1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
|
<chapter xmlns="http://docbook.org/ns/docbook"
xmlns:xlink="http://www.w3.org/1999/xlink"
xml:id="chap-quick-start">
<title>Quick Start to Adding a Package</title>
<para>
To add a package to Nixpkgs:
<orderedlist>
<listitem>
<para>
Checkout the Nixpkgs source tree:
<screen>
<prompt>$ </prompt>git clone https://github.com/NixOS/nixpkgs
<prompt>$ </prompt>cd nixpkgs</screen>
</para>
</listitem>
<listitem>
<para>
Find a good place in the Nixpkgs tree to add the Nix expression for your package. For instance, a library package typically goes into <filename>pkgs/development/libraries/<replaceable>pkgname</replaceable></filename>, while a web browser goes into <filename>pkgs/applications/networking/browsers/<replaceable>pkgname</replaceable></filename>. See <xref linkend="sec-organisation" /> for some hints on the tree organisation. Create a directory for your package, e.g.
<screen>
<prompt>$ </prompt>mkdir pkgs/development/libraries/libfoo</screen>
</para>
</listitem>
<listitem>
<para>
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 <emphasis>function</emphasis> 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 <filename>default.nix</filename>.
<screen>
<prompt>$ </prompt>emacs pkgs/development/libraries/libfoo/default.nix
<prompt>$ </prompt>git add pkgs/development/libraries/libfoo/default.nix</screen>
</para>
<para>
You can have a look at the existing Nix expressions under <filename>pkgs/</filename> to see how it’s done. Here are some good ones:
<itemizedlist>
<listitem>
<para>
GNU Hello: <link
xlink:href="https://github.com/NixOS/nixpkgs/blob/master/pkgs/applications/misc/hello/default.nix"><filename>pkgs/applications/misc/hello/default.nix</filename></link>. Trivial package, which specifies some <varname>meta</varname> attributes which is good practice.
</para>
</listitem>
<listitem>
<para>
GNU cpio: <link
xlink:href="https://github.com/NixOS/nixpkgs/blob/master/pkgs/tools/archivers/cpio/default.nix"><filename>pkgs/tools/archivers/cpio/default.nix</filename></link>. Also a simple package. The generic builder in <varname>stdenv</varname> does everything for you. It has no dependencies beyond <varname>stdenv</varname>.
</para>
</listitem>
<listitem>
<para>
GNU Multiple Precision arithmetic library (GMP): <link
xlink:href="https://github.com/NixOS/nixpkgs/blob/master/pkgs/development/libraries/gmp/5.1.x.nix"><filename>pkgs/development/libraries/gmp/5.1.x.nix</filename></link>. Also done by the generic builder, but has a dependency on <varname>m4</varname>.
</para>
</listitem>
<listitem>
<para>
Pan, a GTK-based newsreader: <link
xlink:href="https://github.com/NixOS/nixpkgs/blob/master/pkgs/applications/networking/newsreaders/pan/default.nix"><filename>pkgs/applications/networking/newsreaders/pan/default.nix</filename></link>. Has an optional dependency on <varname>gtkspell</varname>, which is only built if <varname>spellCheck</varname> is <literal>true</literal>.
</para>
</listitem>
<listitem>
<para>
Apache HTTPD: <link
xlink:href="https://github.com/NixOS/nixpkgs/blob/master/pkgs/servers/http/apache-httpd/2.4.nix"><filename>pkgs/servers/http/apache-httpd/2.4.nix</filename></link>. A bunch of optional features, variable substitutions in the configure flags, a post-install hook, and miscellaneous hackery.
</para>
</listitem>
<listitem>
<para>
Thunderbird: <link
xlink:href="https://github.com/NixOS/nixpkgs/blob/master/pkgs/applications/networking/mailreaders/thunderbird/default.nix"><filename>pkgs/applications/networking/mailreaders/thunderbird/default.nix</filename></link>. Lots of dependencies.
</para>
</listitem>
<listitem>
<para>
JDiskReport, a Java utility: <link
xlink:href="https://github.com/NixOS/nixpkgs/blob/master/pkgs/tools/misc/jdiskreport/default.nix"><filename>pkgs/tools/misc/jdiskreport/default.nix</filename></link>. Nixpkgs doesn’t have a decent <varname>stdenv</varname> for Java yet so this is pretty ad-hoc.
</para>
</listitem>
<listitem>
<para>
XML::Simple, a Perl module: <link
xlink:href="https://github.com/NixOS/nixpkgs/blob/master/pkgs/top-level/perl-packages.nix"><filename>pkgs/top-level/perl-packages.nix</filename></link> (search for the <varname>XMLSimple</varname> attribute). Most Perl modules are so simple to build that they are defined directly in <filename>perl-packages.nix</filename>; no need to make a separate file for them.
</para>
</listitem>
<listitem>
<para>
Adobe Reader: <link
xlink:href="https://github.com/NixOS/nixpkgs/blob/master/pkgs/applications/misc/adobe-reader/default.nix"><filename>pkgs/applications/misc/adobe-reader/default.nix</filename></link>. Shows how binary-only packages can be supported. In particular the <link
xlink:href="https://github.com/NixOS/nixpkgs/blob/master/pkgs/applications/misc/adobe-reader/builder.sh">builder</link> uses <command>patchelf</command> to set the RUNPATH and ELF interpreter of the executables so that the right libraries are found at runtime.
</para>
</listitem>
</itemizedlist>
</para>
<para>
Some notes:
<itemizedlist>
<listitem>
<para>
All <varname linkend="chap-meta">meta</varname> attributes are optional, but it’s still a good idea to provide at least the <varname>description</varname>, <varname>homepage</varname> and <varname
linkend="sec-meta-license">license</varname>.
</para>
</listitem>
<listitem>
<para>
You can use <command>nix-prefetch-url</command> <replaceable>url</replaceable> to get the SHA-256 hash of source distributions. There are similar commands as <command>nix-prefetch-git</command> and <command>nix-prefetch-hg</command> available in <literal>nix-prefetch-scripts</literal> package.
</para>
</listitem>
<listitem>
<para>
A list of schemes for <literal>mirror://</literal> URLs can be found in <link
xlink:href="https://github.com/NixOS/nixpkgs/blob/master/pkgs/build-support/fetchurl/mirrors.nix"><filename>pkgs/build-support/fetchurl/mirrors.nix</filename></link>.
</para>
</listitem>
</itemizedlist>
</para>
<para>
The exact syntax and semantics of the Nix expression language, including the built-in function, are described in the Nix manual in the <link
xlink:href="http://hydra.nixos.org/job/nix/trunk/tarball/latest/download-by-type/doc/manual/#chap-writing-nix-expressions">chapter on writing Nix expressions</link>.
</para>
</listitem>
<listitem>
<para>
Add a call to the function defined in the previous step to <link
xlink:href="https://github.com/NixOS/nixpkgs/blob/master/pkgs/top-level/all-packages.nix"><filename>pkgs/top-level/all-packages.nix</filename></link> with some descriptive name for the variable, e.g. <varname>libfoo</varname>.
<screen>
<prompt>$ </prompt>emacs pkgs/top-level/all-packages.nix</screen>
</para>
<para>
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.
</para>
</listitem>
<listitem>
<para>
To test whether the package builds, run the following command from the root of the nixpkgs source tree:
<screen>
<prompt>$ </prompt>nix-build -A libfoo</screen>
where <varname>libfoo</varname> should be the variable name defined in the previous step. You may want to add the flag <option>-K</option> to keep the temporary build directory in case something fails. If the build succeeds, a symlink <filename>./result</filename> to the package in the Nix store is created.
</para>
</listitem>
<listitem>
<para>
If you want to install the package into your profile (optional), do
<screen>
<prompt>$ </prompt>nix-env -f . -iA libfoo</screen>
</para>
</listitem>
<listitem>
<para>
Optionally commit the new package and open a pull request <link
xlink:href="https://github.com/NixOS/nixpkgs/pulls">to nixpkgs</link>, or use <link
xlink:href="https://discourse.nixos.org/t/about-the-patches-category/477"> the Patches category</link> on Discourse for sending a patch without a GitHub account.
</para>
</listitem>
</orderedlist>
</para>
</chapter>
|