example, if we want to
+compile `diesel_cli` only with the `postgres` feature, and no default
+features, we would write:
+
+```nix
+(callPackage ./diesel.nix {}).diesel {
+  default = false;
+  postgres = true;
+}
+```
+
+Where `diesel.nix` is the file generated by Carnix, as explained above.
+
+## Setting Up `nix-shell` {#setting-up-nix-shell}
+
+Oftentimes you want to develop code from within `nix-shell`. Unfortunately
+`buildRustCrate` does not support common `nix-shell` operations directly
+(see [this issue](https://github.com/NixOS/nixpkgs/issues/37945))
+so we will use `stdenv.mkDerivation` instead.
+
+Using the example `hello` project above, we want to do the following:
+
+- Have access to `cargo` and `rustc`
+- Have the `openssl` library available to a crate through it's _normal_
+  compilation mechanism (`pkg-config`).
+
+A typical `shell.nix` might look like:
+
+```nix
+with import <nixpkgs> {};
+
+stdenv.mkDerivation {
+  name = "rust-env";
+  nativeBuildInputs = [
+    rustc cargo
+
+    # Example Build-time Additional Dependencies
+    pkg-config
+  ];
+  buildInputs = [
+    # Example Run-time Additional Dependencies
+    openssl
+  ];
+
+  # Set Environment Variables
+  RUST_BACKTRACE = 1;
+}
+```
+
+You should now be able to run the following:
+
+```ShellSession
+$ nix-shell --pure
+$ cargo build
+$ cargo test
+```
+
+### Controlling Rust Version Inside `nix-shell` {#controlling-rust-version-inside-nix-shell}
+
+To control your rust version (i.e. use nightly) from within `shell.nix` (or
+other nix expressions) you can use the following `shell.nix`
+
+```nix
+# Latest Nightly
+with import <nixpkgs> {};
+let src = fetchFromGitHub {
+      owner = "mozilla";
+      repo = "nixpkgs-mozilla";
+      # commit from: 2019-05-15
+      rev = "9f35c4b09fd44a77227e79ff0c1b4b6a69dff533";
+      sha256 = "18h0nvh55b5an4gmlgfbvwbyqj91bklf1zymis6lbdh75571qaz0";
+   };
+in
+with import "${src.out}/rust-overlay.nix" pkgs pkgs;
+stdenv.mkDerivation {
+  name = "rust-env";
+  buildInputs = [
+    # Note: to use stable, just replace `nightly` with `stable`
+    latest.rustChannels.nightly.rust
+
+    # Add some extra dependencies from `pkgs`
+    pkg-config openssl
+  ];
+
+  # Set Environment Variables
+  RUST_BACKTRACE = 1;
+}
+```
+
+Now run:
+
+```ShellSession
+$ rustc --version
+rustc 1.26.0-nightly (188e693b3 2018-03-26)
+```
+
+To see that you are using nightly.
+
+## Using community Rust overlays {#using-community-rust-overlays}
+
+There are two community maintained approaches to Rust toolchain management:
+- [oxalica's Rust overlay](https://github.com/oxalica/rust-overlay)
+- [fenix](https://github.com/nix-community/fenix)
+
+Oxalica's overlay allows you to select a particular Rust version and components.
+See [their documentation](https://github.com/oxalica/rust-overlay#rust-overlay) for more
+detailed usage.
+
+Fenix is an alternative to `rustup` and can also be used as an overlay.
+
+Both oxalica's overlay and fenix better integrate with nix and cache optimizations.
+Because of this and ergonomics, either of those community projects
+should be preferred to the Mozilla's Rust overlay (`nixpkgs-mozilla`).
+
+### How to select a specific `rustc` and toolchain version {#how-to-select-a-specific-rustc-and-toolchain-version}
+
+You can consume the oxalica overlay and use it to grab a specific Rust toolchain version.
+Here is an example `shell.nix` showing how to grab the current stable toolchain:
+```nix
+{ pkgs ? import <nixpkgs> {
+    overlays = [
+      (import (fetchTarball "https://github.com/oxalica/rust-overlay/archive/master.tar.gz"))
+    ];
+  }
+}:
+pkgs.mkShell {
+  nativeBuildInputs = with pkgs; [
+    pkg-config
+    rust-bin.stable.latest.minimal
+  ];
+}
+```
+
+You can try this out by:
+1. Saving that to `shell.nix`
+2. Executing `nix-shell --pure --command 'rustc --version'`
+
+As of writing, this prints out `rustc 1.56.0 (09c42c458 2021-10-18)`.
+
+### How to use an overlay toolchain in a derivation  {#how-to-use-an-overlay-toolchain-in-a-derivation}
+
+You can also use an overlay's Rust toolchain with `buildRustPackage`.
+The below snippet demonstrates invoking `buildRustPackage` with an oxalica overlay selected Rust toolchain:
+```nix
+with import <nixpkgs> {
+  overlays = [
+    (import (fetchTarball "https://github.com/oxalica/rust-overlay/archive/master.tar.gz"))
+  ];
+};
+
+rustPlatform.buildRustPackage rec {
+  pname = "ripgrep";
+  version = "12.1.1";
+  nativeBuildInputs = [
+    rust-bin.stable.latest.minimal
+  ];
+
+  src = fetchFromGitHub {
+    owner = "BurntSushi";
+    repo = "ripgrep";
+    rev = version;
+    sha256 = "1hqps7l5qrjh9f914r5i6kmcz6f1yb951nv4lby0cjnp5l253kps";
+  };
+
+  cargoSha256 = "03wf9r2csi6jpa7v5sw5lpxkrk4wfzwmzx7k3991q3bdjzcwnnwp";
+
+  meta = with lib; {
+    description = "A fast line-oriented regex search tool, similar to ag and ack";
+    homepage = "https://github.com/BurntSushi/ripgrep";
+    license = licenses.unlicense;
+    maintainers = [ maintainers.tailhook ];
+  };
+}
+```
+
+Follow the below steps to try that snippet.
+1. create a new directory
+1. save the above snippet as `default.nix` in that directory
+1. cd into that directory and run `nix-build`
+
+### Rust overlay installation {#rust-overlay-installation}
+
+You can use this overlay by either changing your local nixpkgs configuration,
+or by adding the overlay declaratively in a nix expression,  e.g. in `configuration.nix`.
+For more information see [the manual on installing overlays](#sec-overlays-install).
+
+### Declarative Rust overlay installation {#declarative-rust-overlay-installation}
+
+This snippet shows how to use oxalica's Rust overlay.
+Add the following to your `configuration.nix`, `home-configuration.nix`, `shell.nix`, or similar:
+
+```nix
+{ pkgs ? import <nixpkgs> {
+    overlays = [
+      (import (builtins.fetchTarball "https://github.com/oxalica/rust-overlay/archive/master.tar.gz"))
+      # Further overlays go here
+    ];
+  };
+};
+```
+
+Note that this will fetch the latest overlay version when rebuilding your system.
diff --git a/doc/languages-frameworks/texlive.section.md b/doc/languages-frameworks/texlive.section.md
new file mode 100644
index 00000000000..6b505cefcc9
--- /dev/null
+++ b/doc/languages-frameworks/texlive.section.md
@@ -0,0 +1,129 @@
+# TeX Live {#sec-language-texlive}
+
+Since release 15.09 there is a new TeX Live packaging that lives entirely under attribute `texlive`.
+
+## User's guide {#sec-language-texlive-user-guide}
+
+- For basic usage just pull `texlive.combined.scheme-basic` for an environment with basic LaTeX support.
+
+- It typically won't work to use separately installed packages together. Instead, you can build a custom set of packages like this:
+
+  ```nix
+  texlive.combine {
+    inherit (texlive) scheme-small collection-langkorean algorithms cm-super;
+  }
+  ```
+
+- There are all the schemes, collections and a few thousand packages, as defined upstream (perhaps with tiny differences).
+
+- By default you only get executables and files needed during runtime, and a little documentation for the core packages. To change that, you need to add `pkgFilter` function to `combine`.
+
+  ```nix
+  texlive.combine {
+    # inherit (texlive) whatever-you-want;
+    pkgFilter = pkg:
+      pkg.tlType == "run" || pkg.tlType == "bin" || pkg.pname == "cm-super";
+    # elem tlType [ "run" "bin" "doc" "source" ]
+    # there are also other attributes: version, name
+  }
+  ```
+
+- You can list packages e.g. by `nix repl`.
+
+  ```ShellSession
+  $ nix repl
+  nix-repl> :l <nixpkgs>
+  nix-repl> texlive.collection-[TAB]
+  ```
+
+- Note that the wrapper assumes that the result has a chance to be useful. For example, the core executables should be present, as well as some core data files. The supported way of ensuring this is by including some scheme, for example `scheme-basic`, into the combination.
+
+## Custom packages {#sec-language-texlive-custom-packages}
+
+
+You may find that you need to use an external TeX package. A derivation for such package has to provide contents of the "texmf" directory in its output and provide the `tlType` attribute. Here is a (very verbose) example:
+
+```nix
+with import <nixpkgs> {};
+
+let
+  foiltex_run = stdenvNoCC.mkDerivation {
+    pname = "latex-foiltex";
+    version = "2.1.4b";
+    passthru.tlType = "run";
+
+    srcs = [
+      (fetchurl {
+        url = "http://mirrors.ctan.org/macros/latex/contrib/foiltex/foiltex.dtx";
+        sha256 = "07frz0krpz7kkcwlayrwrj2a2pixmv0icbngyw92srp9fp23cqpz";
+      })
+      (fetchurl {
+        url = "http://mirrors.ctan.org/macros/latex/contrib/foiltex/foiltex.ins";
+        sha256 = "09wkyidxk3n3zvqxfs61wlypmbhi1pxmjdi1kns9n2ky8ykbff99";
+      })
+    ];
+
+    unpackPhase = ''
+      runHook preUnpack
+
+      for _src in $srcs; do
+        cp "$_src" $(stripHash "$_src")
+      done
+
+      runHook postUnpack
+    '';
+
+    nativeBuildInputs = [ texlive.combined.scheme-small ];
+
+    dontConfigure = true;
+
+    buildPhase = ''
+      runHook preBuild
+
+      # Generate the style files
+      latex foiltex.ins
+
+      runHook postBuild
+    '';
+
+    installPhase = ''
+      runHook preInstall
+
+      path="$out/tex/latex/foiltex"
+      mkdir -p "$path"
+      cp *.{cls,def,clo} "$path/"
+
+      runHook postInstall
+    '';
+
+    meta = with lib; {
+      description = "A LaTeX2e class for overhead transparencies";
+      license = licenses.unfreeRedistributable;
+      maintainers = with maintainers; [ veprbl ];
+      platforms = platforms.all;
+    };
+  };
+  foiltex = { pkgs = [ foiltex_run ]; };
+
+  latex_with_foiltex = texlive.combine {
+    inherit (texlive) scheme-small;
+    inherit foiltex;
+  };
+in
+  runCommand "test.pdf" {
+    nativeBuildInputs = [ latex_with_foiltex ];
+  } ''
+cat >test.tex <<EOF
+\documentclass{foils}
+
+\title{Presentation title}
+\date{}
+
+\begin{document}
+\maketitle
+\end{document}
+EOF
+  pdflatex test.tex
+  cp test.pdf $out
+''
+```
diff --git a/doc/languages-frameworks/titanium.section.md b/doc/languages-frameworks/titanium.section.md
new file mode 100644
index 00000000000..306ad866276
--- /dev/null
+++ b/doc/languages-frameworks/titanium.section.md
@@ -0,0 +1,110 @@
+# Titanium {#titanium}
+
+The Nixpkgs repository contains facilities to deploy a variety of versions of
+the [Titanium SDK](https://www.appcelerator.com) versions, a cross-platform
+mobile app development framework using JavaScript as an implementation language,
+and includes a function abstraction making it possible to build Titanium
+applications for Android and iOS devices from source code.
+
+Not all Titanium features supported -- currently, it can only be used to build
+Android and iOS apps.
+
+## Building a Titanium app {#building-a-titanium-app}
+
+We can build a Titanium app from source for Android or iOS and for debugging or
+release purposes by invoking the `titaniumenv.buildApp {}` function:
+
+```nix
+titaniumenv.buildApp {
+  name = "myapp";
+  src = ./myappsource;
+
+  preBuild = "";
+  target = "android"; # or 'iphone'
+  tiVersion = "7.1.0.GA";
+  release = true;
+
+  androidsdkArgs = {
+    platformVersions = [ "25" "26" ];
+  };
+  androidKeyStore = ./keystore;
+  androidKeyAlias = "myfirstapp";
+  androidKeyStorePassword = "secret";
+
+  xcodeBaseDir = "/Applications/Xcode.app";
+  xcodewrapperArgs = {
+    version = "9.3";
+  };
+  iosMobileProvisioningProfile = ./myprovisioning.profile;
+  iosCertificateName = "My Company";
+  iosCertificate = ./mycertificate.p12;
+  iosCertificatePassword = "secret";
+  iosVersion = "11.3";
+  iosBuildStore = false;
+
+  enableWirelessDistribution = true;
+  installURL = "/installipa.php";
+}
+```
+
+The `titaniumenv.buildApp {}` function takes the following parameters:
+
+* The `name` parameter refers to the name in the Nix store.
+* The `src` parameter refers to the source code location of the app that needs
+  to be built.
+* `preRebuild` contains optional build instructions that are carried out before
+  the build starts.
+* `target` indicates for which device the app must be built. Currently only
+  'android' and 'iphone' (for iOS) are supported.
+* `tiVersion` can be used to optionally override the requested Titanium version
+  in `tiapp.xml`. If not specified, it will use the version in `tiapp.xml`.
+* `release` should be set to true when building an app for submission to the
+  Google Playstore or Apple Appstore. Otherwise, it should be false.
+
+When the `target` has been set to `android`, we can configure the following
+parameters:
+
+* The `androidSdkArgs` parameter refers to an attribute set that propagates all
+  parameters to the `androidenv.composeAndroidPackages {}` function. This can
+  be used to install all relevant Android plugins that may be needed to perform
+  the Android build. If no parameters are given, it will deploy the platform
+  SDKs for API-levels 25 and 26 by default.
+
+When the `release` parameter has been set to true, you need to provide
+parameters to sign the app:
+
+* `androidKeyStore` is the path to the keystore file
+* `androidKeyAlias` is the key alias
+* `androidKeyStorePassword` refers to the password to open the keystore file.
+
+When the `target` has been set to `iphone`, we can configure the following
+parameters:
+
+* The `xcodeBaseDir` parameter refers to the location where Xcode has been
+  installed. When none value is given, the above value is the default.
+* The `xcodewrapperArgs` parameter passes arbitrary parameters to the
+  `xcodeenv.composeXcodeWrapper {}` function. This can, for example, be used
+  to adjust the default version of Xcode.
+
+When `release` has been set to true, you also need to provide the following
+parameters:
+
+* `iosMobileProvisioningProfile` refers to a mobile provisioning profile needed
+  for signing.
+* `iosCertificateName` refers to the company name in the P12 certificate.
+* `iosCertificate` refers to the path to the P12 file.
+* `iosCertificatePassword` contains the password to open the P12 file.
+* `iosVersion` refers to the iOS SDK version to use. It defaults to the latest
+  version.
+* `iosBuildStore` should be set to `true` when building for the Apple Appstore
+  submission. For enterprise or ad-hoc builds it should be set to `false`.
+
+When `enableWirelessDistribution` has been enabled, you must also provide the
+path of the PHP script (`installURL`) (that is included with the iOS build
+environment) to enable wireless ad-hoc installations.
+
+## Emulating or simulating the app {#emulating-or-simulating-the-app}
+
+It is also possible to simulate the correspond iOS simulator build by using
+`xcodeenv.simulateApp {}` and emulate an Android APK by using
+`androidenv.emulateApp {}`.
diff --git a/doc/languages-frameworks/vim.section.md b/doc/languages-frameworks/vim.section.md
new file mode 100644
index 00000000000..a615d585b15
--- /dev/null
+++ b/doc/languages-frameworks/vim.section.md
@@ -0,0 +1,348 @@
+# Vim {#vim}
+
+Both Neovim and Vim can be configured to include your favorite plugins
+and additional libraries.
+
+Loading can be deferred; see examples.
+
+At the moment we support three different methods for managing plugins:
+
+- Vim packages (*recommend*)
+- VAM (=vim-addon-manager)
+- Pathogen
+- vim-plug
+
+## Custom configuration {#custom-configuration}
+
+Adding custom .vimrc lines can be done using the following code:
+
+```nix
+vim_configurable.customize {
+  # `name` specifies the name of the executable and package
+  name = "vim-with-plugins";
+
+  vimrcConfig.customRC = ''
+    set hidden
+  '';
+}
+```
+
+This configuration is used when Vim is invoked with the command specified as name, in this case `vim-with-plugins`.
+
+For Neovim the `configure` argument can be overridden to achieve the same:
+
+```nix
+neovim.override {
+  configure = {
+    customRC = ''
+      # here your custom configuration goes!
+    '';
+  };
+}
+```
+
+If you want to use `neovim-qt` as a graphical editor, you can configure it by overriding Neovim in an overlay
+or passing it an overridden Neovimn:
+
+```nix
+neovim-qt.override {
+  neovim = neovim.override {
+    configure = {
+      customRC = ''
+        # your custom configuration
+      '';
+    };
+  };
+}
+```
+
+## Managing plugins with Vim packages {#managing-plugins-with-vim-packages}
+
+To store you plugins in Vim packages (the native Vim plugin manager, see `:help packages`) the following example can be used:
+
+```nix
+vim_configurable.customize {
+  vimrcConfig.packages.myVimPackage = with pkgs.vimPlugins; {
+    # loaded on launch
+    start = [ youcompleteme fugitive ];
+    # manually loadable by calling `:packadd $plugin-name`
+    # however, if a Vim plugin has a dependency that is not explicitly listed in
+    # opt that dependency will always be added to start to avoid confusion.
+    opt = [ phpCompletion elm-vim ];
+    # To automatically load a plugin when opening a filetype, add vimrc lines like:
+    # autocmd FileType php :packadd phpCompletion
+  };
+}
+```
+
+`myVimPackage` is an arbitrary name for the generated package. You can choose any name you like.
+For Neovim the syntax is:
+
+```nix
+neovim.override {
+  configure = {
+    customRC = ''
+      # here your custom configuration goes!
+    '';
+    packages.myVimPackage = with pkgs.vimPlugins; {
+      # see examples below how to use custom packages
+      start = [ ];
+      # If a Vim plugin has a dependency that is not explicitly listed in
+      # opt that dependency will always be added to start to avoid confusion.
+      opt = [ ];
+    };
+  };
+}
+```
+
+The resulting package can be added to `packageOverrides` in `~/.nixpkgs/config.nix` to make it installable:
+
+```nix
+{
+  packageOverrides = pkgs: with pkgs; {
+    myVim = vim_configurable.customize {
+      # `name` specifies the name of the executable and package
+      name = "vim-with-plugins";
+      # add here code from the example section
+    };
+    myNeovim = neovim.override {
+      configure = {
+      # add here code from the example section
+      };
+    };
+  };
+}
+```
+
+After that you can install your special grafted `myVim` or `myNeovim` packages.
+
+### What if your favourite Vim plugin isn’t already packaged? {#what-if-your-favourite-vim-plugin-isnt-already-packaged}
+
+If one of your favourite plugins isn't packaged, you can package it yourself:
+
+```nix
+{ config, pkgs, ... }:
+
+let
+  easygrep = pkgs.vimUtils.buildVimPlugin {
+    name = "vim-easygrep";
+    src = pkgs.fetchFromGitHub {
+      owner = "dkprice";
+      repo = "vim-easygrep";
+      rev = "d0c36a77cc63c22648e792796b1815b44164653a";
+      sha256 = "0y2p5mz0d5fhg6n68lhfhl8p4mlwkb82q337c22djs4w5zyzggbc";
+    };
+  };
+in
+{
+  environment.systemPackages = [
+    (
+      pkgs.neovim.override {
+        configure = {
+          packages.myPlugins = with pkgs.vimPlugins; {
+          start = [
+            vim-go # already packaged plugin
+            easygrep # custom package
+          ];
+          opt = [];
+        };
+        # ...
+      };
+     }
+    )
+  ];
+}
+```
+
+### Specificities for some plugins
+#### Tree sitter
+
+By default `nvim-treesitter` encourages you to download, compile and install
+the required tree-sitter grammars at run time with `:TSInstall`. This works
+poorly on NixOS.  Instead, to install the `nvim-treesitter` plugins with a set
+of precompiled grammars, you can use `nvim-treesitter.withPlugins` function:
+
+```nix
+(pkgs.neovim.override {
+  configure = {
+    packages.myPlugins = with pkgs.vimPlugins; {
+      start = [
+        (nvim-treesitter.withPlugins (
+          plugins: with plugins; [
+            tree-sitter-nix
+            tree-sitter-python
+          ]
+        ))
+      ];
+    };
+  };
+})
+```
+
+To enable all grammars packaged in nixpkgs, use `(pkgs.vimPlugins.nvim-treesitter.withPlugins (plugins: pkgs.tree-sitter.allGrammars))`.
+
+## Managing plugins with vim-plug {#managing-plugins-with-vim-plug}
+
+To use [vim-plug](https://github.com/junegunn/vim-plug) to manage your Vim
+plugins the following example can be used:
+
+```nix
+vim_configurable.customize {
+  vimrcConfig.packages.myVimPackage = with pkgs.vimPlugins; {
+    # loaded on launch
+    plug.plugins = [ youcompleteme fugitive phpCompletion elm-vim ];
+  };
+}
+```
+
+For Neovim the syntax is:
+
+```nix
+neovim.override {
+  configure = {
+    customRC = ''
+      # here your custom configuration goes!
+    '';
+    plug.plugins = with pkgs.vimPlugins; [
+      vim-go
+    ];
+  };
+}
+```
+
+## Managing plugins with VAM {#managing-plugins-with-vam}
+
+### Handling dependencies of Vim plugins {#handling-dependencies-of-vim-plugins}
+
+VAM introduced .json files supporting dependencies without versioning
+assuming that "using latest version" is ok most of the time.
+
+### Example {#example}
+
+First create a vim-scripts file having one plugin name per line. Example:
+
+```vim
+"tlib"
+{'name': 'vim-addon-sql'}
+{'filetype_regex': '\%(vim)$', 'names': ['reload', 'vim-dev-plugin']}
+```
+
+Such vim-scripts file can be read by VAM as well like this:
+
+```vim
+call vam#Scripts(expand('~/.vim-scripts'), {})
+```
+
+Create a default.nix file:
+
+```nix
+{ nixpkgs ? import <nixpkgs> {}, compiler ? "ghc7102" }:
+nixpkgs.vim_configurable.customize { name = "vim"; vimrcConfig.vam.pluginDictionaries = [ "vim-addon-vim2nix" ]; }
+```
+
+Create a generate.vim file:
+
+```vim
+ActivateAddons vim-addon-vim2nix
+let vim_scripts = "vim-scripts"
+call nix#ExportPluginsForNix({
+\  'path_to_nixpkgs': eval('{"'.substitute(substitute(substitute($NIX_PATH, ':', ',', 'g'), '=',':', 'g'), '\([:,]\)', '"\1"',"g").'"}')["nixpkgs"],
+\  'cache_file': '/tmp/vim2nix-cache',
+\  'try_catch': 0,
+\  'plugin_dictionaries': ["vim-addon-manager"]+map(readfile(vim_scripts), 'eval(v:val)')
+\ })
+```
+
+Then run
+
+```bash
+nix-shell -p vimUtils.vim_with_vim2nix --command "vim -c 'source generate.vim'"
+```
+
+You should get a Vim buffer with the nix derivations (output1) and vam.pluginDictionaries (output2).
+You can add your Vim to your system's configuration file like this and start it by "vim-my":
+
+```nix
+my-vim =
+  let plugins = let inherit (vimUtils) buildVimPluginFrom2Nix; in {
+    copy paste output1 here
+  }; in vim_configurable.customize {
+    name = "vim-my";
+
+    vimrcConfig.vam.knownPlugins = plugins; # optional
+    vimrcConfig.vam.pluginDictionaries = [
+       copy paste output2 here
+    ];
+
+    # Pathogen would be
+    # vimrcConfig.pathogen.knownPlugins = plugins; # plugins
+    # vimrcConfig.pathogen.pluginNames = ["tlib"];
+  };
+```
+
+Sample output1:
+
+```nix
+"reload" = buildVimPluginFrom2Nix { # created by nix#NixDerivation
+  name = "reload";
+  src = fetchgit {
+    url = "git://github.com/xolox/vim-reload";
+    rev = "0a601a668727f5b675cb1ddc19f6861f3f7ab9e1";
+    sha256 = "0vb832l9yxj919f5hfg6qj6bn9ni57gnjd3bj7zpq7d4iv2s4wdh";
+  };
+  dependencies = ["nim-misc"];
+
+};
+[...]
+```
+
+Sample output2:
+
+```nix
+[
+  ''vim-addon-manager''
+  ''tlib''
+  { "name" = ''vim-addon-sql''; }
+  { "filetype_regex" = ''\%(vim)$$''; "names" = [ ''reload'' ''vim-dev-plugin'' ]; }
+]
+```
+
+## Adding new plugins to nixpkgs {#adding-new-plugins-to-nixpkgs}
+
+Nix expressions for Vim plugins are stored in [pkgs/applications/editors/vim/plugins](https://github.com/NixOS/nixpkgs/tree/master/pkgs/applications/editors/vim/plugins). For the vast majority of plugins, Nix expressions are automatically generated by running [`./update.py`](https://github.com/NixOS/nixpkgs/blob/master/pkgs/applications/editors/vim/plugins/update.py). This creates a [generated.nix](https://github.com/NixOS/nixpkgs/blob/master/pkgs/applications/editors/vim/plugins/generated.nix) file based on the plugins listed in [vim-plugin-names](https://github.com/NixOS/nixpkgs/blob/master/pkgs/applications/editors/vim/plugins/vim-plugin-names). Plugins are listed in alphabetical order in `vim-plugin-names` using the format `[github username]/[repository]@[gitref]`. For example https://github.com/scrooloose/nerdtree becomes `scrooloose/nerdtree`.
+
+Some plugins require overrides in order to function properly. Overrides are placed in [overrides.nix](https://github.com/NixOS/nixpkgs/blob/master/pkgs/applications/editors/vim/plugins/overrides.nix). Overrides are most often required when a plugin requires some dependencies, or extra steps are required during the build process. For example `deoplete-fish` requires both `deoplete-nvim` and `vim-fish`, and so the following override was added:
+
+```nix
+deoplete-fish = super.deoplete-fish.overrideAttrs(old: {
+  dependencies = with super; [ deoplete-nvim vim-fish ];
+});
+```
+
+Sometimes plugins require an override that must be changed when the plugin is updated. This can cause issues when Vim plugins are auto-updated but the associated override isn't updated. For these plugins, the override should be written so that it specifies all information required to install the plugin, and running `./update.py` doesn't change the derivation for the plugin. Manually updating the override is required to update these types of plugins. An example of such a plugin is `LanguageClient-neovim`.
+
+To add a new plugin, run `./update.py --add "[owner]/[name]"`. **NOTE**: This script automatically commits to your git repository. Be sure to check out a fresh branch before running.
+
+Finally, there are some plugins that are also packaged in nodePackages because they have Javascript-related build steps, such as running webpack. Those plugins are not listed in `vim-plugin-names` or managed by `update.py` at all, and are included separately in `overrides.nix`. Currently, all these plugins are related to the `coc.nvim` ecosystem of Language Server Protocol integration with vim/neovim.
+
+## Updating plugins in nixpkgs {#updating-plugins-in-nixpkgs}
+
+Run the update script with a GitHub API token that has at least `public_repo` access. Running the script without the token is likely to result in rate-limiting (429 errors). For steps on creating an API token, please refer to [GitHub's token documentation](https://docs.github.com/en/free-pro-team@latest/github/authenticating-to-github/creating-a-personal-access-token).
+
+```sh
+GITHUB_API_TOKEN=my_token ./pkgs/applications/editors/vim/plugins/update.py
+```
+
+Alternatively, set the number of processes to a lower count to avoid rate-limiting.
+
+```sh
+./pkgs/applications/editors/vim/plugins/update.py --proc 1
+```
+
+## Important repositories {#important-repositories}
+
+- [vim-pi](https://bitbucket.org/vimcommunity/vim-pi) is a plugin repository
+  from VAM plugin manager meant to be used by others as well used by
+
+- [vim2nix](https://github.com/MarcWeber/vim-addon-vim2nix) which generates the
+  .nix code
diff --git a/doc/manual.xml b/doc/manual.xml
new file mode 100644
index 00000000000..b43021d85ca
--- /dev/null
+++ b/doc/manual.xml
@@ -0,0 +1,42 @@
+<book xmlns="http://docbook.org/ns/docbook"
+      xmlns:xi="http://www.w3.org/2001/XInclude">
+ <info>
+  <title>Nixpkgs Manual</title>
+  <subtitle>Version <xi:include href=".version" parse="text" />
+  </subtitle>
+ </info>
+ <xi:include href="preface.chapter.xml" />
+ <part>
+  <title>Using Nixpkgs</title>
+  <xi:include href="using/configuration.chapter.xml" />
+  <xi:include href="using/overlays.chapter.xml" />
+  <xi:include href="using/overrides.chapter.xml" />
+  <xi:include href="functions.xml" />
+ </part>
+ <part>
+  <title>Standard environment</title>
+  <xi:include href="stdenv/stdenv.chapter.xml" />
+  <xi:include href="stdenv/meta.chapter.xml" />
+  <xi:include href="stdenv/multiple-output.chapter.xml" />
+  <xi:include href="stdenv/cross-compilation.chapter.xml" />
+  <xi:include href="stdenv/platform-notes.chapter.xml" />
+ </part>
+ <part>
+  <title>Builders</title>
+  <xi:include href="builders/fetchers.chapter.xml" />
+  <xi:include href="builders/trivial-builders.chapter.xml" />
+  <xi:include href="builders/special.xml" />
+  <xi:include href="builders/images.xml" />
+  <xi:include href="languages-frameworks/index.xml" />
+  <xi:include href="builders/packages/index.xml" />
+ </part>
+ <part>
+  <title>Contributing to Nixpkgs</title>
+  <xi:include href="contributing/quick-start.chapter.xml" />
+  <xi:include href="contributing/coding-conventions.chapter.xml" />
+  <xi:include href="contributing/submitting-changes.chapter.xml" />
+  <xi:include href="contributing/vulnerability-roundup.chapter.xml" />
+  <xi:include href="contributing/reviewing-contributions.chapter.xml" />
+  <xi:include href="contributing/contributing-to-documentation.chapter.xml" />
+ </part>
+</book>
diff --git a/doc/old/cross.txt b/doc/old/cross.txt
new file mode 100644
index 00000000000..064ca8d37b0
--- /dev/null
+++ b/doc/old/cross.txt
@@ -0,0 +1,329 @@
+Setting up a cross compiler with Nix
+
+"Cross compilation" means compiling a program on one machine for another
+type of machine. A typical use of cross compilation is to compile programs
+for embedded devices. These devices often don't have the computing power
+and memory to compile programs natively.
+
+For a fully working cross compiler the following are needed:
+
+* cross binutils: assembler, archiver, linker, etcetera that understand
+the format of the target system
+
+* cross compiler: a compiler that can generate binary code and object files
+for the target platform
+
+* cross C library: a library to link object files with to create fully
+functional programs
+
+Cross compilers are difficult to set up. A lot of people report that they
+cannot succeed in building a cross toolchain successfully. The answers
+usually consist of "download this pre-built toolchain", which is equally
+unhelpful.
+
+A toolchain is set up in five steps:
+
+1. build binutils to that can run on the host platform, but generate code
+for the target platform
+
+2. build Linux kernel headers for the target platform
+
+3. build a minimal C only version of GCC, that can run on the host platform
+and generate code for the target platform
+
+4. build a C library for the target platform. This includes the dynamic
+linker, C library, etc.
+
+5. build a full GCC
+
+****
+NB:
+
+Keep in mind that many programs are not very well suited for cross
+compilation. Either they are not intended to run on other platforms,
+because the code is highly platform specific, or the configuration process
+is not written with cross compilation in mind.
+
+Nix will not solve these problems for you!
+***
+
+This document describes to set up a cross compiler to generate code for
+arm-linux with uClibc and runs on i686-linux. The "stdenv" used is the
+default from the standard Nix packages collection.
+
+Step 1: build binutils for arm-linux in the stdenv for i686-linux
+
+---
+{stdenv, fetchurl, noSysDirs}:
+
+stdenv.mkDerivation {
+  name = "binutils-2.16.1-arm";
+  builder = ./builder.sh;
+  src = fetchurl {
+    url = "http://ftp.nluug.nl/gnu/binutils/binutils-2.16.1.tar.bz2";
+    sha256 = "1ian3kwh2vg6hr3ymrv48s04gijs539vzrq62xr76bxbhbwnz2np";
+  };
+  inherit noSysDirs;
+  configureFlags = [ "--target=arm-linux" ];
+}
+---
+
+This will compile binutils that will run on i686-linux, but knows the
+format used by arm-linux.
+
+Step 2: build kernel headers for the target architecture
+
+  default.nix for kernel-headers-arm:
+
+---
+{stdenv, fetchurl}:
+
+assert stdenv.buildPlatform.system == "i686-linux";
+
+stdenv.mkDerivation {
+  name = "linux-headers-2.6.13.1-arm";
+  builder = ./builder.sh;
+  src = fetchurl {
+    url = "http://www.kernel.org/pub/linux/kernel/v2.6/linux-2.6.13.1.tar.bz2";
+    sha256 = "12qxmc827fjhaz53kjy7vyrzsaqcg78amiqsb3qm20z26w705lma";
+  };
+}
+---
+
+  builder.sh for kernel-headers-arm:
+
+---
+source $stdenv/setup
+
+
+buildPhase() {
+    make include/linux/version.h
+}
+
+buildPhase=buildPhase
+
+
+installPhase() {
+    mkdir $out
+    mkdir $out/include
+    #cd $out/include
+    #ln -s asm-arm asm
+    make include/asm ARCH=arm
+    cp -prvd include/linux include/asm include/asm-arm include/asm-generic $out/include
+    echo -n > $out/include/linux/autoconf.h
+}
+
+installPhase=installPhase
+
+
+genericBuild
+---
+
+Step 3: build a minimal GCC
+
+Extra/different parameters include the target platform and the kernel
+headers argument (this needs a major cleanup, as well as the name, it
+needs to be different!). Profiled compilers are disabled. The tarball
+used here is just gcc-core. For some reason it doesn't install nicely
+if the whole tarball is used (or is this some braino on my side? -- AH).
+
+Only C is used, because for other languages (such as C++) extra libraries
+need to be compiled, for which libraries compiled for the target system
+are needed.
+
+There is a bit of evilness going on. The cross compiled utilities need
+to be either copied to or be linked from the output tree of the compiler.
+(Is this really true? Back this up with arguments! -- AH)
+
+Symbolic links are not something we want inside the Nix store.
+
+---
+{ stdenv, fetchurl, noSysDirs
+, langC ? true, langCC ? true, langF77 ? false
+, profiledCompiler ? false
+, binutilsArm
+, kernelHeadersArm
+}:
+
+assert langC;
+
+stdenv.mkDerivation {
+  name = "gcc-4.0.2-arm";
+  builder = ./builder.sh;
+  src = fetchurl {
+    url = ftp://ftp.nluug.nl/pub/gnu/gcc/gcc-4.0.2/gcc-core-4.0.2.tar.bz2;
+    sha256 = "02fxh0asflm8825w23l2jq1wvs7hbnam0jayrivg7zdv2ifnc0rc";
+  };
+  # !!! apply only if noSysDirs is set
+  patches = [./no-sys-dirs.patch ./gcc-inhibit.patch];
+  inherit noSysDirs langC langCC langF77 profiledCompiler;
+  buildInputs = [binutilsArm];
+  inherit kernelHeadersArm binutilsArm;
+  platform = "arm-linux";
+}
+---
+
+The builder.sh for a cross-compiler. Note that the binutils are prefixed
+with the architecture name, so arm-linux-ld instead of ld, etc. This is
+necessary because when we cross-compile a lot of programs look for these
+tools with these specific names. The standard gcc-wrapper does not take this
+into account yet.
+
+---
+source $stdenv/setup
+
+
+export NIX_FIXINC_DUMMY=$NIX_BUILD_TOP/dummy
+mkdir $NIX_FIXINC_DUMMY
+
+
+if test "$noSysDirs" = "1"; then
+
+    if test "$noSysDirs" = "1"; then
+        # Figure out what extra flags to pass to the gcc compilers
+        # being generated to make sure that they use our glibc.
+        if test -e $NIX_CC/nix-support/orig-glibc; then
+            glibc=$(cat $NIX_CC/nix-support/orig-glibc)
+            # Ugh.  Copied from gcc-wrapper/builder.sh.  We can't just
+            # source in $NIX_CC/nix-support/add-flags, since that
+            # would cause *this* GCC to be linked against the
+            # *previous* GCC.  Need some more modularity there.
+            extraCFlags="-B$glibc/lib -isystem $glibc/include"
+            extraLDFlags="-B$glibc/lib -L$glibc/lib -Wl,-s \
+              -Wl,-dynamic-linker,$glibc/lib/ld-linux.so.2"
+
+            # Oh, what a hack.  I should be shot for this.
+            # In stage 1, we should link against the previous GCC, but
+            # not afterwards.  Otherwise we retain a dependency.
+            # However, ld-wrapper, which adds the linker flags for the
+            # previous GCC, is also used in stage 2/3.  We can prevent
+            # it from adding them by NIX_GLIBC_FLAGS_SET, but then
+            # gcc-wrapper will also not add them, thereby causing
+            # stage 1 to fail.  So we use a trick to only set the
+            # flags in gcc-wrapper.
+            hook=$(pwd)/ld-wrapper-hook
+            echo "NIX_GLIBC_FLAGS_SET=1" > $hook
+            export NIX_LD_WRAPPER_START_HOOK=$hook
+        fi
+
+        export NIX_EXTRA_CFLAGS=$extraCFlags
+        export NIX_EXTRA_LDFLAGS=$extraLDFlags
+        export CFLAGS=$extraCFlags
+        export CXXFLAGS=$extraCFlags
+        export LDFLAGS=$extraLDFlags
+    fi
+
+else
+    patches=""
+fi
+
+
+preConfigure=preConfigure
+preConfigure() {
+
+    # Determine the frontends to build.
+    langs="c"
+    if test -n "$langCC"; then
+        langs="$langs,c++"
+    fi
+    if test -n "$langF77"; then
+        langs="$langs,f77"
+    fi
+
+    # Cross compiler evilness
+    mkdir -p $out
+    mkdir -p $out/arm-linux
+    mkdir -p $out/arm-linux/bin
+    ln -s $binutilsArm/arm-linux/bin/as $out/arm-linux/bin/as
+    ln -s $binutilsArm/arm-linux/bin/ld $out/arm-linux/bin/ld
+    ln -s $binutilsArm/arm-linux/bin/ar $out/arm-linux/bin/ar
+    ln -s $binutilsArm/arm-linux/bin/ranlib $out/arm-linux/bin/ranlib
+
+    # Perform the build in a different directory.
+    mkdir ../build
+    cd ../build
+
+    configureScript=../$sourceRoot/configure
+    configureFlags="--enable-languages=$langs --target=$platform --disable-threads --disable-libmudflap --disable-shared --with-headers=$kernelHeadersArm/include --disable-multilib"
+}
+
+
+postInstall=postInstall
+postInstall() {
+    # Remove precompiled headers for now.  They are very big and
+    # probably not very useful yet.
+    find $out/include -name "*.gch" -exec rm -rf {} \; -prune
+
+    # Remove `fixincl' to prevent a retained dependency on the
+    # previous gcc.
+    rm -rf $out/libexec/gcc/*/*/install-tools
+}
+
+
+#if test -z "$profiledCompiler"; then
+    #makeFlags="bootstrap"
+#else
+    #makeFlags="profiledbootstrap"
+#fi
+
+genericBuild
+---
+
+Step 4: build a C library for the target platform.
+
+The previous steps are enough to compile a C library. In our case we take
+uClibc. It's intended to be a small sized replacement for glibc. It is widely
+used in embedded environments.
+
+...
+
+Step 5: Build a compiler to link with the newly built C library.
+
+...
+
+If we restrict the compiler to just C programs it is relatively easy,
+since we only need to wrap the GCC we built in the previous step with all
+the right tools and the right C library. Successfully compiled programs with
+this compiler and verified to be working on a HP Jornada 820 running Linux
+are "patch", "make" and "wget".
+
+If we want to build C++ programs it gets a lot more difficult. GCC has a
+three step compilation process. In the first step a simple compiler, called
+xgcc, that can compile only C programs is built. With that compiler it
+compiles itself two more times: one time to build a full compiler, and another
+time to build a full compiler once again with the freshly built compiler from
+step 2. In the second and third step support for C++ is compiled, if this
+is configured.
+
+One of the libraries that has to be built for C++ support step is libstdc++.
+This library uses xgcc, even when cross compiling, since libstdc++ has to be
+compiled for arm-linux.
+
+One of the compiler flags that GCC uses for this compiler is called X_CFLAGS.
+This is used by the Nix build process to set the dynamic linker, glibc
+in the case of i686-linux using the default Nix packages collection.
+
+Obiously, since we need to compile libstc++ for arm-linux with uClibc linking
+will not be done correctly: you can't link object files built for arm-linux
+with a glibc built for i686-linux.
+
+Setting X_CFLAGS to use the uClibc libraries and dynamic linker will fail
+too. Earlier on in the build process these flags are used to compile important
+files like libgcc.a by the host system gcc, which does need to be linked
+to glibc. To make this work correctly you will need to carefully juggle
+with compilation flags. This is still work in progress for Nix.
+
+
+---
+
+After successfully completing the whole toolchain you can start building
+packages with the newly built tools. To make everything build correctly
+you will need a stdenv for your target platform. Setting up this platform
+will take some effort. Right now there is a very experimental setup for
+arm-linux, which needs to be cleaned up before it is production ready.
+
+Please note that many packages are not well suited for cross-compilation.
+Even though the package itself might be very well portable often the
+buildscripts are not. One thing that we have seen that causes frequent
+build failures is the use of the LD variable. This is often set to 'ld'
+and not $(CROSS)-ld.
diff --git a/doc/overrides.css b/doc/overrides.css
new file mode 100644
index 00000000000..73901a3f543
--- /dev/null
+++ b/doc/overrides.css
@@ -0,0 +1,22 @@
+.docbook .xref img[src^=images\/callouts\/],
+.screen img,
+.programlisting img,
+.literallayout img,
+.synopsis img {
+    width: 1em;
+}
+
+.calloutlist img {
+    width: 1.5em;
+}
+
+.prompt,
+.screen img,
+.programlisting img,
+.literallayout img,
+.synopsis img {
+    -moz-user-select: none;
+    -webkit-user-select: none;
+    -ms-user-select: none;
+    user-select: none;
+}
diff --git a/doc/preface.chapter.md b/doc/preface.chapter.md
new file mode 100644
index 00000000000..16f228272b3
--- /dev/null
+++ b/doc/preface.chapter.md
@@ -0,0 +1,46 @@
+# Preface {#preface}
+
+The Nix Packages collection (Nixpkgs) is a set of thousands of packages for the
+[Nix package manager](https://nixos.org/nix/), released under a
+[permissive MIT/X11 license](https://github.com/NixOS/nixpkgs/blob/master/COPYING).
+Packages are available for several platforms, and can be used with the Nix
+package manager on most GNU/Linux distributions as well as [NixOS](https://nixos.org/nixos).
+
+This manual primarily describes how to write packages for the Nix Packages collection
+(Nixpkgs). Thus it’s mainly for packagers and developers who want to add packages to
+Nixpkgs. If you like to learn more about the Nix package manager and the Nix
+expression language, then you are kindly referred to the [Nix manual](https://nixos.org/nix/manual/).
+The NixOS distribution is documented in the [NixOS manual](https://nixos.org/nixos/manual/).
+
+## Overview of Nixpkgs {#overview-of-nixpkgs}
+
+Nix expressions describe how to build packages from source and are collected in
+the [nixpkgs repository](https://github.com/NixOS/nixpkgs). Also included in the
+collection are Nix expressions for
+[NixOS modules](https://nixos.org/nixos/manual/index.html#sec-writing-modules).
+With these expressions the Nix package manager can build binary packages.
+
+Packages, including the Nix packages collection, are distributed through
+[channels](https://nixos.org/nix/manual/#sec-channels). The collection is
+distributed for users of Nix on non-NixOS distributions through the channel
+`nixpkgs`. Users of NixOS generally use one of the `nixos-*` channels, e.g.
+`nixos-19.09`, which includes all packages and modules for the stable NixOS
+19.09. Stable NixOS releases are generally only given
+security updates. More up to date packages and modules are available via the
+`nixos-unstable` channel.
+
+Both `nixos-unstable` and `nixpkgs` follow the `master` branch of the Nixpkgs
+repository, although both do lag the `master` branch by generally
+[a couple of days](https://status.nixos.org/). Updates to a channel are
+distributed as soon as all tests for that channel pass, e.g.
+[this table](https://hydra.nixos.org/job/nixpkgs/trunk/unstable#tabs-constituents)
+shows the status of tests for the `nixpkgs` channel.
+
+The tests are conducted by a cluster called [Hydra](https://nixos.org/hydra/),
+which also builds binary packages from the Nix expressions in Nixpkgs for
+`x86_64-linux`, `i686-linux` and `x86_64-darwin`.
+The binaries are made available via a [binary cache](https://cache.nixos.org).
+
+The current Nix expressions of the channels are available in the
+[`nixpkgs`](https://github.com/NixOS/nixpkgs) repository in branches
+that correspond to the channel names (e.g. `nixos-19.09-small`).
diff --git a/doc/release-notes.xml b/doc/release-notes.xml
new file mode 100644
index 00000000000..a15f5466729
--- /dev/null
+++ b/doc/release-notes.xml
@@ -0,0 +1,650 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<article xmlns="http://docbook.org/ns/docbook"
+         xmlns:xlink="http://www.w3.org/1999/xlink">
+ <title>Nixpkgs Release Notes</title>
+ <section xml:id="release-notes-0.14">
+  <title>Release 0.14 (June 4, 2012)</title>
+
+  <para>
+   In preparation for the switch from Subversion to Git, this release is mainly the prevent the Nixpkgs version number from going backwards. (This would happen because prerelease version numbers produced for the Git repository are lower than those for the Subversion repository.)
+  </para>
+
+  <para>
+   Since the last release, there have been thousands of changes and new packages by numerous contributors. For details, see the commit logs.
+  </para>
+ </section>
+ <section xml:id="release-notes-0.13">
+  <title>Release 0.13 (February 5, 2010)</title>
+
+  <para>
+   As always, there are many changes. Some of the most important updates are:
+   <itemizedlist>
+    <listitem>
+     <para>
+      Glibc 2.9.
+     </para>
+    </listitem>
+    <listitem>
+     <para>
+      GCC 4.3.3.
+     </para>
+    </listitem>
+    <listitem>
+     <para>
+      Linux 2.6.32.
+     </para>
+    </listitem>
+    <listitem>
+     <para>
+      X.org 7.5.
+     </para>
+    </listitem>
+    <listitem>
+     <para>
+      KDE 4.3.4.
+     </para>
+    </listitem>
+   </itemizedlist>
+  </para>
+ </section>
+ <section xml:id="release-notes-0.12">
+  <title>Release 0.12 (April 24, 2009)</title>
+
+  <para>
+   There are way too many additions to Nixpkgs since the last release to list here: for example, the number of packages on Linux has increased from 1002 to 2159. However, some specific improvements are worth listing:
+   <itemizedlist>
+    <listitem>
+     <para>
+      Nixpkgs now has a manual. In particular, it describes the standard build environment in detail.
+     </para>
+    </listitem>
+    <listitem>
+     <para>
+      Major new packages:
+      <itemizedlist>
+       <listitem>
+        <para>
+         KDE 4.
+        </para>
+       </listitem>
+       <listitem>
+        <para>
+         TeXLive.
+        </para>
+       </listitem>
+       <listitem>
+        <para>
+         VirtualBox.
+        </para>
+       </listitem>
+      </itemizedlist>
+      … and many others.
+     </para>
+    </listitem>
+    <listitem>
+     <para>
+      Important updates:
+      <itemizedlist>
+       <listitem>
+        <para>
+         Glibc 2.7.
+        </para>
+       </listitem>
+       <listitem>
+        <para>
+         GCC 4.2.4.
+        </para>
+       </listitem>
+       <listitem>
+        <para>
+         Linux 2.6.25 — 2.6.28.
+        </para>
+       </listitem>
+       <listitem>
+        <para>
+         Firefox 3.
+        </para>
+       </listitem>
+       <listitem>
+        <para>
+         X.org 7.3.
+        </para>
+       </listitem>
+      </itemizedlist>
+     </para>
+    </listitem>
+    <listitem>
+     <para>
+      Support for building derivations in a virtual machine, including RPM and Debian builds in automatically generated VM images. See <filename>pkgs/build-support/vm/default.nix</filename> for details.
+     </para>
+    </listitem>
+    <listitem>
+     <para>
+      Improved support for building Haskell packages.
+     </para>
+    </listitem>
+   </itemizedlist>
+  </para>
+
+  <para>
+   The following people contributed to this release: Andres Löh, Arie Middelkoop, Armijn Hemel, Eelco Dolstra, Lluís Batlle, Ludovic Courtès, Marc Weber, Mart Kolthof, Martin Bravenboer, Michael Raskin, Nicolas Pierron, Peter Simons, Pjotr Prins, Rob Vermaas, Sander van der Burg, Tobias Hammerschmidt, Valentin David, Wouter den Breejen and Yury G. Kudryashov. In addition, several people contributed patches on the <literal>nix-dev</literal> mailing list.
+  </para>
+ </section>
+ <section xml:id="release-notes-0.11">
+  <title>Release 0.11 (September 11, 2007)</title>
+
+  <para>
+   This release has the following improvements:
+   <itemizedlist>
+    <listitem>
+     <para>
+      The standard build environment (<literal>stdenv</literal>) is now pure on the <literal>x86_64-linux</literal> and <literal>powerpc-linux</literal> platforms, just as on <literal>i686-linux</literal>. (Purity means that building and using the standard environment has no dependencies outside of the Nix store. For instance, it doesn’t require an external C compiler such as <filename>/usr/bin/gcc</filename>.) Also, the statically linked binaries used in the bootstrap process are now automatically reproducible, making it easy to update the bootstrap tools and to add support for other Linux platforms. See <filename>pkgs/stdenv/linux/make-bootstrap-tools.nix</filename> for details.
+     </para>
+    </listitem>
+    <listitem>
+     <para>
+      Hook variables in the generic builder are now executed using the <function>eval</function> shell command. This has a major advantage: you can write hooks directly in Nix expressions. For instance, rather than writing a builder like this:
+<programlisting>
+source $stdenv/setup
+
+postInstall=postInstall
+postInstall() {
+    ln -sf gzip $out/bin/gunzip
+    ln -sf gzip $out/bin/zcat
+}
+
+genericBuild</programlisting>
+      (the <literal>gzip</literal> builder), you can just add this attribute to the derivation:
+<programlisting>
+postInstall = "ln -sf gzip $out/bin/gunzip; ln -sf gzip $out/bin/zcat";</programlisting>
+      and so a separate build script becomes unnecessary. This should allow us to get rid of most builders in Nixpkgs.
+     </para>
+    </listitem>
+    <listitem>
+     <para>
+      It is now possible to have the generic builder pass arguments to <command>configure</command> and <command>make</command> that contain whitespace. Previously, for example, you could say in a builder,
+<programlisting>
+configureFlags="CFLAGS=-O0"</programlisting>
+      but not
+<programlisting>
+configureFlags="CFLAGS=-O0 -g"</programlisting>
+      since the <literal>-g</literal> would be interpreted as a separate argument to <command>configure</command>. Now you can say
+<programlisting>
+configureFlagsArray=("CFLAGS=-O0 -g")</programlisting>
+      or similarly
+<programlisting>
+configureFlagsArray=("CFLAGS=-O0 -g" "LDFLAGS=-L/foo -L/bar")</programlisting>
+      which does the right thing. Idem for <literal>makeFlags</literal>, <literal>installFlags</literal>, <literal>checkFlags</literal> and <literal>distFlags</literal>.
+     </para>
+     <para>
+      Unfortunately you can't pass arrays to Bash through the environment, so you can't put the array above in a Nix expression, e.g.,
+<programlisting>
+configureFlagsArray = ["CFLAGS=-O0 -g"];</programlisting>
+      since it would just be flattened to a since string. However, you <emphasis>can</emphasis> use the inline hooks described above:
+<programlisting>
+preConfigure = "configureFlagsArray=(\"CFLAGS=-O0 -g\")";</programlisting>
+     </para>
+    </listitem>
+    <listitem>
+     <para>
+      The function <function>fetchurl</function> now has support for two different kinds of mirroring of files. First, it has support for <emphasis>content-addressable mirrors</emphasis>. For example, given the <function>fetchurl</function> call
+<programlisting>
+fetchurl {
+  url = "http://releases.mozilla.org/<replaceable>...</replaceable>/firefox-2.0.0.6-source.tar.bz2";
+  sha1 = "eb72f55e4a8bf08e8c6ef227c0ade3d068ba1082";
+}</programlisting>
+      <function>fetchurl</function> will first try to download this file from <link
+  xlink:href="http://tarballs.nixos.org/sha1/eb72f55e4a8bf08e8c6ef227c0ade3d068ba1082"/>. If that file doesn’t exist, it will try the original URL. In general, the “content-addressed” location is <replaceable>mirror</replaceable><literal>/</literal><replaceable>hash-type</replaceable><literal>/</literal><replaceable>hash</replaceable>. There is currently only one content-addressable mirror (<link
+  xlink:href="http://tarballs.nixos.org"/>), but more can be specified in the <varname>hashedMirrors</varname> attribute in <filename>pkgs/build-support/fetchurl/mirrors.nix</filename>, or by setting the <envar>NIX_HASHED_MIRRORS</envar> environment variable to a whitespace-separated list of URLs.
+     </para>
+     <para>
+      Second, <function>fetchurl</function> has support for widely-mirrored distribution sites such as SourceForge or the Linux kernel archives. Given a URL of the form <literal>mirror://<replaceable>site</replaceable>/<replaceable>path</replaceable></literal>, it will try to download <replaceable>path</replaceable> from a configurable list of mirrors for <replaceable>site</replaceable>. (This idea was borrowed from Gentoo Linux.) Example:
+<programlisting>
+fetchurl {
+  url = mirror://gnu/gcc/gcc-4.2.0/gcc-core-4.2.0.tar.bz2;
+  sha256 = "0ykhzxhr8857dr97z0j9wyybfz1kjr71xk457cfapfw5fjas4ny1";
+}</programlisting>
+      Currently <replaceable>site</replaceable> can be <literal>sourceforge</literal>, <literal>gnu</literal> and <literal>kernel</literal>. The list of mirrors is defined in <filename>pkgs/build-support/fetchurl/mirrors.nix</filename>. You can override the list of mirrors for a particular site by setting the environment variable <envar>NIX_MIRRORS_<replaceable>site</replaceable></envar>, e.g.
+<programlisting>
+export NIX_MIRRORS_sourceforge=http://osdn.dl.sourceforge.net/sourceforge/</programlisting>
+     </para>
+    </listitem>
+    <listitem>
+     <para>
+      Important updates:
+      <itemizedlist>
+       <listitem>
+        <para>
+         Glibc 2.5.
+        </para>
+       </listitem>
+       <listitem>
+        <para>
+         GCC 4.1.2.
+        </para>
+       </listitem>
+       <listitem>
+        <para>
+         Gnome 2.16.3.
+        </para>
+       </listitem>
+       <listitem>
+        <para>
+         X11R7.2.
+        </para>
+       </listitem>
+       <listitem>
+        <para>
+         Linux 2.6.21.7 and 2.6.22.6.
+        </para>
+       </listitem>
+       <listitem>
+        <para>
+         Emacs 22.1.
+        </para>
+       </listitem>
+      </itemizedlist>
+     </para>
+    </listitem>
+    <listitem>
+     <para>
+      Major new packages:
+      <itemizedlist>
+       <listitem>
+        <para>
+         KDE 3.5.6 Base.
+        </para>
+       </listitem>
+       <listitem>
+        <para>
+         Wine 0.9.43.
+        </para>
+       </listitem>
+       <listitem>
+        <para>
+         OpenOffice 2.2.1.
+        </para>
+       </listitem>
+       <listitem>
+        <para>
+         Many Linux system packages to support NixOS.
+        </para>
+       </listitem>
+      </itemizedlist>
+     </para>
+    </listitem>
+   </itemizedlist>
+  </para>
+
+  <para>
+   The following people contributed to this release: Andres Löh, Arie Middelkoop, Armijn Hemel, Eelco Dolstra, Marc Weber, Mart Kolthof, Martin Bravenboer, Michael Raskin, Wouter den Breejen and Yury G. Kudryashov.
+  </para>
+ </section>
+ <section xml:id="release-notes-0.10">
+  <title>Release 0.10 (October 12, 2006)</title>
+
+  <note>
+   <para>
+    This release of Nixpkgs requires <link
+xlink:href='https://nixos.org/releases/nix/nix-0.10/'>Nix 0.10</link> or higher.
+   </para>
+  </note>
+
+  <para>
+   This release has the following improvements:
+  </para>
+
+  <itemizedlist>
+   <listitem>
+    <para>
+     <filename>pkgs/system/all-packages-generic.nix</filename> is gone, we now just have <filename>pkgs/top-level/all-packages.nix</filename> that contains all available packages. This should cause much less confusion with users. <filename>all-packages.nix</filename> is a function that by default returns packages for the current platform, but you can override this by specifying a different <varname>system</varname> argument.
+    </para>
+   </listitem>
+   <listitem>
+    <para>
+     Certain packages in Nixpkgs are now user-configurable through a configuration file, i.e., without having to edit the Nix expressions in Nixpkgs. For instance, the Firefox provided in the Nixpkgs channel is built without the RealPlayer plugin (for legal reasons). Previously, you could easily enable RealPlayer support by editing the call to the Firefox function in <filename>all-packages.nix</filename>, but such changes are not respected when Firefox is subsequently updated through the Nixpkgs channel.
+    </para>
+    <para>
+     The Nixpkgs configuration file (found in <filename>~/.nixpkgs/config.nix</filename> or through the <envar>NIXPKGS_CONFIG</envar> environment variable) is an attribute set that contains configuration options that <filename>all-packages.nix</filename> reads and uses for certain packages. For instance, the following configuration file:
+<programlisting>
+{
+  firefox = {
+    enableRealPlayer = true;
+  };
+}</programlisting>
+     persistently enables RealPlayer support in the Firefox build.
+    </para>
+    <para>
+     (Actually, <literal>firefox.enableRealPlayer</literal> is the <emphasis>only</emphasis> configuration option currently available, but more are sure to be added.)
+    </para>
+   </listitem>
+   <listitem>
+    <para>
+     Support for new platforms:
+     <itemizedlist>
+      <listitem>
+       <para>
+        <literal>i686-cygwin</literal>, i.e., Windows (using <link xlink:href="http://www.cygwin.com/">Cygwin</link>). The standard environment on <literal>i686-cygwin</literal> by default builds binaries for the Cygwin environment (i.e., it uses Cygwin tools and produces executables that use the Cygwin library). However, there is also a standard environment that produces binaries that use <link
+      xlink:href="http://www.mingw.org/">MinGW</link>. You can use it by calling <filename>all-package.nix</filename> with the <varname>stdenvType</varname> argument set to <literal>"i686-mingw"</literal>.
+       </para>
+      </listitem>
+      <listitem>
+       <para>
+        <literal>i686-darwin</literal>, i.e., Mac OS X on Intel CPUs.
+       </para>
+      </listitem>
+      <listitem>
+       <para>
+        <literal>powerpc-linux</literal>.
+       </para>
+      </listitem>
+      <listitem>
+       <para>
+        <literal>x86_64-linux</literal>, i.e., Linux on 64-bit AMD/Intel CPUs. Unlike <literal>i686-linux</literal>, this platform doesn’t have a pure <literal>stdenv</literal> yet.
+       </para>
+      </listitem>
+     </itemizedlist>
+    </para>
+   </listitem>
+   <listitem>
+    <para>
+     The default compiler is now GCC 4.1.1.
+    </para>
+   </listitem>
+   <listitem>
+    <para>
+     X11 updated to X.org’s X11R7.1.
+    </para>
+   </listitem>
+   <listitem>
+    <para>
+     Notable new packages:
+     <itemizedlist>
+      <listitem>
+       <para>
+        Opera.
+       </para>
+      </listitem>
+      <listitem>
+       <para>
+        Microsoft Visual C++ 2005 Express Edition and the Windows SDK.
+       </para>
+      </listitem>
+     </itemizedlist>
+     In total there are now around 809 packages in Nixpkgs.
+    </para>
+   </listitem>
+   <listitem>
+    <para>
+     It is now <emphasis>much</emphasis> easier to override the default C compiler and other tools in <literal>stdenv</literal> for specific packages. <filename>all-packages.nix</filename> provides two utility functions for this purpose: <function>overrideGCC</function> and <function>overrideInStdenv</function>. Both take a <literal>stdenv</literal> and return an augmented <literal>stdenv</literal>; the formed changes the C compiler, and the latter adds additional packages to the front of <literal>stdenv</literal>’s initial <envar>PATH</envar>, allowing tools to be overridden.
+    </para>
+    <para>
+     For instance, the package <varname>strategoxt</varname> doesn’t build with the GNU Make in <literal>stdenv</literal> (version 3.81), so we call it with an augmented <literal>stdenv</literal> that uses GNU Make 3.80:
+<programlisting>
+strategoxt = (import ../development/compilers/strategoxt) {
+  inherit fetchurl pkgconfig sdf aterm;
+  stdenv = overrideInStdenv stdenv [gnumake380];
+};
+
+gnumake380 = <replaceable>...</replaceable>;</programlisting>
+     Likewise, there are many packages that don’t compile with the default GCC (4.1.1), but that’s easily fixed:
+<programlisting>
+exult = import ../games/exult {
+  inherit fetchurl SDL SDL_mixer zlib libpng unzip;
+  stdenv = overrideGCC stdenv gcc34;
+};</programlisting>
+    </para>
+   </listitem>
+   <listitem>
+    <para>
+     It has also become much easier to experiment with changes to the <literal>stdenv</literal> setup script (which notably contains the generic builder). Since edits to <filename>pkgs/stdenv/generic/setup.sh</filename> trigger a rebuild of <emphasis>everything</emphasis>, this was formerly quite painful. But now <literal>stdenv</literal> contains a function to “regenerate” <literal>stdenv</literal> with a different setup script, allowing the use of a different setup script for specific packages:
+<programlisting>
+pkg = import <replaceable>...</replaceable> {
+  stdenv = stdenv.regenerate ./my-setup.sh;
+  <replaceable>...</replaceable>
+}</programlisting>
+    </para>
+   </listitem>
+   <listitem>
+    <para>
+     Packages can now have a human-readable <emphasis>description</emphasis> field. Package descriptions are shown by <literal>nix-env -qa --description</literal>. In addition, they’re shown on the Nixpkgs release page. A description can be added to a package as follows:
+<programlisting>
+stdenv.mkDerivation {
+  name = "exult-1.2";
+  <replaceable>...</replaceable>
+  meta = {
+    description = "A reimplementation of the Ultima VII game engine";
+  };
+}</programlisting>
+     The <varname>meta</varname> attribute is not passed to the builder, so changes to the description do not trigger a rebuild. Additional <varname>meta</varname> attributes may be defined in the future (such as the URL of the package’s homepage, the license, etc.).
+    </para>
+   </listitem>
+  </itemizedlist>
+
+  <para>
+   The following people contributed to this release: Andres Löh, Armijn Hemel, Christof Douma, Eelco Dolstra, Eelco Visser, Mart Kolthof, Martin Bravenboer, Merijn de Jonge, Rob Vermaas and Roy van den Broek.
+  </para>
+ </section>
+ <section xml:id="release-notes-0.9">
+  <title>Release 0.9 (January 31, 2006)</title>
+
+  <para>
+   There have been zillions of changes since the last release of Nixpkgs. Many packages have been added or updated. The following are some of the more notable changes:
+  </para>
+
+  <itemizedlist>
+   <listitem>
+    <para>
+     Distribution files have been moved to <link
+  xlink:href="https://nixos.org/" />.
+    </para>
+   </listitem>
+   <listitem>
+    <para>
+     The C library on Linux, Glibc, has been updated to version 2.3.6.
+    </para>
+   </listitem>
+   <listitem>
+    <para>
+     The default compiler is now GCC 3.4.5. GCC 4.0.2 is also available.
+    </para>
+   </listitem>
+   <listitem>
+    <para>
+     The old, unofficial Xlibs has been replaced by the official modularised X11 distribution from X.org, i.e., X11R7.0. X11R7.0 consists of 287 (!) packages, all of which are in Nixpkgs though not all have been tested. It is now possible to build a working X server (previously we only had X client libraries). We use a fully Nixified X server on NixOS.
+    </para>
+   </listitem>
+   <listitem>
+    <para>
+     The Sun JDK 5 has been purified, i.e., it doesn’t require any non-Nix components such as <filename>/lib/ld-linux.so.2</filename>. This means that Java applications such as Eclipse and Azureus can run on NixOS.
+    </para>
+   </listitem>
+   <listitem>
+    <para>
+     Hardware-accelerated OpenGL support, used by games like Quake 3 (which is now built from source).
+    </para>
+   </listitem>
+   <listitem>
+    <para>
+     Improved support for FreeBSD on x86.
+    </para>
+   </listitem>
+   <listitem>
+    <para>
+     Improved Haskell support; e.g., the GHC build is now pure.
+    </para>
+   </listitem>
+   <listitem>
+    <para>
+     Some support for cross-compilation: cross-compiling builds of GCC and Binutils, and cross-compiled builds of the C library uClibc.
+    </para>
+   </listitem>
+   <listitem>
+    <para>
+     Notable new packages:
+     <itemizedlist>
+      <listitem>
+       <para>
+        teTeX, including support for building LaTeX documents using Nix (with automatic dependency determination).
+       </para>
+      </listitem>
+      <listitem>
+       <para>
+        Ruby.
+       </para>
+      </listitem>
+      <listitem>
+       <para>
+        System-level packages to support NixOS, e.g. Grub, GNU <literal>parted</literal> and so on.
+       </para>
+      </listitem>
+      <listitem>
+       <para>
+        <literal>ecj</literal>, the Eclipse Compiler for Java, so we finally have a freely distributable compiler that supports Java 5.0.
+       </para>
+      </listitem>
+      <listitem>
+       <para>
+        <literal>php</literal>.
+       </para>
+      </listitem>
+      <listitem>
+       <para>
+        The GIMP.
+       </para>
+      </listitem>
+      <listitem>
+       <para>
+        Inkscape.
+       </para>
+      </listitem>
+      <listitem>
+       <para>
+        GAIM.
+       </para>
+      </listitem>
+      <listitem>
+       <para>
+        <literal>kdelibs</literal>. This allows us to add KDE-based packages (such as <literal>kcachegrind</literal>).
+       </para>
+      </listitem>
+     </itemizedlist>
+    </para>
+   </listitem>
+  </itemizedlist>
+
+  <para>
+   The following people contributed to this release: Andres Löh, Armijn Hemel, Bogdan Dumitriu, Christof Douma, Eelco Dolstra, Eelco Visser, Mart Kolthof, Martin Bravenboer, Rob Vermaas and Roy van den Broek.
+  </para>
+ </section>
+ <section xml:id="release-notes-0.8">
+  <title>Release 0.8 (April 11, 2005)</title>
+
+  <para>
+   This release is mostly to remain synchronised with the changed hashing scheme in Nix 0.8.
+  </para>
+
+  <para>
+   Notable updates:
+   <itemizedlist>
+    <listitem>
+     <para>
+      Adobe Reader 7.0
+     </para>
+    </listitem>
+    <listitem>
+     <para>
+      Various security updates (zlib 1.2.2, etc.)
+     </para>
+    </listitem>
+   </itemizedlist>
+  </para>
+ </section>
+ <section xml:id="release-notes-0.7">
+  <title>Release 0.7 (March 14, 2005)</title>
+
+  <itemizedlist>
+   <listitem>
+    <para>
+     The bootstrap process for the standard build environment on Linux (stdenv-linux) has been improved. It is no longer dependent in its initial bootstrap stages on the system Glibc, GCC, and other tools. Rather, Nixpkgs contains a statically linked bash and curl, and uses that to download other statically linked tools. These are then used to build a Glibc and dynamically linked versions of all other tools.
+    </para>
+    <para>
+     This change also makes the bootstrap process faster. For instance, GCC is built only once instead of three times.
+    </para>
+    <para>
+     (Contributed by Armijn Hemel.)
+    </para>
+   </listitem>
+   <listitem>
+    <para>
+     Tarballs used by Nixpkgs are now obtained from the same server that hosts Nixpkgs (<link
+  xlink:href="http://catamaran.labs.cs.uu.nl/" />). This reduces the risk of packages being unbuildable due to moved or deleted files on various servers.
+    </para>
+   </listitem>
+   <listitem>
+    <para>
+     There now is a generic mechanism for building Perl modules. See the various Perl modules defined in pkgs/system/all-packages-generic.nix.
+    </para>
+   </listitem>
+   <listitem>
+    <para>
+     Notable new packages:
+     <itemizedlist>
+      <listitem>
+       <para>
+        Qt 3
+       </para>
+      </listitem>
+      <listitem>
+       <para>
+        MySQL
+       </para>
+      </listitem>
+      <listitem>
+       <para>
+        MythTV
+       </para>
+      </listitem>
+      <listitem>
+       <para>
+        Mono
+       </para>
+      </listitem>
+      <listitem>
+       <para>
+        MonoDevelop (alpha)
+       </para>
+      </listitem>
+      <listitem>
+       <para>
+        Xine
+       </para>
+      </listitem>
+     </itemizedlist>
+    </para>
+   </listitem>
+   <listitem>
+    <para>
+     Notable updates:
+     <itemizedlist>
+      <listitem>
+       <para>
+        GCC 3.4.3
+       </para>
+      </listitem>
+      <listitem>
+       <para>
+        Glibc 2.3.4
+       </para>
+      </listitem>
+      <listitem>
+       <para>
+        GTK 2.6
+       </para>
+      </listitem>
+     </itemizedlist>
+    </para>
+   </listitem>
+  </itemizedlist>
+ </section>
+</article>
diff --git a/doc/shell.nix b/doc/shell.nix
new file mode 100644
index 00000000000..5fa2b442489
--- /dev/null
+++ b/doc/shell.nix
@@ -0,0 +1,3 @@
+{ pkgs ? import ../. { } }:
+(import ./default.nix { }).overrideAttrs
+(x: { buildInputs = (x.buildInputs or [ ]) ++ [ pkgs.xmloscopy pkgs.ruby ]; })
diff --git a/doc/stdenv/cross-compilation.chapter.md b/doc/stdenv/cross-compilation.chapter.md
new file mode 100644
index 00000000000..f6e61a1af19
--- /dev/null
+++ b/doc/stdenv/cross-compilation.chapter.md
@@ -0,0 +1,211 @@
+# Cross-compilation {#chap-cross}
+
+## Introduction {#sec-cross-intro}
+
+"Cross-compilation" means compiling a program on one machine for another type of machine. For example, a typical use of cross-compilation is to compile programs for embedded devices. These devices often don't have the computing power and memory to compile their own programs. One might think that cross-compilation is a fairly niche concern. However, there are significant advantages to rigorously distinguishing between build-time and run-time environments! Significant, because the benefits apply even when one is developing and deploying on the same machine. Nixpkgs is increasingly adopting the opinion that packages should be written with cross-compilation in mind, and Nixpkgs should evaluate in a similar way (by minimizing cross-compilation-specific special cases) whether or not one is cross-compiling.
+
+This chapter will be organized in three parts. First, it will describe the basics of how to package software in a way that supports cross-compilation. Second, it will describe how to use Nixpkgs when cross-compiling. Third, it will describe the internal infrastructure supporting cross-compilation.
+
+## Packaging in a cross-friendly manner {#sec-cross-packaging}
+
+### Platform parameters {#ssec-cross-platform-parameters}
+
+Nixpkgs follows the [conventions of GNU autoconf](https://gcc.gnu.org/onlinedocs/gccint/Configure-Terms.html). We distinguish between 3 types of platforms when building a derivation: _build_, _host_, and _target_. In summary, _build_ is the platform on which a package is being built, _host_ is the platform on which it will run. The third attribute, _target_, is relevant only for certain specific compilers and build tools.
+
+In Nixpkgs, these three platforms are defined as attribute sets under the names `buildPlatform`, `hostPlatform`, and `targetPlatform`. They are always defined as attributes in the standard environment. That means one can access them like:
+
+```nix
+{ stdenv, fooDep, barDep, ... }: ...stdenv.buildPlatform...
+```
+
+`buildPlatform`
+
+: The "build platform" is the platform on which a package is built. Once someone has a built package, or pre-built binary package, the build platform should not matter and can be ignored.
+
+`hostPlatform`
+
+: The "host platform" is the platform on which a package will be run. This is the simplest platform to understand, but also the one with the worst name.
+
+`targetPlatform`
+
+: The "target platform" attribute is, unlike the other two attributes, not actually fundamental to the process of building software. Instead, it is only relevant for compatibility with building certain specific compilers and build tools. It can be safely ignored for all other packages.
+
+: The build process of certain compilers is written in such a way that the compiler resulting from a single build can itself only produce binaries for a single platform. The task of specifying this single "target platform" is thus pushed to build time of the compiler. The root cause of this is that the compiler (which will be run on the host) and the standard library/runtime (which will be run on the target) are built by a single build process.
+
+: There is no fundamental need to think about a single target ahead of time like this. If the tool supports modular or pluggable backends, both the need to specify the target at build time and the constraint of having only a single target disappear. An example of such a tool is LLVM.
+
+: Although the existence of a "target platform" is arguably a historical mistake, it is a common one: examples of tools that suffer from it are GCC, Binutils, GHC and Autoconf. Nixpkgs tries to avoid sharing in the mistake where possible. Still, because the concept of a target platform is so ingrained, it is best to support it as is.
+
+The exact schema these fields follow is a bit ill-defined due to a long and convoluted evolution, but this is slowly being cleaned up. You can see examples of ones used in practice in `lib.systems.examples`; note how they are not all very consistent. For now, here are few fields can count on them containing:
+
+`system`
+
+: This is a two-component shorthand for the platform. Examples of this would be "x86_64-darwin" and "i686-linux"; see `lib.systems.doubles` for more. The first component corresponds to the CPU architecture of the platform and the second to the operating system of the platform (`[cpu]-[os]`). This format has built-in support in Nix, such as the `builtins.currentSystem` impure string.
+
+`config`
+
+: This is a 3- or 4- component shorthand for the platform. Examples of this would be `x86_64-unknown-linux-gnu` and `aarch64-apple-darwin14`. This is a standard format called the "LLVM target triple", as they are pioneered by LLVM. In the 4-part form, this corresponds to `[cpu]-[vendor]-[os]-[abi]`. This format is strictly more informative than the "Nix host double", as the previous format could analogously be termed. This needs a better name than `config`!
+
+`parsed`
+
+: This is a Nix representation of a parsed LLVM target triple with white-listed components. This can be specified directly, or actually parsed from the `config`. See `lib.systems.parse` for the exact representation.
+
+`libc`
+
+: This is a string identifying the standard C library used. Valid identifiers include "glibc" for GNU libc, "libSystem" for Darwin's Libsystem, and "uclibc" for µClibc. It should probably be refactored to use the module system, like `parse`.
+
+`is*`
+
+: These predicates are defined in `lib.systems.inspect`, and slapped onto every platform. They are superior to the ones in `stdenv` as they force the user to be explicit about which platform they are inspecting. Please use these instead of those.
+
+`platform`
+
+: This is, quite frankly, a dumping ground of ad-hoc settings (it's an attribute set). See `lib.systems.platforms` for examples—there's hopefully one in there that will work verbatim for each platform that is working. Please help us triage these flags and give them better homes!
+
+### Theory of dependency categorization {#ssec-cross-dependency-categorization}
+
+::: {.note}
+This is a rather philosophical description that isn't very Nixpkgs-specific. For an overview of all the relevant attributes given to `mkDerivation`, see [](#ssec-stdenv-dependencies). For a description of how everything is implemented, see [](#ssec-cross-dependency-implementation).
+:::
+
+In this section we explore the relationship between both runtime and build-time dependencies and the 3 Autoconf platforms.
+
+A run time dependency between two packages requires that their host platforms match. This is directly implied by the meaning of "host platform" and "runtime dependency": The package dependency exists while both packages are running on a single host platform.
+
+A build time dependency, however, has a shift in platforms between the depending package and the depended-on package. "build time dependency" means that to build the depending package we need to be able to run the depended-on's package. The depending package's build platform is therefore equal to the depended-on package's host platform.
+
+If both the dependency and depending packages aren't compilers or other machine-code-producing tools, we're done. And indeed `buildInputs` and `nativeBuildInputs` have covered these simpler cases for many years. But if the dependency does produce machine code, we might need to worry about its target platform too. In principle, that target platform might be any of the depending package's build, host, or target platforms, but we prohibit dependencies from a "later" platform to an earlier platform to limit confusion because we've never seen a legitimate use for them.
+
+Finally, if the depending package is a compiler or other machine-code-producing tool, it might need dependencies that run at "emit time". This is for compilers that (regrettably) insist on being built together with their source languages' standard libraries. Assuming build != host != target, a run-time dependency of the standard library cannot be run at the compiler's build time or run time, but only at the run time of code emitted by the compiler.
+
+Putting this all together, that means we have dependencies in the form "host → target", in at most the following six combinations:
+
+#### Possible dependency types {#possible-dependency-types}
+
+| Dependency’s host platform | Dependency’s target platform |
+|----------------------------|------------------------------|
+| build                      | build                        |
+| build                      | host                         |
+| build                      | target                       |
+| host                       | host                         |
+| host                       | target                       |
+| target                     | target                       |
+
+
+Some examples will make this table clearer. Suppose there's some package that is being built with a `(build, host, target)` platform triple of `(foo, bar, baz)`. If it has a build-time library dependency, that would be a "host → build" dependency with a triple of `(foo, foo, *)` (the target platform is irrelevant). If it needs a compiler to be built, that would be a "build → host" dependency with a triple of `(foo, foo, *)` (the target platform is irrelevant). That compiler, would be built with another compiler, also "build → host" dependency, with a triple of `(foo, foo, foo)`.
+
+### Cross packaging cookbook {#ssec-cross-cookbook}
+
+Some frequently encountered problems when packaging for cross-compilation should be answered here. Ideally, the information above is exhaustive, so this section cannot provide any new information, but it is ludicrous and cruel to expect everyone to spend effort working through the interaction of many features just to figure out the same answer to the same common problem. Feel free to add to this list!
+
+#### My package fails to find a binutils command (`cc`/`ar`/`ld` etc.) {#cross-qa-fails-to-find-binutils}
+Many packages assume that an unprefixed binutils (`cc`/`ar`/`ld` etc.) is available, but Nix doesn't provide one. It only provides a prefixed one, just as it only does for all the other binutils programs. It may be necessary to patch the package to fix the build system to use a prefix. For instance, instead of `cc`, use `${stdenv.cc.targetPrefix}cc`.
+
+```nix
+makeFlags = [ "CC=${stdenv.cc.targetPrefix}cc" ];
+```
+
+#### How do I avoid compiling a GCC cross-compiler from source? {#cross-qa-avoid-compiling-gcc-cross-compiler}
+On less powerful machines, it can be inconvenient to cross-compile a package only to find out that GCC has to be compiled from source, which could take up to several hours. Nixpkgs maintains a limited [cross-related jobset on Hydra](https://hydra.nixos.org/jobset/nixpkgs/cross-trunk), which tests cross-compilation to various platforms from build platforms "x86\_64-darwin", "x86\_64-linux", and "aarch64-linux".  See `pkgs/top-level/release-cross.nix` for the full list of target platforms and packages.  For instance, the following invocation fetches the pre-built cross-compiled GCC for `armv6l-unknown-linux-gnueabihf` and builds GNU Hello from source.
+
+```ShellSession
+$ nix-build '<nixpkgs>' -A pkgsCross.raspberryPi.hello
+```
+
+#### What if my package’s build system needs to build a C program to be run under the build environment? {#cross-qa-build-c-program-in-build-environment}
+
+Add the following to your `mkDerivation` invocation.
+
+```nix
+depsBuildBuild = [ buildPackages.stdenv.cc ];
+```
+
+#### My package’s testsuite needs to run host platform code. {#cross-testsuite-runs-host-code}
+
+Add the following to your `mkDerivation` invocation.
+
+```nix
+doCheck = stdenv.hostPlatform == stdenv.buildPlatform;
+```
+
+## Cross-building packages {#sec-cross-usage}
+
+Nixpkgs can be instantiated with `localSystem` alone, in which case there is no cross-compiling and everything is built by and for that system, or also with `crossSystem`, in which case packages run on the latter, but all building happens on the former. Both parameters take the same schema as the 3 (build, host, and target) platforms defined in the previous section. As mentioned above, `lib.systems.examples` has some platforms which are used as arguments for these parameters in practice. You can use them programmatically, or on the command line:
+
+```ShellSession
+$ nix-build '<nixpkgs>' --arg crossSystem '(import <nixpkgs/lib>).systems.examples.fooBarBaz' -A whatever
+```
+
+::: {.note}
+Eventually we would like to make these platform examples an unnecessary convenience so that
+
+```ShellSession
+$ nix-build '<nixpkgs>' --arg crossSystem '{ config = "<arch>-<os>-<vendor>-<abi>"; }' -A whatever
+```
+
+works in the vast majority of cases. The problem today is dependencies on other sorts of configuration which aren't given proper defaults. We rely on the examples to crudely to set those configuration parameters in some vaguely sane manner on the users behalf. Issue [\#34274](https://github.com/NixOS/nixpkgs/issues/34274) tracks this inconvenience along with its root cause in crufty configuration options.
+:::
+
+While one is free to pass both parameters in full, there's a lot of logic to fill in missing fields. As discussed in the previous section, only one of `system`, `config`, and `parsed` is needed to infer the other two. Additionally, `libc` will be inferred from `parse`. Finally, `localSystem.system` is also _impurely_ inferred based on the platform evaluation occurs. This means it is often not necessary to pass `localSystem` at all, as in the command-line example in the previous paragraph.
+
+::: {.note}
+Many sources (manual, wiki, etc) probably mention passing `system`, `platform`, along with the optional `crossSystem` to Nixpkgs: `import <nixpkgs> { system = ..; platform = ..; crossSystem = ..; }`. Passing those two instead of `localSystem` is still supported for compatibility, but is discouraged. Indeed, much of the inference we do for these parameters is motivated by compatibility as much as convenience.
+:::
+
+One would think that `localSystem` and `crossSystem` overlap horribly with the three `*Platforms` (`buildPlatform`, `hostPlatform,` and `targetPlatform`; see `stage.nix` or the manual). Actually, those identifiers are purposefully not used here to draw a subtle but important distinction: While the granularity of having 3 platforms is necessary to properly *build* packages, it is overkill for specifying the user's *intent* when making a build plan or package set. A simple "build vs deploy" dichotomy is adequate: the sliding window principle described in the previous section shows how to interpolate between the these two "end points" to get the 3 platform triple for each bootstrapping stage. That means for any package a given package set, even those not bound on the top level but only reachable via dependencies or `buildPackages`, the three platforms will be defined as one of `localSystem` or `crossSystem`, with the former replacing the latter as one traverses build-time dependencies. A last simple difference is that `crossSystem` should be null when one doesn't want to cross-compile, while the `*Platform`s are always non-null. `localSystem` is always non-null.
+
+## Cross-compilation infrastructure {#sec-cross-infra}
+
+### Implementation of dependencies {#ssec-cross-dependency-implementation}
+
+The categories of dependencies developed in [](#ssec-cross-dependency-categorization) are specified as lists of derivations given to `mkDerivation`, as documented in [](#ssec-stdenv-dependencies). In short, each list of dependencies for "host → target" is called `deps<host><target>` (where `host`, and `target` values are either `build`, `host`, or `target`), with exceptions for backwards compatibility that `depsBuildHost` is instead called `nativeBuildInputs` and `depsHostTarget` is instead called `buildInputs`. Nixpkgs is now structured so that each `deps<host><target>` is automatically taken from `pkgs<host><target>`. (These `pkgs<host><target>`s are quite new, so there is no special case for `nativeBuildInputs` and `buildInputs`.) For example, `pkgsBuildHost.gcc` should be used at build-time, while `pkgsHostTarget.gcc` should be used at run-time.
+
+Now, for most of Nixpkgs's history, there were no `pkgs<host><target>` attributes, and most packages have not been refactored to use it explicitly. Prior to those, there were just `buildPackages`, `pkgs`, and `targetPackages`. Those are now redefined as aliases to `pkgsBuildHost`, `pkgsHostTarget`, and `pkgsTargetTarget`. It is acceptable, even recommended, to use them for libraries to show that the host platform is irrelevant.
+
+But before that, there was just `pkgs`, even though both `buildInputs` and `nativeBuildInputs` existed. \[Cross barely worked, and those were implemented with some hacks on `mkDerivation` to override dependencies.\] What this means is the vast majority of packages do not use any explicit package set to populate their dependencies, just using whatever `callPackage` gives them even if they do correctly sort their dependencies into the multiple lists described above. And indeed, asking that users both sort their dependencies, _and_ take them from the right attribute set, is both too onerous and redundant, so the recommended approach (for now) is to continue just categorizing by list and not using an explicit package set.
+
+To make this work, we "splice" together the six `pkgsFooBar` package sets and have `callPackage` actually take its arguments from that. This is currently implemented in `pkgs/top-level/splice.nix`. `mkDerivation` then, for each dependency attribute, pulls the right derivation out from the splice. This splicing can be skipped when not cross-compiling as the package sets are the same, but still is a bit slow for cross-compiling. We'd like to do something better, but haven't come up with anything yet.
+
+### Bootstrapping {#ssec-bootstrapping}
+
+Each of the package sets described above come from a single bootstrapping stage. While `pkgs/top-level/default.nix`, coordinates the composition of stages at a high level, `pkgs/top-level/stage.nix` "ties the knot" (creates the fixed point) of each stage. The package sets are defined per-stage however, so they can be thought of as edges between stages (the nodes) in a graph. Compositions like `pkgsBuildTarget.targetPackages` can be thought of as paths to this graph.
+
+While there are many package sets, and thus many edges, the stages can also be arranged in a linear chain. In other words, many of the edges are redundant as far as connectivity is concerned. This hinges on the type of bootstrapping we do. Currently for cross it is:
+
+1.  `(native, native, native)`
+
+2.  `(native, native, foreign)`
+
+3.  `(native, foreign, foreign)`
+
+In each stage, `pkgsBuildHost` refers to the previous stage, `pkgsBuildBuild` refers to the one before that, and `pkgsHostTarget` refers to the current one, and `pkgsTargetTarget` refers to the next one. When there is no previous or next stage, they instead refer to the current stage. Note how all the invariants regarding the mapping between dependency and depending packages' build host and target platforms are preserved. `pkgsBuildTarget` and `pkgsHostHost` are more complex in that the stage fitting the requirements isn't always a fixed chain of "prevs" and "nexts" away (modulo the "saturating" self-references at the ends). We just special case each instead. All the primary edges are implemented is in `pkgs/stdenv/booter.nix`, and secondarily aliases in `pkgs/top-level/stage.nix`.
+
+::: {.note}
+The native stages are bootstrapped in legacy ways that predate the current cross implementation. This is why the bootstrapping stages leading up to the final stages are ignored in the previous paragraph.
+:::
+
+If one looks at the 3 platform triples, one can see that they overlap such that one could put them together into a chain like:
+```
+(native, native, native, foreign, foreign)
+```
+
+If one imagines the saturating self references at the end being replaced with infinite stages, and then overlays those platform triples, one ends up with the infinite tuple:
+```
+(native..., native, native, native, foreign, foreign, foreign...)
+```
+One can then imagine any sequence of platforms such that there are bootstrap stages with their 3 platforms determined by "sliding a window" that is the 3 tuple through the sequence. This was the original model for bootstrapping. Without a target platform (assume a better world where all compilers are multi-target and all standard libraries are built in their own derivation), this is sufficient. Conversely if one wishes to cross compile "faster", with a "Canadian Cross" bootstrapping stage where `build != host != target`, more bootstrapping stages are needed since no sliding window provides the pesky `pkgsBuildTarget` package set since it skips the Canadian cross stage's "host".
+
+
+::: {.note}
+It is much better to refer to `buildPackages` than `targetPackages`, or more broadly package sets that do not mention “target”. There are three reasons for this.
+
+First, it is because bootstrapping stages do not have a unique `targetPackages`. For example a `(x86-linux, x86-linux, arm-linux)` and `(x86-linux, x86-linux, x86-windows)` package set both have a `(x86-linux, x86-linux, x86-linux)` package set. Because there is no canonical `targetPackages` for such a native (`build == host == target`) package set, we set their `targetPackages`
+
+Second, it is because this is a frequent source of hard-to-follow "infinite recursions" / cycles. When only package sets that don't mention target are used, the package set forms a directed acyclic graph. This means that all cycles that exist are confined to one stage. This means they are a lot smaller, and easier to follow in the code or a backtrace. It also means they are present in native and cross builds alike, and so more likely to be caught by CI and other users.
+
+Thirdly, it is because everything target-mentioning only exists to accommodate compilers with lousy build systems that insist on the compiler itself and standard library being built together. Of course that is bad because bigger derivations means longer rebuilds. It is also problematic because it tends to make the standard libraries less like other libraries than they could be, complicating code and build systems alike. Because of the other problems, and because of these innate disadvantages, compilers ought to be packaged another way where possible.
+:::
+
+::: {.note}
+If one explores Nixpkgs, they will see derivations with names like `gccCross`. Such `*Cross` derivations is a holdover from before we properly distinguished between the host and target platforms—the derivation with “Cross” in the name covered the `build = host != target` case, while the other covered the `host = target`, with build platform the same or not based on whether one was using its `.nativeDrv` or `.crossDrv`. This ugliness will disappear soon.
+:::
diff --git a/doc/stdenv/meta.chapter.md b/doc/stdenv/meta.chapter.md
new file mode 100644
index 00000000000..d3e1dd5b27d
--- /dev/null
+++ b/doc/stdenv/meta.chapter.md
@@ -0,0 +1,217 @@
+# Meta-attributes {#chap-meta}
+
+Nix packages can declare *meta-attributes* that contain information about a package such as a description, its homepage, its license, and so on. For instance, the GNU Hello package has a `meta` declaration like this:
+
+```nix
+meta = with lib; {
+  description = "A program that produces a familiar, friendly greeting";
+  longDescription = ''
+    GNU Hello is a program that prints "Hello, world!" when you run it.
+    It is fully customizable.
+  '';
+  homepage = "https://www.gnu.org/software/hello/manual/";
+  license = licenses.gpl3Plus;
+  maintainers = [ maintainers.eelco ];
+  platforms = platforms.all;
+};
+```
+
+Meta-attributes are not passed to the builder of the package. Thus, a change to a meta-attribute doesn’t trigger a recompilation of the package. The value of a meta-attribute must be a string.
+
+The meta-attributes of a package can be queried from the command-line using `nix-env`:
+
+```ShellSession
+$ nix-env -qa hello --json
+{
+    "hello": {
+        "meta": {
+            "description": "A program that produces a familiar, friendly greeting",
+            "homepage": "https://www.gnu.org/software/hello/manual/",
+            "license": {
+                "fullName": "GNU General Public License version 3 or later",
+                "shortName": "GPLv3+",
+                "url": "http://www.fsf.org/licensing/licenses/gpl.html"
+            },
+            "longDescription": "GNU Hello is a program that prints \"Hello, world!\" when you run it.\nIt is fully customizable.\n",
+            "maintainers": [
+                "Ludovic Court\u00e8s <ludo@gnu.org>"
+            ],
+            "platforms": [
+                "i686-linux",
+                "x86_64-linux",
+                "armv5tel-linux",
+                "armv7l-linux",
+                "mips32-linux",
+                "x86_64-darwin",
+                "i686-cygwin",
+                "i686-freebsd",
+                "x86_64-freebsd",
+                "i686-openbsd",
+                "x86_64-openbsd"
+            ],
+            "position": "/home/user/dev/nixpkgs/pkgs/applications/misc/hello/default.nix:14"
+        },
+        "name": "hello-2.9",
+        "system": "x86_64-linux"
+    }
+}
+```
+
+`nix-env` knows about the `description` field specifically:
+
+```ShellSession
+$ nix-env -qa hello --description
+hello-2.3  A program that produces a familiar, friendly greeting
+```
+
+## Standard meta-attributes {#sec-standard-meta-attributes}
+
+It is expected that each meta-attribute is one of the following:
+
+### `description` {#var-meta-description}
+
+A short (one-line) description of the package. This is shown by `nix-env -q --description` and also on the Nixpkgs release pages.
+
+Don’t include a period at the end. Don’t include newline characters. Capitalise the first character. For brevity, don’t repeat the name of package --- just describe what it does.
+
+Wrong: `"libpng is a library that allows you to decode PNG images."`
+
+Right: `"A library for decoding PNG images"`
+
+### `longDescription` {#var-meta-longDescription}
+
+An arbitrarily long description of the package.
+
+### `branch` {#var-meta-branch}
+
+Release branch. Used to specify that a package is not going to receive updates that are not in this branch; for example, Linux kernel 3.0 is supposed to be updated to 3.0.X, not 3.1.
+
+### `homepage` {#var-meta-homepage}
+
+The package’s homepage. Example: `https://www.gnu.org/software/hello/manual/`
+
+### `downloadPage` {#var-meta-downloadPage}
+
+The page where a link to the current version can be found. Example: `https://ftp.gnu.org/gnu/hello/`
+
+### `changelog` {#var-meta-changelog}
+
+A link or a list of links to the location of Changelog for a package. A link may use expansion to refer to the correct changelog version. Example: `"https://git.savannah.gnu.org/cgit/hello.git/plain/NEWS?h=v${version}"`
+
+### `license` {#var-meta-license}
+
+The license, or licenses, for the package. One from the attribute set defined in [`nixpkgs/lib/licenses.nix`](https://github.com/NixOS/nixpkgs/blob/master/lib/licenses.nix). At this moment using both a list of licenses and a single license is valid. If the license field is in the form of a list representation, then it means that parts of the package are licensed differently. Each license should preferably be referenced by their attribute. The non-list attribute value can also be a space delimited string representation of the contained attribute `shortNames` or `spdxIds`. The following are all valid examples:
+
+- Single license referenced by attribute (preferred) `lib.licenses.gpl3Only`.
+- Single license referenced by its attribute shortName (frowned upon) `"gpl3Only"`.
+- Single license referenced by its attribute spdxId (frowned upon) `"GPL-3.0-only"`.
+- Multiple licenses referenced by attribute (preferred) `with lib.licenses; [ asl20 free ofl ]`.
+- Multiple licenses referenced as a space delimited string of attribute shortNames (frowned upon) `"asl20 free ofl"`.
+
+For details, see [Licenses](#sec-meta-license).
+
+### `maintainers` {#var-meta-maintainers}
+
+A list of the maintainers of this Nix expression. Maintainers are defined in [`nixpkgs/maintainers/maintainer-list.nix`](https://github.com/NixOS/nixpkgs/blob/master/maintainers/maintainer-list.nix). There is no restriction to becoming a maintainer, just add yourself to that list in a separate commit titled “maintainers: add alice”, and reference maintainers with `maintainers = with lib.maintainers; [ alice bob ]`.
+
+### `mainProgram` {#var-meta-mainProgram}
+
+The name of the main binary for the package. This effects the binary `nix run` executes and falls back to the name of the package. Example: `"rg"`
+
+### `priority` {#var-meta-priority}
+
+The *priority* of the package, used by `nix-env` to resolve file name conflicts between packages. See the Nix manual page for `nix-env` for details. Example: `"10"` (a low-priority package).
+
+### `platforms` {#var-meta-platforms}
+
+The list of Nix platform types on which the package is supported. Hydra builds packages according to the platform specified. If no platform is specified, the package does not have prebuilt binaries. An example is:
+
+```nix
+meta.platforms = lib.platforms.linux;
+```
+
+Attribute Set `lib.platforms` defines [various common lists](https://github.com/NixOS/nixpkgs/blob/master/lib/systems/doubles.nix) of platforms types.
+
+### `tests` {#var-meta-tests}
+
+::: {.warning}
+This attribute is special in that it is not actually under the `meta` attribute set but rather under the `passthru` attribute set. This is due to how `meta` attributes work, and the fact that they are supposed to contain only metadata, not derivations.
+:::
+
+An attribute set with tests as values. A test is a derivation that builds when the test passes and fails to build otherwise.
+
+You can run these tests with:
+
+```ShellSession
+$ cd path/to/nixpkgs
+$ nix-build -A your-package.tests
+```
+
+#### Package tests
+
+Tests that are part of the source package are often executed in the `installCheckPhase`.
+
+Prefer `passthru.tests` for tests that are introduced in nixpkgs because:
+
+* `passthru.tests` tests the 'real' package, independently from the environment in which it was built
+* we can run `passthru.tests` independently
+* `installCheckPhase` adds overhead to each build
+
+For more on how to write and run package tests, see <xref linkend="sec-package-tests"/>.
+
+#### NixOS tests
+
+The NixOS tests are available as `nixosTests` in parameters of derivations. For instance, the OpenSMTPD derivation includes lines similar to:
+
+```nix
+{ /* ... */, nixosTests }:
+{
+  # ...
+  passthru.tests = {
+    basic-functionality-and-dovecot-integration = nixosTests.opensmtpd;
+  };
+}
+```
+
+NixOS tests run in a VM, so they are slower than regular package tests. For more information see [NixOS module tests](https://nixos.org/manual/nixos/stable/#sec-nixos-tests).
+
+### `timeout` {#var-meta-timeout}
+
+A timeout (in seconds) for building the derivation. If the derivation takes longer than this time to build, it can fail due to breaking the timeout. However, all computers do not have the same computing power, hence some builders may decide to apply a multiplicative factor to this value. When filling this value in, try to keep it approximately consistent with other values already present in `nixpkgs`.
+
+### `hydraPlatforms` {#var-meta-hydraPlatforms}
+
+The list of Nix platform types for which the Hydra instance at `hydra.nixos.org` will build the package. (Hydra is the Nix-based continuous build system.) It defaults to the value of `meta.platforms`. Thus, the only reason to set `meta.hydraPlatforms` is if you want `hydra.nixos.org` to build the package on a subset of `meta.platforms`, or not at all, e.g.
+
+```nix
+meta.platforms = lib.platforms.linux;
+meta.hydraPlatforms = [];
+```
+
+### `broken` {#var-meta-broken}
+
+If set to `true`, the package is marked as "broken", meaning that it won’t show up in `nix-env -qa`, and cannot be built or installed. Such packages should be removed from Nixpkgs eventually unless they are fixed.
+
+## Licenses {#sec-meta-license}
+
+The `meta.license` attribute should preferably contain a value from `lib.licenses` defined in [`nixpkgs/lib/licenses.nix`](https://github.com/NixOS/nixpkgs/blob/master/lib/licenses.nix), or in-place license description of the same format if the license is unlikely to be useful in another expression.
+
+Although it’s typically better to indicate the specific license, a few generic options are available:
+
+### `lib.licenses.free`, `"free"` {#lib.licenses.free-free}
+
+Catch-all for free software licenses not listed above.
+
+### `lib.licenses.unfreeRedistributable`, `"unfree-redistributable"` {#lib.licenses.unfreeredistributable-unfree-redistributable}
+
+Unfree package that can be redistributed in binary form. That is, it’s legal to redistribute the *output* of the derivation. This means that the package can be included in the Nixpkgs channel.
+
+Sometimes proprietary software can only be redistributed unmodified. Make sure the builder doesn’t actually modify the original binaries; otherwise we’re breaking the license. For instance, the NVIDIA X11 drivers can be redistributed unmodified, but our builder applies `patchelf` to make them work. Thus, its license is `"unfree"` and it cannot be included in the Nixpkgs channel.
+
+### `lib.licenses.unfree`, `"unfree"` {#lib.licenses.unfree-unfree}
+
+Unfree package that cannot be redistributed. You can build it yourself, but you cannot redistribute the output of the derivation. Thus it cannot be included in the Nixpkgs channel.
+
+### `lib.licenses.unfreeRedistributableFirmware`, `"unfree-redistributable-firmware"` {#lib.licenses.unfreeredistributablefirmware-unfree-redistributable-firmware}
+
+This package supplies unfree, redistributable firmware. This is a separate value from `unfree-redistributable` because not everybody cares whether firmware is free.
diff --git a/doc/stdenv/multiple-output.chapter.md b/doc/stdenv/multiple-output.chapter.md
new file mode 100644
index 00000000000..62bf543e51e
--- /dev/null
+++ b/doc/stdenv/multiple-output.chapter.md
@@ -0,0 +1,128 @@
+# Multiple-output packages {#chap-multiple-output}
+
+## Introduction {#sec-multiple-outputs-introduction}
+
+The Nix language allows a derivation to produce multiple outputs, which is similar to what is utilized by other Linux distribution packaging systems. The outputs reside in separate Nix store paths, so they can be mostly handled independently of each other, including passing to build inputs, garbage collection or binary substitution. The exception is that building from source always produces all the outputs.
+
+The main motivation is to save disk space by reducing runtime closure sizes; consequently also sizes of substituted binaries get reduced. Splitting can be used to have more granular runtime dependencies, for example the typical reduction is to split away development-only files, as those are typically not needed during runtime. As a result, closure sizes of many packages can get reduced to a half or even much less.
+
+::: {.note}
+The reduction effects could be instead achieved by building the parts in completely separate derivations. That would often additionally reduce build-time closures, but it tends to be much harder to write such derivations, as build systems typically assume all parts are being built at once. This compromise approach of single source package producing multiple binary packages is also utilized often by rpm and deb.
+:::
+
+A number of attributes can be used to work with a derivation with multiple outputs. The attribute `outputs` is a list of strings, which are the names of the outputs. For each of these names, an identically named attribute is created, corresponding to that output. The attribute `meta.outputsToInstall` is used to determine the default set of outputs to install when using the derivation name unqualified.
+
+## Installing a split package {#sec-multiple-outputs-installing}
+
+When installing a package with multiple outputs, the package’s `meta.outputsToInstall` attribute determines which outputs are actually installed. `meta.outputsToInstall` is a list whose [default installs binaries and the associated man pages](https://github.com/NixOS/nixpkgs/blob/f1680774340d5443a1409c3421ced84ac1163ba9/pkgs/stdenv/generic/make-derivation.nix#L310-L320). The following sections describe ways to install different outputs.
+
+### Selecting outputs to install via NixOS {#sec-multiple-outputs-installing-nixos}
+
+NixOS provides two ways to select the outputs to install for packages listed in `environment.systemPackages`:
+
+- The configuration option `environment.extraOutputsToInstall` is appended to each package’s `meta.outputsToInstall` attribute to determine the outputs to install. It can for example be used to install `info` documentation or debug symbols for all packages.
+
+- The outputs can be listed as packages in `environment.systemPackages`. For example, the `"out"` and `"info"` outputs for the `coreutils` package can be installed by including `coreutils` and `coreutils.info` in `environment.systemPackages`.
+
+### Selecting outputs to install via `nix-env` {#sec-multiple-outputs-installing-nix-env}
+
+`nix-env` lacks an easy way to select the outputs to install. When installing a package, `nix-env` always installs the outputs listed in `meta.outputsToInstall`, even when the user explicitly selects an output.
+
+::: {.warning}
+`nix-env` silenty disregards the outputs selected by the user, and instead installs the outputs from `meta.outputsToInstall`. For example,
+
+```ShellSession
+$ nix-env -iA nixpkgs.coreutils.info
+```
+
+installs the `"out"` output (`coreutils.meta.outputsToInstall` is `[ "out" ]`) instead of the requested `"info"`.
+:::
+
+The only recourse to select an output with `nix-env` is to override the package’s `meta.outputsToInstall`, using the functions described in [](#chap-overrides). For example, the following overlay adds the `"info"` output for the `coreutils` package:
+
+```nix
+self: super:
+{
+  coreutils = super.coreutils.overrideAttrs (oldAttrs: {
+    meta = oldAttrs.meta // { outputsToInstall = oldAttrs.meta.outputsToInstall or [ "out" ] ++ [ "info" ]; };
+  });
+}
+```
+
+## Using a split package {#sec-multiple-outputs-using-split-packages}
+
+In the Nix language the individual outputs can be reached explicitly as attributes, e.g. `coreutils.info`, but the typical case is just using packages as build inputs.
+
+When a multiple-output derivation gets into a build input of another derivation, the `dev` output is added if it exists, otherwise the first output is added. In addition to that, `propagatedBuildOutputs` of that package which by default contain `$outputBin` and `$outputLib` are also added. (See [](#multiple-output-file-type-groups).)
+
+In some cases it may be desirable to combine different outputs under a single store path. A function `symlinkJoin` can be used to do this. (Note that it may negate some closure size benefits of using a multiple-output package.)
+
+## Writing a split derivation {#sec-multiple-outputs-}
+
+Here you find how to write a derivation that produces multiple outputs.
+
+In nixpkgs there is a framework supporting multiple-output derivations. It tries to cover most cases by default behavior. You can find the source separated in `<nixpkgs/pkgs/build-support/setup-hooks/multiple-outputs.sh>`; it’s relatively well-readable. The whole machinery is triggered by defining the `outputs` attribute to contain the list of desired output names (strings).
+
+```nix
+outputs = [ "bin" "dev" "out" "doc" ];
+```
+
+Often such a single line is enough. For each output an equally named environment variable is passed to the builder and contains the path in nix store for that output. Typically you also want to have the main `out` output, as it catches any files that didn’t get elsewhere.
+
+::: {.note}
+There is a special handling of the `debug` output, described at [](#stdenv-separateDebugInfo).
+:::
+
+### “Binaries first” {#multiple-output-file-binaries-first-convention}
+
+A commonly adopted convention in `nixpkgs` is that executables provided by the package are contained within its first output. This convention allows the dependent packages to reference the executables provided by packages in a uniform manner. For instance, provided with the knowledge that the `perl` package contains a `perl` executable it can be referenced as `${pkgs.perl}/bin/perl` within a Nix derivation that needs to execute a Perl script.
+
+The `glibc` package is a deliberate single exception to the “binaries first” convention. The `glibc` has `libs` as its first output allowing the libraries provided by `glibc` to be referenced directly (e.g. `${stdenv.glibc}/lib/ld-linux-x86-64.so.2`). The executables provided by `glibc` can be accessed via its `bin` attribute (e.g. `${stdenv.glibc.bin}/bin/ldd`).
+
+The reason for why `glibc` deviates from the convention is because referencing a library provided by `glibc` is a very common operation among Nix packages. For instance, third-party executables packaged by Nix are typically patched and relinked with the relevant version of `glibc` libraries from Nix packages (please see the documentation on [patchelf](https://github.com/NixOS/patchelf) for more details).
+
+### File type groups {#multiple-output-file-type-groups}
+
+The support code currently recognizes some particular kinds of outputs and either instructs the build system of the package to put files into their desired outputs or it moves the files during the fixup phase. Each group of file types has an `outputFoo` variable specifying the output name where they should go. If that variable isn’t defined by the derivation writer, it is guessed – a default output name is defined, falling back to other possibilities if the output isn’t defined.
+
+#### `$outputDev` {#outputdev}
+
+is for development-only files. These include C(++) headers (`include/`), pkg-config (`lib/pkgconfig/`), cmake (`lib/cmake/`) and aclocal files (`share/aclocal/`). They go to `dev` or `out` by default.
+
+#### `$outputBin` {#outputbin}
+
+is meant for user-facing binaries, typically residing in `bin/`. They go to `bin` or `out` by default.
+
+#### `$outputLib` {#outputlib}
+
+is meant for libraries, typically residing in `lib/` and `libexec/`. They go to `lib` or `out` by default.
+
+#### `$outputDoc` {#outputdoc}
+
+is for user documentation, typically residing in `share/doc/`. It goes to `doc` or `out` by default.
+
+#### `$outputDevdoc` {#outputdevdoc}
+
+is for _developer_ documentation. Currently we count gtk-doc and devhelp books, typically residing in `share/gtk-doc/` and `share/devhelp/`, in there. It goes to `devdoc` or is removed (!) by default. This is because e.g. gtk-doc tends to be rather large and completely unused by nixpkgs users.
+
+#### `$outputMan` {#outputman}
+
+is for man pages (except for section 3), typically residing in `share/man/man[0-9]/`. They go to `man` or `$outputBin` by default.
+
+#### `$outputDevman` {#outputdevman}
+
+is for section 3 man pages, typically residing in `share/man/man[0-9]/`. They go to `devman` or `$outputMan` by default.
+
+#### `$outputInfo` {#outputinfo}
+
+is for info pages, typically residing in `share/info/`. They go to `info` or `$outputBin` by default.
+
+### Common caveats {#sec-multiple-outputs-caveats}
+
+- Some configure scripts don’t like some of the parameters passed by default by the framework, e.g. `--docdir=/foo/bar`. You can disable this by setting `setOutputFlags = false;`.
+
+- The outputs of a single derivation can retain references to each other, but note that circular references are not allowed. (And each strongly-connected component would act as a single output anyway.)
+
+- Most of split packages contain their core functionality in libraries. These libraries tend to refer to various kind of data that typically gets into `out`, e.g. locale strings, so there is often no advantage in separating the libraries into `lib`, as keeping them in `out` is easier.
+
+- Some packages have hidden assumptions on install paths, which complicates splitting.
diff --git a/doc/stdenv/platform-notes.chapter.md b/doc/stdenv/platform-notes.chapter.md
new file mode 100644
index 00000000000..03e61e333f8
--- /dev/null
+++ b/doc/stdenv/platform-notes.chapter.md
@@ -0,0 +1,62 @@
+# Platform Notes {#chap-platform-notes}
+
+## Darwin (macOS) {#sec-darwin}
+
+Some common issues when packaging software for Darwin:
+
+- The Darwin `stdenv` uses clang instead of gcc. When referring to the compiler `$CC` or `cc` will work in both cases. Some builds hardcode gcc/g++ in their build scripts, that can usually be fixed with using something like `makeFlags = [ "CC=cc" ];` or by patching the build scripts.
+
+  ```nix
+  stdenv.mkDerivation {
+    name = "libfoo-1.2.3";
+    # ...
+    buildPhase = ''
+      $CC -o hello hello.c
+    '';
+  }
+  ```
+
+- On Darwin, libraries are linked using absolute paths, libraries are resolved by their `install_name` at link time. Sometimes packages won’t set this correctly causing the library lookups to fail at runtime. This can be fixed by adding extra linker flags or by running `install_name_tool -id` during the `fixupPhase`.
+
+  ```nix
+  stdenv.mkDerivation {
+    name = "libfoo-1.2.3";
+    # ...
+    makeFlags = lib.optional stdenv.isDarwin "LDFLAGS=-Wl,-install_name,$(out)/lib/libfoo.dylib";
+  }
+  ```
+
+- Even if the libraries are linked using absolute paths and resolved via their `install_name` correctly, tests can sometimes fail to run binaries. This happens because the `checkPhase` runs before the libraries are installed.
+
+  This can usually be solved by running the tests after the `installPhase` or alternatively by using `DYLD_LIBRARY_PATH`. More information about this variable can be found in the *dyld(1)* manpage.
+
+  ```
+  dyld: Library not loaded: /nix/store/7hnmbscpayxzxrixrgxvvlifzlxdsdir-jq-1.5-lib/lib/libjq.1.dylib
+  Referenced from: /private/tmp/nix-build-jq-1.5.drv-0/jq-1.5/tests/../jq
+  Reason: image not found
+  ./tests/jqtest: line 5: 75779 Abort trap: 6
+  ```
+
+  ```nix
+  stdenv.mkDerivation {
+    name = "libfoo-1.2.3";
+    # ...
+    doInstallCheck = true;
+    installCheckTarget = "check";
+  }
+  ```
+
+- Some packages assume xcode is available and use `xcrun` to resolve build tools like `clang`, etc. This causes errors like `xcode-select: error: no developer tools were found at '/Applications/Xcode.app'` while the build doesn’t actually depend on xcode.
+
+  ```nix
+  stdenv.mkDerivation {
+    name = "libfoo-1.2.3";
+    # ...
+    prePatch = ''
+      substituteInPlace Makefile \
+          --replace '/usr/bin/xcrun clang' clang
+    '';
+  }
+  ```
+
+  The package `xcbuild` can be used to build projects that really depend on Xcode. However, this replacement is not 100% compatible with Xcode and can occasionally cause issues.
diff --git a/doc/stdenv/stdenv.chapter.md b/doc/stdenv/stdenv.chapter.md
new file mode 100644
index 00000000000..1d4ca99e3cb
--- /dev/null
+++ b/doc/stdenv/stdenv.chapter.md
@@ -0,0 +1,1269 @@
+# The Standard Environment {#chap-stdenv}
+
+The standard build environment in the Nix Packages collection provides an environment for building Unix packages that does a lot of common build tasks automatically. In fact, for Unix packages that use the standard `./configure; make; make install` build interface, you don’t need to write a build script at all; the standard environment does everything automatically. If `stdenv` doesn’t do what you need automatically, you can easily customise or override the various build phases.
+
+## Using `stdenv` {#sec-using-stdenv}
+
+To build a package with the standard environment, you use the function `stdenv.mkDerivation`, instead of the primitive built-in function `derivation`, e.g.
+
+```nix
+stdenv.mkDerivation {
+  name = "libfoo-1.2.3";
+  src = fetchurl {
+    url = "http://example.org/libfoo-1.2.3.tar.bz2";
+    sha256 = "0x2g1jqygyr5wiwg4ma1nd7w4ydpy82z9gkcv8vh2v8dn3y58v5m";
+  };
+}
+```
+
+(`stdenv` needs to be in scope, so if you write this in a separate Nix expression from `pkgs/all-packages.nix`, you need to pass it as a function argument.) Specifying a `name` and a `src` is the absolute minimum Nix requires. For convenience, you can also use `pname` and `version` attributes and `mkDerivation` will automatically set `name` to `"${pname}-${version}"` by default. Since [RFC 0035](https://github.com/NixOS/rfcs/pull/35), this is preferred for packages in Nixpkgs, as it allows us to reuse the version easily:
+
+```nix
+stdenv.mkDerivation rec {
+  pname = "libfoo";
+  version = "1.2.3";
+  src = fetchurl {
+    url = "http://example.org/libfoo-source-${version}.tar.bz2";
+    sha256 = "0x2g1jqygyr5wiwg4ma1nd7w4ydpy82z9gkcv8vh2v8dn3y58v5m";
+  };
+}
+```
+
+Many packages have dependencies that are not provided in the standard environment. It’s usually sufficient to specify those dependencies in the `buildInputs` attribute:
+
+```nix
+stdenv.mkDerivation {
+  name = "libfoo-1.2.3";
+  ...
+  buildInputs = [libbar perl ncurses];
+}
+```
+
+This attribute ensures that the `bin` subdirectories of these packages appear in the `PATH` environment variable during the build, that their `include` subdirectories are searched by the C compiler, and so on. (See [](#ssec-setup-hooks) for details.)
+
+Often it is necessary to override or modify some aspect of the build. To make this easier, the standard environment breaks the package build into a number of *phases*, all of which can be overridden or modified individually: unpacking the sources, applying patches, configuring, building, and installing. (There are some others; see [](#sec-stdenv-phases).) For instance, a package that doesn’t supply a makefile but instead has to be compiled "manually" could be handled like this:
+
+```nix
+stdenv.mkDerivation {
+  name = "fnord-4.5";
+  ...
+  buildPhase = ''
+    gcc foo.c -o foo
+  '';
+  installPhase = ''
+    mkdir -p $out/bin
+    cp foo $out/bin
+  '';
+}
+```
+
+(Note the use of `''`-style string literals, which are very convenient for large multi-line script fragments because they don’t need escaping of `"` and `\`, and because indentation is intelligently removed.)
+
+There are many other attributes to customise the build. These are listed in [](#ssec-stdenv-attributes).
+
+While the standard environment provides a generic builder, you can still supply your own build script:
+
+```nix
+stdenv.mkDerivation {
+  name = "libfoo-1.2.3";
+  ...
+  builder = ./builder.sh;
+}
+```
+
+where the builder can do anything it wants, but typically starts with
+
+```bash
+source $stdenv/setup
+```
+
+to let `stdenv` set up the environment (e.g., process the `buildInputs`). If you want, you can still use `stdenv`’s generic builder:
+
+```bash
+source $stdenv/setup
+
+buildPhase() {
+  echo "... this is my custom build phase ..."
+  gcc foo.c -o foo
+}
+
+installPhase() {
+  mkdir -p $out/bin
+  cp foo $out/bin
+}
+
+genericBuild
+```
+
+## Tools provided by `stdenv` {#sec-tools-of-stdenv}
+
+The standard environment provides the following packages:
+
+- The GNU C Compiler, configured with C and C++ support.
+- GNU coreutils (contains a few dozen standard Unix commands).
+- GNU findutils (contains `find`).
+- GNU diffutils (contains `diff`, `cmp`).
+- GNU `sed`.
+- GNU `grep`.
+- GNU `awk`.
+- GNU `tar`.
+- `gzip`, `bzip2` and `xz`.
+- GNU Make.
+- Bash. This is the shell used for all builders in the Nix Packages collection. Not using `/bin/sh` removes a large source of portability problems.
+- The `patch` command.
+
+On Linux, `stdenv` also includes the `patchelf` utility.
+
+## Specifying dependencies {#ssec-stdenv-dependencies}
+
+As described in the Nix manual, almost any `*.drv` store path in a derivation’s attribute set will induce a dependency on that derivation. `mkDerivation`, however, takes a few attributes intended to include all the dependencies of a package. This is done both for structure and consistency, but also so that certain other setup can take place. For example, certain dependencies need their bin directories added to the `PATH`. That is built-in, but other setup is done via a pluggable mechanism that works in conjunction with these dependency attributes. See [](#ssec-setup-hooks) for details.
+
+Dependencies can be broken down along three axes: their host and target platforms relative to the new derivation’s, and whether they are propagated. The platform distinctions are motivated by cross compilation; see [](#chap-cross) for exactly what each platform means. [^footnote-stdenv-ignored-build-platform] But even if one is not cross compiling, the platforms imply whether or not the dependency is needed at run-time or build-time, a concept that makes perfect sense outside of cross compilation. By default, the run-time/build-time distinction is just a hint for mental clarity, but with `strictDeps` set it is mostly enforced even in the native case.
+
+The extension of `PATH` with dependencies, alluded to above, proceeds according to the relative platforms alone. The process is carried out only for dependencies whose host platform matches the new derivation’s build platform i.e. dependencies which run on the platform where the new derivation will be built. [^footnote-stdenv-native-dependencies-in-path] For each dependency \<dep\> of those dependencies, `dep/bin`, if present, is added to the `PATH` environment variable.
+
+A dependency is said to be **propagated** when some of its other-transitive (non-immediate) downstream dependencies also need it as an immediate dependency.
+[^footnote-stdenv-propagated-dependencies]
+
+It is important to note that dependencies are not necessarily propagated as the same sort of dependency that they were before, but rather as the corresponding sort so that the platform rules still line up. To determine the exact rules for dependency propagation, we start by assigning to each dependency a couple of ternary numbers (`-1` for `build`, `0` for `host`, and `1` for `target`), representing how respectively its host and target platforms are "offset" from the depending derivation’s platforms. The following table summarize the different combinations that can be obtained:
+
+| `host → target`     | attribute name      | offset   |
+| ------------------- | ------------------- | -------- |
+| `build --> build`   | `depsBuildBuild`    | `-1, -1` |
+| `build --> host`    | `nativeBuildInputs` | `-1, 0`  |
+| `build --> target`  | `depsBuildTarget`   | `-1, 1`  |
+| `host --> host`     | `depsHostHost`      | `0, 0`   |
+| `host --> target`   | `buildInputs`       | `0, 1`   |
+| `target --> target` | `depsTargetTarget`  | `1, 1`   |
+
+Algorithmically, we traverse propagated inputs, accumulating every propagated dependency’s propagated dependencies and adjusting them to account for the “shift in perspective” described by the current dependency’s platform offsets. This results is sort of a transitive closure of the dependency relation, with the offsets being approximately summed when two dependency links are combined. We also prune transitive dependencies whose combined offsets go out-of-bounds, which can be viewed as a filter over that transitive closure removing dependencies that are blatantly absurd.
+
+We can define the process precisely with [Natural Deduction](https://en.wikipedia.org/wiki/Natural_deduction) using the inference rules. This probably seems a bit obtuse, but so is the bash code that actually implements it! [^footnote-stdenv-find-inputs-location] They’re confusing in very different ways so… hopefully if something doesn’t make sense in one presentation, it will in the other!
+
+```
+let mapOffset(h, t, i) = i + (if i <= 0 then h else t - 1)
+
+propagated-dep(h0, t0, A, B)
+propagated-dep(h1, t1, B, C)
+h0 + h1 in {-1, 0, 1}
+h0 + t1 in {-1, 0, 1}
+-------------------------------------- Transitive property
+propagated-dep(mapOffset(h0, t0, h1),
+               mapOffset(h0, t0, t1),
+               A, C)
+```
+
+```
+let mapOffset(h, t, i) = i + (if i <= 0 then h else t - 1)
+
+dep(h0, _, A, B)
+propagated-dep(h1, t1, B, C)
+h0 + h1 in {-1, 0, 1}
+h0 + t1 in {-1, 0, -1}
+----------------------------- Take immediate dependencies' propagated dependencies
+propagated-dep(mapOffset(h0, t0, h1),
+               mapOffset(h0, t0, t1),
+               A, C)
+```
+
+```
+propagated-dep(h, t, A, B)
+----------------------------- Propagated dependencies count as dependencies
+dep(h, t, A, B)
+```
+
+Some explanation of this monstrosity is in order. In the common case, the target offset of a dependency is the successor to the target offset: `t = h + 1`. That means that:
+
+```
+let f(h, t, i) = i + (if i <= 0 then h else t - 1)
+let f(h, h + 1, i) = i + (if i <= 0 then h else (h + 1) - 1)
+let f(h, h + 1, i) = i + (if i <= 0 then h else h)
+let f(h, h + 1, i) = i + h
+```
+
+This is where “sum-like” comes in from above: We can just sum all of the host offsets to get the host offset of the transitive dependency. The target offset is the transitive dependency is simply the host offset + 1, just as it was with the dependencies composed to make this transitive one; it can be ignored as it doesn’t add any new information.
+
+Because of the bounds checks, the uncommon cases are `h = t` and `h + 2 = t`. In the former case, the motivation for `mapOffset` is that since its host and target platforms are the same, no transitive dependency of it should be able to “discover” an offset greater than its reduced target offsets. `mapOffset` effectively “squashes” all its transitive dependencies’ offsets so that none will ever be greater than the target offset of the original `h = t` package. In the other case, `h + 1` is skipped over between the host and target offsets. Instead of squashing the offsets, we need to “rip” them apart so no transitive dependencies’ offset is that one.
+
+Overall, the unifying theme here is that propagation shouldn’t be introducing transitive dependencies involving platforms the depending package is unaware of. \[One can imagine the dependending package asking for dependencies with the platforms it knows about; other platforms it doesn’t know how to ask for. The platform description in that scenario is a kind of unforagable capability.\] The offset bounds checking and definition of `mapOffset` together ensure that this is the case. Discovering a new offset is discovering a new platform, and since those platforms weren’t in the derivation “spec” of the needing package, they cannot be relevant. From a capability perspective, we can imagine that the host and target platforms of a package are the capabilities a package requires, and the depending package must provide the capability to the dependency.
+
+### Variables specifying dependencies {#variables-specifying-dependencies}
+
+#### `depsBuildBuild` {#var-stdenv-depsBuildBuild}
+
+A list of dependencies whose host and target platforms are the new derivation’s build platform. These are programs and libraries used at build time that produce programs and libraries also used at build time. If the dependency doesn’t care about the target platform (i.e. isn’t a compiler or similar tool), put it in `nativeBuildInputs` instead. The most common use of this `buildPackages.stdenv.cc`, the default C compiler for this role. That example crops up more than one might think in old commonly used C libraries.
+
+Since these packages are able to be run at build-time, they are always added to the `PATH`, as described above. But since these packages are only guaranteed to be able to run then, they shouldn’t persist as run-time dependencies. This isn’t currently enforced, but could be in the future.
+
+#### `nativeBuildInputs` {#var-stdenv-nativeBuildInputs}
+
+A list of dependencies whose host platform is the new derivation’s build platform, and target platform is the new derivation’s host platform. These are programs and libraries used at build-time that, if they are a compiler or similar tool, produce code to run at run-time—i.e. tools used to build the new derivation. If the dependency doesn’t care about the target platform (i.e. isn’t a compiler or similar tool), put it here, rather than in `depsBuildBuild` or `depsBuildTarget`. This could be called `depsBuildHost` but `nativeBuildInputs` is used for historical continuity.
+
+Since these packages are able to be run at build-time, they are added to the `PATH`, as described above. But since these packages are only guaranteed to be able to run then, they shouldn’t persist as run-time dependencies. This isn’t currently enforced, but could be in the future.
+
+#### `depsBuildTarget` {#var-stdenv-depsBuildTarget}
+
+A list of dependencies whose host platform is the new derivation’s build platform, and target platform is the new derivation’s target platform. These are programs used at build time that produce code to run with code produced by the depending package. Most commonly, these are tools used to build the runtime or standard library that the currently-being-built compiler will inject into any code it compiles. In many cases, the currently-being-built-compiler is itself employed for that task, but when that compiler won’t run (i.e. its build and host platform differ) this is not possible. Other times, the compiler relies on some other tool, like binutils, that is always built separately so that the dependency is unconditional.
+
+This is a somewhat confusing concept to wrap one’s head around, and for good reason. As the only dependency type where the platform offsets, `-1` and `1`, are not adjacent integers, it requires thinking of a bootstrapping stage *two* away from the current one. It and its use-case go hand in hand and are both considered poor form: try to not need this sort of dependency, and try to avoid building standard libraries and runtimes in the same derivation as the compiler produces code using them. Instead strive to build those like a normal library, using the newly-built compiler just as a normal library would. In short, do not use this attribute unless you are packaging a compiler and are sure it is needed.
+
+Since these packages are able to run at build time, they are added to the `PATH`, as described above. But since these packages are only guaranteed to be able to run then, they shouldn’t persist as run-time dependencies. This isn’t currently enforced, but could be in the future.
+
+#### `depsHostHost` {#var-stdenv-depsHostHost}
+
+A list of dependencies whose host and target platforms match the new derivation’s host platform. In practice, this would usually be tools used by compilers for macros or a metaprogramming system, or libraries used by the macros or metaprogramming code itself. It’s always preferable to use a `depsBuildBuild` dependency in the derivation being built over a `depsHostHost` on the tool doing the building for this purpose.
+
+#### `buildInputs` {#var-stdenv-buildInputs}
+
+A list of dependencies whose host platform and target platform match the new derivation’s. This would be called `depsHostTarget` but for historical continuity. If the dependency doesn’t care about the target platform (i.e. isn’t a compiler or similar tool), put it here, rather than in `depsBuildBuild`.
+
+These are often programs and libraries used by the new derivation at *run*-time, but that isn’t always the case. For example, the machine code in a statically-linked library is only used at run-time, but the derivation containing the library is only needed at build-time. Even in the dynamic case, the library may also be needed at build-time to appease the linker.
+
+#### `depsTargetTarget` {#var-stdenv-depsTargetTarget}
+
+A list of dependencies whose host platform matches the new derivation’s target platform. These are packages that run on the target platform, e.g. the standard library or run-time deps of standard library that a compiler insists on knowing about. It’s poor form in almost all cases for a package to depend on another from a future stage \[future stage corresponding to positive offset\]. Do not use this attribute unless you are packaging a compiler and are sure it is needed.
+
+#### `depsBuildBuildPropagated` {#var-stdenv-depsBuildBuildPropagated}
+
+The propagated equivalent of `depsBuildBuild`. This perhaps never ought to be used, but it is included for consistency \[see below for the others\].
+
+#### `propagatedNativeBuildInputs` {#var-stdenv-propagatedNativeBuildInputs}
+
+The propagated equivalent of `nativeBuildInputs`. This would be called `depsBuildHostPropagated` but for historical continuity. For example, if package `Y` has `propagatedNativeBuildInputs = [X]`, and package `Z` has `buildInputs = [Y]`, then package `Z` will be built as if it included package `X` in its `nativeBuildInputs`. If instead, package `Z` has `nativeBuildInputs = [Y]`, then `Z` will be built as if it included `X` in the `depsBuildBuild` of package `Z`, because of the sum of the two `-1` host offsets.
+
+#### `depsBuildTargetPropagated` {#var-stdenv-depsBuildTargetPropagated}
+
+The propagated equivalent of `depsBuildTarget`. This is prefixed for the same reason of alerting potential users.
+
+#### `depsHostHostPropagated` {#var-stdenv-depsHostHostPropagated}
+
+The propagated equivalent of `depsHostHost`.
+
+#### `propagatedBuildInputs` {#var-stdenv-propagatedBuildInputs}
+
+The propagated equivalent of `buildInputs`. This would be called `depsHostTargetPropagated` but for historical continuity.
+
+#### `depsTargetTargetPropagated` {#var-stdenv-depsTargetTargetPropagated}
+
+The propagated equivalent of `depsTargetTarget`. This is prefixed for the same reason of alerting potential users.
+
+## Attributes {#ssec-stdenv-attributes}
+
+### Variables affecting `stdenv` initialisation {#variables-affecting-stdenv-initialisation}
+
+#### `NIX_DEBUG` {#var-stdenv-NIX_DEBUG}
+
+A natural number indicating how much information to log. If set to 1 or higher, `stdenv` will print moderate debugging information during the build. In particular, the `gcc` and `ld` wrapper scripts will print out the complete command line passed to the wrapped tools. If set to 6 or higher, the `stdenv` setup script will be run with `set -x` tracing. If set to 7 or higher, the `gcc` and `ld` wrapper scripts will also be run with `set -x` tracing.
+
+### Attributes affecting build properties {#attributes-affecting-build-properties}
+
+#### `enableParallelBuilding` {#var-stdenv-enableParallelBuilding}
+
+If set to `true`, `stdenv` will pass specific flags to `make` and other build tools to enable parallel building with up to `build-cores` workers.
+
+Unless set to `false`, some build systems with good support for parallel building including `cmake`, `meson`, and `qmake` will set it to `true`.
+
+### Special variables {#special-variables}
+
+#### `passthru` {#var-stdenv-passthru}
+
+This is an attribute set which can be filled with arbitrary values. For example:
+
+```nix
+passthru = {
+  foo = "bar";
+  baz = {
+    value1 = 4;
+    value2 = 5;
+  };
+}
+```
+
+Values inside it are not passed to the builder, so you can change them without triggering a rebuild. However, they can be accessed outside of a derivation directly, as if they were set inside a derivation itself, e.g. `hello.baz.value1`. We don’t specify any usage or schema of `passthru` - it is meant for values that would be useful outside the derivation in other parts of a Nix expression (e.g. in other derivations). An example would be to convey some specific dependency of your derivation which contains a program with plugins support. Later, others who make derivations with plugins can use passed-through dependency to ensure that their plugin would be binary-compatible with built program.
+
+#### `passthru.updateScript` {#var-passthru-updateScript}
+
+A script to be run by `maintainers/scripts/update.nix` when the package is matched. It needs to be an executable file, either on the file system:
+
+```nix
+passthru.updateScript = ./update.sh;
+```
+
+or inside the expression itself:
+
+```nix
+passthru.updateScript = writeScript "update-zoom-us" ''
+  #!/usr/bin/env nix-shell
+  #!nix-shell -i bash -p curl pcre common-updater-scripts
+
+  set -eu -o pipefail
+
+  version="$(curl -sI https://zoom.us/client/latest/zoom_x86_64.tar.xz | grep -Fi 'Location:' | pcregrep -o1 '/(([0-9]\.?)+)/')"
+  update-source-version zoom-us "$version"
+'';
+```
+
+The attribute can also contain a list, a script followed by arguments to be passed to it:
+
+```nix
+passthru.updateScript = [ ../../update.sh pname "--requested-release=unstable" ];
+```
+
+The script will be run with `UPDATE_NIX_ATTR_PATH` environment variable set to the attribute path it is supposed to update.
+
+::: {.note}
+The script will be usually run from the root of the Nixpkgs repository but you should not rely on that. Also note that the update scripts will be run in parallel by default; you should avoid running `git commit` or any other commands that cannot handle that.
+:::
+
+For information about how to run the updates, execute `nix-shell maintainers/scripts/update.nix`.
+
+## Phases {#sec-stdenv-phases}
+
+`stdenv.mkDerivation` sets the Nix [derivation](https://nixos.org/manual/nix/stable/expressions/derivations.html#derivations)'s builder to a script that loads the stdenv `setup.sh` bash library and calls `genericBuild`. Most packaging functions rely on this default builder.
+
+This generic command invokes a number of *phases*. Package builds are split into phases to make it easier to override specific parts of the build (e.g., unpacking the sources or installing the binaries).
+
+Each phase can be overridden in its entirety either by setting the environment variable `namePhase` to a string containing some shell commands to be executed, or by redefining the shell function `namePhase`. The former is convenient to override a phase from the derivation, while the latter is convenient from a build script. However, typically one only wants to *add* some commands to a phase, e.g. by defining `postInstall` or `preFixup`, as skipping some of the default actions may have unexpected consequences. The default script for each phase is defined in the file `pkgs/stdenv/generic/setup.sh`.
+
+When overriding a phase, for example `installPhase`, it is important to start with `runHook preInstall` and end it with `runHook postInstall`, otherwise `preInstall` and `postInstall` will not be run. Even if you don't use them directly, it is good practice to do so anyways for downstream users who would want to add a `postInstall` by overriding your derivation.
+
+While inside an interactive `nix-shell`, if you wanted to run all phases in the order they would be run in an actual build, you can invoke `genericBuild` yourself.
+
+### Controlling phases {#ssec-controlling-phases}
+
+There are a number of variables that control what phases are executed and in what order:
+
+#### Variables affecting phase control {#variables-affecting-phase-control}
+
+##### `phases` {#var-stdenv-phases}
+
+Specifies the phases. You can change the order in which phases are executed, or add new phases, by setting this variable. If it’s not set, the default value is used, which is `$prePhases unpackPhase patchPhase $preConfigurePhases configurePhase $preBuildPhases buildPhase checkPhase $preInstallPhases installPhase fixupPhase installCheckPhase $preDistPhases distPhase $postPhases`.
+
+It is discouraged to set this variable, as it is easy to miss some important functionality hidden in some of the less obviously needed phases (like `fixupPhase` which patches the shebang of scripts).
+Usually, if you just want to add a few phases, it’s more convenient to set one of the variables below (such as `preInstallPhases`).
+
+##### `prePhases` {#var-stdenv-prePhases}
+
+Additional phases executed before any of the default phases.
+
+##### `preConfigurePhases` {#var-stdenv-preConfigurePhases}
+
+Additional phases executed just before the configure phase.
+
+##### `preBuildPhases` {#var-stdenv-preBuildPhases}
+
+Additional phases executed just before the build phase.
+
+##### `preInstallPhases` {#var-stdenv-preInstallPhases}
+
+Additional phases executed just before the install phase.
+
+##### `preFixupPhases` {#var-stdenv-preFixupPhases}
+
+Additional phases executed just before the fixup phase.
+
+##### `preDistPhases` {#var-stdenv-preDistPhases}
+
+Additional phases executed just before the distribution phase.
+
+##### `postPhases` {#var-stdenv-postPhases}
+
+Additional phases executed after any of the default phases.
+
+### The unpack phase {#ssec-unpack-phase}
+
+The unpack phase is responsible for unpacking the source code of the package. The default implementation of `unpackPhase` unpacks the source files listed in the `src` environment variable to the current directory. It supports the following files by default:
+
+#### Tar files {#tar-files}
+
+These can optionally be compressed using `gzip` (`.tar.gz`, `.tgz` or `.tar.Z`), `bzip2` (`.tar.bz2`, `.tbz2` or `.tbz`) or `xz` (`.tar.xz`, `.tar.lzma` or `.txz`).
+
+#### Zip files {#zip-files}
+
+Zip files are unpacked using `unzip`. However, `unzip` is not in the standard environment, so you should add it to `nativeBuildInputs` yourself.
+
+#### Directories in the Nix store {#directories-in-the-nix-store}
+
+These are simply copied to the current directory. The hash part of the file name is stripped, e.g. `/nix/store/1wydxgby13cz...-my-sources` would be copied to `my-sources`.
+
+Additional file types can be supported by setting the `unpackCmd` variable (see below).
+
+#### Variables controlling the unpack phase {#variables-controlling-the-unpack-phase}
+
+##### `srcs` / `src` {#var-stdenv-src}
+
+The list of source files or directories to be unpacked or copied. One of these must be set. Note that if you use `srcs`, you should also set `sourceRoot` or `setSourceRoot`.
+
+##### `sourceRoot` {#var-stdenv-sourceRoot}
+
+After running `unpackPhase`, the generic builder changes the current directory to the directory created by unpacking the sources. If there are multiple source directories, you should set `sourceRoot` to the name of the intended directory. Set `sourceRoot = ".";` if you use `srcs` and control the unpack phase yourself.
+
+##### `setSourceRoot` {#var-stdenv-setSourceRoot}
+
+Alternatively to setting `sourceRoot`, you can set `setSourceRoot` to a shell command to be evaluated by the unpack phase after the sources have been unpacked. This command must set `sourceRoot`.
+
+##### `preUnpack` {#var-stdenv-preUnpack}
+
+Hook executed at the start of the unpack phase.
+
+##### `postUnpack` {#var-stdenv-postUnpack}
+
+Hook executed at the end of the unpack phase.
+
+##### `dontUnpack` {#var-stdenv-dontUnpack}
+
+Set to true to skip the unpack phase.
+
+##### `dontMakeSourcesWritable` {#var-stdenv-dontMakeSourcesWritable}
+
+If set to `1`, the unpacked sources are *not* made writable. By default, they are made writable to prevent problems with read-only sources. For example, copied store directories would be read-only without this.
+
+##### `unpackCmd` {#var-stdenv-unpackCmd}
+
+The unpack phase evaluates the string `$unpackCmd` for any unrecognised file. The path to the current source file is contained in the `curSrc` variable.
+
+### The patch phase {#ssec-patch-phase}
+
+The patch phase applies the list of patches defined in the `patches` variable.
+
+#### Variables controlling the patch phase {#variables-controlling-the-patch-phase}
+
+##### `dontPatch` {#var-stdenv-dontPatch}
+
+Set to true to skip the patch phase.
+
+##### `patches` {#var-stdenv-patches}
+
+The list of patches. They must be in the format accepted by the `patch` command, and may optionally be compressed using `gzip` (`.gz`), `bzip2` (`.bz2`) or `xz` (`.xz`).
+
+##### `patchFlags` {#var-stdenv-patchFlags}
+
+Flags to be passed to `patch`. If not set, the argument `-p1` is used, which causes the leading directory component to be stripped from the file names in each patch.
+
+##### `prePatch` {#var-stdenv-prePatch}
+
+Hook executed at the start of the patch phase.
+
+##### `postPatch` {#var-stdenv-postPatch}
+
+Hook executed at the end of the patch phase.
+
+### The configure phase {#ssec-configure-phase}
+
+The configure phase prepares the source tree for building. The default `configurePhase` runs `./configure` (typically an Autoconf-generated script) if it exists.
+
+#### Variables controlling the configure phase {#variables-controlling-the-configure-phase}
+
+##### `configureScript` {#var-stdenv-configureScript}
+
+The name of the configure script. It defaults to `./configure` if it exists; otherwise, the configure phase is skipped. This can actually be a command (like `perl ./Configure.pl`).
+
+##### `configureFlags` {#var-stdenv-configureFlags}
+
+A list of strings passed as additional arguments to the configure script.
+
+##### `dontConfigure` {#var-stdenv-dontConfigure}
+
+Set to true to skip the configure phase.
+
+##### `configureFlagsArray` {#var-stdenv-configureFlagsArray}
+
+A shell array containing additional arguments passed to the configure script. You must use this instead of `configureFlags` if the arguments contain spaces.
+
+##### `dontAddPrefix` {#var-stdenv-dontAddPrefix}
+
+By default, the flag `--prefix=$prefix` is added to the configure flags. If this is undesirable, set this variable to true.
+
+##### `prefix` {#var-stdenv-prefix}
+
+The prefix under which the package must be installed, passed via the `--prefix` option to the configure script. It defaults to `$out`.
+
+##### `prefixKey` {#var-stdenv-prefixKey}
+
+The key to use when specifying the prefix. By default, this is set to `--prefix=` as that is used by the majority of packages.
+
+##### `dontAddStaticConfigureFlags`
+
+By default, when building statically, stdenv will try to add build system appropriate configure flags to try to enable static builds.
+
+If this is undesirable, set this variable to true.
+
+##### `dontAddDisableDepTrack` {#var-stdenv-dontAddDisableDepTrack}
+
+By default, the flag `--disable-dependency-tracking` is added to the configure flags to speed up Automake-based builds. If this is undesirable, set this variable to true.
+
+##### `dontFixLibtool` {#var-stdenv-dontFixLibtool}
+
+By default, the configure phase applies some special hackery to all files called `ltmain.sh` before running the configure script in order to improve the purity of Libtool-based packages [^footnote-stdenv-sys-lib-search-path] . If this is undesirable, set this variable to true.
+
+##### `dontDisableStatic` {#var-stdenv-dontDisableStatic}
+
+By default, when the configure script has `--enable-static`, the option `--disable-static` is added to the configure flags.
+
+If this is undesirable, set this variable to true.  It is automatically set to true when building statically, for example through `pkgsStatic`.
+
+##### `configurePlatforms` {#var-stdenv-configurePlatforms}
+
+By default, when cross compiling, the configure script has `--build=...` and `--host=...` passed. Packages can instead pass `[ "build" "host" "target" ]` or a subset to control exactly which platform flags are passed. Compilers and other tools can use this to also pass the target platform. [^footnote-stdenv-build-time-guessing-impurity]
+
+##### `preConfigure` {#var-stdenv-preConfigure}
+
+Hook executed at the start of the configure phase.
+
+##### `postConfigure` {#var-stdenv-postConfigure}
+
+Hook executed at the end of the configure phase.
+
+### The build phase {#build-phase}
+
+The build phase is responsible for actually building the package (e.g. compiling it). The default `buildPhase` simply calls `make` if a file named `Makefile`, `makefile` or `GNUmakefile` exists in the current directory (or the `makefile` is explicitly set); otherwise it does nothing.
+
+#### Variables controlling the build phase {#variables-controlling-the-build-phase}
+
+##### `dontBuild` {#var-stdenv-dontBuild}
+
+Set to true to skip the build phase.
+
+##### `makefile` {#var-stdenv-makefile}
+
+The file name of the Makefile.
+
+##### `makeFlags` {#var-stdenv-makeFlags}
+
+A list of strings passed as additional flags to `make`. These flags are also used by the default install and check phase. For setting make flags specific to the build phase, use `buildFlags` (see below).
+
+```nix
+makeFlags = [ "PREFIX=$(out)" ];
+```
+
+::: {.note}
+The flags are quoted in bash, but environment variables can be specified by using the make syntax.
+:::
+
+##### `makeFlagsArray` {#var-stdenv-makeFlagsArray}
+
+A shell array containing additional arguments passed to `make`. You must use this instead of `makeFlags` if the arguments contain spaces, e.g.
+
+```nix
+preBuild = ''
+  makeFlagsArray+=(CFLAGS="-O0 -g" LDFLAGS="-lfoo -lbar")
+'';
+```
+
+Note that shell arrays cannot be passed through environment variables, so you cannot set `makeFlagsArray` in a derivation attribute (because those are passed through environment variables): you have to define them in shell code.
+
+##### `buildFlags` / `buildFlagsArray` {#var-stdenv-buildFlags}
+
+A list of strings passed as additional flags to `make`. Like `makeFlags` and `makeFlagsArray`, but only used by the build phase.
+
+##### `preBuild` {#var-stdenv-preBuild}
+
+Hook executed at the start of the build phase.
+
+##### `postBuild` {#var-stdenv-postBuild}
+
+Hook executed at the end of the build phase.
+
+You can set flags for `make` through the `makeFlags` variable.
+
+Before and after running `make`, the hooks `preBuild` and `postBuild` are called, respectively.
+
+### The check phase {#ssec-check-phase}
+
+The check phase checks whether the package was built correctly by running its test suite. The default `checkPhase` calls `make check`, but only if the `doCheck` variable is enabled.
+
+#### Variables controlling the check phase {#variables-controlling-the-check-phase}
+
+##### `doCheck` {#var-stdenv-doCheck}
+
+Controls whether the check phase is executed. By default it is skipped, but if `doCheck` is set to true, the check phase is usually executed. Thus you should set
+
+```nix
+doCheck = true;
+```
+
+in the derivation to enable checks. The exception is cross compilation. Cross compiled builds never run tests, no matter how `doCheck` is set, as the newly-built program won’t run on the platform used to build it.
+
+##### `makeFlags` / `makeFlagsArray` / `makefile` {#makeflags-makeflagsarray-makefile}
+
+See the [build phase](#var-stdenv-makeFlags) for details.
+
+##### `checkTarget` {#var-stdenv-checkTarget}
+
+The make target that runs the tests. Defaults to `check`.
+
+##### `checkFlags` / `checkFlagsArray` {#var-stdenv-checkFlags}
+
+A list of strings passed as additional flags to `make`. Like `makeFlags` and `makeFlagsArray`, but only used by the check phase.
+
+##### `checkInputs` {#var-stdenv-checkInputs}
+
+A list of dependencies used by the phase. This gets included in `nativeBuildInputs` when `doCheck` is set.
+
+##### `preCheck` {#var-stdenv-preCheck}
+
+Hook executed at the start of the check phase.
+
+##### `postCheck` {#var-stdenv-postCheck}
+
+Hook executed at the end of the check phase.
+
+### The install phase {#ssec-install-phase}
+
+The install phase is responsible for installing the package in the Nix store under `out`. The default `installPhase` creates the directory `$out` and calls `make install`.
+
+#### Variables controlling the install phase {#variables-controlling-the-install-phase}
+
+##### `dontInstall` {#var-stdenv-dontInstall}
+
+Set to true to skip the install phase.
+
+##### `makeFlags` / `makeFlagsArray` / `makefile` {#makeflags-makeflagsarray-makefile-1}
+
+See the [build phase](#var-stdenv-makeFlags) for details.
+
+##### `installTargets` {#var-stdenv-installTargets}
+
+The make targets that perform the installation. Defaults to `install`. Example:
+
+```nix
+installTargets = "install-bin install-doc";
+```
+
+##### `installFlags` / `installFlagsArray` {#var-stdenv-installFlags}
+
+A list of strings passed as additional flags to `make`. Like `makeFlags` and `makeFlagsArray`, but only used by the install phase.
+
+##### `preInstall` {#var-stdenv-preInstall}
+
+Hook executed at the start of the install phase.
+
+##### `postInstall` {#var-stdenv-postInstall}
+
+Hook executed at the end of the install phase.
+
+### The fixup phase {#ssec-fixup-phase}
+
+The fixup phase performs some (Nix-specific) post-processing actions on the files installed under `$out` by the install phase. The default `fixupPhase` does the following:
+
+- It moves the `man/`, `doc/` and `info/` subdirectories of `$out` to `share/`.
+- It strips libraries and executables of debug information.
+- On Linux, it applies the `patchelf` command to ELF executables and libraries to remove unused directories from the `RPATH` in order to prevent unnecessary runtime dependencies.
+- It rewrites the interpreter paths of shell scripts to paths found in `PATH`. E.g., `/usr/bin/perl` will be rewritten to `/nix/store/some-perl/bin/perl` found in `PATH`.
+
+#### Variables controlling the fixup phase {#variables-controlling-the-fixup-phase}
+
+##### `dontFixup` {#var-stdenv-dontFixup}
+
+Set to true to skip the fixup phase.
+
+##### `dontStrip` {#var-stdenv-dontStrip}
+
+If set, libraries and executables are not stripped. By default, they are.
+
+##### `dontStripHost` {#var-stdenv-dontStripHost}
+
+Like `dontStrip`, but only affects the `strip` command targetting the package’s host platform. Useful when supporting cross compilation, but otherwise feel free to ignore.
+
+##### `dontStripTarget` {#var-stdenv-dontStripTarget}
+
+Like `dontStrip`, but only affects the `strip` command targetting the packages’ target platform. Useful when supporting cross compilation, but otherwise feel free to ignore.
+
+##### `dontMoveSbin` {#var-stdenv-dontMoveSbin}
+
+If set, files in `$out/sbin` are not moved to `$out/bin`. By default, they are.
+
+##### `stripAllList` {#var-stdenv-stripAllList}
+
+List of directories to search for libraries and executables from which *all* symbols should be stripped. By default, it’s empty. Stripping all symbols is risky, since it may remove not just debug symbols but also ELF information necessary for normal execution.
+
+##### `stripAllFlags` {#var-stdenv-stripAllFlags}
+
+Flags passed to the `strip` command applied to the files in the directories listed in `stripAllList`. Defaults to `-s` (i.e. `--strip-all`).
+
+##### `stripDebugList` {#var-stdenv-stripDebugList}
+
+List of directories to search for libraries and executables from which only debugging-related symbols should be stripped. It defaults to `lib lib32 lib64 libexec bin sbin`.
+
+##### `stripDebugFlags` {#var-stdenv-stripDebugFlags}
+
+Flags passed to the `strip` command applied to the files in the directories listed in `stripDebugList`. Defaults to `-S` (i.e. `--strip-debug`).
+
+##### `dontPatchELF` {#var-stdenv-dontPatchELF}
+
+If set, the `patchelf` command is not used to remove unnecessary `RPATH` entries. Only applies to Linux.
+
+##### `dontPatchShebangs` {#var-stdenv-dontPatchShebangs}
+
+If set, scripts starting with `#!` do not have their interpreter paths rewritten to paths in the Nix store.
+
+##### `dontPruneLibtoolFiles` {#var-stdenv-dontPruneLibtoolFiles}
+
+If set, libtool `.la` files associated with shared libraries won’t have their `dependency_libs` field cleared.
+
+##### `forceShare` {#var-stdenv-forceShare}
+
+The list of directories that must be moved from `$out` to `$out/share`. Defaults to `man doc info`.
+
+##### `setupHook` {#var-stdenv-setupHook}
+
+A package can export a [setup hook](#ssec-setup-hooks) by setting this variable. The setup hook, if defined, is copied to `$out/nix-support/setup-hook`. Environment variables are then substituted in it using `substituteAll`.
+
+##### `preFixup` {#var-stdenv-preFixup}
+
+Hook executed at the start of the fixup phase.
+
+##### `postFixup` {#var-stdenv-postFixup}
+
+Hook executed at the end of the fixup phase.
+
+##### `separateDebugInfo` {#stdenv-separateDebugInfo}
+
+If set to `true`, the standard environment will enable debug information in C/C++ builds. After installation, the debug information will be separated from the executables and stored in the output named `debug`. (This output is enabled automatically; you don’t need to set the `outputs` attribute explicitly.) To be precise, the debug information is stored in `debug/lib/debug/.build-id/XX/YYYY…`, where \<XXYYYY…\> is the \<build ID\> of the binary — a SHA-1 hash of the contents of the binary. Debuggers like GDB use the build ID to look up the separated debug information.
+
+For example, with GDB, you can add
+
+```
+set debug-file-directory ~/.nix-profile/lib/debug
+```
+
+to `~/.gdbinit`. GDB will then be able to find debug information installed via `nix-env -i`.
+
+### The installCheck phase {#ssec-installCheck-phase}
+
+The installCheck phase checks whether the package was installed correctly by running its test suite against the installed directories. The default `installCheck` calls `make installcheck`.
+
+It is often better to add tests that are not part of the source distribution to `passthru.tests` (see <xref linkend="var-meta-tests"/>). This avoids adding overhead to every build and enables us to run them independently.
+
+#### Variables controlling the installCheck phase {#variables-controlling-the-installcheck-phase}
+
+##### `doInstallCheck` {#var-stdenv-doInstallCheck}
+
+Controls whether the installCheck phase is executed. By default it is skipped, but if `doInstallCheck` is set to true, the installCheck phase is usually executed. Thus you should set
+
+```nix
+doInstallCheck = true;
+```
+
+in the derivation to enable install checks. The exception is cross compilation. Cross compiled builds never run tests, no matter how `doInstallCheck` is set, as the newly-built program won’t run on the platform used to build it.
+
+##### `installCheckTarget` {#var-stdenv-installCheckTarget}
+
+The make target that runs the install tests. Defaults to `installcheck`.
+
+##### `installCheckFlags` / `installCheckFlagsArray` {#var-stdenv-installCheckFlags}
+
+A list of strings passed as additional flags to `make`. Like `makeFlags` and `makeFlagsArray`, but only used by the installCheck phase.
+
+##### `installCheckInputs` {#var-stdenv-installCheckInputs}
+
+A list of dependencies used by the phase. This gets included in `nativeBuildInputs` when `doInstallCheck` is set.
+
+##### `preInstallCheck` {#var-stdenv-preInstallCheck}
+
+Hook executed at the start of the installCheck phase.
+
+##### `postInstallCheck` {#var-stdenv-postInstallCheck}
+
+Hook executed at the end of the installCheck phase.
+
+### The distribution phase {#ssec-distribution-phase}
+
+The distribution phase is intended to produce a source distribution of the package. The default `distPhase` first calls `make dist`, then it copies the resulting source tarballs to `$out/tarballs/`. This phase is only executed if the attribute `doDist` is set.
+
+#### Variables controlling the distribution phase {#variables-controlling-the-distribution-phase}
+
+##### `distTarget` {#var-stdenv-distTarget}
+
+The make target that produces the distribution. Defaults to `dist`.
+
+##### `distFlags` / `distFlagsArray` {#var-stdenv-distFlags}
+
+Additional flags passed to `make`.
+
+##### `tarballs` {#var-stdenv-tarballs}
+
+The names of the source distribution files to be copied to `$out/tarballs/`. It can contain shell wildcards. The default is `*.tar.gz`.
+
+##### `dontCopyDist` {#var-stdenv-dontCopyDist}
+
+If set, no files are copied to `$out/tarballs/`.
+
+##### `preDist` {#var-stdenv-preDist}
+
+Hook executed at the start of the distribution phase.
+
+##### `postDist` {#var-stdenv-postDist}
+
+Hook executed at the end of the distribution phase.
+
+## Shell functions and utilities {#ssec-stdenv-functions}
+
+The standard environment provides a number of useful functions.
+
+### `makeWrapper` \<executable\> \<wrapperfile\> \<args\> {#fun-makeWrapper}
+
+Constructs a wrapper for a program with various possible arguments. It is defined as part of 2 setup-hooks named `makeWrapper` and `makeBinaryWrapper` that implement the same bash functions. Hence, to use it you have to add `makeWrapper` to your `nativeBuildInputs`. Here's an example usage:
+
+```bash
+# adds `FOOBAR=baz` to `$out/bin/foo`’s environment
+makeWrapper $out/bin/foo $wrapperfile --set FOOBAR baz
+
+# prefixes the binary paths of `hello` and `git`
+# Be advised that paths often should be patched in directly
+# (via string replacements or in `configurePhase`).
+makeWrapper $out/bin/foo $wrapperfile --prefix PATH : ${lib.makeBinPath [ hello git ]}
+```
+
+There’s many more kinds of arguments, they are documented in `nixpkgs/pkgs/build-support/setup-hooks/make-wrapper.sh` for the `makeWrapper` implementation and in `nixpkgs/pkgs/build-support/setup-hooks/make-binary-wrapper.sh` for the `makeBinaryWrapper` implementation.
+
+`wrapProgram` is a convenience function you probably want to use most of the time, implemented by both `makeWrapper` and `makeBinaryWrapper`.
+
+Using the `makeBinaryWrapper` implementation is usually preferred, as it creates a tiny _compiled_ wrapper executable, that can be used as a shebang interpreter. This is needed mostly on Darwin, where shebangs cannot point to scripts, [due to a limitation with the `execve`-syscall](https://stackoverflow.com/questions/67100831/macos-shebang-with-absolute-path-not-working). Compiled wrappers generated by `makeBinaryWrapper` can be inspected with `less <path-to-wrapper>` - by scrolling past the binary data you should be able to see the shell command that generated the executable and there see the environment variables that were injected into the wrapper.
+
+### `remove-references-to -t` \<storepath\> [ `-t` \<storepath\> ... ] \<file\> ... {#fun-remove-references-to}
+
+Removes the references of the specified files to the specified store files. This is done without changing the size of the file by replacing the hash by `eeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee`, and should work on compiled executables. This is meant to be used to remove the dependency of the output on inputs that are known to be unnecessary at runtime. Of course, reckless usage will break the patched programs.
+To use this, add `removeReferencesTo` to `nativeBuildInputs`.
+
+As `remove-references-to` is an actual executable and not a shell function, it can be used with `find`.
+Example removing all references to the compiler in the output:
+```nix
+postInstall = ''
+  find "$out" -type f -exec remove-references-to -t ${stdenv.cc} '{}' +
+'';
+```
+
+### `substitute` \<infile\> \<outfile\> \<subs\> {#fun-substitute}
+
+Performs string substitution on the contents of \<infile\>, writing the result to \<outfile\>. The substitutions in \<subs\> are of the following form:
+
+#### `--replace` \<s1\> \<s2\>
+
+Replace every occurrence of the string \<s1\> by \<s2\>.
+
+#### `--subst-var` \<varName\>
+
+Replace every occurrence of `@varName@` by the contents of the environment variable \<varName\>. This is useful for generating files from templates, using `@...@` in the template as placeholders.
+
+#### `--subst-var-by` \<varName\> \<s\>
+
+Replace every occurrence of `@varName@` by the string \<s\>.
+
+Example:
+
+```shell
+substitute ./foo.in ./foo.out \
+    --replace /usr/bin/bar $bar/bin/bar \
+    --replace "a string containing spaces" "some other text" \
+    --subst-var someVar
+```
+
+### `substituteInPlace` \<file\> \<subs\> {#fun-substituteInPlace}
+
+Like `substitute`, but performs the substitutions in place on the file \<file\>.
+
+### `substituteAll` \<infile\> \<outfile\> {#fun-substituteAll}
+
+Replaces every occurrence of `@varName@`, where \<varName\> is any environment variable, in \<infile\>, writing the result to \<outfile\>. For instance, if \<infile\> has the contents
+
+```bash
+#! @bash@/bin/sh
+PATH=@coreutils@/bin
+echo @foo@
+```
+
+and the environment contains `bash=/nix/store/bmwp0q28cf21...-bash-3.2-p39` and `coreutils=/nix/store/68afga4khv0w...-coreutils-6.12`, but does not contain the variable `foo`, then the output will be
+
+```bash
+#! /nix/store/bmwp0q28cf21...-bash-3.2-p39/bin/sh
+PATH=/nix/store/68afga4khv0w...-coreutils-6.12/bin
+echo @foo@
+```
+
+That is, no substitution is performed for undefined variables.
+
+Environment variables that start with an uppercase letter or an underscore are filtered out, to prevent global variables (like `HOME`) or private variables (like `__ETC_PROFILE_DONE`) from accidentally getting substituted. The variables also have to be valid bash "names", as defined in the bash manpage (alphanumeric or `_`, must not start with a number).
+
+### `substituteAllInPlace` \<file\> {#fun-substituteAllInPlace}
+
+Like `substituteAll`, but performs the substitutions in place on the file \<file\>.
+
+### `stripHash` \<path\> {#fun-stripHash}
+
+Strips the directory and hash part of a store path, outputting the name part to `stdout`. For example:
+
+```bash
+# prints coreutils-8.24
+stripHash "/nix/store/9s9r019176g7cvn2nvcw41gsp862y6b4-coreutils-8.24"
+```
+
+If you wish to store the result in another variable, then the following idiom may be useful:
+
+```bash
+name="/nix/store/9s9r019176g7cvn2nvcw41gsp862y6b4-coreutils-8.24"
+someVar=$(stripHash $name)
+```
+
+### `wrapProgram` \<executable\> \<makeWrapperArgs\> {#fun-wrapProgram}
+
+Convenience function for `makeWrapper` that replaces `<\executable\>` with a wrapper that executes the original program. It takes all the same arguments as `makeWrapper`, except for `--inherit-argv0` (used by the `makeBinaryWrapper` implementation) and `--argv0` (used by both `makeWrapper` and `makeBinaryWrapper` wrapper implementations).
+
+If you will apply it multiple times, it will overwrite the wrapper file and you will end up with double wrapping, which should be avoided.
+
+## Package setup hooks {#ssec-setup-hooks}
+
+Nix itself considers a build-time dependency as merely something that should previously be built and accessible at build time—packages themselves are on their own to perform any additional setup. In most cases, that is fine, and the downstream derivation can deal with its own dependencies. But for a few common tasks, that would result in almost every package doing the same sort of setup work—depending not on the package itself, but entirely on which dependencies were used.
+
+In order to alleviate this burden, the setup hook mechanism was written, where any package can include a shell script that \[by convention rather than enforcement by Nix\], any downstream reverse-dependency will source as part of its build process. That allows the downstream dependency to merely specify its dependencies, and lets those dependencies effectively initialize themselves. No boilerplate mirroring the list of dependencies is needed.
+
+The setup hook mechanism is a bit of a sledgehammer though: a powerful feature with a broad and indiscriminate area of effect. The combination of its power and implicit use may be expedient, but isn’t without costs. Nix itself is unchanged, but the spirit of added dependencies being effect-free is violated even if the letter isn’t. For example, if a derivation path is mentioned more than once, Nix itself doesn’t care and simply makes sure the dependency derivation is already built just the same—depending is just needing something to exist, and needing is idempotent. However, a dependency specified twice will have its setup hook run twice, and that could easily change the build environment (though a well-written setup hook will therefore strive to be idempotent so this is in fact not observable). More broadly, setup hooks are anti-modular in that multiple dependencies, whether the same or different, should not interfere and yet their setup hooks may well do so.
+
+The most typical use of the setup hook is actually to add other hooks which are then run (i.e. after all the setup hooks) on each dependency. For example, the C compiler wrapper’s setup hook feeds itself flags for each dependency that contains relevant libraries and headers. This is done by defining a bash function, and appending its name to one of `envBuildBuildHooks`, `envBuildHostHooks`, `envBuildTargetHooks`, `envHostHostHooks`, `envHostTargetHooks`, or `envTargetTargetHooks`. These 6 bash variables correspond to the 6 sorts of dependencies by platform (there’s 12 total but we ignore the propagated/non-propagated axis).
+
+Packages adding a hook should not hard code a specific hook, but rather choose a variable *relative* to how they are included. Returning to the C compiler wrapper example, if the wrapper itself is an `n` dependency, then it only wants to accumulate flags from `n + 1` dependencies, as only those ones match the compiler’s target platform. The `hostOffset` variable is defined with the current dependency’s host offset `targetOffset` with its target offset, before its setup hook is sourced. Additionally, since most environment hooks don’t care about the target platform, that means the setup hook can append to the right bash array by doing something like
+
+```bash
+addEnvHooks "$hostOffset" myBashFunction
+```
+
+The *existence* of setups hooks has long been documented and packages inside Nixpkgs are free to use this mechanism. Other packages, however, should not rely on these mechanisms not changing between Nixpkgs versions. Because of the existing issues with this system, there’s little benefit from mandating it be stable for any period of time.
+
+First, let’s cover some setup hooks that are part of Nixpkgs default stdenv. This means that they are run for every package built using `stdenv.mkDerivation`. Some of these are platform specific, so they may run on Linux but not Darwin or vice-versa.
+
+### `move-docs.sh` {#move-docs.sh}
+
+This setup hook moves any installed documentation to the `/share` subdirectory directory. This includes the man, doc and info directories. This is needed for legacy programs that do not know how to use the `share` subdirectory.
+
+### `compress-man-pages.sh` {#compress-man-pages.sh}
+
+This setup hook compresses any man pages that have been installed. The compression is done using the gzip program. This helps to reduce the installed size of packages.
+
+### `strip.sh` {#strip.sh}
+
+This runs the strip command on installed binaries and libraries. This removes unnecessary information like debug symbols when they are not needed. This also helps to reduce the installed size of packages.
+
+### `patch-shebangs.sh` {#patch-shebangs.sh}
+
+This setup hook patches installed scripts to use the full path to the shebang interpreter. A shebang interpreter is the first commented line of a script telling the operating system which program will run the script (e.g `#!/bin/bash`). In Nix, we want an exact path to that interpreter to be used. This often replaces `/bin/sh` with a path in the Nix store.
+
+### `audit-tmpdir.sh` {#audit-tmpdir.sh}
+
+This verifies that no references are left from the install binaries to the directory used to build those binaries. This ensures that the binaries do not need things outside the Nix store. This is currently supported in Linux only.
+
+### `multiple-outputs.sh` {#multiple-outputs.sh}
+
+This setup hook adds configure flags that tell packages to install files into any one of the proper outputs listed in `outputs`. This behavior can be turned off by setting `setOutputFlags` to false in the derivation environment. See [](#chap-multiple-output) for more information.
+
+### `move-sbin.sh` {#move-sbin.sh}
+
+This setup hook moves any binaries installed in the `sbin/` subdirectory into `bin/`. In addition, a link is provided from `sbin/` to `bin/` for compatibility.
+
+### `move-lib64.sh` {#move-lib64.sh}
+
+This setup hook moves any libraries installed in the `lib64/` subdirectory into `lib/`. In addition, a link is provided from `lib64/` to `lib/` for compatibility.
+
+### `move-systemd-user-units.sh` {#move-systemd-user-units.sh}
+
+This setup hook moves any systemd user units installed in the `lib/` subdirectory into `share/`. In addition, a link is provided from `share/` to `lib/` for compatibility. This is needed for systemd to find user services when installed into the user profile.
+
+### `set-source-date-epoch-to-latest.sh` {#set-source-date-epoch-to-latest.sh}
+
+This sets `SOURCE_DATE_EPOCH` to the modification time of the most recent file.
+
+### Bintools Wrapper {#bintools-wrapper}
+
+The Bintools Wrapper wraps the binary utilities for a bunch of miscellaneous purposes. These are GNU Binutils when targetting Linux, and a mix of cctools and GNU binutils for Darwin. \[The “Bintools” name is supposed to be a compromise between “Binutils” and “cctools” not denoting any specific implementation.\] Specifically, the underlying bintools package, and a C standard library (glibc or Darwin’s libSystem, just for the dynamic loader) are all fed in, and dependency finding, hardening (see below), and purity checks for each are handled by the Bintools Wrapper. Packages typically depend on CC Wrapper, which in turn (at run time) depends on the Bintools Wrapper.
+
+The Bintools Wrapper was only just recently split off from CC Wrapper, so the division of labor is still being worked out. For example, it shouldn’t care about the C standard library, but just take a derivation with the dynamic loader (which happens to be the glibc on linux). Dependency finding however is a task both wrappers will continue to need to share, and probably the most important to understand. It is currently accomplished by collecting directories of host-platform dependencies (i.e. `buildInputs` and `nativeBuildInputs`) in environment variables. The Bintools Wrapper’s setup hook causes any `lib` and `lib64` subdirectories to be added to `NIX_LDFLAGS`. Since the CC Wrapper and the Bintools Wrapper use the same strategy, most of the Bintools Wrapper code is sparsely commented and refers to the CC Wrapper. But the CC Wrapper’s code, by contrast, has quite lengthy comments. The Bintools Wrapper merely cites those, rather than repeating them, to avoid falling out of sync.
+
+A final task of the setup hook is defining a number of standard environment variables to tell build systems which executables fulfill which purpose. They are defined to just be the base name of the tools, under the assumption that the Bintools Wrapper’s binaries will be on the path. Firstly, this helps poorly-written packages, e.g. ones that look for just `gcc` when `CC` isn’t defined yet `clang` is to be used. Secondly, this helps packages not get confused when cross-compiling, in which case multiple Bintools Wrappers may simultaneously be in use. [^footnote-stdenv-per-platform-wrapper] `BUILD_`- and `TARGET_`-prefixed versions of the normal environment variable are defined for additional Bintools Wrappers, properly disambiguating them.
+
+A problem with this final task is that the Bintools Wrapper is honest and defines `LD` as `ld`. Most packages, however, firstly use the C compiler for linking, secondly use `LD` anyways, defining it as the C compiler, and thirdly, only so define `LD` when it is undefined as a fallback. This triple-threat means Bintools Wrapper will break those packages, as LD is already defined as the actual linker which the package won’t override yet doesn’t want to use. The workaround is to define, just for the problematic package, `LD` as the C compiler. A good way to do this would be `preConfigure = "LD=$CC"`.
+
+### CC Wrapper {#cc-wrapper}
+
+The CC Wrapper wraps a C toolchain for a bunch of miscellaneous purposes. Specifically, a C compiler (GCC or Clang), wrapped binary tools, and a C standard library (glibc or Darwin’s libSystem, just for the dynamic loader) are all fed in, and dependency finding, hardening (see below), and purity checks for each are handled by the CC Wrapper. Packages typically depend on the CC Wrapper, which in turn (at run-time) depends on the Bintools Wrapper.
+
+Dependency finding is undoubtedly the main task of the CC Wrapper. This works just like the Bintools Wrapper, except that any `include` subdirectory of any relevant dependency is added to `NIX_CFLAGS_COMPILE`. The setup hook itself contains some lengthy comments describing the exact convoluted mechanism by which this is accomplished.
+
+Similarly, the CC Wrapper follows the Bintools Wrapper in defining standard environment variables with the names of the tools it wraps, for the same reasons described above. Importantly, while it includes a `cc` symlink to the c compiler for portability, the `CC` will be defined using the compiler’s “real name” (i.e. `gcc` or `clang`). This helps lousy build systems that inspect on the name of the compiler rather than run it.
+
+Here are some more packages that provide a setup hook. Since the list of hooks is extensible, this is not an exhaustive list. The mechanism is only to be used as a last resort, so it might cover most uses.
+
+### Perl {#setup-hook-perl}
+
+Adds the `lib/site_perl` subdirectory of each build input to the `PERL5LIB` environment variable. For instance, if `buildInputs` contains Perl, then the `lib/site_perl` subdirectory of each input is added to the `PERL5LIB` environment variable.
+
+### Python {#setup-hook-python}
+
+Adds the `lib/${python.libPrefix}/site-packages` subdirectory of each build input to the `PYTHONPATH` environment variable.
+
+### pkg-config {#setup-hook-pkg-config}
+
+Adds the `lib/pkgconfig` and `share/pkgconfig` subdirectories of each build input to the `PKG_CONFIG_PATH` environment variable.
+
+### Automake {#setup-hook-automake}
+
+Adds the `share/aclocal` subdirectory of each build input to the `ACLOCAL_PATH` environment variable.
+
+### Autoconf {#setup-hook-autoconf}
+
+The `autoreconfHook` derivation adds `autoreconfPhase`, which runs autoreconf, libtoolize and automake, essentially preparing the configure script in autotools-based builds. Most autotools-based packages come with the configure script pre-generated, but this hook is necessary for a few packages and when you need to patch the package’s configure scripts.
+
+### libxml2 {#setup-hook-libxml2}
+
+Adds every file named `catalog.xml` found under the `xml/dtd` and `xml/xsl` subdirectories of each build input to the `XML_CATALOG_FILES` environment variable.
+
+### teTeX / TeX Live {#tetex-tex-live}
+
+Adds the `share/texmf-nix` subdirectory of each build input to the `TEXINPUTS` environment variable.
+
+### Qt 4 {#qt-4}
+
+Sets the `QTDIR` environment variable to Qt’s path.
+
+### gdk-pixbuf {#setup-hook-gdk-pixbuf}
+
+Exports `GDK_PIXBUF_MODULE_FILE` environment variable to the builder. Add librsvg package to `buildInputs` to get svg support. See also the [setup hook description in GNOME platform docs](#ssec-gnome-hooks-gdk-pixbuf).
+
+### GHC {#ghc}
+
+Creates a temporary package database and registers every Haskell build input in it (TODO: how?).
+
+### GNOME platform {#gnome-platform}
+
+Hooks related to GNOME platform and related libraries like GLib, GTK and GStreamer are described in [](#sec-language-gnome).
+
+### autoPatchelfHook {#setup-hook-autopatchelfhook}
+
+This is a special setup hook which helps in packaging proprietary software in that it automatically tries to find missing shared library dependencies of ELF files based on the given `buildInputs` and `nativeBuildInputs`.
+
+You can also specify a `runtimeDependencies` variable which lists dependencies to be unconditionally added to rpath of all executables. This is useful for programs that use dlopen 3 to load libraries at runtime.
+
+In certain situations you may want to run the main command (`autoPatchelf`) of the setup hook on a file or a set of directories instead of unconditionally patching all outputs. This can be done by setting the `dontAutoPatchelf` environment variable to a non-empty value.
+
+By default `autoPatchelf` will fail as soon as any ELF file requires a dependency which cannot be resolved via the given build inputs. In some situations you might prefer to just leave missing dependencies unpatched and continue to patch the rest. This can be achieved by setting the `autoPatchelfIgnoreMissingDeps` environment variable to a non-empty value.
+
+The `autoPatchelf` command also recognizes a `--no-recurse` command line flag, which prevents it from recursing into subdirectories.
+
+### breakpointHook {#breakpointhook}
+
+This hook will make a build pause instead of stopping when a failure happens. It prevents nix from cleaning up the build environment immediately and allows the user to attach to a build environment using the `cntr` command. Upon build error it will print instructions on how to use `cntr`, which can be used to enter the environment for debugging. Installing cntr and running the command will provide shell access to the build sandbox of failed build. At `/var/lib/cntr` the sandboxed filesystem is mounted. All commands and files of the system are still accessible within the shell. To execute commands from the sandbox use the cntr exec subcommand. `cntr` is only supported on Linux-based platforms. To use it first add `cntr` to your `environment.systemPackages` on NixOS or alternatively to the root user on non-NixOS systems. Then in the package that is supposed to be inspected, add `breakpointHook` to `nativeBuildInputs`.
+
+```nix
+nativeBuildInputs = [ breakpointHook ];
+```
+
+When a build failure happens there will be an instruction printed that shows how to attach with `cntr` to the build sandbox.
+
+::: {.note}
+::: {.title}
+Caution with remote builds
+:::
+
+This won’t work with remote builds as the build environment is on a different machine and can’t be accessed by `cntr`. Remote builds can be turned off by setting `--option builders ''` for `nix-build` or `--builders ''` for `nix build`.
+:::
+
+### installShellFiles {#installshellfiles}
+
+This hook helps with installing manpages and shell completion files. It exposes 2 shell functions `installManPage` and `installShellCompletion` that can be used from your `postInstall` hook.
+
+The `installManPage` function takes one or more paths to manpages to install. The manpages must have a section suffix, and may optionally be compressed (with `.gz` suffix). This function will place them into the correct directory.
+
+The `installShellCompletion` function takes one or more paths to shell completion files. By default it will autodetect the shell type from the completion file extension, but you may also specify it by passing one of `--bash`, `--fish`, or `--zsh`. These flags apply to all paths listed after them (up until another shell flag is given). Each path may also have a custom installation name provided by providing a flag `--name NAME` before the path. If this flag is not provided, zsh completions will be renamed automatically such that `foobar.zsh` becomes `_foobar`. A root name may be provided for all paths using the flag `--cmd NAME`; this synthesizes the appropriate name depending on the shell (e.g. `--cmd foo` will synthesize the name `foo.bash` for bash and `_foo` for zsh). The path may also be a fifo or named fd (such as produced by `<(cmd)`), in which case the shell and name must be provided.
+
+```nix
+nativeBuildInputs = [ installShellFiles ];
+postInstall = ''
+  installManPage doc/foobar.1 doc/barfoo.3
+  # explicit behavior
+  installShellCompletion --bash --name foobar.bash share/completions.bash
+  installShellCompletion --fish --name foobar.fish share/completions.fish
+  installShellCompletion --zsh --name _foobar share/completions.zsh
+  # implicit behavior
+  installShellCompletion share/completions/foobar.{bash,fish,zsh}
+  # using named fd
+  installShellCompletion --cmd foobar \
+    --bash <($out/bin/foobar --bash-completion) \
+    --fish <($out/bin/foobar --fish-completion) \
+    --zsh <($out/bin/foobar --zsh-completion)
+'';
+```
+
+### libiconv, libintl {#libiconv-libintl}
+
+A few libraries automatically add to `NIX_LDFLAGS` their library, making their symbols automatically available to the linker. This includes libiconv and libintl (gettext). This is done to provide compatibility between GNU Linux, where libiconv and libintl are bundled in, and other systems where that might not be the case. Sometimes, this behavior is not desired. To disable this behavior, set `dontAddExtraLibs`.
+
+### validatePkgConfig {#validatepkgconfig}
+
+The `validatePkgConfig` hook validates all pkg-config (`.pc`) files in a package. This helps catching some common errors in pkg-config files, such as undefined variables.
+
+### cmake {#cmake}
+
+Overrides the default configure phase to run the CMake command. By default, we use the Make generator of CMake. In addition, dependencies are added automatically to CMAKE_PREFIX_PATH so that packages are correctly detected by CMake. Some additional flags are passed in to give similar behavior to configure-based packages. You can disable this hook’s behavior by setting configurePhase to a custom value, or by setting dontUseCmakeConfigure. cmakeFlags controls flags passed only to CMake. By default, parallel building is enabled as CMake supports parallel building almost everywhere. When Ninja is also in use, CMake will detect that and use the ninja generator.
+
+### xcbuildHook {#xcbuildhook}
+
+Overrides the build and install phases to run the "xcbuild" command. This hook is needed when a project only comes with build files for the XCode build system. You can disable this behavior by setting buildPhase and configurePhase to a custom value. xcbuildFlags controls flags passed only to xcbuild.
+
+### Meson {#meson}
+
+Overrides the configure phase to run meson to generate Ninja files. To run these files, you should accompany Meson with ninja. By default, `enableParallelBuilding` is enabled as Meson supports parallel building almost everywhere.
+
+#### Variables controlling Meson {#variables-controlling-meson}
+
+##### `mesonFlags` {#mesonflags}
+
+Controls the flags passed to meson.
+
+##### `mesonBuildType` {#mesonbuildtype}
+
+Which [`--buildtype`](https://mesonbuild.com/Builtin-options.html#core-options) to pass to Meson. We default to `plain`.
+
+##### `mesonAutoFeatures` {#mesonautofeatures}
+
+What value to set [`-Dauto_features=`](https://mesonbuild.com/Builtin-options.html#core-options) to. We default to `enabled`.
+
+##### `mesonWrapMode` {#mesonwrapmode}
+
+What value to set [`-Dwrap_mode=`](https://mesonbuild.com/Builtin-options.html#core-options) to. We default to `nodownload` as we disallow network access.
+
+##### `dontUseMesonConfigure` {#dontusemesonconfigure}
+
+Disables using Meson’s `configurePhase`.
+
+### ninja {#ninja}
+
+Overrides the build, install, and check phase to run ninja instead of make. You can disable this behavior with the `dontUseNinjaBuild`, `dontUseNinjaInstall`, and `dontUseNinjaCheck`, respectively. Parallel building is enabled by default in Ninja.
+
+### unzip {#unzip}
+
+This setup hook will allow you to unzip .zip files specified in `$src`. There are many similar packages like `unrar`, `undmg`, etc.
+
+### wafHook {#wafhook}
+
+Overrides the configure, build, and install phases. This will run the “waf” script used by many projects. If `wafPath` (default `./waf`) doesn’t exist, it will copy the version of waf available in Nixpkgs. `wafFlags` can be used to pass flags to the waf script.
+
+### scons {#scons}
+
+Overrides the build, install, and check phases. This uses the scons build system as a replacement for make. scons does not provide a configure phase, so everything is managed at build and install time.
+
+## Purity in Nixpkgs {#sec-purity-in-nixpkgs}
+
+*Measures taken to prevent dependencies on packages outside the store, and what you can do to prevent them.*
+
+GCC doesn’t search in locations such as `/usr/include`. In fact, attempts to add such directories through the `-I` flag are filtered out. Likewise, the linker (from GNU binutils) doesn’t search in standard locations such as `/usr/lib`. Programs built on Linux are linked against a GNU C Library that likewise doesn’t search in the default system locations.
+
+## Hardening in Nixpkgs {#sec-hardening-in-nixpkgs}
+
+There are flags available to harden packages at compile or link-time. These can be toggled using the `stdenv.mkDerivation` parameters `hardeningDisable` and `hardeningEnable`.
+
+Both parameters take a list of flags as strings. The special `"all"` flag can be passed to `hardeningDisable` to turn off all hardening. These flags can also be used as environment variables for testing or development purposes.
+
+For more in-depth information on these hardening flags and hardening in general, refer to the [Debian Wiki](https://wiki.debian.org/Hardening), [Ubuntu Wiki](https://wiki.ubuntu.com/Security/Features), [Gentoo Wiki](https://wiki.gentoo.org/wiki/Project:Hardened), and the [Arch Wiki](https://wiki.archlinux.org/title/Security).
+
+### Hardening flags enabled by default {#sec-hardening-flags-enabled-by-default}
+
+The following flags are enabled by default and might require disabling with `hardeningDisable` if the program to package is incompatible.
+
+#### `format` {#format}
+
+Adds the `-Wformat -Wformat-security -Werror=format-security` compiler options. At present, this warns about calls to `printf` and `scanf` functions where the format string is not a string literal and there are no format arguments, as in `printf(foo);`. This may be a security hole if the format string came from untrusted input and contains `%n`.
+
+This needs to be turned off or fixed for errors similar to:
+
+```
+/tmp/nix-build-zynaddsubfx-2.5.2.drv-0/zynaddsubfx-2.5.2/src/UI/guimain.cpp:571:28: error: format not a string literal and no format arguments [-Werror=format-security]
+         printf(help_message);
+                            ^
+cc1plus: some warnings being treated as errors
+```
+
+#### `stackprotector` {#stackprotector}
+
+Adds the `-fstack-protector-strong --param ssp-buffer-size=4` compiler options. This adds safety checks against stack overwrites rendering many potential code injection attacks into aborting situations. In the best case this turns code injection vulnerabilities into denial of service or into non-issues (depending on the application).
+
+This needs to be turned off or fixed for errors similar to:
+
+```
+bin/blib.a(bios_console.o): In function `bios_handle_cup':
+/tmp/nix-build-ipxe-20141124-5cbdc41.drv-0/ipxe-5cbdc41/src/arch/i386/firmware/pcbios/bios_console.c:86: undefined reference to `__stack_chk_fail'
+```
+
+#### `fortify` {#fortify}
+
+Adds the `-O2 -D_FORTIFY_SOURCE=2` compiler options. During code generation the compiler knows a great deal of information about buffer sizes (where possible), and attempts to replace insecure unlimited length buffer function calls with length-limited ones. This is especially useful for old, crufty code. Additionally, format strings in writable memory that contain `%n` are blocked. If an application depends on such a format string, it will need to be worked around.
+
+Additionally, some warnings are enabled which might trigger build failures if compiler warnings are treated as errors in the package build. In this case, set `NIX_CFLAGS_COMPILE` to `-Wno-error=warning-type`.
+
+This needs to be turned off or fixed for errors similar to:
+
+```
+malloc.c:404:15: error: return type is an incomplete type
+malloc.c:410:19: error: storage size of 'ms' isn't known
+
+strdup.h:22:1: error: expected identifier or '(' before '__extension__'
+
+strsep.c:65:23: error: register name not specified for 'delim'
+
+installwatch.c:3751:5: error: conflicting types for '__open_2'
+
+fcntl2.h:50:4: error: call to '__open_missing_mode' declared with attribute error: open with O_CREAT or O_TMPFILE in second argument needs 3 arguments
+```
+
+#### `pic` {#pic}
+
+Adds the `-fPIC` compiler options. This options adds support for position independent code in shared libraries and thus making ASLR possible.
+
+Most notably, the Linux kernel, kernel modules and other code not running in an operating system environment like boot loaders won’t build with PIC enabled. The compiler will is most cases complain that PIC is not supported for a specific build.
+
+This needs to be turned off or fixed for assembler errors similar to:
+
+```
+ccbLfRgg.s: Assembler messages:
+ccbLfRgg.s:33: Error: missing or invalid displacement expression `private_key_len@GOTOFF'
+```
+
+#### `strictoverflow` {#strictoverflow}
+
+Signed integer overflow is undefined behaviour according to the C standard. If it happens, it is an error in the program as it should check for overflow before it can happen, not afterwards. GCC provides built-in functions to perform arithmetic with overflow checking, which are correct and faster than any custom implementation. As a workaround, the option `-fno-strict-overflow` makes gcc behave as if signed integer overflows were defined.
+
+This flag should not trigger any build or runtime errors.
+
+#### `relro` {#relro}
+
+Adds the `-z relro` linker option. During program load, several ELF memory sections need to be written to by the linker, but can be turned read-only before turning over control to the program. This prevents some GOT (and .dtors) overwrite attacks, but at least the part of the GOT used by the dynamic linker (.got.plt) is still vulnerable.
+
+This flag can break dynamic shared object loading. For instance, the module systems of Xorg and OpenCV are incompatible with this flag. In almost all cases the `bindnow` flag must also be disabled and incompatible programs typically fail with similar errors at runtime.
+
+#### `bindnow` {#bindnow}
+
+Adds the `-z bindnow` linker option. During program load, all dynamic symbols are resolved, allowing for the complete GOT to be marked read-only (due to `relro`). This prevents GOT overwrite attacks. For very large applications, this can incur some performance loss during initial load while symbols are resolved, but this shouldn’t be an issue for daemons.
+
+This flag can break dynamic shared object loading. For instance, the module systems of Xorg and PHP are incompatible with this flag. Programs incompatible with this flag often fail at runtime due to missing symbols, like:
+
+```
+intel_drv.so: undefined symbol: vgaHWFreeHWRec
+```
+
+### Hardening flags disabled by default {#sec-hardening-flags-disabled-by-default}
+
+The following flags are disabled by default and should be enabled with `hardeningEnable` for packages that take untrusted input like network services.
+
+#### `pie` {#pie}
+
+This flag is disabled by default for normal `glibc` based NixOS package builds, but enabled by default for `musl` based package builds.
+
+Adds the `-fPIE` compiler and `-pie` linker options. Position Independent Executables are needed to take advantage of Address Space Layout Randomization, supported by modern kernel versions. While ASLR can already be enforced for data areas in the stack and heap (brk and mmap), the code areas must be compiled as position-independent. Shared libraries already do this with the `pic` flag, so they gain ASLR automatically, but binary .text regions need to be build with `pie` to gain ASLR. When this happens, ROP attacks are much harder since there are no static locations to bounce off of during a memory corruption attack.
+
+Static libraries need to be compiled with `-fPIE` so that executables can link them in with the `-pie` linker option.
+If the libraries lack `-fPIE`, you will get the error `recompile with -fPIE`.
+
+[^footnote-stdenv-ignored-build-platform]: The build platform is ignored because it is a mere implementation detail of the package satisfying the dependency: As a general programming principle, dependencies are always *specified* as interfaces, not concrete implementation.
+[^footnote-stdenv-native-dependencies-in-path]: Currently, this means for native builds all dependencies are put on the `PATH`. But in the future that may not be the case for sake of matching cross: the platforms would be assumed to be unique for native and cross builds alike, so only the `depsBuild*` and `nativeBuildInputs` would be added to the `PATH`.
+[^footnote-stdenv-propagated-dependencies]: Nix itself already takes a package’s transitive dependencies into account, but this propagation ensures nixpkgs-specific infrastructure like setup hooks (mentioned above) also are run as if the propagated dependency.
+[^footnote-stdenv-find-inputs-location]: The `findInputs` function, currently residing in `pkgs/stdenv/generic/setup.sh`, implements the propagation logic.
+[^footnote-stdenv-sys-lib-search-path]: It clears the `sys_lib_*search_path` variables in the Libtool script to prevent Libtool from using libraries in `/usr/lib` and such.
+[^footnote-stdenv-build-time-guessing-impurity]: Eventually these will be passed building natively as well, to improve determinism: build-time guessing, as is done today, is a risk of impurity.
+[^footnote-stdenv-per-platform-wrapper]: Each wrapper targets a single platform, so if binaries for multiple platforms are needed, the underlying binaries must be wrapped multiple times. As this is a property of the wrapper itself, the multiple wrappings are needed whether or not the same underlying binaries can target multiple platforms.
diff --git a/doc/style.css b/doc/style.css
new file mode 100644
index 00000000000..474dd32e3fb
--- /dev/null
+++ b/doc/style.css
@@ -0,0 +1,291 @@
+/* Copied from http://bakefile.sourceforge.net/, which appears
+   licensed under the GNU GPL. */
+
+
+/***************************************************************************
+                             Basic headers and text:
+ ***************************************************************************/
+
+body
+{
+    font-family: "Nimbus Sans L", sans-serif;
+    font-size: 1em;
+    background: white;
+    margin: 2em 1em 2em 1em;
+}
+
+h1, h2, h3, h4
+{
+    color: #005aa0;
+}
+
+h1 /* title */
+{
+    font-size: 200%;
+}
+
+h2 /* chapters, appendices, subtitle */
+{
+    font-size: 180%;
+}
+
+div.book
+{
+    text-align: center;
+}
+
+div.book > div
+{
+    /*
+     * based on https://medium.com/@zkareemz/golden-ratio-62b3b6d4282a
+     * we do 70 characters per line to fit code listings better
+     * 70 * (font-size / 1.618)
+     * expression for emacs:
+     * (* 70 (/ 1 1.618))
+     */
+    max-width: 43.2em;
+    text-align: left;
+    margin: auto;
+}
+
+/* Extra space between chapters, appendices. */
+div.chapter > div.titlepage h2, div.appendix > div.titlepage h2
+{
+    margin-top: 1.5em;
+}
+
+div.section > div.titlepage h2 /* sections */
+{
+    font-size: 150%;
+    margin-top: 1.5em;
+}
+
+h3 /* subsections */
+{
+    font-size: 125%;
+}
+
+div.simplesect h2
+{
+    font-size: 110%;
+}
+
+div.appendix h3
+{
+    font-size: 150%;
+    margin-top: 1.5em;
+}
+
+div.refnamediv h2, div.refsynopsisdiv h2, div.refsection h2 /* refentry parts */
+{
+    margin-top: 1.4em;
+    font-size: 125%;
+}
+
+div.refsection h3
+{
+    font-size: 110%;
+}
+
+
+/***************************************************************************
+                               Examples:
+ ***************************************************************************/
+
+div.example
+{
+    border: 1px solid #b0b0b0;
+    padding: 6px 6px;
+    margin-left: 1.5em;
+    margin-right: 1.5em;
+    background: #f4f4f8;
+    border-radius: 0.4em;
+    box-shadow: 0.4em 0.4em 0.5em #e0e0e0;
+}
+
+div.example p.title
+{
+    margin-top: 0em;
+}
+
+div.example pre
+{
+    box-shadow: none;
+}
+
+
+/***************************************************************************
+                            Screen dumps:
+ ***************************************************************************/
+
+pre.screen, pre.programlisting
+{
+    border: 1px solid #b0b0b0;
+    padding: 3px 3px;
+    margin-left: 0.5em;
+    margin-right: 0.5em;
+
+    background: #f4f4f8;
+    font-family: monospace;
+    border-radius: 0.4em;
+    box-shadow: 0.4em 0.4em 0.5em #e0e0e0;
+}
+
+div.example pre.programlisting
+{
+    border: 0px;
+    padding: 0 0;
+    margin: 0 0 0 0;
+}
+
+/***************************************************************************
+                               Notes, warnings etc:
+ ***************************************************************************/
+
+.note, .warning
+{
+    border: 1px solid #b0b0b0;
+    padding: 3px 3px;
+    margin-left: 1.5em;
+    margin-right: 1.5em;
+    margin-bottom: 1em;
+    padding: 0.3em 0.3em 0.3em 0.3em;
+    background: #fffff5;
+    border-radius: 0.4em;
+    box-shadow: 0.4em 0.4em 0.5em #e0e0e0;
+}
+
+div.note, div.warning
+{
+    font-style: italic;
+}
+
+div.note h3, div.warning h3
+{
+    color: red;
+    font-size: 100%;
+    padding-right: 0.5em;
+    display: inline;
+}
+
+div.note p, div.warning p
+{
+    margin-bottom: 0em;
+}
+
+div.note h3 + p, div.warning h3 + p
+{
+    display: inline;
+}
+
+div.note h3
+{
+    color: blue;
+    font-size: 100%;
+}
+
+div.navfooter *
+{
+    font-size: 90%;
+}
+
+
+/***************************************************************************
+                        Links colors and highlighting:
+ ***************************************************************************/
+
+a { text-decoration: none; }
+a:hover { text-decoration: underline; }
+a:link { color: #0048b3; }
+a:visited { color: #002a6a; }
+
+
+/***************************************************************************
+                              Table of contents:
+ ***************************************************************************/
+
+div.toc
+{
+    font-size: 90%;
+}
+
+div.toc dl
+{
+    margin-top: 0em;
+    margin-bottom: 0em;
+}
+
+
+/***************************************************************************
+                               Special elements:
+ ***************************************************************************/
+
+tt, code
+{
+    color: #400000;
+}
+
+.term
+{
+    font-weight: bold;
+
+}
+
+div.variablelist dd p, div.glosslist dd p
+{
+    margin-top: 0em;
+}
+
+div.variablelist dd, div.glosslist dd
+{
+    margin-left: 1.5em;
+}
+
+div.glosslist dt
+{
+    font-style: italic;
+}
+
+.varname
+{
+    color: #400000;
+}
+
+span.command strong
+{
+    font-weight: normal;
+    color: #400000;
+}
+
+div.calloutlist table
+{
+    box-shadow: none;
+}
+
+table
+{
+    border-collapse: collapse;
+    box-shadow: 0.4em 0.4em 0.5em #e0e0e0;
+}
+
+table.simplelist
+{
+    text-align: left;
+    color: #005aa0;
+    border: 0;
+    padding: 5px;
+    background: #fffff5;
+    font-weight: normal;
+    font-style: italic;
+    box-shadow: none;
+    margin-bottom: 1em;
+}
+
+div.navheader table, div.navfooter table {
+    box-shadow: none;
+}
+
+div.affiliation
+{
+    font-style: italic;
+}
diff --git a/doc/using/configuration.chapter.md b/doc/using/configuration.chapter.md
new file mode 100644
index 00000000000..932b24237c0
--- /dev/null
+++ b/doc/using/configuration.chapter.md
@@ -0,0 +1,356 @@
+# Global configuration {#chap-packageconfig}
+
+Nix comes with certain defaults about what packages can and cannot be installed, based on a package's metadata. By default, Nix will prevent installation if any of the following criteria are true:
+
+-   The package is thought to be broken, and has had its `meta.broken` set to `true`.
+
+-   The package isn't intended to run on the given system, as none of its `meta.platforms` match the given system.
+
+-   The package's `meta.license` is set to a license which is considered to be unfree.
+
+-   The package has known security vulnerabilities but has not or can not be updated for some reason, and a list of issues has been entered in to the package's `meta.knownVulnerabilities`.
+
+Note that all this is checked during evaluation already, and the check includes any package that is evaluated. In particular, all build-time dependencies are checked. `nix-env -qa` will (attempt to) hide any packages that would be refused.
+
+Each of these criteria can be altered in the nixpkgs configuration.
+
+The nixpkgs configuration for a NixOS system is set in the `configuration.nix`, as in the following example:
+
+```nix
+{
+  nixpkgs.config = {
+    allowUnfree = true;
+  };
+}
+```
+
+However, this does not allow unfree software for individual users. Their configurations are managed separately.
+
+A user's nixpkgs configuration is stored in a user-specific configuration file located at `~/.config/nixpkgs/config.nix`. For example:
+
+```nix
+{
+  allowUnfree = true;
+}
+```
+
+Note that we are not able to test or build unfree software on Hydra due to policy. Most unfree licenses prohibit us from either executing or distributing the software.
+
+## Installing broken packages {#sec-allow-broken}
+
+There are two ways to try compiling a package which has been marked as broken.
+
+-   For allowing the build of a broken package once, you can use an environment variable for a single invocation of the nix tools:
+
+    ```ShellSession
+    $ export NIXPKGS_ALLOW_BROKEN=1
+    ```
+
+-   For permanently allowing broken packages to be built, you may add `allowBroken = true;` to your user's configuration file, like this:
+
+    ```nix
+    {
+      allowBroken = true;
+    }
+    ```
+
+
+## Installing packages on unsupported systems {#sec-allow-unsupported-system}
+
+There are also two ways to try compiling a package which has been marked as unsupported for the given system.
+
+-   For allowing the build of an unsupported package once, you can use an environment variable for a single invocation of the nix tools:
+
+    ```ShellSession
+    $ export NIXPKGS_ALLOW_UNSUPPORTED_SYSTEM=1
+    ```
+
+-   For permanently allowing unsupported packages to be built, you may add `allowUnsupportedSystem = true;` to your user's configuration file, like this:
+
+    ```nix
+    {
+      allowUnsupportedSystem = true;
+    }
+    ```
+
+The difference between a package being unsupported on some system and being broken is admittedly a bit fuzzy. If a program *ought* to work on a certain platform, but doesn't, the platform should be included in `meta.platforms`, but marked as broken with e.g.  `meta.broken = !hostPlatform.isWindows`. Of course, this begs the question of what \"ought\" means exactly. That is left to the package maintainer.
+
+## Installing unfree packages {#sec-allow-unfree}
+
+There are several ways to tweak how Nix handles a package which has been marked as unfree.
+
+-   To temporarily allow all unfree packages, you can use an environment variable for a single invocation of the nix tools:
+
+    ```ShellSession
+    $ export NIXPKGS_ALLOW_UNFREE=1
+    ```
+
+-   It is possible to permanently allow individual unfree packages, while still blocking unfree packages by default using the `allowUnfreePredicate` configuration option in the user configuration file.
+
+    This option is a function which accepts a package as a parameter, and returns a boolean. The following example configuration accepts a package and always returns false:
+
+    ```nix
+    {
+      allowUnfreePredicate = (pkg: false);
+    }
+    ```
+
+    For a more useful example, try the following. This configuration only allows unfree packages named roon-server and visual studio code:
+
+    ```nix
+    {
+      allowUnfreePredicate = pkg: builtins.elem (lib.getName pkg) [
+        "roon-server"
+        "vscode"
+      ];
+    }
+    ```
+
+-   It is also possible to allow and block licenses that are specifically acceptable or not acceptable, using `allowlistedLicenses` and `blocklistedLicenses`, respectively.
+
+    The following example configuration allowlists the licenses `amd` and `wtfpl`:
+
+    ```nix
+    {
+      allowlistedLicenses = with lib.licenses; [ amd wtfpl ];
+    }
+    ```
+
+    The following example configuration blocklists the `gpl3Only` and `agpl3Only` licenses:
+
+    ```nix
+    {
+      blocklistedLicenses = with lib.licenses; [ agpl3Only gpl3Only ];
+    }
+    ```
+
+    Note that `allowlistedLicenses` only applies to unfree licenses unless `allowUnfree` is enabled. It is not a generic allowlist for all types of licenses. `blocklistedLicenses` applies to all licenses.
+
+A complete list of licenses can be found in the file `lib/licenses.nix` of the nixpkgs tree.
+
+## Installing insecure packages {#sec-allow-insecure}
+
+There are several ways to tweak how Nix handles a package which has been marked as insecure.
+
+-   To temporarily allow all insecure packages, you can use an environment variable for a single invocation of the nix tools:
+
+    ```ShellSession
+    $ export NIXPKGS_ALLOW_INSECURE=1
+    ```
+
+-   It is possible to permanently allow individual insecure packages, while still blocking other insecure packages by default using the `permittedInsecurePackages` configuration option in the user configuration file.
+
+    The following example configuration permits the installation of the hypothetically insecure package `hello`, version `1.2.3`:
+
+    ```nix
+    {
+      permittedInsecurePackages = [
+        "hello-1.2.3"
+      ];
+    }
+    ```
+
+-   It is also possible to create a custom policy around which insecure packages to allow and deny, by overriding the `allowInsecurePredicate` configuration option.
+
+    The `allowInsecurePredicate` option is a function which accepts a package and returns a boolean, much like `allowUnfreePredicate`.
+
+    The following configuration example only allows insecure packages with very short names:
+
+    ```nix
+    {
+      allowInsecurePredicate = pkg: builtins.stringLength (lib.getName pkg) <= 5;
+    }
+    ```
+
+    Note that `permittedInsecurePackages` is only checked if `allowInsecurePredicate` is not specified.
+
+## Modify packages via `packageOverrides` {#sec-modify-via-packageOverrides}
+
+You can define a function called `packageOverrides` in your local `~/.config/nixpkgs/config.nix` to override Nix packages. It must be a function that takes pkgs as an argument and returns a modified set of packages.
+
+```nix
+{
+  packageOverrides = pkgs: rec {
+    foo = pkgs.foo.override { ... };
+  };
+}
+```
+
+## Declarative Package Management {#sec-declarative-package-management}
+
+### Build an environment {#sec-building-environment}
+
+Using `packageOverrides`, it is possible to manage packages declaratively. This means that we can list all of our desired packages within a declarative Nix expression. For example, to have `aspell`, `bc`, `ffmpeg`, `coreutils`, `gdb`, `nixUnstable`, `emscripten`, `jq`, `nox`, and `silver-searcher`, we could use the following in `~/.config/nixpkgs/config.nix`:
+
+```nix
+{
+  packageOverrides = pkgs: with pkgs; {
+    myPackages = pkgs.buildEnv {
+      name = "my-packages";
+      paths = [
+        aspell
+        bc
+        coreutils
+        gdb
+        ffmpeg
+        nixUnstable
+        emscripten
+        jq
+        nox
+        silver-searcher
+      ];
+    };
+  };
+}
+```
+
+To install it into our environment, you can just run `nix-env -iA nixpkgs.myPackages`. If you want to load the packages to be built from a working copy of `nixpkgs` you just run `nix-env -f. -iA myPackages`. To explore what's been installed, just look through `~/.nix-profile/`. You can see that a lot of stuff has been installed. Some of this stuff is useful some of it isn't. Let's tell Nixpkgs to only link the stuff that we want:
+
+```nix
+{
+  packageOverrides = pkgs: with pkgs; {
+    myPackages = pkgs.buildEnv {
+      name = "my-packages";
+      paths = [
+        aspell
+        bc
+        coreutils
+        gdb
+        ffmpeg
+        nixUnstable
+        emscripten
+        jq
+        nox
+        silver-searcher
+      ];
+      pathsToLink = [ "/share" "/bin" ];
+    };
+  };
+}
+```
+
+`pathsToLink` tells Nixpkgs to only link the paths listed which gets rid of the extra stuff in the profile. `/bin` and `/share` are good defaults for a user environment, getting rid of the clutter. If you are running on Nix on MacOS, you may want to add another path as well, `/Applications`, that makes GUI apps available.
+
+### Getting documentation {#sec-getting-documentation}
+
+After building that new environment, look through `~/.nix-profile` to make sure everything is there that we wanted. Discerning readers will note that some files are missing. Look inside `~/.nix-profile/share/man/man1/` to verify this. There are no man pages for any of the Nix tools! This is because some packages like Nix have multiple outputs for things like documentation (see section 4). Let's make Nix install those as well.
+
+```nix
+{
+  packageOverrides = pkgs: with pkgs; {
+    myPackages = pkgs.buildEnv {
+      name = "my-packages";
+      paths = [
+        aspell
+        bc
+        coreutils
+        ffmpeg
+        nixUnstable
+        emscripten
+        jq
+        nox
+        silver-searcher
+      ];
+      pathsToLink = [ "/share/man" "/share/doc" "/bin" ];
+      extraOutputsToInstall = [ "man" "doc" ];
+    };
+  };
+}
+```
+
+This provides us with some useful documentation for using our packages.  However, if we actually want those manpages to be detected by man, we need to set up our environment. This can also be managed within Nix expressions.
+
+```nix
+{
+  packageOverrides = pkgs: with pkgs; rec {
+    myProfile = writeText "my-profile" ''
+      export PATH=$HOME/.nix-profile/bin:/nix/var/nix/profiles/default/bin:/sbin:/bin:/usr/sbin:/usr/bin
+      export MANPATH=$HOME/.nix-profile/share/man:/nix/var/nix/profiles/default/share/man:/usr/share/man
+    '';
+    myPackages = pkgs.buildEnv {
+      name = "my-packages";
+      paths = [
+        (runCommand "profile" {} ''
+          mkdir -p $out/etc/profile.d
+          cp ${myProfile} $out/etc/profile.d/my-profile.sh
+        '')
+        aspell
+        bc
+        coreutils
+        ffmpeg
+        man
+        nixUnstable
+        emscripten
+        jq
+        nox
+        silver-searcher
+      ];
+      pathsToLink = [ "/share/man" "/share/doc" "/bin" "/etc" ];
+      extraOutputsToInstall = [ "man" "doc" ];
+    };
+  };
+}
+```
+
+For this to work fully, you must also have this script sourced when you are logged in. Try adding something like this to your `~/.profile` file:
+
+```ShellSession
+#!/bin/sh
+if [ -d $HOME/.nix-profile/etc/profile.d ]; then
+  for i in $HOME/.nix-profile/etc/profile.d/*.sh; do
+    if [ -r $i ]; then
+      . $i
+    fi
+  done
+fi
+```
+
+Now just run `source $HOME/.profile` and you can starting loading man pages from your environment.
+
+### GNU info setup {#sec-gnu-info-setup}
+
+Configuring GNU info is a little bit trickier than man pages. To work correctly, info needs a database to be generated. This can be done with some small modifications to our environment scripts.
+
+```nix
+{
+  packageOverrides = pkgs: with pkgs; rec {
+    myProfile = writeText "my-profile" ''
+      export PATH=$HOME/.nix-profile/bin:/nix/var/nix/profiles/default/bin:/sbin:/bin:/usr/sbin:/usr/bin
+      export MANPATH=$HOME/.nix-profile/share/man:/nix/var/nix/profiles/default/share/man:/usr/share/man
+      export INFOPATH=$HOME/.nix-profile/share/info:/nix/var/nix/profiles/default/share/info:/usr/share/info
+    '';
+    myPackages = pkgs.buildEnv {
+      name = "my-packages";
+      paths = [
+        (runCommand "profile" {} ''
+          mkdir -p $out/etc/profile.d
+          cp ${myProfile} $out/etc/profile.d/my-profile.sh
+        '')
+        aspell
+        bc
+        coreutils
+        ffmpeg
+        man
+        nixUnstable
+        emscripten
+        jq
+        nox
+        silver-searcher
+        texinfoInteractive
+      ];
+      pathsToLink = [ "/share/man" "/share/doc" "/share/info" "/bin" "/etc" ];
+      extraOutputsToInstall = [ "man" "doc" "info" ];
+      postBuild = ''
+        if [ -x $out/bin/install-info -a -w $out/share/info ]; then
+          shopt -s nullglob
+          for i in $out/share/info/*.info $out/share/info/*.info.gz; do
+              $out/bin/install-info $i $out/share/info/dir
+          done
+        fi
+      '';
+    };
+  };
+}
+```
+
+`postBuild` tells Nixpkgs to run a command after building the environment. In this case, `install-info` adds the installed info pages to `dir` which is GNU info's default root node. Note that `texinfoInteractive` is added to the environment to give the `install-info` command.
diff --git a/doc/using/overlays.chapter.md b/doc/using/overlays.chapter.md
new file mode 100644
index 00000000000..a51aa9ee8fc
--- /dev/null
+++ b/doc/using/overlays.chapter.md
@@ -0,0 +1,167 @@
+# Overlays {#chap-overlays}
+
+This chapter describes how to extend and change Nixpkgs using overlays.  Overlays are used to add layers in the fixed-point used by Nixpkgs to compose the set of all packages.
+
+Nixpkgs can be configured with a list of overlays, which are applied in order. This means that the order of the overlays can be significant if multiple layers override the same package.
+
+## Installing overlays {#sec-overlays-install}
+
+The list of overlays can be set either explicitly in a Nix expression, or through `<nixpkgs-overlays>` or user configuration files.
+
+### Set overlays in NixOS or Nix expressions {#sec-overlays-argument}
+
+On a NixOS system the value of the `nixpkgs.overlays` option, if present, is passed to the system Nixpkgs directly as an argument. Note that this does not affect the overlays for non-NixOS operations (e.g.  `nix-env`), which are [looked up](#sec-overlays-lookup) independently.
+
+The list of overlays can be passed explicitly when importing nixpkgs, for example `import <nixpkgs> { overlays = [ overlay1 overlay2 ]; }`.
+
+NOTE: DO NOT USE THIS in nixpkgs. Further overlays can be added by calling the `pkgs.extend` or `pkgs.appendOverlays`, although it is often preferable to avoid these functions, because they recompute the Nixpkgs fixpoint, which is somewhat expensive to do.
+
+### Install overlays via configuration lookup {#sec-overlays-lookup}
+
+The list of overlays is determined as follows.
+
+1.  First, if an [`overlays` argument](#sec-overlays-argument) to the Nixpkgs function itself is given, then that is used and no path lookup will be performed.
+
+2.  Otherwise, if the Nix path entry `<nixpkgs-overlays>` exists, we look for overlays at that path, as described below.
+
+    See the section on `NIX_PATH` in the Nix manual for more details on how to set a value for `<nixpkgs-overlays>.`
+
+3.  If one of `~/.config/nixpkgs/overlays.nix` and `~/.config/nixpkgs/overlays/` exists, then we look for overlays at that path, as described below. It is an error if both exist.
+
+If we are looking for overlays at a path, then there are two cases:
+
+-   If the path is a file, then the file is imported as a Nix expression and used as the list of overlays.
+
+-   If the path is a directory, then we take the content of the directory, order it lexicographically, and attempt to interpret each as an overlay by:
+
+    -   Importing the file, if it is a `.nix` file.
+
+    -   Importing a top-level `default.nix` file, if it is a directory.
+
+Because overlays that are set in NixOS configuration do not affect non-NixOS operations such as `nix-env`, the `overlays.nix` option provides a convenient way to use the same overlays for a NixOS system configuration and user configuration: the same file can be used as `overlays.nix` and imported as the value of `nixpkgs.overlays`.
+
+## Defining overlays {#sec-overlays-definition}
+
+Overlays are Nix functions which accept two arguments, conventionally called `self` and `super`, and return a set of packages. For example, the following is a valid overlay.
+
+```nix
+self: super:
+
+{
+  boost = super.boost.override {
+    python = self.python3;
+  };
+  rr = super.callPackage ./pkgs/rr {
+    stdenv = self.stdenv_32bit;
+  };
+}
+```
+
+The first argument (`self`) corresponds to the final package set. You should use this set for the dependencies of all packages specified in your overlay. For example, all the dependencies of `rr` in the example above come from `self`, as well as the overridden dependencies used in the `boost` override.
+
+The second argument (`super`) corresponds to the result of the evaluation of the previous stages of Nixpkgs. It does not contain any of the packages added by the current overlay, nor any of the following overlays. This set should be used either to refer to packages you wish to override, or to access functions defined in Nixpkgs. For example, the original recipe of `boost` in the above example, comes from `super`, as well as the `callPackage` function.
+
+The value returned by this function should be a set similar to `pkgs/top-level/all-packages.nix`, containing overridden and/or new packages.
+
+Overlays are similar to other methods for customizing Nixpkgs, in particular the `packageOverrides` attribute described in [](#sec-modify-via-packageOverrides). Indeed, `packageOverrides` acts as an overlay with only the `super` argument. It is therefore appropriate for basic use, but overlays are more powerful and easier to distribute.
+
+## Using overlays to configure alternatives {#sec-overlays-alternatives}
+
+Certain software packages have different implementations of the same interface. Other distributions have functionality to switch between these. For example, Debian provides [DebianAlternatives](https://wiki.debian.org/DebianAlternatives).  Nixpkgs has what we call `alternatives`, which are configured through overlays.
+
+### BLAS/LAPACK {#sec-overlays-alternatives-blas-lapack}
+
+In Nixpkgs, we have multiple implementations of the BLAS/LAPACK numerical linear algebra interfaces. They are:
+
+-   [OpenBLAS](https://www.openblas.net/)
+
+    The Nixpkgs attribute is `openblas` for ILP64 (integer width = 64 bits) and `openblasCompat` for LP64 (integer width = 32 bits).  `openblasCompat` is the default.
+
+-   [LAPACK reference](http://www.netlib.org/lapack/) (also provides BLAS and CBLAS)
+
+    The Nixpkgs attribute is `lapack-reference`.
+
+-   [Intel MKL](https://software.intel.com/en-us/mkl) (only works on the x86_64 architecture, unfree)
+
+    The Nixpkgs attribute is `mkl`.
+
+-   [BLIS](https://github.com/flame/blis)
+
+    BLIS, available through the attribute `blis`, is a framework for linear algebra kernels. In addition, it implements the BLAS interface.
+
+-   [AMD BLIS/LIBFLAME](https://developer.amd.com/amd-aocl/blas-library/) (optimized for modern AMD x86_64 CPUs)
+
+    The AMD fork of the BLIS library, with attribute `amd-blis`, extends BLIS with optimizations for modern AMD CPUs. The changes are usually submitted to the upstream BLIS project after some time. However, AMD BLIS typically provides some performance improvements on AMD Zen CPUs. The complementary AMD LIBFLAME library, with attribute `amd-libflame`, provides a LAPACK implementation.
+
+Introduced in [PR #83888](https://github.com/NixOS/nixpkgs/pull/83888), we are able to override the `blas` and `lapack` packages to use different implementations, through the `blasProvider` and `lapackProvider` argument. This can be used to select a different provider. BLAS providers will have symlinks in `$out/lib/libblas.so.3` and `$out/lib/libcblas.so.3` to their respective BLAS libraries.  Likewise, LAPACK providers will have symlinks in `$out/lib/liblapack.so.3` and `$out/lib/liblapacke.so.3` to their respective LAPACK libraries. For example, Intel MKL is both a BLAS and LAPACK provider. An overlay can be created to use Intel MKL that looks like:
+
+```nix
+self: super:
+
+{
+  blas = super.blas.override {
+    blasProvider = self.mkl;
+  };
+
+  lapack = super.lapack.override {
+    lapackProvider = self.mkl;
+  };
+}
+```
+
+This overlay uses Intel's MKL library for both BLAS and LAPACK interfaces. Note that the same can be accomplished at runtime using `LD_LIBRARY_PATH` of `libblas.so.3` and `liblapack.so.3`. For instance:
+
+```ShellSession
+$ LD_LIBRARY_PATH=$(nix-build -A mkl)/lib${LD_LIBRARY_PATH:+:}$LD_LIBRARY_PATH nix-shell -p octave --run octave
+```
+
+Intel MKL requires an `openmp` implementation when running with multiple processors. By default, `mkl` will use Intel's `iomp` implementation if no other is specified, but this is a runtime-only dependency and binary compatible with the LLVM implementation. To use that one instead, Intel recommends users set it with `LD_PRELOAD`. Note that `mkl` is only available on `x86_64-linux` and `x86_64-darwin`. Moreover, Hydra is not building and distributing pre-compiled binaries using it.
+
+To override `blas` and `lapack` with its reference implementations (i.e. for development purposes), one can use the following overlay:
+
+```nix
+self: super:
+
+{
+  blas = super.blas.override {
+    blasProvider = self.lapack-reference;
+  };
+
+  lapack = super.lapack.override {
+    lapackProvider = self.lapack-reference;
+  };
+}
+```
+
+For BLAS/LAPACK switching to work correctly, all packages must depend on `blas` or `lapack`. This ensures that only one BLAS/LAPACK library is used at one time. There are two versions of BLAS/LAPACK currently in the wild, `LP64` (integer size = 32 bits) and `ILP64` (integer size = 64 bits). The attributes `blas` and `lapack` are `LP64` by default. Their `ILP64` version are provided through the attributes `blas-ilp64` and `lapack-ilp64`. Some software needs special flags or patches to work with `ILP64`. You can check if `ILP64` is used in Nixpkgs with `blas.isILP64` and `lapack.isILP64`. Some software does NOT work with `ILP64`, and derivations need to specify an assertion to prevent this. You can prevent `ILP64` from being used with the following:
+
+```nix
+{ stdenv, blas, lapack, ... }:
+
+assert (!blas.isILP64) && (!lapack.isILP64);
+
+stdenv.mkDerivation {
+  ...
+}
+```
+
+### Switching the MPI implementation {#sec-overlays-alternatives-mpi}
+
+All programs that are built with [MPI](https://en.wikipedia.org/wiki/Message_Passing_Interface) support use the generic attribute `mpi` as an input. At the moment Nixpkgs natively provides two different MPI implementations:
+
+-   [Open MPI](https://www.open-mpi.org/) (default), attribute name
+    `openmpi`
+
+-   [MPICH](https://www.mpich.org/), attribute name `mpich`
+
+-   [MVAPICH](https://mvapich.cse.ohio-state.edu/), attribute name `mvapich`
+
+To provide MPI enabled applications that use `MPICH`, instead of the default `Open MPI`, simply use the following overlay:
+
+```nix
+self: super:
+
+{
+  mpi = self.mpich;
+}
+```
diff --git a/doc/using/overrides.chapter.md b/doc/using/overrides.chapter.md
new file mode 100644
index 00000000000..66e5103531a
--- /dev/null
+++ b/doc/using/overrides.chapter.md
@@ -0,0 +1,104 @@
+# Overriding {#chap-overrides}
+
+Sometimes one wants to override parts of `nixpkgs`, e.g. derivation attributes, the results of derivations.
+
+These functions are used to make changes to packages, returning only single packages. [Overlays](#chap-overlays), on the other hand, can be used to combine the overridden packages across the entire package set of Nixpkgs.
+
+## &lt;pkg&gt;.override {#sec-pkg-override}
+
+The function `override` is usually available for all the derivations in the nixpkgs expression (`pkgs`).
+
+It is used to override the arguments passed to a function.
+
+Example usages:
+
+```nix
+pkgs.foo.override { arg1 = val1; arg2 = val2; ... }
+```
+
+<!-- TODO: move below programlisting to a new section about extending and overlays and reference it -->
+
+```nix
+import pkgs.path { overlays = [ (self: super: {
+  foo = super.foo.override { barSupport = true ; };
+  })]};
+```
+
+```nix
+mypkg = pkgs.callPackage ./mypkg.nix {
+  mydep = pkgs.mydep.override { ... };
+  }
+```
+
+In the first example, `pkgs.foo` is the result of a function call with some default arguments, usually a derivation. Using `pkgs.foo.override` will call the same function with the given new arguments.
+
+## &lt;pkg&gt;.overrideAttrs {#sec-pkg-overrideAttrs}
+
+The function `overrideAttrs` allows overriding the attribute set passed to a `stdenv.mkDerivation` call, producing a new derivation based on the original one. This function is available on all derivations produced by the `stdenv.mkDerivation` function, which is most packages in the nixpkgs expression `pkgs`.
+
+Example usage:
+
+```nix
+helloWithDebug = pkgs.hello.overrideAttrs (oldAttrs: rec {
+  separateDebugInfo = true;
+});
+```
+
+In the above example, the `separateDebugInfo` attribute is overridden to be true, thus building debug info for `helloWithDebug`, while all other attributes will be retained from the original `hello` package.
+
+The argument `oldAttrs` is conventionally used to refer to the attr set originally passed to `stdenv.mkDerivation`.
+
+::: {.note}
+Note that `separateDebugInfo` is processed only by the `stdenv.mkDerivation` function, not the generated, raw Nix derivation. Thus, using `overrideDerivation` will not work in this case, as it overrides only the attributes of the final derivation. It is for this reason that `overrideAttrs` should be preferred in (almost) all cases to `overrideDerivation`, i.e. to allow using `stdenv.mkDerivation` to process input arguments, as well as the fact that it is easier to use (you can use the same attribute names you see in your Nix code, instead of the ones generated (e.g. `buildInputs` vs `nativeBuildInputs`), and it involves less typing).
+:::
+
+## &lt;pkg&gt;.overrideDerivation {#sec-pkg-overrideDerivation}
+
+::: {.warning}
+You should prefer `overrideAttrs` in almost all cases, see its documentation for the reasons why. `overrideDerivation` is not deprecated and will continue to work, but is less nice to use and does not have as many abilities as `overrideAttrs`.
+:::
+
+::: {.warning}
+Do not use this function in Nixpkgs as it evaluates a Derivation before modifying it, which breaks package abstraction and removes error-checking of function arguments. In addition, this evaluation-per-function application incurs a performance penalty, which can become a problem if many overrides are used. It is only intended for ad-hoc customisation, such as in `~/.config/nixpkgs/config.nix`.
+:::
+
+The function `overrideDerivation` creates a new derivation based on an existing one by overriding the original's attributes with the attribute set produced by the specified function. This function is available on all derivations defined using the `makeOverridable` function. Most standard derivation-producing functions, such as `stdenv.mkDerivation`, are defined using this function, which means most packages in the nixpkgs expression, `pkgs`, have this function.
+
+Example usage:
+
+```nix
+mySed = pkgs.gnused.overrideDerivation (oldAttrs: {
+  name = "sed-4.2.2-pre";
+  src = fetchurl {
+    url = ftp://alpha.gnu.org/gnu/sed/sed-4.2.2-pre.tar.bz2;
+    sha256 = "11nq06d131y4wmf3drm0yk502d2xc6n5qy82cg88rb9nqd2lj41k";
+  };
+  patches = [];
+});
+```
+
+In the above example, the `name`, `src`, and `patches` of the derivation will be overridden, while all other attributes will be retained from the original derivation.
+
+The argument `oldAttrs` is used to refer to the attribute set of the original derivation.
+
+::: {.note}
+A package's attributes are evaluated *before* being modified by the `overrideDerivation` function. For example, the `name` attribute reference in `url = "mirror://gnu/hello/${name}.tar.gz";` is filled-in *before* the `overrideDerivation` function modifies the attribute set. This means that overriding the `name` attribute, in this example, *will not* change the value of the `url` attribute. Instead, we need to override both the `name` *and* `url` attributes.
+:::
+
+## lib.makeOverridable {#sec-lib-makeOverridable}
+
+The function `lib.makeOverridable` is used to make the result of a function easily customizable. This utility only makes sense for functions that accept an argument set and return an attribute set.
+
+Example usage:
+
+```nix
+f = { a, b }: { result = a+b; };
+c = lib.makeOverridable f { a = 1; b = 2; };
+```
+
+The variable `c` is the value of the `f` function applied with some default arguments. Hence the value of `c.result` is `3`, in this example.
+
+The variable `c` however also has some additional functions, like
+[c.override](#sec-pkg-override) which can be used to override the
+default arguments. In this example the value of
+`(c.override { a = 4; }).result` is 6.