Revert "build-sys: substitute strings in systemd.unit(5)"

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

<?xml version="1.0"?>
<!--*-nxml-*-->
<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN" "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
<!--
  This file is part of systemd.

  Copyright 2011 Lennart Poettering

  systemd is free software; you can redistribute it and/or modify it
  under the terms of the GNU Lesser General Public License as published by
  the Free Software Foundation; either version 2.1 of the License, or
  (at your option) any later version.

  systemd is distributed in the hope that it will be useful, but
  WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  Lesser General Public License for more details.

  You should have received a copy of the GNU Lesser General Public License
  along with systemd; If not, see <http://www.gnu.org/licenses/>.
-->
<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>At boot,
                <citerefentry><refentrytitle>systemd-sysctl.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>
                reads configuration files from the above directories
                to configure
                <citerefentry><refentrytitle>sysctl</refentrytitle><manvolnum>8</manvolnum></citerefentry>
                kernel parameters.</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><replaceable>program</replaceable>.conf</filename>.
                Files in <filename>/etc/</filename> override files
                with the same name in <filename>/usr/lib/</filename>
                and <filename>/run/</filename>.  Files in
                <filename>/run/</filename> override files with the same
                name in <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 files installed by vendor packages. All
                configuration files are sorted by their filename 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 later 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> bearing the
                same file 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>systemd-sysctl.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
                        <citerefentry><refentrytitle>systemd-delta</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>