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-<section xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xml:id="sec-release-21.05">
-  <title>Release 21.05 (<quote>Okapi</quote>, 2021.05/31)</title>
-  <para>
-    Support is planned until the end of December 2021, handing over to
-    21.11.
-  </para>
-  <section xml:id="sec-release-21.05-highlights">
-    <title>Highlights</title>
-    <para>
-      In addition to numerous new and upgraded packages, this release
-      has the following highlights:
-    </para>
-    <itemizedlist>
-      <listitem>
-        <para>
-          Core version changes:
-        </para>
-        <itemizedlist>
-          <listitem>
-            <para>
-              gcc: 9.3.0 -&gt; 10.3.0
-            </para>
-          </listitem>
-          <listitem>
-            <para>
-              glibc: 2.30 -&gt; 2.32
-            </para>
-          </listitem>
-          <listitem>
-            <para>
-              default linux: 5.4 -&gt; 5.10, all supported kernels
-              available
-            </para>
-          </listitem>
-          <listitem>
-            <para>
-              mesa: 20.1.7 -&gt; 21.0.1
-            </para>
-          </listitem>
-        </itemizedlist>
-      </listitem>
-      <listitem>
-        <para>
-          Desktop Environments:
-        </para>
-        <itemizedlist>
-          <listitem>
-            <para>
-              GNOME: 3.36 -&gt; 40, see its
-              <link xlink:href="https://help.gnome.org/misc/release-notes/40.0/">release
-              notes</link>
-            </para>
-          </listitem>
-          <listitem>
-            <para>
-              Plasma5: 5.18.5 -&gt; 5.21.3
-            </para>
-          </listitem>
-          <listitem>
-            <para>
-              kdeApplications: 20.08.1 -&gt; 20.12.3
-            </para>
-          </listitem>
-          <listitem>
-            <para>
-              cinnamon: 4.6 -&gt; 4.8.1
-            </para>
-          </listitem>
-        </itemizedlist>
-      </listitem>
-      <listitem>
-        <para>
-          Programming Languages and Frameworks:
-        </para>
-        <itemizedlist spacing="compact">
-          <listitem>
-            <para>
-              Python optimizations were disabled again. Builds with
-              optimizations enabled are not reproducible. Optimizations
-              can now be enabled with an option.
-            </para>
-          </listitem>
-        </itemizedlist>
-      </listitem>
-      <listitem>
-        <para>
-          The linux_latest kernel was updated to the 5.13 series. It
-          currently is not officially supported for use with the zfs
-          filesystem. If you use zfs, you should use a different kernel
-          version (either the LTS kernel, or track a specific one).
-        </para>
-      </listitem>
-    </itemizedlist>
-  </section>
-  <section xml:id="sec-release-21.05-new-services">
-    <title>New Services</title>
-    <para>
-      The following new services were added since the last release:
-    </para>
-    <itemizedlist>
-      <listitem>
-        <para>
-          <link xlink:href="https://www.gnuradio.org/">GNURadio</link>
-          3.8 and 3.9 were
-          <link xlink:href="https://github.com/NixOS/nixpkgs/issues/82263">finally</link>
-          packaged, along with a rewrite to the Nix expressions,
-          allowing users to override the features upstream supports
-          selecting to compile or not to. Additionally, the attribute
-          <literal>gnuradio</literal> (3.9),
-          <literal>gnuradio3_8</literal> and
-          <literal>gnuradio3_7</literal> now point to an externally
-          wrapped by default derivations, that allow you to also add
-          `extraPythonPackages` to the Python interpreter used by
-          GNURadio. Missing environmental variables needed for
-          operational GUI were also added
-          (<link xlink:href="https://github.com/NixOS/nixpkgs/issues/75478">#75478</link>).
-        </para>
-      </listitem>
-      <listitem>
-        <para>
-          <link xlink:href="https://www.keycloak.org/">Keycloak</link>,
-          an open source identity and access management server with
-          support for
-          <link xlink:href="https://openid.net/connect/">OpenID
-          Connect</link>, <link xlink:href="https://oauth.net/2/">OAUTH
-          2.0</link> and
-          <link xlink:href="https://en.wikipedia.org/wiki/SAML_2.0">SAML
-          2.0</link>.
-        </para>
-        <para>
-          See the <link linkend="module-services-keycloak">Keycloak
-          section of the NixOS manual</link> for more information.
-        </para>
-      </listitem>
-      <listitem>
-        <para>
-          <link xlink:href="options.html#opt-services.samba-wsdd.enable">services.samba-wsdd.enable</link>
-          Web Services Dynamic Discovery host daemon
-        </para>
-      </listitem>
-      <listitem>
-        <para>
-          <link xlink:href="https://www.discourse.org/">Discourse</link>,
-          a modern and open source discussion platform.
-        </para>
-        <para>
-          See the <link linkend="module-services-discourse">Discourse
-          section of the NixOS manual</link> for more information.
-        </para>
-      </listitem>
-      <listitem>
-        <para>
-          <link xlink:href="options.html#opt-services.nebula.networks">services.nebula.networks</link>
-          <link xlink:href="https://github.com/slackhq/nebula">Nebula
-          VPN</link>
-        </para>
-      </listitem>
-    </itemizedlist>
-  </section>
-  <section xml:id="sec-release-21.05-incompatibilities">
-    <title>Backward Incompatibilities</title>
-    <para>
-      When upgrading from a previous release, please be aware of the
-      following incompatible changes:
-    </para>
-    <itemizedlist>
-      <listitem>
-        <para>
-          GNOME desktop environment was upgraded to 40, see the release
-          notes for
-          <link xlink:href="https://help.gnome.org/misc/release-notes/40.0/">40.0</link>
-          and
-          <link xlink:href="https://help.gnome.org/misc/release-notes/3.38/">3.38</link>.
-          The <literal>gnome3</literal> attribute set has been renamed
-          to <literal>gnome</literal> and so have been the NixOS
-          options.
-        </para>
-      </listitem>
-      <listitem>
-        <para>
-          If you are using <literal>services.udev.extraRules</literal>
-          to assign custom names to network interfaces, this may stop
-          working due to a change in the initialisation of dhcpcd and
-          systemd networkd. To avoid this, either move them to
-          <literal>services.udev.initrdRules</literal> or see the new
-          <link linkend="sec-custom-ifnames">Assigning custom
-          names</link> section of the NixOS manual for an example using
-          networkd links.
-        </para>
-      </listitem>
-      <listitem>
-        <para>
-          The <literal>security.hideProcessInformation</literal> module
-          has been removed. It was broken since the switch to
-          cgroups-v2.
-        </para>
-      </listitem>
-      <listitem>
-        <para>
-          The <literal>linuxPackages.ati_drivers_x11</literal> kernel
-          modules have been removed. The drivers only supported kernels
-          prior to 4.2, and thus have become obsolete.
-        </para>
-      </listitem>
-      <listitem>
-        <para>
-          The <literal>systemConfig</literal> kernel parameter is no
-          longer added to boot loader entries. It has been unused since
-          September 2010, but if do have a system generation from that
-          era, you will now be unable to boot into them.
-        </para>
-      </listitem>
-      <listitem>
-        <para>
-          <literal>systemd-journal2gelf</literal> no longer parses json
-          and expects the receiving system to handle it. How to achieve
-          this with Graylog is described in this
-          <link xlink:href="https://github.com/parse-nl/SystemdJournal2Gelf/issues/10">GitHub
-          issue</link>.
-        </para>
-      </listitem>
-      <listitem>
-        <para>
-          If the <literal>services.dbus</literal> module is enabled,
-          then the user D-Bus session is now always socket activated.
-          The associated options
-          <literal>services.dbus.socketActivated</literal> and
-          <literal>services.xserver.startDbusSession</literal> have
-          therefore been removed and you will receive a warning if they
-          are present in your configuration. This change makes the user
-          D-Bus session available also for non-graphical logins.
-        </para>
-      </listitem>
-      <listitem>
-        <para>
-          The <literal>networking.wireless.iwd</literal> module now
-          installs the upstream-provided 80-iwd.link file, which sets
-          the NamePolicy= for all wlan devices to &quot;keep
-          kernel&quot;, to avoid race conditions between iwd and
-          networkd. If you don't want this, you can set
-          <literal>systemd.network.links.&quot;80-iwd&quot; = lib.mkForce {}</literal>.
-        </para>
-      </listitem>
-      <listitem>
-        <para>
-          <literal>rubyMinimal</literal> was removed due to being unused
-          and unusable. The default ruby interpreter includes JIT
-          support, which makes it reference it's compiler. Since JIT
-          support is probably needed by some Gems, it was decided to
-          enable this feature with all cc references by default, and
-          allow to build a Ruby derivation without references to cc, by
-          setting <literal>jitSupport = false;</literal> in an overlay.
-          See
-          <link xlink:href="https://github.com/NixOS/nixpkgs/pull/90151">#90151</link>
-          for more info.
-        </para>
-      </listitem>
-      <listitem>
-        <para>
-          Setting
-          <literal>services.openssh.authorizedKeysFiles</literal> now
-          also affects which keys
-          <literal>security.pam.enableSSHAgentAuth</literal> will use.
-          WARNING: If you are using these options in combination do make
-          sure that any key paths you use are present in
-          <literal>services.openssh.authorizedKeysFiles</literal>!
-        </para>
-      </listitem>
-      <listitem>
-        <para>
-          The option <literal>fonts.enableFontDir</literal> has been
-          renamed to
-          <link xlink:href="options.html#opt-fonts.fontDir.enable">fonts.fontDir.enable</link>.
-          The path of font directory has also been changed to
-          <literal>/run/current-system/sw/share/X11/fonts</literal>, for
-          consistency with other X11 resources.
-        </para>
-      </listitem>
-      <listitem>
-        <para>
-          A number of options have been renamed in the kicad interface.
-          <literal>oceSupport</literal> has been renamed to
-          <literal>withOCE</literal>, <literal>withOCCT</literal> has
-          been renamed to <literal>withOCC</literal>,
-          <literal>ngspiceSupport</literal> has been renamed to
-          <literal>withNgspice</literal>, and
-          <literal>scriptingSupport</literal> has been renamed to
-          <literal>withScripting</literal>. Additionally,
-          <literal>kicad/base.nix</literal> no longer provides default
-          argument values since these are provided by
-          <literal>kicad/default.nix</literal>.
-        </para>
-      </listitem>
-      <listitem>
-        <para>
-          The socket for the <literal>pdns-recursor</literal> module was
-          moved from <literal>/var/lib/pdns-recursor</literal> to
-          <literal>/run/pdns-recursor</literal> to match upstream.
-        </para>
-      </listitem>
-      <listitem>
-        <para>
-          Paperwork was updated to version 2. The on-disk format
-          slightly changed, and it is not possible to downgrade from
-          Paperwork 2 back to Paperwork 1.3. Back your documents up
-          before upgrading. See
-          <link xlink:href="https://forum.openpaper.work/t/paperwork-2-0/112/5">this
-          thread</link> for more details.
-        </para>
-      </listitem>
-      <listitem>
-        <para>
-          PowerDNS has been updated from <literal>4.2.x</literal> to
-          <literal>4.3.x</literal>. Please be sure to review the
-          <link xlink:href="https://doc.powerdns.com/authoritative/upgrading.html#x-to-4-3-0">Upgrade
-          Notes</link> provided by upstream before upgrading. Worth
-          specifically noting is that the service now runs entirely as a
-          dedicated <literal>pdns</literal> user, instead of starting as
-          <literal>root</literal> and dropping privileges, as well as
-          the default <literal>socket-dir</literal> location changing
-          from <literal>/var/lib/powerdns</literal> to
-          <literal>/run/pdns</literal>.
-        </para>
-      </listitem>
-      <listitem>
-        <para>
-          The <literal>mediatomb</literal> service is now using by
-          default the new and maintained fork <literal>gerbera</literal>
-          package instead of the unmaintained
-          <literal>mediatomb</literal> package. If you want to keep the
-          old behavior, you must declare it with:
-        </para>
-        <programlisting language="bash">
-{
-  services.mediatomb.package = pkgs.mediatomb;
-}
-</programlisting>
-        <para>
-          One new option <literal>openFirewall</literal> has been
-          introduced which defaults to false. If you relied on the
-          service declaration to add the firewall rules itself before,
-          you should now declare it with:
-        </para>
-        <programlisting language="bash">
-{
-  services.mediatomb.openFirewall = true;
-}
-</programlisting>
-      </listitem>
-      <listitem>
-        <para>
-          xfsprogs was update from 4.19 to 5.11. It now enables reflink
-          support by default on filesystem creation. Support for
-          reflinks was added with an experimental status to kernel 4.9
-          and deemed stable in kernel 4.16. If you want to be able to
-          mount XFS filesystems created with this release of xfsprogs on
-          kernel releases older than those, you need to format them with
-          <literal>mkfs.xfs -m reflink=0</literal>.
-        </para>
-      </listitem>
-      <listitem>
-        <para>
-          The uWSGI server is now built with POSIX capabilities. As a
-          consequence, root is no longer required in emperor mode and
-          the service defaults to running as the unprivileged
-          <literal>uwsgi</literal> user. Any additional capability can
-          be added via the new option
-          <link xlink:href="options.html#opt-services.uwsgi.capabilities">services.uwsgi.capabilities</link>.
-          The previous behaviour can be restored by setting:
-        </para>
-        <programlisting language="bash">
-{
-  services.uwsgi.user = &quot;root&quot;;
-  services.uwsgi.group = &quot;root&quot;;
-  services.uwsgi.instance =
-    {
-      uid = &quot;uwsgi&quot;;
-      gid = &quot;uwsgi&quot;;
-    };
-}
-</programlisting>
-        <para>
-          Another incompatibility from the previous release is that
-          vassals running under a different user or group need to use
-          <literal>immediate-{uid,gid}</literal> instead of the usual
-          <literal>uid,gid</literal> options.
-        </para>
-      </listitem>
-      <listitem>
-        <para>
-          btc1 has been abandoned upstream, and removed.
-        </para>
-      </listitem>
-      <listitem>
-        <para>
-          cpp_ethereum (aleth) has been abandoned upstream, and removed.
-        </para>
-      </listitem>
-      <listitem>
-        <para>
-          riak-cs package removed along with
-          <literal>services.riak-cs</literal> module.
-        </para>
-      </listitem>
-      <listitem>
-        <para>
-          stanchion package removed along with
-          <literal>services.stanchion</literal> module.
-        </para>
-      </listitem>
-      <listitem>
-        <para>
-          mutt has been updated to a new major version (2.x), which
-          comes with some backward incompatible changes that are
-          described in the
-          <link xlink:href="http://www.mutt.org/relnotes/2.0/">release
-          notes for Mutt 2.0</link>.
-        </para>
-      </listitem>
-      <listitem>
-        <para>
-          <literal>vim</literal> and <literal>neovim</literal> switched
-          to Python 3, dropping all Python 2 support.
-        </para>
-      </listitem>
-      <listitem>
-        <para>
-          <link xlink:href="options.html#opt-networking.wireguard.interfaces">networking.wireguard.interfaces.&lt;name&gt;.generatePrivateKeyFile</link>,
-          which is off by default, had a <literal>chmod</literal> race
-          condition fixed. As an aside, the parent directory's
-          permissions were widened, and the key files were made
-          owner-writable. This only affects newly created keys. However,
-          if the exact permissions are important for your setup, read
-          <link xlink:href="https://github.com/NixOS/nixpkgs/pull/121294">#121294</link>.
-        </para>
-      </listitem>
-      <listitem>
-        <para>
-          <link xlink:href="options.html#opt-boot.zfs.forceImportAll">boot.zfs.forceImportAll</link>
-          previously did nothing, but has been fixed. However its
-          default has been changed to <literal>false</literal> to
-          preserve the existing default behaviour. If you have this
-          explicitly set to <literal>true</literal>, please note that
-          your non-root pools will now be forcibly imported.
-        </para>
-      </listitem>
-      <listitem>
-        <para>
-          openafs now points to openafs_1_8, which is the new stable
-          release. OpenAFS 1.6 was removed.
-        </para>
-      </listitem>
-      <listitem>
-        <para>
-          The WireGuard module gained a new option
-          <literal>networking.wireguard.interfaces.&lt;name&gt;.peers.*.dynamicEndpointRefreshSeconds</literal>
-          that implements refreshing the IP of DNS-based endpoints
-          periodically (which WireGuard itself
-          <link xlink:href="https://lists.zx2c4.com/pipermail/wireguard/2017-November/002028.html">cannot
-          do</link>).
-        </para>
-      </listitem>
-      <listitem>
-        <para>
-          MariaDB has been updated to 10.5. Before you upgrade, it would
-          be best to take a backup of your database and read
-          <link xlink:href="https://mariadb.com/kb/en/upgrading-from-mariadb-104-to-mariadb-105/#incompatible-changes-between-104-and-105">
-          Incompatible Changes Between 10.4 and 10.5</link>. After the
-          upgrade you will need to run <literal>mysql_upgrade</literal>.
-        </para>
-      </listitem>
-      <listitem>
-        <para>
-          The TokuDB storage engine dropped in mariadb 10.5 and removed
-          in mariadb 10.6. It is recommended to switch to RocksDB. See
-          also
-          <link xlink:href="https://mariadb.com/kb/en/tokudb/">TokuDB</link>
-          and
-          <link xlink:href="https://jira.mariadb.org/browse/MDEV-19780">MDEV-19780:
-          Remove the TokuDB storage engine</link>.
-        </para>
-      </listitem>
-      <listitem>
-        <para>
-          The <literal>openldap</literal> module now has support for
-          OLC-style configuration, users of the
-          <literal>configDir</literal> option may wish to migrate. If
-          you continue to use <literal>configDir</literal>, ensure that
-          <literal>olcPidFile</literal> is set to
-          <literal>/run/slapd/slapd.pid</literal>.
-        </para>
-        <para>
-          As a result, <literal>extraConfig</literal> and
-          <literal>extraDatabaseConfig</literal> are removed. To help
-          with migration, you can convert your
-          <literal>slapd.conf</literal> file to OLC configuration with
-          the following script (find the location of this configuration
-          file by running <literal>systemctl status openldap</literal>,
-          it is the <literal>-f</literal> option.
-        </para>
-        <programlisting>
-$ TMPDIR=$(mktemp -d)
-$ slaptest -f /path/to/slapd.conf -F $TMPDIR
-$ slapcat -F $TMPDIR -n0 -H 'ldap:///???(!(objectClass=olcSchemaConfig))'
-</programlisting>
-        <para>
-          This will dump your current configuration in LDIF format,
-          which should be straightforward to convert into Nix settings.
-          This does not show your schema configuration, as this is
-          unnecessarily verbose for users of the default schemas and
-          <literal>slaptest</literal> is buggy with schemas directly in
-          the config file.
-        </para>
-      </listitem>
-      <listitem>
-        <para>
-          Amazon EC2 and OpenStack Compute (nova) images now re-fetch
-          instance meta data and user data from the instance metadata
-          service (IMDS) on each boot. For example: stopping an EC2
-          instance, changing its user data, and restarting the instance
-          will now cause it to fetch and apply the new user data.
-        </para>
-        <warning>
-          <para>
-            Specifically, <literal>/etc/ec2-metadata</literal> is
-            re-populated on each boot. Some NixOS scripts that read from
-            this directory are guarded to only run if the files they
-            want to manipulate do not already exist, and so will not
-            re-apply their changes if the IMDS response changes.
-            Examples: <literal>root</literal>'s SSH key is only added if
-            <literal>/root/.ssh/authorized_keys</literal> does not
-            exist, and SSH host keys are only set from user data if they
-            do not exist in <literal>/etc/ssh</literal>.
-          </para>
-        </warning>
-      </listitem>
-      <listitem>
-        <para>
-          The <literal>rspamd</literal> services is now sandboxed. It is
-          run as a dynamic user instead of root, so secrets and other
-          files may have to be moved or their permissions may have to be
-          fixed. The sockets are now located in
-          <literal>/run/rspamd</literal> instead of
-          <literal>/run</literal>.
-        </para>
-      </listitem>
-      <listitem>
-        <para>
-          Enabling the Tor client no longer silently also enables and
-          configures Privoxy, and the
-          <literal>services.tor.client.privoxy.enable</literal> option
-          has been removed. To enable Privoxy, and to configure it to
-          use Tor's faster port, use the following configuration:
-        </para>
-        <programlisting language="bash">
-{
-  opt-services.privoxy.enable = true;
-  opt-services.privoxy.enableTor = true;
-}
-</programlisting>
-      </listitem>
-      <listitem>
-        <para>
-          The <literal>services.tor</literal> module has a new
-          exhaustively typed
-          <link xlink:href="options.html#opt-services.tor.settings">services.tor.settings</link>
-          option following RFC 0042; backward compatibility with old
-          options has been preserved when aliasing was possible. The
-          corresponding systemd service has been hardened, but there is
-          a chance that the service still requires more permissions, so
-          please report any related trouble on the bugtracker. Onion
-          services v3 are now supported in
-          <link xlink:href="options.html#opt-services.tor.relay.onionServices">services.tor.relay.onionServices</link>.
-          A new
-          <link xlink:href="options.html#opt-services.tor.openFirewall">services.tor.openFirewall</link>
-          option as been introduced for allowing connections on all the
-          TCP ports configured.
-        </para>
-      </listitem>
-      <listitem>
-        <para>
-          The options
-          <literal>services.slurm.dbdserver.storagePass</literal> and
-          <literal>services.slurm.dbdserver.configFile</literal> have
-          been removed. Use
-          <literal>services.slurm.dbdserver.storagePassFile</literal>
-          instead to provide the database password. Extra config options
-          can be given via the option
-          <literal>services.slurm.dbdserver.extraConfig</literal>. The
-          actual configuration file is created on the fly on startup of
-          the service. This avoids that the password gets exposed in the
-          nix store.
-        </para>
-      </listitem>
-      <listitem>
-        <para>
-          The <literal>wafHook</literal> hook does not wrap Python
-          anymore. Packages depending on <literal>wafHook</literal> need
-          to include any Python into their
-          <literal>nativeBuildInputs</literal>.
-        </para>
-      </listitem>
-      <listitem>
-        <para>
-          Starting with version 1.7.0, the project formerly named
-          <literal>CodiMD</literal> is now named
-          <literal>HedgeDoc</literal>. New installations will no longer
-          use the old name for users, state directories and such, this
-          needs to be considered when moving state to a more recent
-          NixOS installation. Based on
-          <link xlink:href="options.html#opt-system.stateVersion">system.stateVersion</link>,
-          existing installations will continue to work.
-        </para>
-      </listitem>
-      <listitem>
-        <para>
-          The fish-foreign-env package has been replaced with
-          fishPlugins.foreign-env, in which the fish functions have been
-          relocated to the <literal>vendor_functions.d</literal>
-          directory to be loaded automatically.
-        </para>
-      </listitem>
-      <listitem>
-        <para>
-          The prometheus json exporter is now managed by the prometheus
-          community. Together with additional features some backwards
-          incompatibilities were introduced. Most importantly the
-          exporter no longer accepts a fixed command-line parameter to
-          specify the URL of the endpoint serving JSON. It now expects
-          this URL to be passed as an URL parameter, when scraping the
-          exporter's <literal>/probe</literal> endpoint. In the
-          prometheus scrape configuration the scrape target might look
-          like this:
-        </para>
-        <programlisting>
-http://some.json-exporter.host:7979/probe?target=https://example.com/some/json/endpoint
-</programlisting>
-        <para>
-          Existing configuration for the exporter needs to be updated,
-          but can partially be re-used. Documentation is available in
-          the upstream repository and a small example for NixOS is
-          available in the corresponding NixOS test.
-        </para>
-        <para>
-          These changes also affect
-          <link xlink:href="options.html#opt-services.prometheus.exporters.rspamd.enable">services.prometheus.exporters.rspamd.enable</link>,
-          which is just a preconfigured instance of the json exporter.
-        </para>
-        <para>
-          For more information, take a look at the
-          <link xlink:href="https://github.com/prometheus-community/json_exporter">
-          official documentation</link> of the json_exporter.
-        </para>
-      </listitem>
-      <listitem>
-        <para>
-          Androidenv was updated, removing the
-          <literal>includeDocs</literal> and
-          <literal>lldbVersions</literal> arguments. Docs only covered a
-          single version of the Android SDK, LLDB is now bundled with
-          the NDK, and both are no longer available to download from the
-          Android package repositories. Additionally, since the package
-          lists have been updated, some older versions of Android
-          packages may not be bundled. If you depend on older versions
-          of Android packages, we recommend overriding the repo.
-        </para>
-        <para>
-          Android packages are now loaded from a repo.json file created
-          by parsing Android repo XML files. The arguments
-          <literal>repoJson</literal> and <literal>repoXmls</literal>
-          have been added to allow overriding the built-in androidenv
-          repo.json with your own. Additionally, license files are now
-          written to allow compatibility with Gradle-based tools, and
-          the <literal>extraLicenses</literal> argument has been added
-          to accept more SDK licenses if your project requires it. See
-          the androidenv documentation for more details.
-        </para>
-      </listitem>
-      <listitem>
-        <para>
-          The attribute <literal>mpi</literal> is now consistently used
-          to provide a default, system-wide MPI implementation. The
-          default implementation is openmpi, which has been used before
-          by all derivations affects by this change. Note that all
-          packages that have used <literal>mpi ? null</literal> in the
-          input for optional MPI builds, have been changed to the
-          boolean input paramater <literal>useMpi</literal> to enable
-          building with MPI. Building all packages with
-          <literal>mpich</literal> instead of the default
-          <literal>openmpi</literal> can now be achived like this:
-        </para>
-        <programlisting language="bash">
-self: super:
-{
-  mpi = super.mpich;
-}
-</programlisting>
-      </listitem>
-      <listitem>
-        <para>
-          The Searx module has been updated with the ability to
-          configure the service declaratively and uWSGI integration. The
-          option <literal>services.searx.configFile</literal> has been
-          renamed to
-          <link xlink:href="options.html#opt-services.searx.settingsFile">services.searx.settingsFile</link>
-          for consistency with the new
-          <link xlink:href="options.html#opt-services.searx.settings">services.searx.settings</link>.
-          In addition, the <literal>searx</literal> uid and gid
-          reservations have been removed since they were not necessary:
-          the service is now running with a dynamically allocated uid.
-        </para>
-      </listitem>
-      <listitem>
-        <para>
-          The libinput module has been updated with the ability to
-          configure mouse and touchpad settings separately. The options
-          in <literal>services.xserver.libinput</literal> have been
-          renamed to
-          <literal>services.xserver.libinput.touchpad</literal>, while
-          there is a new
-          <literal>services.xserver.libinput.mouse</literal> for mouse
-          related configuration.
-        </para>
-        <para>
-          Since touchpad options no longer apply to all devices, you may
-          want to replicate your touchpad configuration in mouse
-          section.
-        </para>
-      </listitem>
-      <listitem>
-        <para>
-          ALSA OSS emulation
-          (<literal>sound.enableOSSEmulation</literal>) is now disabled
-          by default.
-        </para>
-      </listitem>
-      <listitem>
-        <para>
-          Thinkfan as been updated to <literal>1.2.x</literal>, which
-          comes with a new YAML based configuration format. For this
-          reason, several NixOS options of the thinkfan module have been
-          changed to non-backward compatible types. In addition, a new
-          <link xlink:href="options.html#opt-services.thinkfan.settings">services.thinkfan.settings</link>
-          option has been added.
-        </para>
-        <para>
-          Please read the
-          <link xlink:href="https://github.com/vmatare/thinkfan#readme">
-          thinkfan documentation</link> before updating.
-        </para>
-      </listitem>
-      <listitem>
-        <para>
-          Adobe Flash Player support has been dropped from the tree. In
-          particular, the following packages no longer support it:
-        </para>
-        <itemizedlist>
-          <listitem>
-            <para>
-              chromium
-            </para>
-          </listitem>
-          <listitem>
-            <para>
-              firefox
-            </para>
-          </listitem>
-          <listitem>
-            <para>
-              qt48
-            </para>
-          </listitem>
-          <listitem>
-            <para>
-              qt5.qtwebkit
-            </para>
-          </listitem>
-        </itemizedlist>
-        <para>
-          Additionally, packages flashplayer and hal-flash were removed
-          along with the <literal>services.flashpolicyd</literal>
-          module.
-        </para>
-      </listitem>
-      <listitem>
-        <para>
-          The <literal>security.rngd</literal> module has been removed.
-          It was disabled by default in 20.09 as it was functionally
-          redundant with krngd in the linux kernel. It is not necessary
-          for any device that the kernel recognises as an hardware RNG,
-          as it will automatically run the krngd task to periodically
-          collect random data from the device and mix it into the
-          kernel's RNG.
-        </para>
-        <para>
-          The default SMTP port for GitLab has been changed to
-          <literal>25</literal> from its previous default of
-          <literal>465</literal>. If you depended on this default, you
-          should now set the
-          <link xlink:href="options.html#opt-services.gitlab.smtp.port">services.gitlab.smtp.port</link>
-          option.
-        </para>
-      </listitem>
-      <listitem>
-        <para>
-          The default version of ImageMagick has been updated from 6 to
-          7. You can use imagemagick6, imagemagick6_light, and
-          imagemagick6Big if you need the older version.
-        </para>
-      </listitem>
-      <listitem>
-        <para>
-          <link xlink:href="options.html#opt-services.xserver.videoDrivers">services.xserver.videoDrivers</link>
-          no longer uses the deprecated <literal>cirrus</literal> and
-          <literal>vesa</literal> device dependent X drivers by default.
-          It also enables both <literal>amdgpu</literal> and
-          <literal>nouveau</literal> drivers by default now.
-        </para>
-      </listitem>
-      <listitem>
-        <para>
-          The <literal>kindlegen</literal> package is gone, because it
-          is no longer supported or hosted by Amazon. Sadly, its
-          replacement, Kindle Previewer, has no Linux support. However,
-          there are other ways to generate MOBI files. See
-          <link xlink:href="https://github.com/NixOS/nixpkgs/issues/96439">the
-          discussion</link> for more info.
-        </para>
-      </listitem>
-      <listitem>
-        <para>
-          The apacheKafka packages are now built with version-matched
-          JREs. Versions 2.6 and above, the ones that recommend it, use
-          jdk11, while versions below remain on jdk8. The NixOS service
-          has been adjusted to start the service using the same version
-          as the package, adjustable with the new
-          <link xlink:href="options.html#opt-services.apache-kafka.jre">services.apache-kafka.jre</link>
-          option. Furthermore, the default list of
-          <link xlink:href="options.html#opt-services.apache-kafka.jvmOptions">services.apache-kafka.jvmOptions</link>
-          have been removed. You should set your own according to the
-          <link xlink:href="https://kafka.apache.org/documentation/#java">upstream
-          documentation</link> for your Kafka version.
-        </para>
-      </listitem>
-      <listitem>
-        <para>
-          The kodi package has been modified to allow concise addon
-          management. Consider the following configuration from previous
-          releases of NixOS to install kodi, including the
-          kodiPackages.inputstream-adaptive and kodiPackages.vfs-sftp
-          addons:
-        </para>
-        <programlisting language="bash">
-{
-  environment.systemPackages = [
-    pkgs.kodi
-  ];
-
-  nixpkgs.config.kodi = {
-    enableInputStreamAdaptive = true;
-    enableVFSSFTP = true;
-  };
-}
-</programlisting>
-        <para>
-          All Kodi <literal>config</literal> flags have been removed,
-          and as a result the above configuration should now be written
-          as:
-        </para>
-        <programlisting language="bash">
-{
-  environment.systemPackages = [
-    (pkgs.kodi.withPackages (p: with p; [
-      inputstream-adaptive
-      vfs-sftp
-    ]))
-  ];
-}
-</programlisting>
-      </listitem>
-      <listitem>
-        <para>
-          <literal>environment.defaultPackages</literal> now includes
-          the nano package. If pkgs.nano is not added to the list, make
-          sure another editor is installed and the
-          <literal>EDITOR</literal> environment variable is set to it.
-          Environment variables can be set using
-          <literal>environment.variables</literal>.
-        </para>
-      </listitem>
-      <listitem>
-        <para>
-          <literal>services.minio.dataDir</literal> changed type to a
-          list of paths, required for specifiyng multiple data
-          directories for using with erasure coding. Currently, the
-          service doesn't enforce nor checks the correct number of paths
-          to correspond to minio requirements.
-        </para>
-      </listitem>
-      <listitem>
-        <para>
-          All CUDA toolkit versions prior to CUDA 10 have been removed.
-        </para>
-      </listitem>
-      <listitem>
-        <para>
-          The kbdKeymaps package was removed since dvp and neo are now
-          included in kbd. If you want to use the Programmer Dvorak
-          Keyboard Layout, you have to use
-          <literal>dvorak-programmer</literal> in
-          <literal>console.keyMap</literal> now instead of
-          <literal>dvp</literal>. In
-          <literal>services.xserver.xkbVariant</literal> it's still
-          <literal>dvp</literal>.
-        </para>
-      </listitem>
-      <listitem>
-        <para>
-          The babeld service is now being run as an unprivileged user.
-          To achieve that the module configures
-          <literal>skip-kernel-setup true</literal> and takes care of
-          setting forwarding and rp_filter sysctls by itself as well as
-          for each interface in
-          <literal>services.babeld.interfaces</literal>.
-        </para>
-      </listitem>
-      <listitem>
-        <para>
-          The <literal>services.zigbee2mqtt.config</literal> option has
-          been renamed to
-          <literal>services.zigbee2mqtt.settings</literal> and now
-          follows
-          <link xlink:href="https://github.com/NixOS/rfcs/blob/master/rfcs/0042-config-option.md">RFC
-          0042</link>.
-        </para>
-      </listitem>
-    </itemizedlist>
-    <para>
-      The yadm dotfile manager has been updated from 2.x to 3.x, which
-      has new (XDG) default locations for some data/state files. Most
-      yadm commands will fail and print a legacy path warning (which
-      describes how to upgrade/migrate your repository). If you have
-      scripts, daemons, scheduled jobs, shell profiles, etc. that invoke
-      yadm, expect them to fail or misbehave until you perform this
-      migration and prepare accordingly.
-    </para>
-    <itemizedlist>
-      <listitem>
-        <para>
-          Instead of determining
-          <literal>services.radicale.package</literal> automatically
-          based on <literal>system.stateVersion</literal>, the latest
-          version is always used because old versions are not officially
-          supported.
-        </para>
-        <para>
-          Furthermore, Radicale's systemd unit was hardened which might
-          break some deployments. In particular, a non-default
-          <literal>filesystem_folder</literal> has to be added to
-          <literal>systemd.services.radicale.serviceConfig.ReadWritePaths</literal>
-          if the deprecated <literal>services.radicale.config</literal>
-          is used.
-        </para>
-      </listitem>
-      <listitem>
-        <para>
-          In the <literal>security.acme</literal> module, use of
-          <literal>--reuse-key</literal> parameter for Lego has been
-          removed. It was introduced for HKPK, but this security feature
-          is now deprecated. It is a better security practice to rotate
-          key pairs instead of always keeping the same. If you need to
-          keep this parameter, you can add it back using
-          <literal>extraLegoRenewFlags</literal> as an option for the
-          appropriate certificate.
-        </para>
-      </listitem>
-    </itemizedlist>
-  </section>
-  <section xml:id="sec-release-21.05-notable-changes">
-    <title>Other Notable Changes</title>
-    <itemizedlist>
-      <listitem>
-        <para>
-          <literal>stdenv.lib</literal> has been deprecated and will
-          break eval in 21.11. Please use <literal>pkgs.lib</literal>
-          instead. See
-          <link xlink:href="https://github.com/NixOS/nixpkgs/issues/108938">#108938</link>
-          for details.
-        </para>
-      </listitem>
-      <listitem>
-        <para>
-          <link xlink:href="https://www.gnuradio.org/">GNURadio</link>
-          has a <literal>pkgs</literal> attribute set, and there's a
-          <literal>gnuradio.callPackage</literal> function that extends
-          <literal>pkgs</literal> with a
-          <literal>mkDerivation</literal>, and a
-          <literal>mkDerivationWith</literal>, like Qt5. Now all
-          <literal>gnuradio.pkgs</literal> are defined with
-          <literal>gnuradio.callPackage</literal> and some packages that
-          depend on gnuradio are defined with this as well.
-        </para>
-      </listitem>
-      <listitem>
-        <para>
-          <link xlink:href="https://www.privoxy.org/">Privoxy</link> has
-          been updated to version 3.0.32 (See
-          <link xlink:href="https://lists.privoxy.org/pipermail/privoxy-announce/2021-February/000007.html">announcement</link>).
-          Compared to the previous release, Privoxy has gained support
-          for HTTPS inspection (still experimental), Brotli
-          decompression, several new filters and lots of bug fixes,
-          including security ones. In addition, the package is now built
-          with compression and external filters support, which were
-          previously disabled.
-        </para>
-        <para>
-          Regarding the NixOS module, new options for HTTPS inspection
-          have been added and
-          <literal>services.privoxy.extraConfig</literal> has been
-          replaced by the new
-          <link xlink:href="options.html#opt-services.privoxy.settings">services.privoxy.settings</link>
-          (See
-          <link xlink:href="https://github.com/NixOS/rfcs/blob/master/rfcs/0042-config-option.md">RFC
-          0042</link> for the motivation).
-        </para>
-      </listitem>
-      <listitem>
-        <para>
-          <link xlink:href="https://kodi.tv/">Kodi</link> has been
-          updated to version 19.1 &quot;Matrix&quot;. See the
-          <link xlink:href="https://kodi.tv/article/kodi-19-0-matrix-release">announcement</link>
-          for further details.
-        </para>
-      </listitem>
-      <listitem>
-        <para>
-          The <literal>services.packagekit.backend</literal> option has
-          been removed as it only supported a single setting which would
-          always be the default. Instead new
-          <link xlink:href="https://github.com/NixOS/rfcs/blob/master/rfcs/0042-config-option.md">RFC
-          0042</link> compliant
-          <link xlink:href="options.html#opt-services.packagekit.settings">services.packagekit.settings</link>
-          and
-          <link xlink:href="options.html#opt-services.packagekit.vendorSettings">services.packagekit.vendorSettings</link>
-          options have been introduced.
-        </para>
-      </listitem>
-      <listitem>
-        <para>
-          <link xlink:href="https://nginx.org">Nginx</link> has been
-          updated to stable version 1.20.0. Now nginx uses the zlib-ng
-          library by default.
-        </para>
-      </listitem>
-      <listitem>
-        <para>
-          KDE Gear (formerly KDE Applications) is upgraded to 21.04, see
-          its
-          <link xlink:href="https://kde.org/announcements/gear/21.04/">release
-          notes</link> for details.
-        </para>
-        <para>
-          The <literal>kdeApplications</literal> package set is now
-          <literal>kdeGear</literal>, in keeping with the new name. The
-          old name remains for compatibility, but it is deprecated.
-        </para>
-      </listitem>
-      <listitem>
-        <para>
-          <link xlink:href="https://libreswan.org/">Libreswan</link> has
-          been updated to version 4.4. The package now includes example
-          configurations and manual pages by default. The NixOS module
-          has been changed to use the upstream systemd units and write
-          the configuration in the <literal>/etc/ipsec.d/ </literal>
-          directory. In addition, two new options have been added to
-          specify connection policies
-          (<link xlink:href="options.html#opt-services.libreswan.policies">services.libreswan.policies</link>)
-          and disable send/receive redirects
-          (<link xlink:href="options.html#opt-services.libreswan.disableRedirects">services.libreswan.disableRedirects</link>).
-        </para>
-      </listitem>
-      <listitem>
-        <para>
-          The Mailman NixOS module (<literal>services.mailman</literal>)
-          has a new option
-          <link xlink:href="options.html#opt-services.mailman.enablePostfix">services.mailman.enablePostfix</link>,
-          defaulting to true, that controls integration with Postfix.
-        </para>
-        <para>
-          If this option is disabled, default MTA config becomes not set
-          and you should set the options in
-          <literal>services.mailman.settings.mta</literal> according to
-          the desired configuration as described in
-          <link xlink:href="https://mailman.readthedocs.io/en/latest/src/mailman/docs/mta.html">Mailman
-          documentation</link>.
-        </para>
-      </listitem>
-      <listitem>
-        <para>
-          The default-version of <literal>nextcloud</literal> is
-          nextcloud21. Please note that it's <emphasis>not</emphasis>
-          possible to upgrade <literal>nextcloud</literal> across
-          multiple major versions! This means that it's e.g. not
-          possible to upgrade from nextcloud18 to nextcloud20 in a
-          single deploy and most <literal>20.09</literal> users will
-          have to upgrade to nextcloud20 first.
-        </para>
-        <para>
-          The package can be manually upgraded by setting
-          <link xlink:href="options.html#opt-services.nextcloud.package">services.nextcloud.package</link>
-          to nextcloud21.
-        </para>
-      </listitem>
-      <listitem>
-        <para>
-          The setting
-          <link xlink:href="options.html#opt-services.redis.bind">services.redis.bind</link>
-          defaults to <literal>127.0.0.1</literal> now, making Redis
-          listen on the loopback interface only, and not all public
-          network interfaces.
-        </para>
-      </listitem>
-      <listitem>
-        <para>
-          NixOS now emits a deprecation warning if systemd's
-          <literal>StartLimitInterval</literal> setting is used in a
-          <literal>serviceConfig</literal> section instead of in a
-          <literal>unitConfig</literal>; that setting is deprecated and
-          now undocumented for the service section by systemd upstream,
-          but still effective and somewhat buggy there, which can be
-          confusing. See
-          <link xlink:href="https://github.com/NixOS/nixpkgs/issues/45785">#45785</link>
-          for details.
-        </para>
-        <para>
-          All services should use
-          <link xlink:href="options.html#opt-systemd.services._name_.startLimitIntervalSec">systemd.services.<emphasis>name</emphasis>.startLimitIntervalSec</link>
-          or <literal>StartLimitIntervalSec</literal> in
-          <link xlink:href="options.html#opt-systemd.services._name_.unitConfig">systemd.services.<emphasis>name</emphasis>.unitConfig</link>
-          instead.
-        </para>
-      </listitem>
-      <listitem>
-        <para>
-          The <literal>mediatomb</literal> service declares new options.
-          It also adapts existing options so the configuration
-          generation is now lazy. The existing option
-          <literal>customCfg</literal> (defaults to false), when
-          enabled, stops the service configuration generation
-          completely. It then expects the users to provide their own
-          correct configuration at the right location (whereas the
-          configuration was generated and not used at all before). The
-          new option <literal>transcodingOption</literal> (defaults to
-          no) allows a generated configuration. It makes the mediatomb
-          service pulls the necessary runtime dependencies in the nix
-          store (whereas it was generated with hardcoded values before).
-          The new option <literal>mediaDirectories</literal> allows the
-          users to declare autoscan media directories from their nixos
-          configuration:
-        </para>
-        <programlisting language="bash">
-{
-  services.mediatomb.mediaDirectories = [
-    { path = &quot;/var/lib/mediatomb/pictures&quot;; recursive = false; hidden-files = false; }
-    { path = &quot;/var/lib/mediatomb/audio&quot;; recursive = true; hidden-files = false; }
-  ];
-}
-</programlisting>
-      </listitem>
-      <listitem>
-        <para>
-          The Unbound DNS resolver service
-          (<literal>services.unbound</literal>) has been refactored to
-          allow reloading, control sockets and to fix startup ordering
-          issues.
-        </para>
-        <para>
-          It is now possible to enable a local UNIX control socket for
-          unbound by setting the
-          <link xlink:href="options.html#opt-services.unbound.localControlSocketPath">services.unbound.localControlSocketPath</link>
-          option.
-        </para>
-        <para>
-          Previously we just applied a very minimal set of restrictions
-          and trusted unbound to properly drop root privs and
-          capabilities.
-        </para>
-        <para>
-          As of this we are (for the most part) just using the upstream
-          example unit file for unbound. The main difference is that we
-          start unbound as <literal>unbound</literal> user with the
-          required capabilities instead of letting unbound do the chroot
-          &amp; uid/gid changes.
-        </para>
-        <para>
-          The upstream unit configuration this is based on is a lot
-          stricter with all kinds of permissions then our previous
-          variant. It also came with the default of having the
-          <literal>Type</literal> set to <literal>notify</literal>,
-          therefore we are now also using the
-          <literal>unbound-with-systemd</literal> package here. Unbound
-          will start up, read the configuration files and start
-          listening on the configured ports before systemd will declare
-          the unit <literal>active (running)</literal>. This will likely
-          help with startup order and the occasional race condition
-          during system activation where the DNS service is started but
-          not yet ready to answer queries. Services depending on
-          <literal>nss-lookup.target</literal> or
-          <literal>unbound.service</literal> are now be able to use
-          unbound when those targets have been reached.
-        </para>
-        <para>
-          Additionally to the much stricter runtime environment the
-          <literal>/dev/urandom</literal> mount lines we previously had
-          in the code (that randomly failed during the stop-phase) have
-          been removed as systemd will take care of those for us.
-        </para>
-        <para>
-          The <literal>preStart</literal> script is now only required if
-          we enabled the trust anchor updates (which are still enabled
-          by default).
-        </para>
-        <para>
-          Another benefit of the refactoring is that we can now issue
-          reloads via either <literal>pkill -HUP unbound</literal> and
-          <literal>systemctl reload unbound</literal> to reload the
-          running configuration without taking the daemon offline. A
-          prerequisite of this was that unbound configuration is
-          available on a well known path on the file system. We are
-          using the path <literal>/etc/unbound/unbound.conf</literal> as
-          that is the default in the CLI tooling which in turn enables
-          us to use <literal>unbound-control</literal> without passing a
-          custom configuration location.
-        </para>
-        <para>
-          The module has also been reworked to be
-          <link xlink:href="https://github.com/NixOS/rfcs/blob/master/rfcs/0042-config-option.md">RFC
-          0042</link> compliant. As such,
-          <literal>sevices.unbound.extraConfig</literal> has been
-          removed and replaced by
-          <link xlink:href="options.html#opt-services.unbound.settings">services.unbound.settings</link>.
-          <literal>services.unbound.interfaces</literal> has been
-          renamed to
-          <literal>services.unbound.settings.server.interface</literal>.
-        </para>
-        <para>
-          <literal>services.unbound.forwardAddresses</literal> and
-          <literal>services.unbound.allowedAccess</literal> have also
-          been changed to use the new settings interface. You can follow
-          the instructions when executing
-          <literal>nixos-rebuild</literal> to upgrade your configuration
-          to use the new interface.
-        </para>
-      </listitem>
-      <listitem>
-        <para>
-          The <literal>services.dnscrypt-proxy2</literal> module now
-          takes the upstream's example configuration and updates it with
-          the user's settings. An option has been added to restore the
-          old behaviour if you prefer to declare the configuration from
-          scratch.
-        </para>
-      </listitem>
-      <listitem>
-        <para>
-          NixOS now defaults to the unified cgroup hierarchy
-          (cgroupsv2). See the
-          <link xlink:href="https://www.redhat.com/sysadmin/fedora-31-control-group-v2">Fedora
-          Article for 31</link> for details on why this is desirable,
-          and how it impacts containers.
-        </para>
-        <para>
-          If you want to run containers with a runtime that does not yet
-          support cgroupsv2, you can switch back to the old behaviour by
-          setting
-          <link xlink:href="options.html#opt-systemd.enableUnifiedCgroupHierarchy">systemd.enableUnifiedCgroupHierarchy</link>
-          = <literal>false</literal>; and rebooting.
-        </para>
-      </listitem>
-      <listitem>
-        <para>
-          PulseAudio was upgraded to 14.0, with changes to the handling
-          of default sinks. See its
-          <link xlink:href="https://www.freedesktop.org/wiki/Software/PulseAudio/Notes/14.0/">release
-          notes</link>.
-        </para>
-      </listitem>
-      <listitem>
-        <para>
-          GNOME users may wish to delete their
-          <literal>~/.config/pulse</literal> due to the changes to
-          stream routing logic. See
-          <link xlink:href="https://gitlab.freedesktop.org/pulseaudio/pulseaudio/-/issues/832">PulseAudio
-          bug 832</link> for more information.
-        </para>
-      </listitem>
-      <listitem>
-        <para>
-          The zookeeper package does not provide
-          <literal>zooInspector.sh</literal> anymore, as that
-          &quot;contrib&quot; has been dropped from upstream releases.
-        </para>
-      </listitem>
-      <listitem>
-        <para>
-          In the ACME module, the data used to build the hash for the
-          account directory has changed to accomodate new features to
-          reduce account rate limit issues. This will trigger new
-          account creation on the first rebuild following this update.
-          No issues are expected to arise from this, thanks to the new
-          account creation handling.
-        </para>
-      </listitem>
-      <listitem>
-        <para>
-          <link xlink:href="options.html#opt-users.users._name_.createHome">users.users.<emphasis>name</emphasis>.createHome</link>
-          now always ensures home directory permissions to be
-          <literal>0700</literal>. Permissions had previously been
-          ignored for already existing home directories, possibly
-          leaving them readable by others. The option's description was
-          incorrect regarding ownership management and has been
-          simplified greatly.
-        </para>
-      </listitem>
-      <listitem>
-        <para>
-          When defining a new user, one of
-          <link xlink:href="options.html#opt-users.users._name_.isNormalUser">users.users.<emphasis>name</emphasis>.isNormalUser</link>
-          and
-          <link xlink:href="options.html#opt-users.users._name_.isSystemUser">users.users.<emphasis>name</emphasis>.isSystemUser</link>
-          is now required. This is to prevent accidentally giving a UID
-          above 1000 to system users, which could have unexpected
-          consequences, like running user activation scripts for system
-          users. Note that users defined with an explicit UID below 500
-          are exempted from this check, as
-          <link xlink:href="options.html#opt-users.users._name_.isSystemUser">users.users.<emphasis>name</emphasis>.isSystemUser</link>
-          has no effect for those.
-        </para>
-      </listitem>
-      <listitem>
-        <para>
-          The <literal>security.apparmor</literal> module, for the
-          <link xlink:href="https://gitlab.com/apparmor/apparmor/-/wikis/Documentation">AppArmor</link>
-          Mandatory Access Control system, has been substantialy
-          improved along with related tools, so that module maintainers
-          can now more easily write AppArmor profiles for NixOS. The
-          most notable change on the user-side is the new option
-          <link xlink:href="options.html#opt-security.apparmor.policies">security.apparmor.policies</link>,
-          replacing the previous <literal>profiles</literal> option to
-          provide a way to disable a profile and to select whether to
-          confine in enforce mode (default) or in complain mode (see
-          <literal>journalctl -b --grep apparmor</literal>).
-          Security-minded users may also want to enable
-          <link xlink:href="options.html#opt-security.apparmor.killUnconfinedConfinables">security.apparmor.killUnconfinedConfinables</link>,
-          at the cost of having some of their processes killed when
-          updating to a NixOS version introducing new AppArmor profiles.
-        </para>
-      </listitem>
-      <listitem>
-        <para>
-          The GNOME desktop manager once again installs gnome.epiphany
-          by default.
-        </para>
-      </listitem>
-      <listitem>
-        <para>
-          NixOS now generates empty <literal>/etc/netgroup</literal>.
-          <literal>/etc/netgroup</literal> defines network-wide groups
-          and may affect to setups using NIS.
-        </para>
-      </listitem>
-      <listitem>
-        <para>
-          Platforms, like <literal>stdenv.hostPlatform</literal>, no
-          longer have a <literal>platform</literal> attribute. It has
-          been (mostly) flattened away:
-        </para>
-        <itemizedlist>
-          <listitem>
-            <para>
-              <literal>platform.gcc</literal> is now
-              <literal>gcc</literal>
-            </para>
-          </listitem>
-          <listitem>
-            <para>
-              <literal>platform.kernel*</literal> is now
-              <literal>linux-kernel.*</literal>
-            </para>
-          </listitem>
-        </itemizedlist>
-        <para>
-          Additionally, <literal>platform.kernelArch</literal> moved to
-          the top level as <literal>linuxArch</literal> to match the
-          other <literal>*Arch</literal> variables.
-        </para>
-        <para>
-          The <literal>platform</literal> grouping of these things never
-          meant anything, and was just a historial/implementation
-          artifact that was overdue removal.
-        </para>
-      </listitem>
-      <listitem>
-        <para>
-          <literal>services.restic</literal> now uses a dedicated cache
-          directory for every backup defined in
-          <literal>services.restic.backups</literal>. The old global
-          cache directory, <literal>/root/.cache/restic</literal>, is
-          now unused and can be removed to free up disk space.
-        </para>
-      </listitem>
-      <listitem>
-        <para>
-          <literal>isync</literal>: The <literal>isync</literal>
-          compatibility wrapper was removed and the Master/Slave
-          terminology has been deprecated and should be replaced with
-          Far/Near in the configuration file.
-        </para>
-      </listitem>
-      <listitem>
-        <para>
-          The nix-gc service now accepts randomizedDelaySec (default: 0)
-          and persistent (default: true) parameters. By default nix-gc
-          will now run immediately if it would have been triggered at
-          least once during the time when the timer was inactive.
-        </para>
-      </listitem>
-      <listitem>
-        <para>
-          The <literal>rustPlatform.buildRustPackage</literal> function
-          is split into several hooks: cargoSetupHook to set up
-          vendoring for Cargo-based projects, cargoBuildHook to build a
-          project using Cargo, cargoInstallHook to install a project
-          using Cargo, and cargoCheckHook to run tests in Cargo-based
-          projects. With this change, mixed-language projects can use
-          the relevant hooks within builders other than
-          <literal>buildRustPackage</literal>. However, these changes
-          also required several API changes to
-          <literal>buildRustPackage</literal> itself:
-        </para>
-        <itemizedlist>
-          <listitem>
-            <para>
-              The <literal>target</literal> argument was removed.
-              Instead, <literal>buildRustPackage</literal> will always
-              use the same target as the C/C++ compiler that is used.
-            </para>
-          </listitem>
-          <listitem>
-            <para>
-              The <literal>cargoParallelTestThreads</literal> argument
-              was removed. Parallel tests are now disabled through
-              <literal>dontUseCargoParallelTests</literal>.
-            </para>
-          </listitem>
-        </itemizedlist>
-      </listitem>
-      <listitem>
-        <para>
-          The <literal>rustPlatform.maturinBuildHook</literal> hook was
-          added. This hook can be used with
-          <literal>buildPythonPackage</literal> to build Python packages
-          that are written in Rust and use Maturin as their build tool.
-        </para>
-      </listitem>
-      <listitem>
-        <para>
-          Kubernetes has
-          <link xlink:href="https://kubernetes.io/blog/2020/12/02/dont-panic-kubernetes-and-docker/">deprecated
-          docker</link> as container runtime. As a consequence, the
-          Kubernetes module now has support for configuration of custom
-          remote container runtimes and enables containerd by default.
-          Note that containerd is more strict regarding container image
-          OCI-compliance. As an example, images with CMD or ENTRYPOINT
-          defined as strings (not lists) will fail on containerd, while
-          working fine on docker. Please test your setup and container
-          images with containerd prior to upgrading.
-        </para>
-      </listitem>
-      <listitem>
-        <para>
-          The GitLab module now has support for automatic backups. A
-          schedule can be set with the
-          <link xlink:href="options.html#opt-services.gitlab.backup.startAt">services.gitlab.backup.startAt</link>
-          option.
-        </para>
-      </listitem>
-      <listitem>
-        <para>
-          Prior to this release, systemd would also read system units
-          from an undocumented
-          <literal>/etc/systemd-mutable/system</literal> path. This path
-          has been dropped from the defaults. That path (or others) can
-          be re-enabled by adding it to the
-          <link xlink:href="options.html#opt-boot.extraSystemdUnitPaths">boot.extraSystemdUnitPaths</link>
-          list.
-        </para>
-      </listitem>
-      <listitem>
-        <para>
-          PostgreSQL 9.5 is scheduled EOL during the 21.05 life cycle
-          and has been removed.
-        </para>
-      </listitem>
-      <listitem>
-        <para>
-          <link xlink:href="https://www.xfce.org/">Xfce4</link> relies
-          on GIO/GVfs for userspace virtual filesystem access in
-          applications like
-          <link xlink:href="https://docs.xfce.org/xfce/thunar/">thunar</link>
-          and
-          <link xlink:href="https://docs.xfce.org/apps/gigolo/">gigolo</link>.
-          For that to work, the gvfs nixos service is enabled by
-          default, and it can be configured with the specific package
-          that provides GVfs. Until now Xfce4 was setting it to use a
-          lighter version of GVfs (without support for samba). To avoid
-          conflicts with other desktop environments this setting has
-          been dropped. Users that still want it should add the
-          following to their system configuration:
-        </para>
-        <programlisting language="bash">
-{
-  services.gvfs.package = pkgs.gvfs.override { samba = null; };
-}
-</programlisting>
-      </listitem>
-      <listitem>
-        <para>
-          The newly enabled <literal>systemd-pstore.service</literal>
-          now automatically evacuates crashdumps and panic logs from the
-          persistent storage to
-          <literal>/var/lib/systemd/pstore</literal>. This prevents
-          NVRAM from filling up, which ensures the latest diagnostic
-          data is always stored and alleviates problems with writing new
-          boot configurations.
-        </para>
-      </listitem>
-      <listitem>
-        <para>
-          Nixpkgs now contains
-          <link xlink:href="https://github.com/NixOS/nixpkgs/pull/118232">automatically
-          packaged GNOME Shell extensions</link> from the
-          <link xlink:href="https://extensions.gnome.org/">GNOME
-          Extensions</link> portal. You can find them, filed by their
-          UUID, under <literal>gnome38Extensions</literal> attribute for
-          GNOME 3.38 and under <literal>gnome40Extensions</literal> for
-          GNOME 40. Finally, the <literal>gnomeExtensions</literal>
-          attribute contains extensions for the latest GNOME Shell
-          version in Nixpkgs, listed under a more human-friendly name.
-          The unqualified attribute scope also contains manually
-          packaged extensions. Note that the automatically packaged
-          extensions are provided for convenience and are not checked or
-          guaranteed to work.
-        </para>
-      </listitem>
-      <listitem>
-        <para>
-          Erlang/OTP versions older than R21 got dropped. We also
-          dropped the cuter package, as it was purely an example of how
-          to build a package. We also dropped <literal>lfe_1_2</literal>
-          as it could not build with R21+. Moving forward, we expect to
-          only support 3 yearly releases of OTP.
-        </para>
-      </listitem>
-    </itemizedlist>
-  </section>
-</section>