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diff --git a/man/sysctl.d.xml b/man/sysctl.d.xml new file mode 100644 index 0000000..4d810e6 --- /dev/null +++ b/man/sysctl.d.xml @@ -0,0 +1,193 @@ +<?xml version="1.0"?> <!--*-nxml-*--> +<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN" + "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd"> +<!-- SPDX-License-Identifier: LGPL-2.1-or-later --> +<refentry id="sysctl.d" + xmlns:xi="http://www.w3.org/2001/XInclude"> + + <refentryinfo> + <title>sysctl.d</title> + <productname>systemd</productname> + </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> + + <programlisting>key.name.under.proc.sys = some value +key/name/under/proc/sys = some value +key/middle.part.with.dots/foo = 123 +key.middle/part/with/dots.foo = 123 +-key.that.will.not.fail = value +key.pattern.*.with.glob = whatever +-key.pattern.excluded.with.glob +key.pattern.overridden.with.glob = custom +</programlisting> + </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 project='man-pages'><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 <literal>#</literal> or + <literal>;</literal> are ignored.</para> + + <para>Note that either <literal>/</literal> or <literal>.</literal> may be used as separators within + sysctl variable names. If the first separator is a slash, remaining slashes and dots are left intact. If + the first separator is a dot, dots and slashes are interchanged. + <literal>kernel.domainname=foo</literal> and <literal>kernel/domainname=foo</literal> are equivalent and + will cause <literal>foo</literal> to be written to + <filename>/proc/sys/kernel/domainname</filename>. Either + <literal>net.ipv4.conf.enp3s0/200.forwarding</literal> or + <literal>net/ipv4/conf/enp3s0.200/forwarding</literal> may be used to refer to + <filename>/proc/sys/net/ipv4/conf/enp3s0.200/forwarding</filename>. A glob + <citerefentry project='man-pages'><refentrytitle>glob</refentrytitle><manvolnum>7</manvolnum></citerefentry> pattern may be + used to write the same value to all matching keys. Keys for which an explicit pattern exists will be + excluded from any glob matching. In addition, a key may be explicitly excluded from being set by any + matching glob patterns by specifying the key name prefixed with a <literal>-</literal> character and not + followed by <literal>=</literal>, see SYNOPSIS.</para> + + <para>Any access permission errors and attempts to write variables not present on the local system are + logged at debug level and do not cause the service to fail. Other types of errors when setting variables + are logged with higher priority and cause the service to return failure at the end (after processing + other variables). As an exception, if a variable assignment is prefixed with a single + <literal>-</literal> character, failure to set the variable for any reason will be logged at debug level + and will not cause the service to fail.</para> + + <para>The settings configured with <filename>sysctl.d</filename> files will be applied early on boot. The + network interface-specific options will also be applied individually for each network interface as it + shows up in the system. (More specifically, <filename>net.ipv4.conf.*</filename>, + <filename>net.ipv6.conf.*</filename>, <filename>net.ipv4.neigh.*</filename> and + <filename>net.ipv6.neigh.*</filename>).</para> + + <para>Many sysctl parameters only become available when certain + kernel modules are loaded. Modules are usually loaded on demand, + e.g. when certain hardware is plugged in or network brought up. + This means that + <citerefentry><refentrytitle>systemd-sysctl.service</refentrytitle><manvolnum>8</manvolnum></citerefentry> + which runs during early boot will not configure such parameters if + they become available after it has run. To set such parameters, it + is recommended to add an + <citerefentry><refentrytitle>udev</refentrytitle><manvolnum>7</manvolnum></citerefentry> + rule to set those parameters when they become available. + Alternatively, a slightly simpler and less efficient option is to + add the module to + <citerefentry><refentrytitle>modules-load.d</refentrytitle><manvolnum>5</manvolnum></citerefentry>, + causing it to be loaded statically before sysctl settings are + applied (see example below).</para> + </refsect1> + + <xi:include href="standard-conf.xml" xpointer="confd" /> + + <refsect1> + <title>Examples</title> + <example> + <title>Set kernel YP domain name</title> + <para><filename>/etc/sysctl.d/domain-name.conf</filename>: + </para> + + <programlisting>kernel.domainname=example.com</programlisting> + </example> + + <example> + <title>Apply settings available only when a certain module is loaded (method one)</title> + <para><filename>/etc/udev/rules.d/99-bridge.rules</filename>: + </para> + + <programlisting>ACTION=="add", SUBSYSTEM=="module", KERNEL=="br_netfilter", \ + RUN+="/usr/lib/systemd/systemd-sysctl --prefix=/net/bridge" +</programlisting> + + <para><filename>/etc/sysctl.d/bridge.conf</filename>: + </para> + + <programlisting>net.bridge.bridge-nf-call-ip6tables = 0 +net.bridge.bridge-nf-call-iptables = 0 +net.bridge.bridge-nf-call-arptables = 0 +</programlisting> + + <para>This method applies settings when the module is + loaded. Please note that, unless the <filename>br_netfilter</filename> + module is loaded, bridged packets will not be filtered by + Netfilter (starting with kernel 3.18), so simply not loading the + module is sufficient to avoid filtering.</para> + </example> + + <example> + <title>Apply settings available only when a certain module is loaded (method two)</title> + <para><filename>/etc/modules-load.d/bridge.conf</filename>: + </para> + + <programlisting>br_netfilter</programlisting> + + <para><filename>/etc/sysctl.d/bridge.conf</filename>: + </para> + + <programlisting>net.bridge.bridge-nf-call-ip6tables = 0 +net.bridge.bridge-nf-call-iptables = 0 +net.bridge.bridge-nf-call-arptables = 0 +</programlisting> + + <para>This method forces the module to be always loaded. Please + note that, unless the <filename>br_netfilter</filename> module is + loaded, bridged packets will not be filtered with Netfilter + (starting with kernel 3.18), so simply not loading the module is + sufficient to avoid filtering.</para> + </example> + + <example> + <title>Set network routing properties for all interfaces</title> + <para><filename>/etc/sysctl.d/20-rp_filter.conf</filename>:</para> + + <programlisting>net.ipv4.conf.default.rp_filter = 2 +net.ipv4.conf.*.rp_filter = 2 +-net.ipv4.conf.all.rp_filter +net.ipv4.conf.hub0.rp_filter = 1 +</programlisting> + + <para>The <option>rp_filter</option> key will be set to "2" for all interfaces, except "hub0". We set + <filename>net.ipv4.conf.default.rp_filter</filename> first, so any interfaces which are added + <emphasis>later</emphasis> will get this value (this also covers any interfaces detected while we're + running). The glob matches any interfaces which were detected <emphasis>earlier</emphasis>. The glob + will also match <filename>net.ipv4.conf.all.rp_filter</filename>, which we don't want to set at all, so + it is explicitly excluded. And "hub0" is excluded from the glob because it has an explicit setting. + </para> + </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 project='man-pages'><refentrytitle>sysctl</refentrytitle><manvolnum>8</manvolnum></citerefentry>, + <citerefentry project='man-pages'><refentrytitle>sysctl.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>, + <citerefentry project='man-pages'><refentrytitle>modprobe</refentrytitle><manvolnum>8</manvolnum></citerefentry> + </para> + </refsect1> + +</refentry> |