70 lines
2.5 KiB
XML
70 lines
2.5 KiB
XML
<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>
|
||
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>
|
||
cat /proc/config.gz | gunzip
|
||
</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 <option>boot.kernelModules</option>, e.g.
|
||
<programlisting>
|
||
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
|
||
<option>boot.initrd.extraKernelModules</option>:
|
||
<programlisting>
|
||
boot.initrd.extraKernelModules = [ "cifs" ];
|
||
</programlisting>
|
||
This causes the specified modules and their dependencies to be added
|
||
to the initial ramdark.</para>
|
||
|
||
<para>Kernel runtime parameters can be set through
|
||
<option>boot.kernel.sysctl</option>, e.g.
|
||
<programlisting>
|
||
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>
|
||
|
||
</chapter>
|