diff options
Diffstat (limited to 'nixos/doc/manual/from_md/configuration/linux-kernel.chapter.xml')
| -rw-r--r-- | nixos/doc/manual/from_md/configuration/linux-kernel.chapter.xml | 157 |
1 files changed, 157 insertions, 0 deletions
diff --git a/nixos/doc/manual/from_md/configuration/linux-kernel.chapter.xml b/nixos/doc/manual/from_md/configuration/linux-kernel.chapter.xml new file mode 100644 index 00000000000..a1d6815af29 --- /dev/null +++ b/nixos/doc/manual/from_md/configuration/linux-kernel.chapter.xml @@ -0,0 +1,157 @@ +<chapter xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xml:id="sec-kernel-config"> + <title>Linux Kernel</title> + <para> + You can override the Linux kernel and associated packages using the + option <literal>boot.kernelPackages</literal>. For instance, this + selects the Linux 3.10 kernel: + </para> + <programlisting language="bash"> +boot.kernelPackages = pkgs.linuxKernel.packages.linux_3_10; +</programlisting> + <para> + Note that this not only replaces the kernel, but also packages that + are specific to the kernel version, such as the NVIDIA video + drivers. This ensures that driver packages are consistent with the + kernel. + </para> + <para> + While <literal>pkgs.linuxKernel.packages</literal> contains all + available kernel packages, you may want to use one of the + unversioned <literal>pkgs.linuxPackages_*</literal> aliases such as + <literal>pkgs.linuxPackages_latest</literal>, that are kept up to + date with new versions. + </para> + <para> + The default Linux kernel configuration should be fine for most + users. You can see the configuration of your current kernel with the + following command: + </para> + <programlisting> +zcat /proc/config.gz +</programlisting> + <para> + If you want to change the kernel configuration, you can use the + <literal>packageOverrides</literal> feature (see + <xref linkend="sec-customising-packages" />). For instance, to + enable support for the kernel debugger KGDB: + </para> + <programlisting language="bash"> +nixpkgs.config.packageOverrides = pkgs: pkgs.lib.recursiveUpdate pkgs { + linuxKernel.kernels.linux_5_10 = pkgs.linuxKernel.kernels.linux_5_10.override { + extraConfig = '' + KGDB y + ''; + }; +}; +</programlisting> + <para> + <literal>extraConfig</literal> takes a list of Linux kernel + configuration options, one per line. The name of the option should + not include the prefix <literal>CONFIG_</literal>. The option value + is typically <literal>y</literal>, <literal>n</literal> or + <literal>m</literal> (to build something as a kernel module). + </para> + <para> + Kernel modules for hardware devices are generally loaded + automatically by <literal>udev</literal>. You can force a module to + be loaded via <xref linkend="opt-boot.kernelModules" />, e.g. + </para> + <programlisting language="bash"> +boot.kernelModules = [ "fuse" "kvm-intel" "coretemp" ]; +</programlisting> + <para> + If the module is required early during the boot (e.g. to mount the + root file system), you can use + <xref linkend="opt-boot.initrd.kernelModules" />: + </para> + <programlisting language="bash"> +boot.initrd.kernelModules = [ "cifs" ]; +</programlisting> + <para> + This causes the specified modules and their dependencies to be added + to the initial ramdisk. + </para> + <para> + Kernel runtime parameters can be set through + <xref linkend="opt-boot.kernel.sysctl" />, e.g. + </para> + <programlisting language="bash"> +boot.kernel.sysctl."net.ipv4.tcp_keepalive_time" = 120; +</programlisting> + <para> + sets the kernel’s TCP keepalive time to 120 seconds. To see the + available parameters, run <literal>sysctl -a</literal>. + </para> + <section xml:id="sec-linux-config-customizing"> + <title>Customize your kernel</title> + <para> + The first step before compiling the kernel is to generate an + appropriate <literal>.config</literal> configuration. Either you + pass your own config via the <literal>configfile</literal> setting + of <literal>linuxKernel.manualConfig</literal>: + </para> + <programlisting language="bash"> +custom-kernel = let base_kernel = linuxKernel.kernels.linux_4_9; + in super.linuxKernel.manualConfig { + inherit (super) stdenv hostPlatform; + inherit (base_kernel) src; + version = "${base_kernel.version}-custom"; + + configfile = /home/me/my_kernel_config; + allowImportFromDerivation = true; +}; +</programlisting> + <para> + You can edit the config with this snippet (by default + <literal>make menuconfig</literal> won't work out of the box on + nixos): + </para> + <programlisting> +nix-shell -E 'with import <nixpkgs> {}; kernelToOverride.overrideAttrs (o: {nativeBuildInputs=o.nativeBuildInputs ++ [ pkg-config ncurses ];})' +</programlisting> + <para> + or you can let nixpkgs generate the configuration. Nixpkgs + generates it via answering the interactive kernel utility + <literal>make config</literal>. The answers depend on parameters + passed to + <literal>pkgs/os-specific/linux/kernel/generic.nix</literal> + (which you can influence by overriding + <literal>extraConfig, autoModules, modDirVersion, preferBuiltin, extraConfig</literal>). + </para> + <programlisting language="bash"> +mptcp93.override ({ + name="mptcp-local"; + + ignoreConfigErrors = true; + autoModules = false; + kernelPreferBuiltin = true; + + enableParallelBuilding = true; + + extraConfig = '' + DEBUG_KERNEL y + FRAME_POINTER y + KGDB y + KGDB_SERIAL_CONSOLE y + DEBUG_INFO y + ''; +}); +</programlisting> + </section> + <section xml:id="sec-linux-config-developing-modules"> + <title>Developing kernel modules</title> + <para> + When developing kernel modules it's often convenient to run + edit-compile-run loop as quickly as possible. See below snippet as + an example of developing <literal>mellanox</literal> drivers. + </para> + <programlisting> +$ nix-build '<nixpkgs>' -A linuxPackages.kernel.dev +$ nix-shell '<nixpkgs>' -A linuxPackages.kernel +$ unpackPhase +$ 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 +</programlisting> + </section> +</chapter> |