man/sysctl.d.xml

   1 <?xml version="1.0"?>
   2 <!--*-nxml-*-->
   3 <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN" "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
   4 <!--
   5   This file is part of systemd.
   6
   7   Copyright 2011 Lennart Poettering
   8
   9   systemd is free software; you can redistribute it and/or modify it
  10   under the terms of the GNU Lesser General Public License as published by
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  17   Lesser General Public License for more details.
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  22 <refentry id="sysctl.d">
  23
  24         <refentryinfo>
  25                 <title>sysctl.d</title>
  26                 <productname>systemd</productname>
  27
  28                 <authorgroup>
  29                         <author>
  30                                 <contrib>Developer</contrib>
  31                                 <firstname>Lennart</firstname>
  32                                 <surname>Poettering</surname>
  33                                 <email>lennart@poettering.net</email>
  34                         </author>
  35                 </authorgroup>
  36         </refentryinfo>
  37
  38         <refmeta>
  39                 <refentrytitle>sysctl.d</refentrytitle>
  40                 <manvolnum>5</manvolnum>
  41         </refmeta>
  42
  43         <refnamediv>
  44                 <refname>sysctl.d</refname>
  45                 <refpurpose>Configure kernel parameters at boot</refpurpose>
  46         </refnamediv>
  47
  48         <refsynopsisdiv>
  49                 <para><filename>/etc/sysctl.d/*.conf</filename></para>
  50                 <para><filename>/run/sysctl.d/*.conf</filename></para>
  51                 <para><filename>/usr/lib/sysctl.d/*.conf</filename></para>
  52         </refsynopsisdiv>
  53
  54         <refsect1>
  55                 <title>Description</title>
  56
  57                 <para>At boot,
  58                 <citerefentry><refentrytitle>systemd-sysctl.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>
  59                 reads configuration files from the above directories
  60                 to configure
  61                 <citerefentry><refentrytitle>sysctl</refentrytitle><manvolnum>8</manvolnum></citerefentry>
  62                 kernel parameters.</para>
  63         </refsect1>
  64
  65         <refsect1>
  66                 <title>Configuration Format</title>
  67
  68                 <para>The configuration files contain a list of
  69                 variable assignments, separated by newlines. Empty
  70                 lines and lines whose first non-whitespace character
  71                 is <literal>#</literal> or <literal>;</literal> are
  72                 ignored.</para>
  73
  74                 <para>Note that either <literal>/</literal> or
  75                 <literal>.</literal> may be used as separators within
  76                 sysctl variable names. If the first separator is a
  77                 slash, remaining slashes and dots are left intact. If
  78                 the first separator is a dot, dots and slashes are
  79                 interchanged. <literal>kernel.domainname=foo</literal>
  80                 and <literal>kernel/domainname=foo</literal> are
  81                 equivalent and will cause <literal>foo</literal> to
  82                 be written to
  83                 <filename>/proc/sys/kernel/domainname</filename>.
  84                 Either
  85                 <literal>net.ipv4.conf.enp3s0/200.forwarding</literal>
  86                 or
  87                 <literal>net/ipv4/conf/enp3s0.200/forwarding</literal>
  88                 may be used to refer to
  89                 <filename>/proc/sys/net/ipv4/conf/enp3s0.200/forwarding</filename>.
  90                 </para>
  91
  92                 <para>Each configuration file shall be named in the
  93                 style of <filename><replaceable>program</replaceable>.conf</filename>.
  94                 Files in <filename>/etc/</filename> override files
  95                 with the same name in <filename>/usr/lib/</filename>
  96                 and <filename>/run/</filename>.  Files in
  97                 <filename>/run/</filename> override files with the same
  98                 name in <filename>/usr/lib/</filename>. Packages
  99                 should install their configuration files in
 100                 <filename>/usr/lib/</filename>. Files in
 101                 <filename>/etc/</filename> are reserved for the local
 102                 administrator, who may use this logic to override the
 103                 configuration files installed by vendor packages. All
 104                 configuration files are sorted by their filename in
 105                 lexicographic order, regardless of which of the
 106                 directories they reside in. If multiple files specify the
 107                 same variable name, the entry in the file with the
 108                 lexicographically latest name will be applied. It is
 109                 recommended to prefix all filenames with a two-digit
 110                 number and a dash, to simplify the ordering of the
 111                 files.</para>
 112
 113                 <para>If the administrator wants to disable a
 114                 configuration file supplied by the vendor, the
 115                 recommended way is to place a symlink to
 116                 <filename>/dev/null</filename> in
 117                 <filename>/etc/sysctl.d/</filename> bearing the
 118                 same filename.</para>
 119
 120                 <para>The settings configured with
 121                 <filename>sysctl.d</filename> files will be applied
 122                 early on boot. The network interface-specific options
 123                 will also be applied individually for each network
 124                 interface as it shows up in the system. (More
 125                 specifically,
 126                 <filename>net.ipv4.conf.*</filename>,
 127                 <filename>net.ipv6.conf.*</filename>,
 128                 <filename>net.ipv4.neigh.*</filename> and <filename>net.ipv6.neigh.*</filename>)</para>
 129         </refsect1>
 130
 131         <refsect1>
 132                 <title>Example</title>
 133                 <example>
 134                         <title>/etc/sysctl.d/domain-name.conf example:</title>
 135
 136                         <programlisting># Set kernel YP domain name
 137 kernel.domainname=example.com</programlisting>
 138                 </example>
 139         </refsect1>
 140
 141         <refsect1>
 142                 <title>See Also</title>
 143                 <para>
 144                         <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 145                         <citerefentry><refentrytitle>systemd-sysctl.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 146                         <citerefentry><refentrytitle>systemd-delta</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 147                         <citerefentry><refentrytitle>sysctl</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 148                         <citerefentry><refentrytitle>sysctl.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>
 149                 </para>
 150         </refsect1>
 151
 152 </refentry>