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-<section xmlns="http://docbook.org/ns/docbook"
-         xmlns:xlink="http://www.w3.org/1999/xlink"
-         xmlns:xi="http://www.w3.org/2001/XInclude"
-         version="5.0"
-         xml:id="sec-release-20.09">
- <title>Release 20.09 (“Nightingale”, 2020.09/??)</title>
-
- <section xmlns="http://docbook.org/ns/docbook"
-         xmlns:xlink="http://www.w3.org/1999/xlink"
-         xmlns:xi="http://www.w3.org/2001/XInclude"
-         version="5.0"
-         xml:id="sec-release-20.09-highlights">
-  <title>Highlights</title>
-
-  <para>
-   In addition to numerous new and upgraded packages, this release has the
-   following highlights:
-  </para>
-
-  <itemizedlist>
-   <listitem>
-    <para>
-     Support is planned until the end of April 2021, handing over to 21.03.
-    </para>
-   </listitem>
-   <listitem>
-    <para>GNOME desktop environment was upgraded to 3.36, see its <link xlink:href="https://help.gnome.org/misc/release-notes/3.36/">release notes</link>.</para>
-   </listitem>
-   <listitem>
-    <para>
-    <package>maxx</package> package removed along with <varname>services.xserver.desktopManager.maxx</varname> module.
-    Please migrate to <package>cdesktopenv</package> and <varname>services.xserver.desktopManager.cde</varname> module.
-    </para>
-   </listitem>
-   <listitem>
-    <para>
-     We now distribute a GNOME ISO.
-    </para>
-   </listitem>
-   <listitem>
-    <para>
-     PHP now defaults to PHP 7.4, updated from 7.3.
-    </para>
-   </listitem>
-   <listitem>
-    <para>
-     PHP 7.2 is no longer supported due to upstream not supporting this version for the entire lifecycle of the 20.09 release.
-    </para>
-   </listitem>
-   <listitem>
-    <para>
-     Python 3 now defaults to Python 3.8 instead of 3.7.
-    </para>
-   </listitem>
-   <listitem>
-    <para>
-     Two new options, <link linkend="opt-services.openssh.authorizedKeysCommand">authorizedKeysCommand</link>
-     and <link linkend="opt-services.openssh.authorizedKeysCommandUser">authorizedKeysCommandUser</link>, have
-     been added to the <literal>openssh</literal> module. If you have <literal>AuthorizedKeysCommand</literal>
-     in your <link linkend="opt-services.openssh.extraConfig">services.openssh.extraConfig</link> you should
-     make use of these new options instead.
-    </para>
-   </listitem>
-   <listitem>
-    <para>
-     There is a new module for Podman(<varname>virtualisation.podman</varname>), a drop-in replacement for the Docker command line.
-    </para>
-   </listitem>
-   <listitem>
-    <para>
-     The new <varname>virtualisation.containers</varname> module manages configuration shared by the CRI-O and Podman modules.
-    </para>
-   </listitem>
-   <listitem>
-    <para>
-      Declarative Docker containers are renamed from <varname>docker-containers</varname> to <varname>virtualisation.oci-containers.containers</varname>.
-      This is to make it possible to use <literal>podman</literal> instead of <literal>docker</literal>.
-    </para>
-   </listitem>
-   <listitem>
-    <para>
-      MariaDB has been updated to 10.4, MariaDB Galera to 26.4.
-      Before you upgrade, it would be best to take a backup of your database.
-      For MariaDB Galera Cluster, see <link xlink:href="https://mariadb.com/kb/en/upgrading-from-mariadb-103-to-mariadb-104-with-galera-cluster/">Upgrading
-      from MariaDB 10.3 to MariaDB 10.4 with Galera Cluster</link> instead.
-      Before doing the upgrade read <link xlink:href="https://mariadb.com/kb/en/upgrading-from-mariadb-103-to-mariadb-104/#incompatible-changes-between-103-and-104">Incompatible
-      Changes Between 10.3 and 10.4</link>.
-      After the upgrade you will need to run <literal>mysql_upgrade</literal>.
-      MariaDB 10.4 introduces a number of changes to the authentication process, intended to make things easier and more
-      intuitive. See <link xlink:href="https://mariadb.com/kb/en/authentication-from-mariadb-104/">Authentication from MariaDB 10.4</link>.
-      unix_socket auth plugin does not use a password, and uses the connecting user's UID instead. When a new MariaDB data directory is initialized, two MariaDB users are
-      created and can be used with new unix_socket auth plugin, as well as traditional mysql_native_password plugin: root@localhost and mysql@localhost. To actually use
-      the traditional mysql_native_password plugin method, one must run the following:
-<programlisting>
-services.mysql.initialScript = pkgs.writeText "mariadb-init.sql" ''
-  ALTER USER root@localhost IDENTIFIED VIA mysql_native_password USING PASSWORD("verysecret");
-'';
-</programlisting>
-      When MariaDB data directory is just upgraded (not initialized), the users are not created or modified.
-    </para>
-   </listitem>
-   <listitem>
-    <para>
-      MySQL server is now started with additional systemd sandbox/hardening options for better security. The PrivateTmp, ProtectHome, and ProtectSystem options
-      may be problematic when MySQL is attempting to read from or write to your filesystem anywhere outside of its own state directory, for example when
-      calling <literal>LOAD DATA INFILE or SELECT * INTO OUTFILE</literal>. In this scenario a variant of the following may be required:
-        - allow MySQL to read from /home and /tmp directories when using <literal>LOAD DATA INFILE</literal>
-<programlisting>
-systemd.services.mysql.serviceConfig.ProtectHome = lib.mkForce "read-only";
-</programlisting>
-        - allow MySQL to write to custom folder <literal>/var/data</literal> when using <literal>SELECT * INTO OUTFILE</literal>, assuming the mysql user has write
-          access to <literal>/var/data</literal>
-<programlisting>
-systemd.services.mysql.serviceConfig.ReadWritePaths = [ "/var/data" ];
-</programlisting>
-    </para>
-    <para>
-      The MySQL service no longer runs its <literal>systemd</literal> service startup script as <literal>root</literal> anymore. A dedicated non <literal>root</literal>
-      super user account is required for operation. This means users with an existing MySQL or MariaDB database server are required to run the following SQL statements
-      as a super admin user before upgrading:
-<programlisting>
-CREATE USER IF NOT EXISTS 'mysql'@'localhost' identified with unix_socket;
-GRANT ALL PRIVILEGES ON *.* TO 'mysql'@'localhost' WITH GRANT OPTION;
-</programlisting>
-      If you use MySQL instead of MariaDB please replace <literal>unix_socket</literal> with <literal>auth_socket</literal>. If you have changed the value of <xref linkend="opt-services.mysql.user"/>
-      from the default of <literal>mysql</literal> to a different user please change <literal>'mysql'@'localhost'</literal> to the corresponding user instead.
-    </para>
-   </listitem>
-   <listitem>
-    <para>
-      The new option <link linkend="opt-documentation.man.generateCaches">documentation.man.generateCaches</link>
-      has been added to automatically generate the <literal>man-db</literal> caches, which are needed by utilities
-      like <command>whatis</command> and <command>apropos</command>. The caches are generated during the build of
-      the NixOS configuration: since this can be expensive when a large number of packages are installed, the
-      feature is disabled by default.
-    </para>
-   </listitem>
-   <listitem>
-    <para>
-     <varname>services.postfix.sslCACert</varname> was replaced by <varname>services.postfix.tlsTrustedAuthorities</varname> which now defaults to system certificate authorities.
-    </para>
-   </listitem>
-   <listitem>
-    <para>
-      Subordinate GID and UID mappings are now set up automatically for all normal users.
-      This will make container tools like Podman work as non-root users out of the box.
-    </para>
-   </listitem>
-   <listitem>
-     <para>
-       The various documented workarounds to use steam have been converted to a module. <varname>programs.steam.enable</varname> enables steam, controller support and the workarounds.
-     </para>
-   </listitem>
-   <listitem>
-     <para>
-       Support for built-in LCDs in various pieces of Logitech hardware (keyboards and USB speakers). <varname>hardware.logitech.lcd.enable</varname> enables support for all hardware supported by the g15daemon project.
-     </para>
-   </listitem>
-   <listitem>
-    <para>
-      Zabbix now defaults to 5.0, updated from 4.4. Please carefully read through
-      <link xlink:href="https://www.zabbix.com/documentation/current/manual/installation/upgrade/sources">the upgrade guide</link>
-      and apply any changes required. Be sure to take special note of the section on
-      <link xlink:href="https://www.zabbix.com/documentation/current/manual/installation/upgrade_notes_500#enabling_extended_range_of_numeric_float_values">enabling extended range of numeric (float) values</link>
-      as you will need to apply this database migration manually.
-    </para>
-    <para>
-      If you are using Zabbix Server with a MySQL or MariaDB database you should note that using a character set of <literal>utf8</literal> and a collate of <literal>utf8_bin</literal> has become mandatory with
-      this release. See the upstream <link xlink:href="https://support.zabbix.com/browse/ZBX-17357">issue</link> for further discussion. Before upgrading you should check the character set and collation used by
-      your database and ensure they are correct:
-<programlisting>
-  SELECT
-    default_character_set_name,
-    default_collation_name
-  FROM
-    information_schema.schemata
-  WHERE
-    schema_name = 'zabbix';
-</programlisting>
-      If these values are not correct you should take a backup of your database and convert the character set and collation as required. Here is an
-      <link xlink:href="https://www.zabbix.com/forum/zabbix-help/396573-reinstall-after-upgrade?p=396891#post396891">example</link> of how to do so, taken from
-      the Zabbix forums:
-<programlisting>
-  ALTER DATABASE `zabbix` DEFAULT CHARACTER SET utf8 COLLATE utf8_bin;
-
-  -- the following will produce a list of SQL commands you should subsequently execute
-  SELECT CONCAT("ALTER TABLE ", TABLE_NAME," CONVERT TO CHARACTER SET utf8 COLLATE utf8_bin;") AS ExecuteTheString
-  FROM information_schema.`COLUMNS`
-  WHERE table_schema = "zabbix" AND COLLATION_NAME = "utf8_general_ci";
-</programlisting>
-    </para>
-   </listitem>
-   <listitem>
-     <para>
-      The NixOS module system now supports freeform modules as a mix between <literal>types.attrsOf</literal> and <literal>types.submodule</literal>. These allow you to explicitly declare a subset of options while still permitting definitions without an associated option. See <xref linkend='sec-freeform-modules'/> for how to use them.
-     </para>
-   </listitem>
-   <listitem>
-     <para>
-       The GRUB module gained support for basic password protection, which
-       allows to restrict non-default entries in the boot menu to one or more
-       users. The users and passwords are defined via the option
-       <option>boot.loader.grub.users</option>.
-       Note: Password support is only avaiable in GRUB version 2.
-     </para>
-   </listitem>
-  </itemizedlist>
- </section>
-
- <section xmlns="http://docbook.org/ns/docbook"
-         xmlns:xlink="http://www.w3.org/1999/xlink"
-         xmlns:xi="http://www.w3.org/2001/XInclude"
-         version="5.0"
-         xml:id="sec-release-20.09-new-services">
-  <title>New Services</title>
-
-  <para>
-   The following new services were added since the last release:
-  </para>
-
-  <itemizedlist>
-   <listitem>
-    <para>
-      There is a new <xref linkend="opt-security.doas.enable"/> module that provides <command>doas</command>, a lighter alternative to <command>sudo</command> with many of the same features.
-    </para>
-   </listitem>
-  </itemizedlist>
-
- </section>
-
- <section xmlns="http://docbook.org/ns/docbook"
-         xmlns:xlink="http://www.w3.org/1999/xlink"
-         xmlns:xi="http://www.w3.org/2001/XInclude"
-         version="5.0"
-         xml:id="sec-release-20.09-incompatibilities">
-  <title>Backward Incompatibilities</title>
-
-  <para>
-   When upgrading from a previous release, please be aware of the following
-   incompatible changes:
-  </para>
-
-  <itemizedlist>
-   <listitem>
-    <para>
-     <literal>buildGoModule</literal> now internally creates a vendor directory
-     in the source tree for downloaded modules instead of using go's <link
-     xlink:href="https://golang.org/cmd/go/#hdr-Module_proxy_protocol">module
-     proxy protocol</link>. This storage format is simpler and therefore less
-     likely to break with future versions of go. As a result
-     <literal>buildGoModule</literal> switched from
-     <literal>modSha256</literal> to the <literal>vendorSha256</literal>
-     attribute to pin fetched version data.
-    </para>
-   </listitem>
-   <listitem>
-    <para>
-     Grafana is now built without support for phantomjs by default. Phantomjs support has been
-     <link xlink:href="https://grafana.com/docs/grafana/latest/guides/whats-new-in-v6-4/">deprecated in Grafana</link>
-     and the <package>phantomjs</package> project is
-     <link xlink:href="https://github.com/ariya/phantomjs/issues/15344#issue-302015362">currently unmaintained</link>.
-     It can still be enabled by providing <literal>phantomJsSupport = true</literal> to the package instantiation:
-<programlisting>{
-  services.grafana.package = pkgs.grafana.overrideAttrs (oldAttrs: rec {
-    phantomJsSupport = false;
-  });
-}</programlisting>
-    </para>
-   </listitem>
-   <listitem>
-    <para>
-      The <link linkend="opt-services.supybot.enable">supybot</link> module now uses <literal>/var/lib/supybot</literal>
-      as its default <link linkend="opt-services.supybot.stateDir">stateDir</link> path if <literal>stateVersion</literal>
-      is 20.09 or higher. It also enables a number of
-      <link xlink:href="https://www.freedesktop.org/software/systemd/man/systemd.exec.html#Sandboxing">systemd sandboxing options</link>
-      which may possibly interfere with some plugins. If this is the case you can disable the options through attributes in
-      <option>systemd.services.supybot.serviceConfig</option>.
-    </para>
-   </listitem>
-   <listitem>
-    <para>
-      The <literal>security.duosec.skey</literal> option, which stored a secret in the
-      nix store, has been replaced by a new
-      <link linkend="opt-security.duosec.secretKeyFile">security.duosec.secretKeyFile</link>
-      option for better security.
-    </para>
-    <para>
-      <literal>security.duosec.ikey</literal> has been renamed to
-      <link linkend="opt-security.duosec.integrationKey">security.duosec.integrationKey</link>.
-    </para>
-   </listitem>
-   <listitem>
-    <para>
-      <literal>vmware</literal> has been removed from the <literal>services.x11.videoDrivers</literal> defaults.
-      For VMWare guests set <literal>virtualisation.vmware.guest.enable</literal> to <literal>true</literal> which will include the appropriate drivers.
-    </para>
-   </listitem>
-   <listitem>
-    <para>
-     The initrd SSH support now uses OpenSSH rather than Dropbear to
-     allow the use of Ed25519 keys and other OpenSSH-specific
-     functionality. Host keys must now be in the OpenSSH format, and at
-     least one pre-generated key must be specified.
-    </para>
-    <para>
-     If you used the <option>boot.initrd.network.ssh.host*Key</option>
-     options, you'll get an error explaining how to convert your host
-     keys and migrate to the new
-     <option>boot.initrd.network.ssh.hostKeys</option> option.
-     Otherwise, if you don't have any host keys set, you'll need to
-     generate some; see the <option>hostKeys</option> option
-     documentation for instructions.
-    </para>
-   </listitem>
-   <listitem>
-     <para>
-       Since this release there's an easy way to customize your PHP
-       install to get a much smaller base PHP with only wanted
-       extensions enabled. See the following snippet installing a
-       smaller PHP with the extensions <literal>imagick</literal>,
-       <literal>opcache</literal>, <literal>pdo</literal> and
-       <literal>pdo_mysql</literal> loaded:
-
-       <programlisting>
-environment.systemPackages = [
-  (pkgs.php.withExtensions
-    ({ all, ... }: with all; [
-      imagick
-      opcache
-      pdo
-      pdo_mysql
-    ])
-  )
-];</programlisting>
-
-       The default <literal>php</literal> attribute hasn't lost any
-       extensions. The <literal>opcache</literal> extension has been
-       added.
-
-       All upstream PHP extensions are available under <package><![CDATA[php.extensions.<name?>]]></package>.
-     </para>
-     <para>
-       All PHP <literal>config</literal> flags have been removed for
-       the following reasons:
-
-       <itemizedlist>
-         <listitem>
-           <para>
-             The updated <literal>php</literal> attribute is now easily
-             customizable to your liking by using
-             <literal>php.withExtensions</literal> or
-             <literal>php.buildEnv</literal> instead of writing config files
-             or changing configure flags.
-           </para>
-         </listitem>
-         <listitem>
-           <para>
-             The remaining configuration flags can now be set directly on
-             the <literal>php</literal> attribute. For example, instead of
-
-             <programlisting>
-php.override {
-  config.php.embed = true;
-  config.php.apxs2 = false;
-}
-             </programlisting>
-
-             you should now write
-
-             <programlisting>
-php.override {
-  embedSupport = true;
-  apxs2Support = false;
-}
-             </programlisting>
-           </para>
-         </listitem>
-       </itemizedlist>
-
-     </para>
-   </listitem>
-   <listitem>
-     <para>
-      Gollum received a major update to version 5.x and you may have to change
-      some links in your wiki when migrating from gollum 4.x. More information
-      can be found
-      <link xlink:href="https://github.com/gollum/gollum/wiki/5.0-release-notes#migrating-your-wiki">here</link>.
-     </para>
-   </listitem>
-   <listitem>
-     <para>
-       Deluge 2.x was added and is used as default for new NixOS
-       installations where stateVersion is >= 20.09. If you are upgrading from a previous
-       NixOS version, you can set <literal>service.deluge.package = pkgs.deluge-2_x</literal>
-       to upgrade to Deluge 2.x and migrate the state to the new format.
-       Be aware that backwards state migrations are not supported by Deluge.
-     </para>
-   </listitem>
-   <listitem>
-     <para>
-       Add option <literal>services.nginx.enableSandbox</literal> to starting Nginx web server with additional sandbox/hardening options.
-       By default, write access to <literal>services.nginx.stateDir</literal> is allowed. To allow writing to other folders,
-       use <literal>systemd.services.nginx.serviceConfig.ReadWritePaths</literal>
-       <programlisting>
-systemd.services.nginx.serviceConfig.ReadWritePaths = [ "/var/www" ];
-       </programlisting>
-     </para>
-   </listitem>
-   <listitem>
-    <para>
-      The NixOS options <literal>nesting.clone</literal> and
-      <literal>nesting.children</literal> have been deleted, and
-      replaced with named <xref linkend="opt-specialisation"/>
-      configurations.
-    </para>
-
-    <para>
-      Replace a <literal>nesting.clone</literal> entry with:
-
-<programlisting>{
-<link xlink:href="#opt-specialisation">specialisation.example-sub-configuration</link> = {
-  <link xlink:href="#opt-specialisation._name_.configuration">configuration</link> = {
-    ...
-  };
-};</programlisting>
-
-    </para>
-    <para>
-      Replace a <literal>nesting.children</literal> entry with:
-
-<programlisting>{
-<link xlink:href="#opt-specialisation">specialisation.example-sub-configuration</link> = {
-  <link xlink:href="#opt-specialisation._name_.inheritParentConfig">inheritParentConfig</link> = false;
-  <link xlink:href="#opt-specialisation._name_.configuration">configuration</link> = {
-    ...
-  };
-};</programlisting>
-    </para>
-
-    <para>
-     To switch to a specialised configuration at runtime you need to
-     run:
-<programlisting>
-# sudo /run/current-system/specialisation/example-sub-configuration/bin/switch-to-configuration test
-</programlisting>
-     Before you would have used:
-<programlisting>
-# sudo /run/current-system/fine-tune/child-1/bin/switch-to-configuration test
-</programlisting>
-    </para>
-   </listitem>
-   <listitem>
-    <para>
-      The Nginx log directory has been moved to <literal>/var/log/nginx</literal>, the cache directory
-      to <literal>/var/cache/nginx</literal>. The option <literal>services.nginx.stateDir</literal> has
-      been removed.
-    </para>
-   </listitem>
-   <listitem>
-    <para>
-     The httpd web server previously started its main process as root
-     privileged, then ran worker processes as a less privileged identity user.
-     This was changed to start all of httpd as a less privileged user (defined by
-     <xref linkend="opt-services.httpd.user"/> and
-     <xref linkend="opt-services.httpd.group"/>). As a consequence, all files that
-     are needed for httpd to run (included configuration fragments, SSL
-     certificates and keys, etc.) must now be readable by this less privileged
-     user/group.
-    </para>
-    <para>
-     The default value for <xref linkend="opt-services.httpd.mpm"/>
-     has been changed from <literal>prefork</literal> to <literal>event</literal>. Along with
-     this change the default value for
-     <link linkend="opt-services.httpd.virtualHosts">services.httpd.virtualHosts.&lt;name&gt;.http2</link>
-     has been set to <literal>true</literal>.
-    </para>
-   </listitem>
-   <listitem>
-    <para>
-      The <literal>systemd-networkd</literal> option
-      <literal>systemd.network.networks.&lt;name&gt;.dhcp.CriticalConnection</literal>
-      has been removed following upstream systemd's deprecation of the same. It is recommended to use
-      <literal>systemd.network.networks.&lt;name&gt;.networkConfig.KeepConfiguration</literal> instead.
-      See <citerefentry><refentrytitle>systemd.network</refentrytitle>
-      <manvolnum>5</manvolnum></citerefentry> for details.
-    </para>
-   </listitem>
-   <listitem>
-    <para>
-     The <literal>systemd-networkd</literal> option
-     <literal>systemd.network.networks._name_.dhcpConfig</literal>
-     has been renamed to
-     <xref linkend="opt-systemd.network.networks._name_.dhcpV4Config"/>
-     following upstream systemd's documentation change.
-     See <citerefentry><refentrytitle>systemd.network</refentrytitle>
-     <manvolnum>5</manvolnum></citerefentry> for details.
-    </para>
-   </listitem>
-   <listitem>
-    <para>
-      In the <literal>picom</literal> module, several options that accepted
-      floating point numbers encoded as strings (for example
-      <xref linkend="opt-services.picom.activeOpacity"/>) have been changed
-      to the (relatively) new native <literal>float</literal> type. To migrate
-      your configuration simply remove the quotes around the numbers.
-    </para>
-   </listitem>
-   <listitem>
-    <para>
-      When using <literal>buildBazelPackage</literal> from Nixpkgs,
-      <literal>flat</literal> hash mode is now used for dependencies
-      instead of <literal>recursive</literal>. This is to better allow
-      using hashed mirrors where needed. As a result, these hashes
-      will have changed.
-    </para>
-   </listitem>
-   <listitem>
-    <para>
-      The rkt module has been removed, it was archived by upstream.
-    </para>
-   </listitem>
-   <listitem>
-    <para>
-      The <link xlink:href="https://bazaar.canonical.com">Bazaar</link> VCS is
-      unmaintained and, as consequence of the Python 2 EOL, the packages
-      <literal>bazaar</literal> and <literal>bazaarTools</literal> were
-      removed. Breezy, the backward compatible fork of Bazaar (see the
-      <link xlink:href="https://www.jelmer.uk/breezy-intro.html">announcement</link>),
-      was packaged as <literal>breezy</literal> and can be used instead.
-    </para>
-    <para>
-      Regarding Nixpkgs, <literal>fetchbzr</literal>,
-      <literal>nix-prefetch-bzr</literal> and Bazaar support in Hydra will
-      continue to work through Breezy.
-    </para>
-   </listitem>
-   <listitem>
-     <para>
-       In addition to the hostname, the fully qualified domain name (FQDN),
-       which consists of <literal>${cfg.hostName}</literal> and
-       <literal>${cfg.domain}</literal> is now added to
-       <literal>/etc/hosts</literal>, to allow local FQDN resolution, as used by the
-       <literal>hostname --fqdn</literal> command and other applications that
-       try to determine the FQDN. These new entries take precedence over entries
-       from the DNS which could cause regressions in some very specific setups.
-       Additionally the hostname is now resolved to <literal>127.0.0.2</literal>
-       instead of <literal>127.0.1.1</literal> to be consistent with what
-       <literal>nss-myhostname</literal> (from systemd) returns.
-       The old behaviour can e.g. be restored by using
-       <literal>networking.hosts = lib.mkForce { "127.0.1.1" = [ config.networking.hostName ]; };</literal>.
-     </para>
-   </listitem>
-   <listitem>
-     <para>
-       The hostname (<literal>networking.hostName</literal>) must now be a valid
-       DNS label (see RFC 1035) and as such must not contain the domain part.
-       This means that the hostname must start with a letter, end with a letter
-       or digit, and have as interior characters only letters, digits, and
-       hyphen. The maximum length is 63 characters. Additionally it is
-       recommended to only use lower-case characters.
-     </para>
-   </listitem>
-   <listitem>
-    <para>
-     The GRUB specific option <option>boot.loader.grub.extraInitrd</option>
-     has been replaced with the generic option
-     <option>boot.initrd.secrets</option>. This option creates a secondary
-     initrd from the specified files, rather than using a manually created
-     initrd file.
-
-     Due to an existing bug with <option>boot.loader.grub.extraInitrd</option>,
-     it is not possible to directly boot an older generation that used that
-     option. It is still possible to rollback to that generation if the required
-     initrd file has not been deleted.
-    </para>
-   </listitem>
-   <listitem>
-    <para>
-     The <link xlink:href="https://github.com/okTurtles/dnschain">DNSChain</link>
-     package and NixOS module have been removed from Nixpkgs as the software is
-     unmaintained and can't be built. For more information see issue
-     <link xlink:href="https://github.com/NixOS/nixpkgs/issues/89205">#89205</link>.
-    </para>
-   </listitem>
-   <listitem>
-    <para>
-     In the <literal>resilio</literal> module, <xref linkend="opt-services.resilio.httpListenAddr"/> has been changed to listen to <literal>[::1]</literal> instead of <literal>0.0.0.0</literal>.
-     </para>
-   </listitem>
-   <listitem>
-    <para>
-     Users of <link xlink:href="http://openafs.org">OpenAFS 1.6</link> must
-     upgrade their services to OpenAFS 1.8! In this release, the OpenAFS package
-     version 1.6.24 is marked broken but can be used during transition to
-     OpenAFS 1.8.x. Use the options
-     <option>services.openafsClient.packages.module</option>,
-     <option>services.openafsClient.packages.programs</option> and
-     <option>services.openafsServer.package</option> to select a different
-     OpenAFS package. OpenAFS 1.6 will be removed in the next release. The
-     package <literal>openafs</literal> and the service options will then
-     silently point to the OpenAFS 1.8 release.
-    </para>
-    <para>
-     See also the OpenAFS <link
-     xlink:href="http://docs.openafs.org/AdminGuide/index.html">Administrator
-     Guide</link> for instructions. Beware of the following when updating
-     servers:
-     <itemizedlist>
-      <listitem>
-       <para>
-       The storage format of the server key has changed and the key must be converted before running the new release.
-       </para>
-      </listitem>
-      <listitem>
-       <para>
-       When updating multiple database servers, turn off the database servers
-       from the highest IP down to the lowest with resting periods in
-       between. Start up in reverse order. Do not concurrently run database
-       servers working with different OpenAFS releases!
-       </para>
-      </listitem>
-      <listitem>
-       <para>
-       Update servers first, then clients.
-       </para>
-      </listitem>
-     </itemizedlist>
-    </para>
-   </listitem>
-   <listitem>
-    <para>
-     Radicale's default package has changed from 2.x to 3.x. An upgrade
-     checklist can be found
-     <link xlink:href="https://github.com/Kozea/Radicale/blob/3.0.x/NEWS.md#upgrade-checklist">here</link>.
-     You can use the newer version in the NixOS service by setting the
-     <literal>package</literal> to <literal>radicale3</literal>, which is done
-     automatically if <literal>stateVersion</literal> is 20.09 or higher.
-    </para>
-   </listitem>
-   <listitem>
-    <para>
-      <literal>udpt</literal> experienced a complete rewrite from C++ to rust. The configuration format changed from ini to toml.
-      The new configuration documentation can be found at
-      <link xlink:href="https://naim94a.github.io/udpt/config.html">the official website</link> and example
-      configuration is packaged in <literal>${udpt}/share/udpt/udpt.toml</literal>.
-    </para>
-   </listitem>
-   <listitem>
-    <para>
-     We now have a unified <xref linkend="opt-services.xserver.displayManager.autoLogin"/> option interface
-     to be used for every display-manager in NixOS.
-    </para>
-   </listitem>
-   <listitem>
-    <para>
-     The <literal>bitcoind</literal> module has changed to multi-instance, using submodules.
-     Therefore, it is now mandatory to name each instance.
-     To use this new multi-instance config with an existing bitcoind data directory and user,
-     you have to adjust the original config, e.g.:
-<programlisting>
-  services.bitcoind = {
-    enable = true;
-    extraConfig = "...";
-    ...
-  };
-</programlisting>
-     To something similar:
-<programlisting>
-  services.bitcoind.mainnet = {
-    enable = true;
-    dataDir = "/var/lib/bitcoind";
-    user = "bitcoin";
-    extraConfig = "...";
-    ...
-  };
-</programlisting>
-     The key settings are:
-     <itemizedlist>
-      <listitem>
-       <para>
-        <literal>dataDir</literal> - to continue using the same data directory.
-       </para>
-      </listitem>
-      <listitem>
-       <para>
-        <literal>user</literal> - to continue using the same user so that bitcoind maintains access to its files.
-       </para>
-      </listitem>
-     </itemizedlist>
-    </para>
-   </listitem>
-   <listitem>
-    <para>
-      Graylog introduced a change in the LDAP server certificate validation behaviour for version 3.3.3 which might break existing setups.
-      When updating Graylog from a version before 3.3.3 make sure to check the Graylog <link xlink:href="https://www.graylog.org/post/announcing-graylog-v3-3-3">release info</link> for information on how to avoid the issue.
-    </para>
-   </listitem>
-   <listitem>
-    <para>
-     The <literal>dokuwiki</literal> module has changed to multi-instance, using submodules.
-     Therefore, it is now mandatory to name each instance. Moreover, forcing SSL by default has been dropped, so
-     <literal>nginx.forceSSL</literal> and <literal>nginx.enableACME</literal> are no longer set to <literal>true</literal>.
-     To continue using your service with the original SSL settings, you have to adjust the original config, e.g.:
-<programlisting>
-services.dokuwiki = {
-  enable = true;
-  ...
-};
-</programlisting>
-     To something similar:
-<programlisting>
-services.dokuwiki."mywiki" = {
-  enable = true;
-  nginx = {
-    forceSSL = true;
-    enableACME = true;
-  };
-  ...
-};
-</programlisting>
-     The base package has also been upgraded to the 2020-07-29 "Hogfather" release. Plugins might be incompatible or require upgrading.
-    </para>
-   </listitem>
-   <listitem>
-    <para>
-      The <xref linkend="opt-services.postgresql.dataDir"/> option is now set to <literal>"/var/lib/postgresql/${cfg.package.psqlSchema}"</literal> regardless of your
-      <xref linkend="opt-system.stateVersion"/>. Users with an existing postgresql install that have a <xref linkend="opt-system.stateVersion"/> of <literal>17.03</literal> or below
-      should double check what the value of their <xref linkend="opt-services.postgresql.dataDir"/> option is (<literal>/var/db/postgresql</literal>) and then explicitly
-      set this value to maintain compatibility:
-<programlisting>
-services.postgresql.dataDir = "/var/db/postgresql";
-</programlisting>
-    </para>
-    <para>
-     The postgresql module now expects there to be a database super user account called <literal>postgres</literal> regardless of your <xref linkend="opt-system.stateVersion"/>. Users
-     with an existing postgresql install that have a <xref linkend="opt-system.stateVersion"/> of <literal>17.03</literal> or below should run the following SQL statements as a
-     database super admin user before upgrading:
-<programlisting>
-CREATE ROLE postgres LOGIN SUPERUSER;
-</programlisting>
-    </para>
-   </listitem>
-   <listitem>
-    <para>
-     The USBGuard module now removes options and instead hardcodes values for <literal>IPCAccessControlFiles</literal>, <literal>ruleFiles</literal>, and <literal>auditFilePath</literal>. Audit logs can be found in the journal.
-    </para>
-   </listitem>
-   <listitem>
-    <para>
-     The NixOS module system now evaluates option definitions more strictly, allowing it to detect a larger set of problems.
-     As a result, what previously evaluated may not do so anymore.
-     See <link xlink:href="https://github.com/NixOS/nixpkgs/pull/82743#issuecomment-674520472">the PR that changed this</link> for more info.
-    </para>
-   </listitem>
-  </itemizedlist>
- </section>
-
- <section xmlns="http://docbook.org/ns/docbook"
-         xmlns:xlink="http://www.w3.org/1999/xlink"
-         xmlns:xi="http://www.w3.org/2001/XInclude"
-         version="5.0"
-         xml:id="sec-release-20.09-notable-changes">
-  <title>Other Notable Changes</title>
-
-  <itemizedlist>
-   <listitem>
-    <para>SD images are now compressed by default using <literal>zstd</literal>. The compression for ISO images has also been changed to <literal>zstd</literal>, but ISO images are still not compressed by default.</para>
-   </listitem>
-   <listitem>
-    <para>
-     <option>services.journald.rateLimitBurst</option> was updated from
-     <literal>1000</literal> to <literal>10000</literal> to follow the new
-     upstream systemd default.
-    </para>
-   </listitem>
-   <listitem>
-    <para>
-     The <package>notmuch</package> package move its emacs-related binaries and
-     emacs lisp files to a separate output. They're not part
-     of the default <literal>out</literal> output anymore - if you relied on the
-     <literal>notmuch-emacs-mua</literal> binary or the emacs lisp files, access them via
-     the <literal>notmuch.emacs</literal> output.
-    </para>
-   </listitem>
-   <listitem>
-    <para>
-      The default output of <literal>buildGoPackage</literal> is now <literal>$out</literal> instead of <literal>$bin</literal>.
-    </para>
-   </listitem>
-   <listitem>
-    <para>
-     <literal>buildGoModule</literal> <literal>doCheck</literal> now defaults to <literal>true</literal>.
-    </para>
-   </listitem>
-   <listitem>
-    <para>
-     Packages built using <literal>buildRustPackage</literal> now use <literal>release</literal>
-     mode for the <literal>checkPhase</literal> by default.
-    </para>
-    <para>
-     Please note that Rust packages utilizing a custom build/install procedure
-     (e.g. by using a <filename>Makefile</filename>) or test suites that rely on the
-     structure of the <filename>target/</filename> directory may break due to those assumptions.
-     For further information, please read the Rust section in the Nixpkgs manual.
-    </para>
-   </listitem>
-   <listitem>
-   <para>
-     The cc- and binutils-wrapper's "infix salt" and <literal>_BUILD_</literal> and <literal>_TARGET_</literal> user infixes have been replaced with with a "suffix salt" and suffixes and <literal>_FOR_BUILD</literal> and <literal>_FOR_TARGET</literal>.
-      This matches the autotools convention for env vars which standard for these things, making interfacing with other tools easier.
-   </para>
-   </listitem>
-   <listitem>
-   <para>
-     Additional Git documentation (HTML and text files) is now available via the <literal>git-doc</literal> package.
-   </para>
-   </listitem>
-   <listitem>
-   <para>
-     Default algorithm for ZRAM swap was changed to <literal>zstd</literal>.
-   </para>
-   </listitem>
-   <listitem>
-    <para>
-     The scripted networking system now uses <literal>.link</literal> files in
-     <literal>/etc/systemd/network</literal> to configure mac address and link MTU,
-     instead of the sometimes buggy <literal>network-link-*</literal> units, which
-     have been removed.
-     Bringing the interface up has been moved to the beginning of the
-     <literal>network-addresses-*</literal> unit.
-     Note this doesn't require <command>systemd-networkd</command> - it's udev that
-     parses <literal>.link</literal> files.
-     Extra care needs to be taken in the presence of <link xlink:href="https://wiki.debian.org/NetworkInterfaceNames#THE_.22PERSISTENT_NAMES.22_SCHEME">legacy udev rules</link>
-     to rename interfaces, as MAC Address and MTU defined in these options can only match on the original link name.
-     In such cases, you most likely want to create a <literal>10-*.link</literal> file through <xref linkend="opt-systemd.network.links"/> and set both name and MAC Address / MTU there.
-    </para>
-   </listitem>
-   <listitem>
-    <para>
-     Grafana received a major update to version 7.x. A plugin is now needed for
-     image rendering support, and plugins must now be signed by default. More
-     information can be found
-     <link xlink:href="https://grafana.com/docs/grafana/latest/installation/upgrading/#upgrading-to-v7-0">in the Grafana documentation</link>.
-    </para>
-   </listitem>
-   <listitem>
-    <para>
-     The <literal>hardware.u2f</literal> module, which was installing udev rules
-     was removed, as udev gained native support to handle FIDO security tokens.
-    </para>
-   </listitem>
-   <listitem>
-    <para>
-     The <literal>services.transmission</literal> module
-     was enhanced with the new options:
-     <xref linkend="opt-services.transmission.credentialsFile"/>,
-     <xref linkend="opt-services.transmission.openFirewall"/>,
-     and <xref linkend="opt-services.transmission.performanceNetParameters"/>.
-    </para>
-    <para>
-     <literal>transmission-daemon</literal> is now started with additional systemd sandbox/hardening options for better security.
-     Please <link xlink:href="https://github.com/NixOS/nixpkgs/issues">report</link>
-     any use case where this is not working well.
-     In particular, the <literal>RootDirectory</literal> option newly set
-     forbids uploading or downloading a torrent outside of the default directory
-     configured at <link linkend="opt-services.transmission.settings">settings.download-dir</link>.
-     If you really need Transmission to access other directories,
-     you must include those directories into the <literal>BindPaths</literal> of the service:
-<programlisting>
-systemd.services.transmission.serviceConfig.BindPaths = [ "/path/to/alternative/download-dir" ];
-</programlisting>
-    </para>
-    <para>
-     Also, connection to the RPC (Remote Procedure Call) of <literal>transmission-daemon</literal>
-     is now only available on the local network interface by default.
-     Use:
-<programlisting>
-services.transmission.settings.rpc-bind-address = "0.0.0.0";
-</programlisting>
-     to get the previous behavior of listening on all network interfaces.
-    </para>
-   </listitem>
-   <listitem>
-    <para>
-     With this release <literal>systemd-networkd</literal> (when enabled through <xref linkend="opt-networking.useNetworkd"/>)
-     has it's netlink socket created through a <literal>systemd.socket</literal> unit. This gives us control over
-     socket buffer sizes and other parameters. For larger setups where networkd has to create a lot of (virtual)
-     devices the default buffer size (currently 128MB) is not enough.
-    </para>
-    <para>
-     On a machine with &gt;100 virtual interfaces (e.g., wireguard tunnels, VLANs, …), that all have to
-     be brought up during system startup, the receive buffer size will spike for a brief period.
-     Eventually some of the message will be dropped since there is not enough (permitted) buffer
-     space available.
-    </para>
-    <para>
-     By having <literal>systemd-networkd</literal> start with a netlink socket created by
-     <literal>systemd</literal> we can configure the <literal>ReceiveBufferSize=</literal> parameter
-     in the socket options (i.e. <literal>systemd.sockets.systemd-networkd.socketOptions.ReceiveBufferSize</literal>)
-     without recompiling <literal>systemd-networkd</literal>.
-    </para>
-    <para>
-     Since the actual memory requirements depend on hardware, timing, exact
-     configurations etc. it isn't currently possible to infer a good default
-     from within the NixOS module system. Administrators are advised to
-     monitor the logs of <literal>systemd-networkd</literal> for <literal>rtnl: kernel receive buffer
-     overrun</literal> spam and increase the memory limit as they see fit.
-    </para>
-    <para>
-     Note: Increasing the <literal>ReceiveBufferSize=</literal> doesn't allocate any memory. It just increases
-     the upper bound on the kernel side. The memory allocation depends on the amount of messages that are
-     queued on the kernel side of the netlink socket.
-    </para>
-   </listitem>
-   <listitem>
-    <para>
-     Specifying <link linkend="opt-services.dovecot2.mailboxes">mailboxes</link> in the <package>dovecot2</package> module
-     as a list is deprecated and will break eval in 21.03. Instead, an attribute-set should be specified where the <literal>name</literal>
-     should be the key of the attribute.
-    </para>
-    <para>
-     This means that a configuration like this
-<programlisting>{
-  <link linkend="opt-services.dovecot2.mailboxes">services.dovecot2.mailboxes</link> = [
-    { name = "Junk";
-      auto = "create";
-    }
-  ];
-}</programlisting>
-    should now look like this:
-<programlisting>{
-  <link linkend="opt-services.dovecot2.mailboxes">services.dovecot2.mailboxes</link> = {
-    Junk.auto = "create";
-  };
-}</programlisting>
-    </para>
-   </listitem>
-   <listitem>
-    <para>
-      <package>netbeans</package> was upgraded to 12.0 and now defaults to OpenJDK 11. This might cause problems if your projects depend on packages that were removed in Java 11.
-    </para>
-   </listitem>
-   <listitem>
-    <para>
-     <package>nextcloud</package> has been updated to <link xlink:href="https://nextcloud.com/blog/nextcloud-hub-brings-productivity-to-home-office/">v19</link>.
-    </para>
-    <para>
-     If you have an existing installation, please make sure that you're on
-     <package>nextcloud18</package> before upgrading to <package>nextcloud19</package>
-     since Nextcloud doesn't support upgrades across multiple major versions.
-    </para>
-     <para>
-       The <literal>nixos-run-vms</literal> script now deletes the
-       previous run machines states on test startup. You can use the
-       <literal>--keep-vm-state</literal> flag to match the previous
-       behaviour and keep the same VM state between different test runs.
-     </para>
-   </listitem>
-   <listitem>
-    <para>
-     The <link linkend="opt-nix.buildMachines">nix.buildMachines</link> option is now type-checked.
-     There are no functional changes, however this may require updating some configurations to use correct types for all attributes.
-    </para>
-   </listitem>
-   <listitem>
-    <para>
-     The <literal>fontconfig</literal> module stopped generating fontconfig 2.10.x config and cache.
-     Fontconfig 2.10.x was removed from Nixpkgs - it hasn't been used in any nixpkgs package anymore.
-    </para>
-   </listitem>
-   <listitem>
-    <para>
-     Nginx module <literal>nginxModules.fastcgi-cache-purge</literal> renamed to official name <literal>nginxModules.cache-purge</literal>.
-     Nginx module <literal>nginxModules.ngx_aws_auth</literal> renamed to official name <literal>nginxModules.aws-auth</literal>.
-      The packages <package>perl</package>, <package>rsync</package> and <package>strace</package> were removed from <option>systemPackages</option>. If you need them, install them again with <code><xref linkend="opt-environment.systemPackages"/> = with pkgs; [ perl rsync strace ];</code> in your <filename>configuration.nix</filename>.
-    </para>
-   </listitem>
-   <listitem>
-    <para>
-      The <literal>undervolt</literal> option no longer needs to apply its
-      settings every 30s. If they still become undone, open an issue and restore
-      the previous behaviour using <literal>undervolt.useTimer</literal>.
-    </para>
-   </listitem>
-  </itemizedlist>
- </section>
-</section>