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Merge pull request #204780 from Ma27/kernel-maintenance-docs

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nixos/manual: document kernel backporting policy and implications of it
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Maximilian Bosch 2022-12-09 11:53:53 +01:00 committed by GitHub
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33
nixos/doc/manual/configuration/linux-kernel.chapter.md
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@ -17,6 +17,16 @@ you may want to use one of the unversioned `pkgs.linuxPackages_*` aliases
such as `pkgs.linuxPackages_latest`, that are kept up to date with new
versions.
Please note that the current convention in NixOS is to only keep actively
maintained kernel versions on both unstable and the currently supported stable
release(s) of NixOS. This means that a non-longterm kernel will be removed after it's
abandoned by the kernel developers, even on stable NixOS versions. If you
pin your kernel onto a non-longterm version, expect your evaluation to fail as
soon as the version is out of maintenance.
Longterm versions of kernels will be removed before the next stable NixOS that will
exceed the maintenance period of the kernel version.
The default Linux kernel configuration should be fine for most users.
You can see the configuration of your current kernel with the following
command:
@ -138,3 +148,26 @@ $ cd linux-*
$ make -C $dev/lib/modules/*/build M=$(pwd)/drivers/net/ethernet/mellanox modules
# insmod ./drivers/net/ethernet/mellanox/mlx5/core/mlx5_core.ko
```
## ZFS {#sec-linux-zfs}
It's a common issue that the latest stable version of ZFS doesn't support the latest
available Linux kernel. It is recommended to use the latest available LTS that's compatible
with ZFS. Usually this is the default kernel provided by nixpkgs (i.e. `pkgs.linuxPackages`).
Alternatively, it's possible to pin the system to the latest available kernel
version *that is supported by ZFS* like this:
```nix
{
boot.kernelPackages = pkgs.zfs.latestCompatibleLinuxPackages;
}
```
Please note that the version this attribute points to isn't monotonic because the latest kernel
version only refers to kernel versions supported by the Linux developers. In other words,
the latest kernel version that ZFS is compatible with may decrease over time.
An example: the latest version ZFS is compatible with is 5.19 which is a non-longterm version. When 5.19
is out of maintenance, the latest supported kernel version is 5.15 because it's longterm and the versions
5.16, 5.17 and 5.18 are already out of maintenance because they're non-longterm.

47
nixos/doc/manual/from_md/configuration/linux-kernel.chapter.xml
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@ -21,6 +21,19 @@ boot.kernelPackages = pkgs.linuxKernel.packages.linux_3_10;
<literal>pkgs.linuxPackages_latest</literal>, that are kept up to
date with new versions.
</para>
<para>
Please note that the current convention in NixOS is to only keep
actively maintained kernel versions on both unstable and the
currently supported stable release(s) of NixOS. This means that a
non-longterm kernel will be removed after it’s abandoned by the
kernel developers, even on stable NixOS versions. If you pin your
kernel onto a non-longterm version, expect your evaluation to fail
as soon as the version is out of maintenance.
</para>
<para>
Longterm versions of kernels will be removed before the next stable
NixOS that will exceed the maintenance period of the kernel version.
</para>
<para>
The default Linux kernel configuration should be fine for most
users. You can see the configuration of your current kernel with the
@ -154,4 +167,38 @@ $ make -C $dev/lib/modules/*/build M=$(pwd)/drivers/net/ethernet/mellanox module
# insmod ./drivers/net/ethernet/mellanox/mlx5/core/mlx5_core.ko
</programlisting>
</section>
<section xml:id="sec-linux-zfs">
<title>ZFS</title>
<para>
It’s a common issue that the latest stable version of ZFS doesn’t
support the latest available Linux kernel. It is recommended to
use the latest available LTS that’s compatible with ZFS. Usually
this is the default kernel provided by nixpkgs (i.e.
<literal>pkgs.linuxPackages</literal>).
</para>
<para>
Alternatively, it’s possible to pin the system to the latest
available kernel version <emphasis>that is supported by
ZFS</emphasis> like this:
</para>
<programlisting language="bash">
{
boot.kernelPackages = pkgs.zfs.latestCompatibleLinuxPackages;
}
</programlisting>
<para>
Please note that the version this attribute points to isn’t
monotonic because the latest kernel version only refers to kernel
versions supported by the Linux developers. In other words, the
latest kernel version that ZFS is compatible with may decrease
over time.
</para>
<para>
An example: the latest version ZFS is compatible with is 5.19
which is a non-longterm version. When 5.19 is out of maintenance,
the latest supported kernel version is 5.15 because it’s longterm
and the versions 5.16, 5.17 and 5.18 are already out of
maintenance because they’re non-longterm.
</para>
</section>
</chapter>

5
nixos/modules/system/boot/kernel.nix
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@ -62,6 +62,11 @@ in
configuration. For instance, if you use the NVIDIA X driver,
then it also needs to contain an attribute
{var}`nvidia_x11`.
Please note that we strictly support kernel versions that are
maintained by the Linux developers only. More information on the
availability of kernel versions is documented
[in the Linux section of the manual](https://nixos.org/manual/nixos/unstable/index.html#sec-kernel-config).
'';
};