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{ boot.kernelPackages = pkgs.linuxKernel.packages.linux_3_10; }
9```
10
11Note that this not only replaces the kernel, but also packages that are
12specific to the kernel version, such as the NVIDIA video drivers. This
13ensures that driver packages are consistent with the kernel.
14
15While `pkgs.linuxKernel.packages` contains all available kernel packages,
16you may want to use one of the unversioned `pkgs.linuxPackages_*` aliases
17such as `pkgs.linuxPackages_latest`, that are kept up to date with new
18versions.
19
20Please note that the current convention in NixOS is to only keep actively
21maintained kernel versions on both unstable and the currently supported stable
22release(s) of NixOS. This means that a non-longterm kernel will be removed after it's
23abandoned by the kernel developers, even on stable NixOS versions. If you
24pin your kernel onto a non-longterm version, expect your evaluation to fail as
25soon as the version is out of maintenance.
26
27A kernel will be removed from nixpkgs when the first batch of stable kernels
28_after_ the final release is published. E.g. when 6.15.11 is the final release
29of the 6.15 series and is released together with 6.16.3 and 6.12.43, it will be
30removed on the release of 6.16.4 and 6.12.44. Custom kernel variants such
31as linux-hardened are also affected by this.
32
33Longterm versions of kernels will be removed before the next stable NixOS that will
34exceed the maintenance period of the kernel version.
35
36The default Linux kernel configuration should be fine for most users.
37You can see the configuration of your current kernel with the following
38command:
39
40```ShellSession
41zcat /proc/config.gz
42```
43
44If you want to change the kernel configuration, you can use the
45`packageOverrides` feature (see [](#sec-customising-packages)). For
46instance, to enable support for the kernel debugger KGDB:
47
48```nix
49{
50 nixpkgs.config.packageOverrides =
51 pkgs:
52 pkgs.lib.recursiveUpdate pkgs {
53 linuxKernel.kernels.linux_5_10 = pkgs.linuxKernel.kernels.linux_5_10.override {
54 extraConfig = ''
55 KGDB y
56 '';
57 };
58 };
59}
60```
61
62`extraConfig` takes a list of Linux kernel configuration options, one
63per line. The name of the option should not include the prefix
64`CONFIG_`. The option value is typically `y`, `n` or `m` (to build
65something as a kernel module).
66
67Kernel modules for hardware devices are generally loaded automatically
68by `udev`. You can force a module to be loaded via
69[](#opt-boot.kernelModules), e.g.
70
71```nix
72{
73 boot.kernelModules = [
74 "fuse"
75 "kvm-intel"
76 "coretemp"
77 ];
78}
79```
80
81If the module is required early during the boot (e.g. to mount the root
82file system), you can use [](#opt-boot.initrd.kernelModules):
83
84```nix
85{ boot.initrd.kernelModules = [ "cifs" ]; }
86```
87
88This causes the specified modules and their dependencies to be added to
89the initial ramdisk.
90
91Kernel runtime parameters can be set through
92[](#opt-boot.kernel.sysctl), e.g.
93
94```nix
95{ boot.kernel.sysctl."net.ipv4.tcp_keepalive_time" = 120; }
96```
97
98sets the kernel's TCP keepalive time to 120 seconds. To see the
99available parameters, run `sysctl -a`.
100
101## Building a custom kernel {#sec-linux-config-customizing}
102
103Please refer to the Nixpkgs manual for the various ways of [building a custom kernel](https://nixos.org/nixpkgs/manual#sec-linux-kernel).
104
105To use your custom kernel package in your NixOS configuration, set
106
107```nix
108{ boot.kernelPackages = pkgs.linuxPackagesFor yourCustomKernel; }
109```
110
111## Rust {#sec-linux-rust}
112
113The Linux kernel does not have Rust language support enabled by
114default. For kernel versions 6.7 or newer, experimental Rust support
115can be enabled. In a NixOS configuration, set:
116
117```nix
118{
119 boot.kernelPatches = [
120 {
121 name = "Rust Support";
122 patch = null;
123 features = {
124 rust = true;
125 };
126 }
127 ];
128}
129```
130
131## Developing kernel modules {#sec-linux-config-developing-modules}
132
133This section was moved to the [Nixpkgs manual](https://nixos.org/nixpkgs/manual#sec-linux-kernel-developing-modules).
134
135## ZFS {#sec-linux-zfs}
136
137It's a common issue that the latest stable version of ZFS doesn't support the latest
138available Linux kernel. It is recommended to use the latest available LTS that's compatible
139with ZFS. Usually this is the default kernel provided by nixpkgs (i.e. `pkgs.linuxPackages`).