<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”, 2020.10/27)</title>

  <para>
   Support is planned until the end of June 2021, handing over to 21.05.
   (Plans <link xlink:href="https://github.com/NixOS/rfcs/blob/master/rfcs/0080-nixos-release-schedule.md#core-changes">
   have shifted</link> by two months since release of 20.09.)
  </para>
 <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 7349 new, 14442 updated, and 8181 removed packages, this release has the
   following highlights:
  </para>

  <itemizedlist>
   <listitem>
    <para>
     Core version changes:
    </para>
    <itemizedlist>
     <listitem>
      <para>
       gcc: 9.2.0 -> 9.3.0
      </para>
     </listitem>
     <listitem>
      <para>
       glibc: 2.30 -> 2.31
      </para>
     </listitem>
     <listitem>
      <para>
       linux: still defaults to 5.4.x, all supported kernels available
      </para>
     </listitem>
     <listitem>
      <para>
       mesa: 19.3.5 -> 20.1.7
      </para>
     </listitem>
    </itemizedlist>
   </listitem>
   <listitem>
    <para>
     Desktop Environments:
    </para>
    <itemizedlist>
     <listitem>
      <para>
       plasma5: 5.17.5 -> 5.18.5
      </para>
     </listitem>
     <listitem>
      <para>
       kdeApplications: 19.12.3 -> 20.08.1
      </para>
     </listitem>
     <listitem>
      <para>
       gnome3: 3.34 -> 3.36, see its <link xlink:href="https://help.gnome.org/misc/release-notes/3.36/">release notes</link>
      </para>
     </listitem>
      <listitem>
       <para>
        cinnamon: added at 4.6
      </para>
     </listitem>
     <listitem>
      <para>
       NixOS now distributes an official <link xlink:href="https://nixos.org/download.html#nixos-iso">GNOME ISO</link>
      </para>
     </listitem>
    </itemizedlist>
   </listitem>

   <listitem>
    <para>
     Programming Languages and Frameworks:
    </para>
    <itemizedlist>

     <listitem>
      <para>
       Agda ecosystem was heavily reworked (see more details below)
      </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>
       Python 3.5 reached its upstream EOL at the end of September 2020: it
       has been removed from the list of available packages
      </para>
     </listitem>
    </itemizedlist>
   </listitem>

   <listitem>
    <para>
     Databases and Service Monitoring:
    </para>
    <itemizedlist>
     <listitem>
      <para>
       MariaDB has been updated to 10.4, MariaDB Galera to 26.4. Please read the related upgrade instructions under <link linkend="sec-release-20.09-incompatibilities">backwards incompatibilities</link> before upgrading.
      </para>
     </listitem>
     <listitem>
      <para>
        Zabbix now defaults to 5.0, updated from 4.4. Please read related sections under <link linkend="sec-release-20.09-incompatibilities">backwards compatibilities</link> before upgrading.
      </para>
     </listitem>
    </itemizedlist>
   </listitem>

   <listitem>
    <para>
     Major module changes:
    </para>
    <itemizedlist>
     <listitem>
      <para>
       Quickly configure a complete, private, self-hosted video
       conferencing solution with the new Jitsi Meet module.
      </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>
        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>
         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 <link xlink:href="https://sourceforge.net/projects/g15daemon/">g15daemon project</link>.
       </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 available in GRUB version 2.
       </para>
     </listitem>
    </itemizedlist>
   </listitem>

   <listitem>
    <para>
     NixOS module changes:
    </para>
    <itemizedlist>
     <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>
       Following its deprecation in 20.03, the Perl NixOS test driver has been removed.
       All remaining tests have been ported to the Python test framework.
       Code outside nixpkgs using <filename>make-test.nix</filename> or
       <filename>testing.nix</filename> needs to be ported to
       <filename>make-test-python.nix</filename> and
       <filename>testing-python.nix</filename> respectively.
      </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>
    </itemizedlist>
   </listitem>
   <listitem>
    <para>
     Starting with this release, the hydra-build-result
     <literal>nixos-<replaceable>YY.MM</replaceable></literal>
     branches no longer exist in the <link
     xlink:href="https://github.com/nixos/nixpkgs-channels">deprecated
     nixpkgs-channels repository</link>.  These branches are now in
     <link xlink:href="https://github.com/nixos/nixpkgs">the main nixpkgs
     repository</link>.
    </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>
   In addition to 1119 new, 118 updated, and 476 removed options; 61 new modules were added since the last release:
  </para>

  <itemizedlist>
   <listitem>
    <para>
       Hardware:
    </para>
    <itemizedlist>
     <listitem>
      <para>
       <xref linkend="opt-hardware.system76.firmware-daemon.enable" /> adds easy support of system76 firmware
      </para>
     </listitem>
     <listitem>
      <para>
       <xref linkend="opt-hardware.uinput.enable" /> loads uinput kernel module
      </para>
     </listitem>
     <listitem>
      <para>
       <xref linkend="opt-hardware.video.hidpi.enable" /> enable good defaults for HiDPI displays
      </para>
     </listitem>
     <listitem>
      <para>
       <xref linkend="opt-hardware.wooting.enable" /> support for Wooting keyboards
      </para>
     </listitem>
     <listitem>
      <para>
       <xref linkend="opt-hardware.xpadneo.enable" /> xpadneo driver for Xbox One wireless controllers
      </para>
     </listitem>
    </itemizedlist>
   </listitem>
   <listitem>
    <para>
       Programs:
    </para>
    <itemizedlist>
     <listitem>
      <para>
       <xref linkend="opt-programs.hamster.enable" /> enable hamster time tracking
      </para>
     </listitem>
     <listitem>
      <para>
       <xref linkend="opt-programs.steam.enable" /> adds easy enablement of steam and related system configuration
      </para>
     </listitem>
    </itemizedlist>
   </listitem>
   <listitem>
    <para>
       Security:
    </para>
    <itemizedlist>
     <listitem>
      <para>
       <xref linkend="opt-security.doas.enable" /> alternative to sudo, allows non-root users to execute commands as root
      </para>
     </listitem>
     <listitem>
      <para>
       <xref linkend="opt-security.tpm2.enable" /> add Trusted Platform Module 2 support
      </para>
     </listitem>
    </itemizedlist>
   </listitem>
   <listitem>
    <para>
       System:
    </para>
    <itemizedlist>
     <listitem>
      <para>
       <xref linkend="opt-boot.initrd.network.openvpn.enable" /> start an OpenVPN client during initrd boot
      </para>
     </listitem>
    </itemizedlist>
   </listitem>
   <listitem>
    <para>
       Virtualization:
    </para>
    <itemizedlist>
     <listitem>
      <para>
       <xref linkend="opt-boot.enableContainers" /> use nixos-containers
      </para>
     </listitem>
     <listitem>
      <para>
       <xref linkend="opt-virtualisation.oci-containers.containers" /> run OCI (Docker) containers
      </para>
     </listitem>
     <listitem>
      <para>
       <xref linkend="opt-virtualisation.podman.enable" /> daemonless container engine
      </para>
     </listitem>
    </itemizedlist>
   </listitem>

   <listitem>
    <para>
       Services:
    </para>
    <itemizedlist>
     <listitem>
      <para>
       <xref linkend="opt-services.ankisyncd.enable" /> Anki sync server
      </para>
     </listitem>
     <listitem>
      <para>
       <xref linkend="opt-services.bazarr.enable" /> Subtitle manager for Sonarr and Radarr
      </para>
     </listitem>
     <listitem>
      <para>
       <xref linkend="opt-services.biboumi.enable" /> Biboumi XMPP gateway to IRC
      </para>
     </listitem>
     <listitem>
      <para>
       <xref linkend="opt-services.blockbook-frontend" /> Blockbook-frontend, a service for the Trezor wallet
      </para>
     </listitem>
     <listitem>
      <para>
       <xref linkend="opt-services.cage.enable" /> Wayland cage service
      </para>
     </listitem>
     <listitem>
      <para>
       <xref linkend="opt-services.convos.enable" /> IRC daemon, which can be accessed throught the browser
      </para>
     </listitem>
     <listitem>
      <para>
       <xref linkend="opt-services.engelsystem.enable" /> Tool for coordinating volunteers and shifts on large events
      </para>
     </listitem>
     <listitem>
      <para>
       <xref linkend="opt-services.espanso.enable" /> text-expander written in rust
      </para>
     </listitem>
     <listitem>
      <para>
       <xref linkend="opt-services.foldingathome.enable" /> Folding@home client
      </para>
     </listitem>
     <listitem>
      <para>
       <xref linkend="opt-services.gerrit.enable" /> Web-based team code collaboration tool
      </para>
     </listitem>
     <listitem>
      <para>
       <xref linkend="opt-services.go-neb.enable" /> Matrix bot
      </para>
     </listitem>
     <listitem>
      <para>
       <xref linkend="opt-services.hardware.xow.enable" /> xow as a systemd service
      </para>
     </listitem>
     <listitem>
      <para>
       <xref linkend="opt-services.hercules-ci-agent.enable" /> Hercules CI build agent
      </para>
     </listitem>
     <listitem>
      <para>
       <xref linkend="opt-services.jicofo.enable" /> Jitsi Conference Focus, component of Jitsi Meet
      </para>
     </listitem>
     <listitem>
      <para>
       <xref linkend="opt-services.jirafeau.enable" /> A web file repository
      </para>
     </listitem>
     <listitem>
      <para>
       <xref linkend="opt-services.jitsi-meet.enable" /> Secure, simple and scalable video conferences
      </para>
     </listitem>
     <listitem>
      <para>
       <xref linkend="opt-services.jitsi-videobridge.enable" /> Jitsi Videobridge, a WebRTC compatible router
      </para>
     </listitem>
     <listitem>
      <para>
       <xref linkend="opt-services.jupyterhub.enable" /> Jupyterhub development server
      </para>
     </listitem>
     <listitem>
      <para>
       <xref linkend="opt-services.k3s.enable" /> Lightweight Kubernetes distribution
      </para>
     </listitem>
     <listitem>
      <para>
       <xref linkend="opt-services.magic-wormhole-mailbox-server.enable" /> Magic Wormhole Mailbox Server
      </para>
     </listitem>
     <listitem>
      <para>
       <xref linkend="opt-services.malcontent.enable" /> Parental Control support
      </para>
     </listitem>
     <listitem>
      <para>
       <xref linkend="opt-services.matrix-appservice-discord.enable" /> Matrix and Discord bridge
      </para>
     </listitem>
     <listitem>
      <para>
       <xref linkend="opt-services.mautrix-telegram.enable" /> Matrix-Telegram puppeting/relaybot bridge
      </para>
     </listitem>
     <listitem>
      <para>
       <xref linkend="opt-services.mirakurun.enable" /> Japanese DTV Tuner Server Service
      </para>
     </listitem>
     <listitem>
      <para>
       <xref linkend="opt-services.molly-brown.enable" /> Molly-Brown Gemini server
      </para>
     </listitem>
     <listitem>
      <para>
       <xref linkend="opt-services.mullvad-vpn.enable" /> Mullvad VPN daemon
      </para>
     </listitem>
     <listitem>
      <para>
       <xref linkend="opt-services.ncdns.enable" /> Namecoin to DNS bridge
      </para>
     </listitem>
     <listitem>
      <para>
       <xref linkend="opt-services.nextdns.enable" /> NextDNS to DoH Proxy service
      </para>
     </listitem>
     <listitem>
      <para>
       <xref linkend="opt-services.nix-store-gcs-proxy" /> Google storage bucket to be used as a nix store
      </para>
     </listitem>
     <listitem>
      <para>
       <xref linkend="opt-services.onedrive.enable" /> OneDrive sync service
      </para>
     </listitem>
     <listitem>
      <para>
       <xref linkend="opt-services.pinnwand.enable" /> Pastebin-like service
      </para>
     </listitem>
     <listitem>
      <para>
       <xref linkend="opt-services.pixiecore.enable" /> Manage network booting of machines
      </para>
     </listitem>
     <listitem>
      <para>
       <xref linkend="opt-services.privacyidea.enable" /> Privacy authentication server
      </para>
     </listitem>
     <listitem>
      <para>
       <xref linkend="opt-services.quorum.enable" /> Quorum blockchain daemon
      </para>
     </listitem>
     <listitem>
      <para>
       <xref linkend="opt-services.robustirc-bridge.enable" /> RobustIRC bridge
      </para>
     </listitem>
     <listitem>
      <para>
       <xref linkend="opt-services.rss-bridge.enable" /> Generate RSS and Atom feeds
      </para>
     </listitem>
     <listitem>
      <para>
       <xref linkend="opt-services.rtorrent.enable" /> rTorrent service
      </para>
     </listitem>
     <listitem>
      <para>
       <xref linkend="opt-services.smartdns.enable" /> SmartDNS DNS server
      </para>
     </listitem>
     <listitem>
      <para>
       <xref linkend="opt-services.sogo.enable" /> SOGo groupware
      </para>
     </listitem>
     <listitem>
      <para>
       <xref linkend="opt-services.teeworlds.enable" /> Teeworlds game server
      </para>
     </listitem>
     <listitem>
      <para>
       <xref linkend="opt-services.torque.mom.enable" /> torque computing node
      </para>
     </listitem>
     <listitem>
      <para>
       <xref linkend="opt-services.torque.server.enable" /> torque server
      </para>
     </listitem>
     <listitem>
      <para>
       <xref linkend="opt-services.tuptime.enable" /> A total uptime service
      </para>
     </listitem>
     <listitem>
      <para>
       <xref linkend="opt-services.urserver.enable" /> X11 remote server
      </para>
     </listitem>
     <listitem>
      <para>
       <xref linkend="opt-services.wasabibackend.enable" /> Wasabi backend service
      </para>
     </listitem>
     <listitem>
      <para>
       <xref linkend="opt-services.yubikey-agent.enable" /> Yubikey agent
      </para>
     </listitem>
     <listitem>
      <para>
       <xref linkend="opt-services.zigbee2mqtt.enable" /> Zigbee to MQTT bridge
      </para>
     </listitem>
    </itemizedlist>
   </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>
      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>
      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>
    <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>
     The <link linkend="opt-services.matrix-synapse.enable">matrix-synapse</link> module no longer includes optional dependencies by default, they have to be added through the <link linkend="opt-services.matrix-synapse.plugins">plugins</link> option.
    </para>
   </listitem>
   <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 = true;
  });
}</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>
     The ACME module has been overhauled for simplicity and maintainability.
     Cert generation now implicitly uses the <literal>acme</literal>
     user, and the <literal>security.acme.certs._name_.user</literal> option
     has been removed. Instead, certificate access from other services is now
     managed through group permissions. The module no longer runs lego
     twice under certain conditions, and will correctly renew certificates if
     their configuration is changed. Services which reload nginx and httpd after
     certificate renewal are now properly configured too so you no longer have
     to do this manually if you are using HTTPS enabled virtual hosts. A mechanism
     for regenerating certs on demand has also been added and documented.
    </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>
       Nginx web server now starting with additional sandbox/hardening options. By default, write access
       to <literal>/var/log/nginx</literal> and <literal>/var/cache/nginx</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>
     <para>
       Nginx is also started with the systemd option <literal>ProtectHome = mkDefault true;</literal>
       which forbids it to read anything from <literal>/home</literal>, <literal>/root</literal>
       and <literal>/run/user</literal> (see
       <link xlink:href="https://www.freedesktop.org/software/systemd/man/systemd.exec.html#ProtectHome=">ProtectHome docs</link>
       for details).
       If you require serving files from home directories, you may choose to set e.g.
<programlisting>
systemd.services.nginx.serviceConfig.ProtectHome = "read-only";
</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 syntax of the PostgreSQL configuration file is now checked at build
      time. If your configuration includes a file inaccessible inside the build
      sandbox, set <varname>services.postgresql.checkConfig</varname> to
        <literal>false</literal>.
    </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>${networking.hostName}</literal> and
       <literal>${networking.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, RFC 1123) and as such must not contain the domain part.
       This means that the hostname must start with a letter or digit, 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.
       If (e.g. for legacy reasons) a FQDN is required as the Linux kernel network node hostname
       (<literal>uname --nodename</literal>) the option
       <literal>boot.kernel.sysctl."kernel.hostname"</literal>
       can be used as a workaround (but be aware of the 64 character limit).
     </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>
         <literal>sslh</literal> has been updated to version
           <literal>1.21</literal>. The <literal>ssl</literal> probe must be
             renamed to <literal>tls</literal> in <xref linkend="opt-services.sslh.appendConfig"/>.
    </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>
   <listitem>
    <para>
     For NixOS configuration options, the type <literal>loaOf</literal>, after
     its initial deprecation in release 20.03, has been removed. In NixOS and
     Nixpkgs options using this type have been converted to <literal>attrsOf</literal>.
     For more information on this change have look at these links:
     <link xlink:href="https://github.com/NixOS/nixpkgs/issues/1800">issue #1800</link>,
     <link xlink:href="https://github.com/NixOS/nixpkgs/pull/63103">PR #63103</link>.
    </para>
   </listitem>
   <listitem>
    <para>
      <literal>config.systemd.services.${name}.path</literal> now returns a list of paths instead of a colon-separated string.
    </para>
   </listitem>
   <listitem>
    <para>
     Caddy module now uses Caddy v2 by default. Caddy v1 can still be used by setting
     <xref linkend="opt-services.caddy.package"/> to <literal>pkgs.caddy1</literal>.
    </para>
    <para>
     New option <xref linkend="opt-services.caddy.adapter"/> has been added.
    </para>
   </listitem>
   <listitem>
    <para>
     The <link linkend="opt-services.jellyfin.enable">jellyfin</link> module will use and stay on the Jellyfin version <literal>10.5.5</literal>
     if <literal>stateVersion</literal> is lower than <literal>20.09</literal>. This is because significant changes were made to the database schema,
     and it is highly recommended to backup your instance before upgrading. After making your backup, you can upgrade to the latest version either by
     setting your <literal>stateVersion</literal> to <literal>20.09</literal> or higher, or set the <option>services.jellyfin.package</option> to
     <literal>pkgs.jellyfin</literal>. If you do not wish to upgrade Jellyfin, but want to change your <literal>stateVersion</literal>, you can set
     the value of <option>services.jellyfin.package</option> to <literal>pkgs.jellyfin_10_5</literal>.
    </para>
   </listitem>
   <listitem>
    <para>
     The <literal>security.rngd</literal> service is now disabled by default.
     This choice was made because there's krngd in the linux kernel space making it (for most usecases)
     functionally redundent.
    </para>
   </listitem>
   <listitem>
    <para>
     The <literal>hardware.nvidia.optimus_prime.enable</literal> service has been renamed to
     <literal>hardware.nvidia.prime.sync.enable</literal> and has many new enhancements.
     Related nvidia prime settings may have also changed.
    </para>
   </listitem>
   <listitem>
    <para>
     The package <package>nextcloud17</package> has been removed and <package>nextcloud18</package> was marked as insecure
     since both of them will <link xlink:href="https://docs.nextcloud.com/server/19/admin_manual/release_schedule.html">
     will be EOL (end of life) within the lifetime of 20.09</link>.
    </para>
    <para>
     It's necessary to upgrade to <package>nextcloud19</package>:
     <itemizedlist>
      <listitem>
       <para>
        From <package>nextcloud17</package>, you have to upgrade to <package>nextcloud18</package> first as
        Nextcloud doesn't allow going multiple major revisions forward in a single upgrade. This is possible
        by setting <xref linkend="opt-services.nextcloud.package" /> to <package>nextcloud18</package>.
       </para>
      </listitem>
      <listitem>
       <para>
        From <package>nextcloud18</package>, it's possible to directly upgrade to <package>nextcloud19</package>
        by setting <xref linkend="opt-services.nextcloud.package" /> to <package>nextcloud19</package>.
       </para>
      </listitem>
     </itemizedlist>
    </para>
   </listitem>
   <listitem>
    <para>
      The GNOME desktop manager no longer default installs <package>gnome3.epiphany</package>.
      It was chosen to do this as it has a usability breaking issue (see issue <link xlink:href="https://github.com/NixOS/nixpkgs/issues/98819">#98819</link>)
      that makes it unsuitable to be a default app.
    </para>
    <note>
      <para>
        Issue <link
        xlink:href="https://github.com/NixOS/nixpkgs/issues/98819">#98819</link>
        is now fixed and <package>gnome3.epiphany</package> is once
        again installed by default.
      </para>
    </note>
   </listitem>
   <listitem>
     <para>
       If you want to manage the configuration of <package>wpa_supplicant</package> outside of NixOS you must ensure that none of <xref linkend="opt-networking.wireless.networks" />, <xref linkend="opt-networking.wireless.extraConfig" /> or <xref linkend="opt-networking.wireless.userControlled.enable" /> is being used or <literal>true</literal>.
       Using any of those options will cause <package>wpa_supplicant</package> to be started with a NixOS generated configuration file instead of your own.
    </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.

     Device tree overlay support was improved in
     <link xlink:href="https://github.com/NixOS/nixpkgs/pull/79370">#79370</link>
     and now uses <xref linkend="opt-hardware.deviceTree.kernelPackage"/>
     instead of <option>hardware.deviceTree.base</option>.

     <xref linkend="opt-hardware.deviceTree.overlays"/> configuration was
     extended to support <literal>.dts</literal> files with symbols.

     Device trees can now be filtered by setting
     <xref linkend="opt-hardware.deviceTree.filter"/> option.
    </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 installer now enables sshd by default. This improves installation on headless machines especially ARM single-board-computer.
    To login through ssh, either a password or an ssh key must be set for the root user or the nixos user.
    </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 21.05. 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>
   </listitem>
   <listitem>
     <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 config and cache files for fontconfig 2.10.x, the <filename>/etc/fonts/fonts.conf</filename> now belongs to the latest fontconfig, just like on other Linux distributions, and we will <link xlink:href="https://github.com/NixOS/nixpkgs/pull/95358">no longer</link> be versioning the config directories.
    </para>
    <para>
     Fontconfig 2.10.x was removed from Nixpkgs since it hasn’t been used in any Nixpkgs package for years now.
    </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>.
    </para>
   </listitem>
   <listitem>
    <para>
      The option <option>defaultPackages</option> was added. It installs the packages <package>perl</package>, <package>rsync</package> and <package>strace</package> for now. They were added unconditionally to <option>systemPackages</option> before, but are not strictly necessary for a minimal NixOS install. You can set it to an empty list to have a more minimal system. Be aware that some functionality might still have an impure dependency on those packages, so things might break.
    </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>
   <listitem>
     <para>
      Agda has been heavily reworked.
      <itemizedlist>
       <listitem>
         <para>
           <literal>agda.mkDerivation</literal> has been heavily changed and
           is now located at <package>agdaPackages.mkDerivation</package>.
         </para>
       </listitem>
       <listitem>
         <para>
           New top-level packages <package>agda</package> and
           <literal>agda.withPackages</literal> have been added, the second
           of which sets up agda with access to chosen libraries.
         </para>
       </listitem>
       <listitem>
         <para>
           All agda libraries now live under
           <literal>agdaPackages</literal>.
         </para>
       </listitem>
       <listitem>
         <para>
           Many broken libraries have been removed.
         </para>
       </listitem>
      </itemizedlist>
      See the <link
      xlink:href="https://nixos.org/nixpkgs/manual/#agda">new
      documentation</link> for more information.
    </para>
   </listitem>
   <listitem>
    <para>
      The <literal>deepin</literal> package set has been removed from
      nixpkgs. It was a work in progress to package the
      <link xlink:href="https://www.deepin.org/en/dde/">Deepin Desktop Environment (DDE)</link>,
      including libraries, tools and applications, and it was still
      missing a service to launch the desktop environment. It has shown
      to no longer be a feasible goal due to reasons discussed in
      <link xlink:href="https://github.com/NixOS/nixpkgs/issues/94870">issue #94870</link>.
      The package <literal>netease-cloud-music</literal> has also been
      removed, as it depends on libraries from deepin.
    </para>
   </listitem>
   <listitem>
     <para>
       The <literal>opendkim</literal> module now uses systemd sandboxing features
       to limit the exposure of the system towards the opendkim service.
     </para>
   </listitem>
  </itemizedlist>
  <itemizedlist>
   <listitem>
    <para />
    <para>
        Kubernetes has been upgraded to 1.19.1, which also means that the
        golang version to build it has been bumped to 1.15. This may have
        consequences for your existing clusters and their certificates. Please
        consider
        <link xlink:href="https://relnotes.k8s.io/?markdown=93264">
            the release notes for Kubernetes 1.19 carefully
        </link>
        before upgrading.
    </para>
   </listitem>
  </itemizedlist>
  <itemizedlist>
    <listitem>
      <para>
        For AMD GPUs, Vulkan can now be used by adding <literal>amdvlk</literal>
        to <literal>hardware.opengl.extraPackages</literal>.
      </para>
    </listitem>
    <listitem>
      <para>
        Similarly, still for AMD GPUs, the ROCm OpenCL stack can now be used by adding
        <literal>rocm-opencl-icd</literal> to
        <literal>hardware.opengl.extraPackages</literal>.
      </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-contributions">
  <title>Contributions</title>
  <para>
        I, Jonathan Ringer, would like to thank the following individuals for their work on nixpkgs. This release could not be done without the hard work of the NixOS community. There were 31282 contributions across 1313 contributors.
  </para>
  <orderedlist>
   <para>
    Top contributors to NixOS/Nixpkgs from the 20.03 release to the 20.09 release:
   </para>
   <listitem>
    <para>
  2288  Mario Rodas
    </para>
   </listitem>
   <listitem>
    <para>
  1837  Frederik Rietdijk
    </para>
   </listitem>
   <listitem>
    <para>
   946  Jörg Thalheim
    </para>
   </listitem>
   <listitem>
    <para>
   925  Maximilian Bosch
    </para>
   </listitem>
   <listitem>
    <para>
   687  Jonathan Ringer
    </para>
   </listitem>
   <listitem>
    <para>
   651  Jan Tojnar
    </para>
   </listitem>
   <listitem>
    <para>
   622  Daniël de Kok
    </para>
   </listitem>
   <listitem>
    <para>
   605  WORLDofPEACE
    </para>
   </listitem>
   <listitem>
    <para>
   597  Florian Klink
    </para>
   </listitem>
   <listitem>
    <para>
   528  José Romildo Malaquias
    </para>
   </listitem>
  </orderedlist>

  <orderedlist>
   <para>
    Top contributors to stabilizing this release (Zero Hydra Failures period):
   </para>
   <listitem>
    <para>
      281  volth
    </para>
   </listitem>
   <listitem>
    <para>
   101  Robert Scott
    </para>
   </listitem>
   <listitem>
    <para>
    86  Tim Steinbach
    </para>
   </listitem>
   <listitem>
    <para>
    76  WORLDofPEACE
    </para>
   </listitem>
   <listitem>
    <para>
    49  Maximilian Bosch
    </para>
   </listitem>
   <listitem>
    <para>
    42  Thomas Tuegel
    </para>
   </listitem>
   <listitem>
    <para>
    37  Doron Behar
    </para>
   </listitem>
   <listitem>
    <para>
    36  Vladimír Čunát
    </para>
   </listitem>
   <listitem>
    <para>
    27  Jonathan Ringer
    </para>
   </listitem>
   <listitem>
    <para>
    27  Maciej Krüger
    </para>
   </listitem>
  </orderedlist>

  <para>
   I, Jonathan Ringer, would also like to personally thank @WORLDofPEACE for their help in mentoring me on the release process. Special thanks also goes to Thomas Tuegel for helping immensely with stabilizing Qt, KDE, and Plasma5; I would also like to thank Robert Scott for his numerous fixes and pull request reviews.
   </para>

 </section>
</section>
