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<?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="systemd-sysctl.service"
xmlns:xi="http://www.w3.org/2001/XInclude">
<refentryinfo>
<title>systemd-sysctl.service</title>
<productname>systemd</productname>
</refentryinfo>
<refmeta>
<refentrytitle>systemd-sysctl.service</refentrytitle>
<manvolnum>8</manvolnum>
</refmeta>
<refnamediv>
<refname>systemd-sysctl.service</refname>
<refname>systemd-sysctl</refname>
<refpurpose>Configure kernel parameters at boot</refpurpose>
</refnamediv>
<refsynopsisdiv>
<cmdsynopsis>
<command>/usr/lib/systemd/systemd-sysctl</command>
<arg choice="opt" rep="repeat">OPTIONS</arg>
<arg choice="opt" rep="repeat"><replaceable>CONFIGFILE</replaceable></arg>
</cmdsynopsis>
<para><filename>systemd-sysctl.service</filename></para>
</refsynopsisdiv>
<refsect1>
<title>Description</title>
<para><filename>systemd-sysctl.service</filename> is an early boot
service that configures
<citerefentry project='man-pages'><refentrytitle>sysctl</refentrytitle><manvolnum>8</manvolnum></citerefentry>
kernel parameters by invoking <command>/usr/lib/systemd/systemd-sysctl</command>.</para>
<para>When invoked with no arguments, <command>/usr/lib/systemd/systemd-sysctl</command> applies
all directives from configuration files listed in
<citerefentry><refentrytitle>sysctl.d</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
If one or more filenames are passed on the command line, only the directives in these files are
applied.</para>
<para>In addition, <option>--prefix=</option> option may be used to limit which sysctl
settings are applied.</para>
<para>See
<citerefentry><refentrytitle>sysctl.d</refentrytitle><manvolnum>5</manvolnum></citerefentry>
for information about the configuration of sysctl settings. After sysctl configuration is
changed on disk, it must be written to the files in <filename>/proc/sys/</filename> before it
takes effect. It is possible to update specific settings, or simply to reload all configuration,
see Examples below.</para>
</refsect1>
<refsect1><title>Options</title>
<variablelist>
<varlistentry id='prefix'>
<term><option>--prefix=</option></term>
<listitem>
<para>Only apply rules with the specified prefix.</para>
</listitem>
</varlistentry>
<varlistentry id='strict'>
<term><option>--strict=</option></term>
<listitem>
<para>Always return non-zero exit code on failure (including invalid sysctl variable
name and insufficient permissions), unless the sysctl variable name is prefixed with a "-"
character.</para>
</listitem>
</varlistentry>
<xi:include href="standard-options.xml" xpointer="cat-config" />
<xi:include href="standard-options.xml" xpointer="no-pager" />
<xi:include href="standard-options.xml" xpointer="help" />
<xi:include href="standard-options.xml" xpointer="version" />
</variablelist>
</refsect1>
<refsect1>
<title>Credentials</title>
<para><command>systemd-sysctl</command> supports the service credentials logic as implemented by
<varname>LoadCredential=</varname>/<varname>SetCredential=</varname> (see
<citerefentry><refentrytitle>systemd.exec</refentrytitle><manvolnum>1</manvolnum></citerefentry> for
details). The following credentials are used when passed in:</para>
<variablelist>
<varlistentry>
<term><literal>sysctl.extra</literal></term>
<listitem><para>The contents of this credential may contain additional lines to operate on. The
credential contents should follow the same format as any other <filename>sysctl.d/</filename> drop-in
configuration file. If this credential is passed it is processed after all of the drop-in files read
from the file system. The settings configured in the credential hence take precedence over those in
the file system.</para></listitem>
</varlistentry>
</variablelist>
<para>Note that by default the <filename>systemd-sysctl.service</filename> unit file is set up to inherit
the <literal>sysctl.extra</literal> credential from the service manager.</para>
</refsect1>
<refsect1>
<title>Examples</title>
<example>
<title>Reset all sysctl settings</title>
<programlisting>systemctl restart systemd-sysctl</programlisting>
</example>
<example>
<title>View coredump handler configuration</title>
<programlisting># sysctl kernel.core_pattern
kernel.core_pattern = |/usr/libexec/abrt-hook-ccpp %s %c %p %u %g %t %P %I
</programlisting>
</example>
<example>
<title>Update coredump handler configuration</title>
<programlisting># /usr/lib/systemd/systemd-sysctl --prefix kernel.core_pattern</programlisting>
<para>This searches all the directories listed in
<citerefentry><refentrytitle>sysctl.d</refentrytitle><manvolnum>5</manvolnum></citerefentry>
for configuration files and writes <filename>/proc/sys/kernel/core_pattern</filename>.</para>
</example>
<example>
<title>Update coredump handler configuration according to a specific file</title>
<programlisting># /usr/lib/systemd/systemd-sysctl 50-coredump.conf</programlisting>
<para>This applies all the settings found in <filename>50-coredump.conf</filename>.
Either <filename>/etc/sysctl.d/50-coredump.conf</filename>, or
<filename>/run/sysctl.d/50-coredump.conf</filename>, or
<filename>/usr/lib/sysctl.d/50-coredump.conf</filename> will be used, in the order
of preference.</para>
</example>
<para>See
<citerefentry project='man-pages'><refentrytitle>sysctl</refentrytitle><manvolnum>8</manvolnum></citerefentry>
for various ways to directly apply sysctl settings.</para>
</refsect1>
<refsect1>
<title>See Also</title>
<para>
<citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
<citerefentry><refentrytitle>sysctl.d</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
<citerefentry project='man-pages'><refentrytitle>sysctl</refentrytitle><manvolnum>8</manvolnum></citerefentry>
</para>
</refsect1>
</refentry>
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