<?xml version="1.0"?>

<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN" "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">

<refentry id="sysctl.d">

<refentryinfo>

<title>sysctl.d</title>

<productname>systemd</productname>

<authorgroup>

<author>

<contrib>Developer</contrib>

<firstname>Lennart</firstname>

<surname>Poettering</surname>

<email>lennart@poettering.net</email>

</author>

</authorgroup>

</refentryinfo>

<refmeta>

<refentrytitle>sysctl.d</refentrytitle>

<manvolnum>5</manvolnum>

</refmeta>

<refnamediv>

<refname>sysctl.d</refname>

<refpurpose>Configure kernel parameters at boot</refpurpose>

</refnamediv>

<refsynopsisdiv>

<para><filename>/etc/sysctl.d/*.conf</filename></para>

<para><filename>/run/sysctl.d/*.conf</filename></para>

<para><filename>/usr/lib/sysctl.d/*.conf</filename></para>

</refsynopsisdiv>

<refsect1>

<title>Description</title>

<para><command>systemd</command> uses configuration

files from the above directories to configure

<citerefentry><refentrytitle>sysctl</refentrytitle><manvolnum>8</manvolnum></citerefentry>

kernel parameters during boot.</para>

</refsect1>

<refsect1>

<title>Configuration Format</title>

<para>The configuration files contain a list of

variable assignments, separated by newlines. Empty

lines and lines whose first non-whitespace character

is # or ; are ignored.</para>

<para>Note that both / and . are accepted as label

separators within sysctl variable

names. <literal>kernel.domainname=foo</literal> and

<literal>kernel/domainname=foo</literal> hence are

entirely equivalent.</para>

<para>Each configuration file shall be named in the

style of <filename>&lt;program&gt;.conf</filename>.

Files in <filename>/run/</filename> override files

with the same name in <filename>/usr/lib/</filename>.

Files in <filename>/etc</filename> override files with

the same name in <filename>/run/</filename> and

<filename>/usr/lib/</filename>. Packages should

install their configuration files in

<filename>/usr/lib/</filename>. Files in

<filename>/etc/</filename> are reserved for the local

administrator, who may use this logic to override the

configuration installed by vendor packages. All

configuration files are sorted by their name in

alphabetical order, regardless in which of the

directories they reside, to guarantee that a specific

configuration file takes precedence over another file

with an alphabetically earlier name, if both files

contain the same variable setting.</para>

<para>If the administrator wants to disable a

configuration file supplied by the vendor the

recommended way is to place a symlink to

<filename>/dev/null</filename> in

<filename>/etc/sysctl.d</filename> carrying with the

same name.</para>

</refsect1>

<refsect1>

<title>Example</title>

<example>

<title>/etc/sysctl.d/domain-name.conf example:</title>

<programlisting># Set kernel YP domain name

kernel.domainname=example.com</programlisting>

</example>

</refsect1>

<refsect1>

<title>See Also</title>

<para>

<citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,

<citerefentry><refentrytitle>sysctl</refentrytitle><manvolnum>8</manvolnum></citerefentry>,

<citerefentry><refentrytitle>sysctl.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>

</para>

</refsect1>

</refentry>