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3802a3d3 | 1 | <?xml version="1.0"?> <!--*-nxml-*--> |
12b42c76 | 2 | <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN" "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd"> |
c91faef3 | 3 | <!-- |
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4 | SPDX-License-Identifier: LGPL-2.1+ |
5 | ||
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6 | This file is part of systemd. |
7 | ||
8 | Copyright 2011 Lennart Poettering | |
9 | ||
10 | systemd is free software; you can redistribute it and/or modify it | |
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11 | under the terms of the GNU Lesser General Public License as published by |
12 | the Free Software Foundation; either version 2.1 of the License, or | |
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13 | (at your option) any later version. |
14 | ||
15 | systemd is distributed in the hope that it will be useful, but | |
16 | WITHOUT ANY WARRANTY; without even the implied warranty of | |
17 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
5430f7f2 | 18 | Lesser General Public License for more details. |
c91faef3 | 19 | |
5430f7f2 | 20 | You should have received a copy of the GNU Lesser General Public License |
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21 | along with systemd; If not, see <http://www.gnu.org/licenses/>. |
22 | --> | |
d3fae78f | 23 | <refentry id="sysctl.d" |
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24 | xmlns:xi="http://www.w3.org/2001/XInclude"> |
25 | ||
26 | <refentryinfo> | |
27 | <title>sysctl.d</title> | |
28 | <productname>systemd</productname> | |
29 | ||
30 | <authorgroup> | |
31 | <author> | |
32 | <contrib>Developer</contrib> | |
33 | <firstname>Lennart</firstname> | |
34 | <surname>Poettering</surname> | |
35 | <email>lennart@poettering.net</email> | |
36 | </author> | |
37 | </authorgroup> | |
38 | </refentryinfo> | |
39 | ||
40 | <refmeta> | |
41 | <refentrytitle>sysctl.d</refentrytitle> | |
42 | <manvolnum>5</manvolnum> | |
43 | </refmeta> | |
44 | ||
45 | <refnamediv> | |
46 | <refname>sysctl.d</refname> | |
47 | <refpurpose>Configure kernel parameters at boot</refpurpose> | |
48 | </refnamediv> | |
49 | ||
50 | <refsynopsisdiv> | |
51 | <para><filename>/etc/sysctl.d/*.conf</filename></para> | |
52 | <para><filename>/run/sysctl.d/*.conf</filename></para> | |
53 | <para><filename>/usr/lib/sysctl.d/*.conf</filename></para> | |
54 | </refsynopsisdiv> | |
55 | ||
56 | <refsect1> | |
57 | <title>Description</title> | |
58 | ||
59 | <para>At boot, | |
60 | <citerefentry><refentrytitle>systemd-sysctl.service</refentrytitle><manvolnum>8</manvolnum></citerefentry> | |
61 | reads configuration files from the above directories to configure | |
3ba3a79d | 62 | <citerefentry project='man-pages'><refentrytitle>sysctl</refentrytitle><manvolnum>8</manvolnum></citerefentry> |
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63 | kernel parameters.</para> |
64 | </refsect1> | |
65 | ||
66 | <refsect1> | |
67 | <title>Configuration Format</title> | |
68 | ||
69 | <para>The configuration files contain a list of variable | |
70 | assignments, separated by newlines. Empty lines and lines whose | |
71 | first non-whitespace character is <literal>#</literal> or | |
72 | <literal>;</literal> are ignored.</para> | |
73 | ||
74 | <para>Note that either <literal>/</literal> or | |
75 | <literal>.</literal> may be used as separators within sysctl | |
76 | variable names. If the first separator is a slash, remaining | |
77 | slashes and dots are left intact. If the first separator is a dot, | |
78 | dots and slashes are interchanged. | |
79 | <literal>kernel.domainname=foo</literal> and | |
80 | <literal>kernel/domainname=foo</literal> are equivalent and will | |
81 | cause <literal>foo</literal> to be written to | |
82 | <filename>/proc/sys/kernel/domainname</filename>. Either | |
83 | <literal>net.ipv4.conf.enp3s0/200.forwarding</literal> or | |
84 | <literal>net/ipv4/conf/enp3s0.200/forwarding</literal> may be used | |
85 | to refer to | |
86 | <filename>/proc/sys/net/ipv4/conf/enp3s0.200/forwarding</filename>. | |
87 | </para> | |
88 | ||
89 | <para>The settings configured with <filename>sysctl.d</filename> | |
90 | files will be applied early on boot. The network | |
91 | interface-specific options will also be applied individually for | |
92 | each network interface as it shows up in the system. (More | |
93 | specifically, <filename>net.ipv4.conf.*</filename>, | |
94 | <filename>net.ipv6.conf.*</filename>, | |
95 | <filename>net.ipv4.neigh.*</filename> and | |
96 | <filename>net.ipv6.neigh.*</filename>).</para> | |
97 | ||
98 | <para>Many sysctl parameters only become available when certain | |
99 | kernel modules are loaded. Modules are usually loaded on demand, | |
100 | e.g. when certain hardware is plugged in or network brought up. | |
101 | This means that | |
102 | <citerefentry><refentrytitle>systemd-sysctl.service</refentrytitle><manvolnum>8</manvolnum></citerefentry> | |
103 | which runs during early boot will not configure such parameters if | |
104 | they become available after it has run. To set such parameters, it | |
105 | is recommended to add an | |
106 | <citerefentry><refentrytitle>udev</refentrytitle><manvolnum>7</manvolnum></citerefentry> | |
107 | rule to set those parameters when they become available. | |
108 | Alternatively, a slightly simpler and less efficient option is to | |
109 | add the module to | |
110 | <citerefentry><refentrytitle>modules-load.d</refentrytitle><manvolnum>5</manvolnum></citerefentry>, | |
111 | causing it to be loaded statically before sysctl settings are | |
112 | applied (see example below).</para> | |
113 | </refsect1> | |
114 | ||
115 | <xi:include href="standard-conf.xml" xpointer="confd" /> | |
116 | ||
117 | <refsect1> | |
118 | <title>Examples</title> | |
119 | <example> | |
120 | <title>Set kernel YP domain name</title> | |
121 | <para><filename>/etc/sysctl.d/domain-name.conf</filename>: | |
122 | </para> | |
123 | ||
124 | <programlisting>kernel.domainname=example.com</programlisting> | |
125 | </example> | |
126 | ||
127 | <example> | |
9407bc2d | 128 | <title>Apply settings available only when a certain module is loaded (method one)</title> |
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129 | <para><filename>/etc/udev/rules.d/99-bridge.rules</filename>: |
130 | </para> | |
131 | ||
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132 | <programlisting>ACTION=="add", SUBSYSTEM=="module", KERNEL=="br_netfilter", \ |
133 | RUN+="/usr/lib/systemd/systemd-sysctl --prefix=/net/bridge" | |
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134 | </programlisting> |
135 | ||
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136 | <para><filename>/etc/sysctl.d/bridge.conf</filename>: |
137 | </para> | |
71418295 | 138 | |
798d3a52 | 139 | <programlisting>net.bridge.bridge-nf-call-ip6tables = 0 |
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140 | net.bridge.bridge-nf-call-iptables = 0 |
141 | net.bridge.bridge-nf-call-arptables = 0 | |
142 | </programlisting> | |
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143 | |
144 | <para>This method applies settings when the module is | |
b938cb90 | 145 | loaded. Please note that, unless the <filename>br_netfilter</filename> |
9407bc2d | 146 | module is loaded, bridged packets will not be filtered by |
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147 | Netfilter (starting with kernel 3.18), so simply not loading the |
148 | module is sufficient to avoid filtering.</para> | |
798d3a52 | 149 | </example> |
71418295 | 150 | |
798d3a52 | 151 | <example> |
9407bc2d | 152 | <title>Apply settings available only when a certain module is loaded (method two)</title> |
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153 | <para><filename>/etc/modules-load.d/bridge.conf</filename>: |
154 | </para> | |
7284335a | 155 | |
9407bc2d | 156 | <programlisting>br_netfilter</programlisting> |
7284335a | 157 | |
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158 | <para><filename>/etc/sysctl.d/bridge.conf</filename>: |
159 | </para> | |
c91faef3 | 160 | |
798d3a52 | 161 | <programlisting>net.bridge.bridge-nf-call-ip6tables = 0 |
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162 | net.bridge.bridge-nf-call-iptables = 0 |
163 | net.bridge.bridge-nf-call-arptables = 0 | |
164 | </programlisting> | |
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165 | |
166 | <para>This method forces the module to be always loaded. Please | |
b938cb90 | 167 | note that, unless the <filename>br_netfilter</filename> module is |
a8eaaee7 | 168 | loaded, bridged packets will not be filtered with Netfilter |
9407bc2d | 169 | (starting with kernel 3.18), so simply not loading the module is |
a8eaaee7 | 170 | sufficient to avoid filtering.</para> |
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171 | </example> |
172 | </refsect1> | |
173 | ||
174 | <refsect1> | |
175 | <title>See Also</title> | |
176 | <para> | |
177 | <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>, | |
178 | <citerefentry><refentrytitle>systemd-sysctl.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>, | |
179 | <citerefentry><refentrytitle>systemd-delta</refentrytitle><manvolnum>1</manvolnum></citerefentry>, | |
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180 | <citerefentry project='man-pages'><refentrytitle>sysctl</refentrytitle><manvolnum>8</manvolnum></citerefentry>, |
181 | <citerefentry project='man-pages'><refentrytitle>sysctl.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>, | |
182 | <citerefentry project='man-pages'><refentrytitle>modprobe</refentrytitle><manvolnum>8</manvolnum></citerefentry> | |
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183 | </para> |
184 | </refsect1> | |
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185 | |
186 | </refentry> |