139 lines
6.1 KiB
XML
139 lines
6.1 KiB
XML
<chapter xmlns="http://docbook.org/ns/docbook"
|
||
xmlns:xlink="http://www.w3.org/1999/xlink"
|
||
version="5.0"
|
||
xml:id="sec-upgrading">
|
||
<title>Upgrading NixOS</title>
|
||
<para>
|
||
The best way to keep your NixOS installation up to date is to use one of the
|
||
NixOS <emphasis>channels</emphasis>. A channel is a Nix mechanism for
|
||
distributing Nix expressions and associated binaries. The NixOS channels are
|
||
updated automatically from NixOS’s Git repository after certain tests have
|
||
passed and all packages have been built. These channels are:
|
||
<itemizedlist>
|
||
<listitem>
|
||
<para>
|
||
<emphasis>Stable channels</emphasis>, such as
|
||
<literal
|
||
xlink:href="https://nixos.org/channels/nixos-20.09">nixos-20.09</literal>.
|
||
These only get conservative bug fixes and package upgrades. For instance,
|
||
a channel update may cause the Linux kernel on your system to be upgraded
|
||
from 4.19.34 to 4.19.38 (a minor bug fix), but not from
|
||
4.19.<replaceable>x</replaceable> to 4.20.<replaceable>x</replaceable> (a
|
||
major change that has the potential to break things). Stable channels are
|
||
generally maintained until the next stable branch is created.
|
||
</para>
|
||
<para></para>
|
||
</listitem>
|
||
<listitem>
|
||
<para>
|
||
The <emphasis>unstable channel</emphasis>,
|
||
<literal
|
||
xlink:href="https://nixos.org/channels/nixos-unstable">nixos-unstable</literal>.
|
||
This corresponds to NixOS’s main development branch, and may thus see
|
||
radical changes between channel updates. It’s not recommended for
|
||
production systems.
|
||
</para>
|
||
</listitem>
|
||
<listitem>
|
||
<para>
|
||
<emphasis>Small channels</emphasis>, such as
|
||
<literal
|
||
xlink:href="https://nixos.org/channels/nixos-20.09-small">nixos-20.09-small</literal>
|
||
or
|
||
<literal
|
||
xlink:href="https://nixos.org/channels/nixos-unstable-small">nixos-unstable-small</literal>.
|
||
These are identical to the stable and unstable channels described above,
|
||
except that they contain fewer binary packages. This means they get
|
||
updated faster than the regular channels (for instance, when a critical
|
||
security patch is committed to NixOS’s source tree), but may require
|
||
more packages to be built from source than usual. They’re mostly
|
||
intended for server environments and as such contain few GUI applications.
|
||
</para>
|
||
</listitem>
|
||
</itemizedlist>
|
||
To see what channels are available, go to
|
||
<link xlink:href="https://nixos.org/channels"/>. (Note that the URIs of the
|
||
various channels redirect to a directory that contains the channel’s latest
|
||
version and includes ISO images and VirtualBox appliances.) Please note that
|
||
during the release process, channels that are not yet released will be
|
||
present here as well. See the Getting NixOS page
|
||
<link xlink:href="https://nixos.org/nixos/download.html"/> to find the newest
|
||
supported stable release.
|
||
</para>
|
||
<para>
|
||
When you first install NixOS, you’re automatically subscribed to the NixOS
|
||
channel that corresponds to your installation source. For instance, if you
|
||
installed from a 20.09 ISO, you will be subscribed to the
|
||
<literal>nixos-20.09</literal> channel. To see which NixOS channel you’re
|
||
subscribed to, run the following as root:
|
||
<screen>
|
||
<prompt># </prompt>nix-channel --list | grep nixos
|
||
nixos https://nixos.org/channels/nixos-unstable
|
||
</screen>
|
||
To switch to a different NixOS channel, do
|
||
<screen>
|
||
<prompt># </prompt>nix-channel --add https://nixos.org/channels/<replaceable>channel-name</replaceable> nixos
|
||
</screen>
|
||
(Be sure to include the <literal>nixos</literal> parameter at the end.) For
|
||
instance, to use the NixOS 20.09 stable channel:
|
||
<screen>
|
||
<prompt># </prompt>nix-channel --add https://nixos.org/channels/nixos-20.09 nixos
|
||
</screen>
|
||
If you have a server, you may want to use the “small” channel instead:
|
||
<screen>
|
||
<prompt># </prompt>nix-channel --add https://nixos.org/channels/nixos-20.09-small nixos
|
||
</screen>
|
||
And if you want to live on the bleeding edge:
|
||
<screen>
|
||
<prompt># </prompt>nix-channel --add https://nixos.org/channels/nixos-unstable nixos
|
||
</screen>
|
||
</para>
|
||
<para>
|
||
You can then upgrade NixOS to the latest version in your chosen channel by
|
||
running
|
||
<screen>
|
||
<prompt># </prompt>nixos-rebuild switch --upgrade
|
||
</screen>
|
||
which is equivalent to the more verbose <literal>nix-channel --update nixos;
|
||
nixos-rebuild switch</literal>.
|
||
</para>
|
||
<note>
|
||
<para>
|
||
Channels are set per user. This means that running <literal> nix-channel
|
||
--add</literal> as a non root user (or without sudo) will not affect
|
||
configuration in <literal>/etc/nixos/configuration.nix</literal>
|
||
</para>
|
||
</note>
|
||
<warning>
|
||
<para>
|
||
It is generally safe to switch back and forth between channels. The only
|
||
exception is that a newer NixOS may also have a newer Nix version, which may
|
||
involve an upgrade of Nix’s database schema. This cannot be undone easily,
|
||
so in that case you will not be able to go back to your original channel.
|
||
</para>
|
||
</warning>
|
||
<section xml:id="sec-upgrading-automatic">
|
||
<title>Automatic Upgrades</title>
|
||
|
||
<para>
|
||
You can keep a NixOS system up-to-date automatically by adding the following
|
||
to <filename>configuration.nix</filename>:
|
||
<programlisting>
|
||
<xref linkend="opt-system.autoUpgrade.enable"/> = true;
|
||
<xref linkend="opt-system.autoUpgrade.allowReboot"/> = true;
|
||
</programlisting>
|
||
This enables a periodically executed systemd service named
|
||
<literal>nixos-upgrade.service</literal>. If the <literal>allowReboot</literal>
|
||
option is <literal>false</literal>, it runs <command>nixos-rebuild switch
|
||
--upgrade</command> to upgrade NixOS to the latest version in the current
|
||
channel. (To see when the service runs, see <command>systemctl list-timers</command>.)
|
||
If <literal>allowReboot</literal> is <literal>true</literal>, then the
|
||
system will automatically reboot if the new generation contains a different
|
||
kernel, initrd or kernel modules.
|
||
You can also specify a channel explicitly, e.g.
|
||
<programlisting>
|
||
<xref linkend="opt-system.autoUpgrade.channel"/> = https://nixos.org/channels/nixos-20.09;
|
||
</programlisting>
|
||
</para>
|
||
</section>
|
||
</chapter>
|