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diff --git a/nixpkgs/nixos/doc/manual/configuration/linux-kernel.xml b/nixpkgs/nixos/doc/manual/configuration/linux-kernel.xml new file mode 100644 index 000000000000..644d3a33ffd2 --- /dev/null +++ b/nixpkgs/nixos/doc/manual/configuration/linux-kernel.xml @@ -0,0 +1,138 @@ +<chapter xmlns="http://docbook.org/ns/docbook" + xmlns:xlink="http://www.w3.org/1999/xlink" + xmlns:xi="http://www.w3.org/2001/XInclude" + version="5.0" + xml:id="sec-kernel-config"> + <title>Linux Kernel</title> + <para> + You can override the Linux kernel and associated packages using the option + <option>boot.kernelPackages</option>. For instance, this selects the Linux + 3.10 kernel: +<programlisting> +<xref linkend="opt-boot.kernelPackages"/> = pkgs.linuxPackages_3_10; +</programlisting> + 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> + The default Linux kernel configuration should be fine for most users. You can + see the configuration of your current kernel with the following command: +<programlisting> +zcat /proc/config.gz +</programlisting> + If you want to change the kernel configuration, you can use the + <option>packageOverrides</option> feature (see + <xref +linkend="sec-customising-packages" />). For instance, to enable support + for the kernel debugger KGDB: +<programlisting> +nixpkgs.config.packageOverrides = pkgs: + { linux_3_4 = pkgs.linux_3_4.override { + extraConfig = + '' + KGDB y + ''; + }; + }; +</programlisting> + <varname>extraConfig</varname> 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 + <command>udev</command>. You can force a module to be loaded via + <xref linkend="opt-boot.kernelModules"/>, e.g. +<programlisting> +<xref linkend="opt-boot.kernelModules"/> = [ "fuse" "kvm-intel" "coretemp" ]; +</programlisting> + 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"/>: +<programlisting> +<xref linkend="opt-boot.initrd.kernelModules"/> = [ "cifs" ]; +</programlisting> + 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. +<programlisting> +<xref linkend="opt-boot.kernel.sysctl"/>."net.ipv4.tcp_keepalive_time" = 120; +</programlisting> + sets the kernel’s TCP keepalive time to 120 seconds. To see the available + parameters, run <command>sysctl -a</command>. + </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>linuxManualConfig</literal>: +<screen><![CDATA[ + custom-kernel = super.linuxManualConfig { + inherit (super) stdenv hostPlatform; + inherit (linux_4_9) src; + version = "${linux_4_9.version}-custom"; + + configfile = /home/me/my_kernel_config; + allowImportFromDerivation = true; + }; + ]]></screen> + You can edit the config with this snippet (by default <command>make + menuconfig</command> won't work out of the box on nixos): +<screen><![CDATA[ + nix-shell -E 'with import <nixpkgs> {}; kernelToOverride.overrideAttrs (o: {nativeBuildInputs=o.nativeBuildInputs ++ [ pkgconfig ncurses ];})' + ]]></screen> + or you can let nixpkgs generate the configuration. Nixpkgs generates it via + answering the interactive kernel utility <command>make config</command>. The + answers depend on parameters passed to + <filename>pkgs/os-specific/linux/kernel/generic.nix</filename> (which you + can influence by overriding <literal>extraConfig, autoModules, + modDirVersion, preferBuiltin, extraConfig</literal>). +<screen><![CDATA[ + + mptcp93.override ({ + name="mptcp-local"; + + ignoreConfigErrors = true; + autoModules = false; + kernelPreferBuiltin = true; + + enableParallelBuilding = true; + + extraConfig = '' + DEBUG_KERNEL y + FRAME_POINTER y + KGDB y + KGDB_SERIAL_CONSOLE y + DEBUG_INFO y + ''; + }); + ]]></screen> + </para> + </section> + <section xml:id="sec-linux-config-developing-modules"> + <title>Developing kernel modules</title> + + <para> + When developing kernel modules it's often convenient to run edit-compile-run + loop as quickly as possible. See below snippet as an example of developing + <literal>mellanox</literal> drivers. + </para> + +<screen><![CDATA[ +$ 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 +]]></screen> + </section> +</chapter> |