pyrox.dev
1# Linux Kernel {#sec-kernel-config}
2
3You can override the Linux kernel and associated packages using the
4option `boot.kernelPackages`. For instance, this selects the Linux 3.10
5kernel:
6
7```nix
8{
9 boot.kernelPackages = pkgs.linuxKernel.packages.linux_3_10;
10}
11```
12
13Note that this not only replaces the kernel, but also packages that are
14specific to the kernel version, such as the NVIDIA video drivers. This
15ensures that driver packages are consistent with the kernel.
16
17While `pkgs.linuxKernel.packages` contains all available kernel packages,
18you may want to use one of the unversioned `pkgs.linuxPackages_*` aliases
19such as `pkgs.linuxPackages_latest`, that are kept up to date with new
20versions.
21
22Please note that the current convention in NixOS is to only keep actively
23maintained kernel versions on both unstable and the currently supported stable
24release(s) of NixOS. This means that a non-longterm kernel will be removed after it's
25abandoned by the kernel developers, even on stable NixOS versions. If you
26pin your kernel onto a non-longterm version, expect your evaluation to fail as
27soon as the version is out of maintenance.
28
29Longterm versions of kernels will be removed before the next stable NixOS that will
30exceed the maintenance period of the kernel version.
31
32The default Linux kernel configuration should be fine for most users.
33You can see the configuration of your current kernel with the following
34command:
35
36```ShellSession
37zcat /proc/config.gz
38```
39
40If you want to change the kernel configuration, you can use the
41`packageOverrides` feature (see [](#sec-customising-packages)). For
42instance, to enable support for the kernel debugger KGDB:
43
44```nix
45{
46 nixpkgs.config.packageOverrides = pkgs: pkgs.lib.recursiveUpdate pkgs {
47 linuxKernel.kernels.linux_5_10 = pkgs.linuxKernel.kernels.linux_5_10.override {
48 extraConfig = ''
49 KGDB y
50 '';
51 };
52 };
53}
54```
55
56`extraConfig` takes a list of Linux kernel configuration options, one
57per line. The name of the option should not include the prefix
58`CONFIG_`. The option value is typically `y`, `n` or `m` (to build
59something as a kernel module).
60
61Kernel modules for hardware devices are generally loaded automatically
62by `udev`. You can force a module to be loaded via
63[](#opt-boot.kernelModules), e.g.
64
65```nix
66{
67 boot.kernelModules = [ "fuse" "kvm-intel" "coretemp" ];
68}
69```
70
71If the module is required early during the boot (e.g. to mount the root
72file system), you can use [](#opt-boot.initrd.kernelModules):
73
74```nix
75{
76 boot.initrd.kernelModules = [ "cifs" ];
77}
78```
79
80This causes the specified modules and their dependencies to be added to
81the initial ramdisk.
82
83Kernel runtime parameters can be set through
84[](#opt-boot.kernel.sysctl), e.g.
85
86```nix
87{
88 boot.kernel.sysctl."net.ipv4.tcp_keepalive_time" = 120;
89}
90```
91
92sets the kernel's TCP keepalive time to 120 seconds. To see the
93available parameters, run `sysctl -a`.
94
95## Building a custom kernel {#sec-linux-config-customizing}
96
97Please refer to the Nixpkgs manual for the various ways of [building a custom kernel](https://nixos.org/nixpkgs/manual#sec-linux-kernel).
98
99To use your custom kernel package in your NixOS configuration, set
100
101```nix
102{
103 boot.kernelPackages = pkgs.linuxPackagesFor yourCustomKernel;
104}
105```
106
107## Rust {#sec-linux-rust}
108
109The Linux kernel does not have Rust language support enabled by
110default. For kernel versions 6.7 or newer, experimental Rust support
111can be enabled. In a NixOS configuration, set:
112
113```nix
114{
115 boot.kernelPatches = [
116 {
117 name = "Rust Support";
118 patch = null;
119 features = {
120 rust = true;
121 };
122 }
123 ];
124}
125```
126
127## Developing kernel modules {#sec-linux-config-developing-modules}
128
129This section was moved to the [Nixpkgs manual](https://nixos.org/nixpkgs/manual#sec-linux-kernel-developing-modules).
130
131## ZFS {#sec-linux-zfs}
132
133It's a common issue that the latest stable version of ZFS doesn't support the latest
134available Linux kernel. It is recommended to use the latest available LTS that's compatible
135with ZFS. Usually this is the default kernel provided by nixpkgs (i.e. `pkgs.linuxPackages`).