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[thirdparty/systemd.git] / man / sysctl.d.xml

<?xml version="1.0"?>
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<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN" "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
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  Copyright 2011 Lennart Poettering

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<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>