Linux kernel: Difference between revisions
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== | == Configuration == | ||
You can choose your kernel simply by setting the <code>boot.kernelPackages</code> option | |||
For example by adding this to <code>/etc/nixos/configuration.nix</code>: | |||
<syntaxHighlight lang="nix"> | |||
boot.kernelPackages = pkgs.linuxPackages_latest; | |||
</syntaxHighlight> | |||
And rebuild your system and reboot to use your new kernel: | |||
<syntaxHighlight lang="console"> | |||
$ sudo nixos-rebuild boot | |||
$ sudo reboot | |||
</syntaxHighlight> | |||
=== List available kernels === | |||
You can list available kernels using <code>nix repl</code> (previously <code>nix-repl</code>) : | |||
<syntaxHighlight lang="console"> | |||
$ nix repl | |||
</syntaxHighlight> | |||
nix-repl> :l <nixpkgs> | |||
Added 8557 variables. | |||
nix-repl> pkgs.linuxPackages | |||
pkgs.linuxPackages pkgs.linuxPackages_latest_hardened | |||
pkgs.linuxPackagesFor pkgs.linuxPackages_latest_xen_dom0 | |||
pkgs.linuxPackages_4_14 pkgs.linuxPackages_latest_xen_dom0_hardened | |||
pkgs.linuxPackages_4_15 pkgs.linuxPackages_mptcp | |||
pkgs.linuxPackages_4_4 pkgs.linuxPackages_rpi | |||
pkgs.linuxPackages_4_9 pkgs.linuxPackages_samus_4_12 | |||
pkgs.linuxPackages_beagleboard pkgs.linuxPackages_samus_latest | |||
pkgs.linuxPackages_copperhead_hardened pkgs.linuxPackages_testing | |||
pkgs.linuxPackages_custom pkgs.linuxPackages_testing_bcachefs | |||
pkgs.linuxPackages_hardened pkgs.linuxPackages_xen_dom0 | |||
=== Custom kernel modules === | |||
Note that if you deviate from the default kernel version, you should also take extra care that extra kernel modules must match the same version. The safest way to do this is to use <code>config.boot.kernelPackages</code> to select the correct module set: | |||
<syntaxHighlight lang="nix"> | |||
{...}: | |||
{ | |||
boot.extraModulePackages = with config.boot.kernelPackages; [ wireguard ]; | |||
} | |||
</syntaxHighlight> | |||
=== Custom configuration === | |||
It is sometimes desirable to change the configuration of your kernel, while keeping the kernel version itself managed through Nixpkgs. To do so, you can add the configuration to a dummy {{nixos:option|boot.kernelPatches}},<ref>[https://logs.nix.samueldr.com/nixos/2018-05-09#1525898458-1525898534; #nixos 2018-05-09]</ref><ref>[https://github.com/NixOS/nixpkgs/blob/03d4694e6110fa9c16e88ee74085ea2068c27494/nixos/modules/misc/crashdump.nix#L63-L73 <tt>nixos/modules/misc/crashdump.nix#L63-L73</tt>]</ref> which will then be merged and applied to the current kernel. As with kernel configuration with NixOS, drop the <tt>CONFIG_</tt> prefix from the kernel configuration names. | |||
This example is from the {{nixos:option|boot.crashDump.enable}} option: | |||
<syntaxhighlight lang=nix> | |||
{ | |||
boot.kernelPatches = [ { | |||
name = "crashdump-config"; | |||
patch = null; | |||
extraConfig = '' | |||
CRASH_DUMP y | |||
DEBUG_INFO y | |||
PROC_VMCORE y | |||
LOCKUP_DETECTOR y | |||
HARDLOCKUP_DETECTOR y | |||
''; | |||
} ]; | |||
} | |||
</syntaxhighlight> | |||
=== Debugging a failed configuration === | |||
As dependencies between kernel configurations items need to be addressed manually, you can inspect the intermediate nix config file after for instance the error | |||
{{bc|note: keeping build directory '/tmp/nix-build-linux-config-4.19.0-mptcp_v0.94.1.drv-0'}} | |||
by opening {{ic|/tmp/nix-build-linux-config-4.19.0-mptcp_v0.94.1.drv-0/.attr-0}}. | |||
== Developing kernel modules == | == Developing kernel modules == | ||
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If the source was unpacked and an initial config exists, you can run <code>make xconfig KCONFIG_CONFIG=build/.config</code> | If the source was unpacked and an initial config exists, you can run <code>make xconfig KCONFIG_CONFIG=build/.config</code> | ||
== | == References == | ||
<references /> | |||