mirror of
https://github.com/systemd/systemd.git
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5430f7f2bc
We finally got the OK from all contributors with non-trivial commits to relicense systemd from GPL2+ to LGPL2.1+. Some udev bits continue to be GPL2+ for now, but we are looking into relicensing them too, to allow free copy/paste of all code within systemd. The bits that used to be MIT continue to be MIT. The big benefit of the relicensing is that closed source code may now link against libsystemd-login.so and friends.
1168 lines
60 KiB
XML
1168 lines
60 KiB
XML
<?xml version='1.0'?> <!--*-nxml-*-->
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<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
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"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
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<!--
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This file is part of systemd.
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Copyright 2010 Lennart Poettering
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systemd is free software; you can redistribute it and/or modify it
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under the terms of the GNU Lesser General Public License as published by
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the Free Software Foundation; either version 2.1 of the License, or
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(at your option) any later version.
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systemd is distributed in the hope that it will be useful, but
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WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public License
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along with systemd; If not, see <http://www.gnu.org/licenses/>.
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-->
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<refentry id="systemd">
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<refentryinfo>
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<title>systemd</title>
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<productname>systemd</productname>
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<authorgroup>
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<author>
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<contrib>Developer</contrib>
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<firstname>Lennart</firstname>
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<surname>Poettering</surname>
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<email>lennart@poettering.net</email>
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</author>
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</authorgroup>
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</refentryinfo>
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<refmeta>
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<refentrytitle>systemd</refentrytitle>
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<manvolnum>1</manvolnum>
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</refmeta>
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<refnamediv>
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<refname>systemd</refname>
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<refname>init</refname>
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<refpurpose>systemd System and Service Manager</refpurpose>
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</refnamediv>
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<refsynopsisdiv>
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<cmdsynopsis>
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<command>systemd <arg choice="opt" rep="repeat">OPTIONS</arg></command>
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</cmdsynopsis>
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<cmdsynopsis>
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<command>init <arg choice="opt" rep="repeat">OPTIONS</arg> <arg choice="req">COMMAND</arg></command>
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</cmdsynopsis>
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</refsynopsisdiv>
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<refsect1>
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<title>Description</title>
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<para>systemd is a system and service manager for
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Linux operating systems. When run as first process on
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boot (as PID 1), it acts as init system that brings
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up and maintains userspace services.</para>
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<para>For compatibility with SysV, if systemd is called
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as <command>init</command> and a PID that is not
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1, it will execute <command>telinit</command> and pass
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all command line arguments unmodified. That means
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<command>init</command> and <command>telinit</command>
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are mostly equivalent when invoked from normal login sessions. See
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<citerefentry><refentrytitle>telinit</refentrytitle><manvolnum>8</manvolnum></citerefentry>
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for more information.</para>
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<para>When run as system instance, systemd interprets
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the configuration file
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<filename>system.conf</filename>, otherwise
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<filename>user.conf</filename>. See
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<citerefentry><refentrytitle>systemd.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>
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for more information.</para>
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</refsect1>
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<refsect1>
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<title>Options</title>
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<para>The following options are understood:</para>
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<variablelist>
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<varlistentry>
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<term><option>-h</option></term>
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<term><option>--help</option></term>
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<listitem><para>Prints a short help
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text and exits.</para></listitem>
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</varlistentry>
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<varlistentry>
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<term><option>--test</option></term>
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<listitem><para>Determine startup
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sequence, dump it and exit. This is an
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option useful for debugging
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only.</para></listitem>
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</varlistentry>
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<varlistentry>
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<term><option>--dump-configuration-items</option></term>
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<listitem><para>Dump understood unit
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configuration items. This outputs a
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terse but complete list of
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configuration items understood in unit
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definition files.</para></listitem>
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</varlistentry>
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<varlistentry>
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<term><option>--introspect=</option></term>
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<listitem><para>Extract D-Bus
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interface introspection data. This is
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mostly useful at install time
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to generate data suitable for the
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D-Bus interfaces
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repository. Optionally the interface
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name for the introspection data may be
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specified. If omitted, the
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introspection data for all interfaces
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is dumped.</para></listitem>
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</varlistentry>
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<varlistentry>
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<term><option>--unit=</option></term>
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<listitem><para>Set default unit to
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activate on startup. If not specified
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defaults to
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<filename>default.target</filename>.</para></listitem>
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</varlistentry>
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<varlistentry>
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<term><option>--system</option></term>
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<term><option>--user</option></term>
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<listitem><para>Tell systemd to run a
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system instance (resp. user
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instance), even if the process ID is
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not 1 (resp. is 1), i.e. systemd is
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not (resp. is) run as init process.
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Normally it should not be necessary to
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pass these options, as systemd
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automatically detects the mode it is
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started in. These options are hence of
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little use except for debugging. Note
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that it is not supported booting and
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maintaining a full system with systemd
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running in <option>--system</option>
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mode, but PID not 1. In practice,
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passing <option>--system</option> explicitly is
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only useful in conjunction with
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<option>--test</option>.</para></listitem>
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</varlistentry>
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<varlistentry>
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<term><option>--dump-core</option></term>
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<listitem><para>Dump core on
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crash. This switch has no effect when
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run as user
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instance.</para></listitem>
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</varlistentry>
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<varlistentry>
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<term><option>--crash-shell</option></term>
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<listitem><para>Run shell on
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crash. This switch has no effect when
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run as user
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instance.</para></listitem>
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</varlistentry>
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<varlistentry>
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<term><option>--confirm-spawn</option></term>
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<listitem><para>Ask for confirmation
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when spawning processes. This switch
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has no effect when run as user
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instance.</para></listitem>
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</varlistentry>
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<varlistentry>
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<term><option>--show-status=</option></term>
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<listitem><para>Show terse service
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status information while booting. This
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switch has no effect when run as user
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instance. Takes a boolean argument
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which may be omitted which is
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interpreted as
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<option>true</option>.</para></listitem>
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</varlistentry>
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<varlistentry>
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<term><option>--sysv-console=</option></term>
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<listitem><para>Controls whether
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output of SysV init scripts will be
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directed to the console. This switch
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has no effect when run as user
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instance. Takes a boolean argument
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which may be omitted which is
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interpreted as
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<option>true</option>.</para></listitem>
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</varlistentry>
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<varlistentry>
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<term><option>--log-target=</option></term>
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<listitem><para>Set log
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target. Argument must be one of
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<option>console</option>,
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<option>journal</option>,
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<option>syslog</option>,
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<option>kmsg</option>,
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<option>journal-or-kmsg</option>,
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<option>syslog-or-kmsg</option>,
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<option>null</option>.</para></listitem>
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</varlistentry>
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<varlistentry>
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<term><option>--log-level=</option></term>
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<listitem><para>Set log level. As
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argument this accepts a numerical log
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level or the well-known <citerefentry><refentrytitle>syslog</refentrytitle><manvolnum>3</manvolnum></citerefentry>
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symbolic names (lowercase):
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<option>emerg</option>,
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<option>alert</option>,
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<option>crit</option>,
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<option>err</option>,
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<option>warning</option>,
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<option>notice</option>,
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<option>info</option>,
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<option>debug</option>.</para></listitem>
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</varlistentry>
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<varlistentry>
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<term><option>--log-color=</option></term>
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<listitem><para>Highlight important
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log messages. Argument is a boolean
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value. If the argument is omitted it
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defaults to
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<option>true</option>.</para></listitem>
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</varlistentry>
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<varlistentry>
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<term><option>--log-location=</option></term>
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<listitem><para>Include code location
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in log messages. This is mostly
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relevant for debugging
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purposes. Argument is a boolean
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value. If the argument is omitted
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it defaults to
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<option>true</option>.</para></listitem>
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</varlistentry>
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<varlistentry>
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<term><option>--default-standard-output=</option></term>
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<term><option>--default-standard-error=</option></term>
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<listitem><para>Sets the default
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output resp. error output for all
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services and sockets, i.e. controls
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the default for
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<option>StandardOutput=</option>
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resp. <option>StandardError=</option>
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(see
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<citerefentry><refentrytitle>systemd.exec</refentrytitle><manvolnum>5</manvolnum></citerefentry>
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for details). Takes one of
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<option>inherit</option>,
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<option>null</option>,
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<option>tty</option>,
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<option>journal</option>,
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<option>journal+console</option>,
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<option>syslog</option>,
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<option>syslog+console</option>,
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<option>kmsg</option>,
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<option>kmsg+console</option>. If the
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argument is omitted
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<option>--default-standard-output=</option>
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defaults to <option>journal</option>
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and
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<option>--default-standard-error=</option>
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to
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<option>inherit</option>.</para></listitem>
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</varlistentry>
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</variablelist>
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</refsect1>
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<refsect1>
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<title>Concepts</title>
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<para>systemd provides a dependency system between
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various entities called "units". Units encapsulate
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various objects that are relevant for system boot-up
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and maintenance. The majority of units are configured
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in unit configuration files, whose syntax and basic
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set of options is described in
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<citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
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however some are created automatically from other
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configuration or dynamically from system state. Units
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may be 'active' (meaning started, bound, plugged in,
|
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... depending on the unit type, see below), or
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'inactive' (meaning stopped, unbound, unplugged, ...),
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as well as in the process of being activated or
|
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deactivated, i.e. between the two states (these states
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are called 'activating', 'deactivating'). A special
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'failed' state is available as well which is very
|
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similar to 'inactive' and is entered when the service
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failed in some way (process returned error code on
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exit, or crashed, or an operation timed out). If this
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state is entered the cause will be logged, for later
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reference. Note that the various unit types may have a
|
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number of additional substates, which are mapped to
|
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the five generalized unit states described
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here.</para>
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<para>The following unit types are available:</para>
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<orderedlist>
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<listitem><para>Service units, which control
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daemons and the processes they consist of. For
|
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details see
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<citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para></listitem>
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<listitem><para>Socket units, which
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encapsulate local IPC or network sockets in
|
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the system, useful for socket-based
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activation. For details about socket units see
|
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<citerefentry><refentrytitle>systemd.socket</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
|
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for details on socket-based activation and
|
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other forms of activation, see
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<citerefentry><refentrytitle>daemon</refentrytitle><manvolnum>7</manvolnum></citerefentry>.</para></listitem>
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<listitem><para>Target units are useful to
|
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group units, or provide well-known
|
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synchronization points during boot-up, see
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<citerefentry><refentrytitle>systemd.target</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para></listitem>
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<listitem><para>Device units expose kernel
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devices in systemd and may be used to
|
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implement device-based activation. For details
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see
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<citerefentry><refentrytitle>systemd.device</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para></listitem>
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<listitem><para>Mount units control mount
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points in the file system, for details see
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<citerefentry><refentrytitle>systemd.mount</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para></listitem>
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<listitem><para>Automount units provide
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automount capabilities, for on-demand mounting
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of file systems as well as parallelized
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boot-up. See
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<citerefentry><refentrytitle>systemd.automount</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para></listitem>
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<listitem><para>Snapshot units can be used to
|
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temporarily save the state of the set of
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systemd units, which later may be restored by
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activating the saved snapshot unit. For more
|
|
information see
|
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<citerefentry><refentrytitle>systemd.snapshot</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para></listitem>
|
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<listitem><para>Timer units are useful for
|
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triggering activation of other units based on
|
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timers. You may find details in
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<citerefentry><refentrytitle>systemd.timer</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para></listitem>
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<listitem><para>Swap units are very similar to
|
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mount units and encapsulate memory swap
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partitions or files of the operating
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system. They are described in <citerefentry><refentrytitle>systemd.swap</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para></listitem>
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<listitem><para>Path units may be used
|
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to activate other services when file system
|
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objects change or are modified. See
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<citerefentry><refentrytitle>systemd.path</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para></listitem>
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</orderedlist>
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<para>Units are named as their configuration
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files. Some units have special semantics. A detailed
|
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list is available in
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<citerefentry><refentrytitle>systemd.special</refentrytitle><manvolnum>7</manvolnum></citerefentry>.</para>
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<para>systemd knows various kinds of dependencies,
|
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including positive and negative requirement
|
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dependencies (i.e. <varname>Requires=</varname> and
|
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<varname>Conflicts=</varname>) as well as ordering
|
|
dependencies (<varname>After=</varname> and
|
|
<varname>Before=</varname>). NB: ordering and
|
|
requirement dependencies are orthogonal. If only a
|
|
requirement dependency exists between two units
|
|
(e.g. <filename>foo.service</filename> requires
|
|
<filename>bar.service</filename>), but no ordering
|
|
dependency (e.g. <filename>foo.service</filename>
|
|
after <filename>bar.service</filename>) and both are
|
|
requested to start, they will be started in
|
|
parallel. It is a common pattern that both requirement
|
|
and ordering dependencies are placed between two
|
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units. Also note that the majority of dependencies are
|
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implicitly created and maintained by systemd. In most
|
|
cases it should be unnecessary to declare additional
|
|
dependencies manually, however it is possible to do
|
|
this.</para>
|
|
|
|
<para>Application programs and units (via
|
|
dependencies) may request state changes of units. In
|
|
systemd, these requests are encapsulated as 'jobs' and
|
|
maintained in a job queue. Jobs may succeed or can
|
|
fail, their execution is ordered based on the ordering
|
|
dependencies of the units they have been scheduled
|
|
for.</para>
|
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|
|
<para>On boot systemd activates the target unit
|
|
<filename>default.target</filename> whose job is to
|
|
activate on-boot services and other on-boot units by
|
|
pulling them in via dependencies. Usually the unit
|
|
name is just an alias (symlink) for either
|
|
<filename>graphical.target</filename> (for
|
|
fully-featured boots into the UI) or
|
|
<filename>multi-user.target</filename> (for limited
|
|
console-only boots for use in embedded or server
|
|
environments, or similar; a subset of
|
|
graphical.target). However it is at the discretion of
|
|
the administrator to configure it as an alias to any
|
|
other target unit. See
|
|
<citerefentry><refentrytitle>systemd.special</refentrytitle><manvolnum>7</manvolnum></citerefentry>
|
|
for details about these target units.</para>
|
|
|
|
<para>Processes systemd spawns are placed in
|
|
individual Linux control groups named after the unit
|
|
which they belong to in the private systemd
|
|
hierarchy. (see <ulink
|
|
url="http://www.kernel.org/doc/Documentation/cgroups/cgroups.txt">cgroups.txt</ulink>
|
|
for more information about control groups, or short
|
|
"cgroups"). systemd uses this to effectively keep
|
|
track of processes. Control group information is
|
|
maintained in the kernel, and is accessible via the
|
|
file system hierarchy (beneath
|
|
<filename>/sys/fs/cgroup/systemd/</filename>), or in tools
|
|
such as
|
|
<citerefentry><refentrytitle>ps</refentrytitle><manvolnum>1</manvolnum></citerefentry>
|
|
(<command>ps xawf -eo pid,user,cgroup,args</command>
|
|
is particularly useful to list all processes and the
|
|
systemd units they belong to.).</para>
|
|
|
|
<para>systemd is compatible with the SysV init system
|
|
to a large degree: SysV init scripts are supported and
|
|
simply read as an alternative (though limited)
|
|
configuration file format. The SysV
|
|
<filename>/dev/initctl</filename> interface is
|
|
provided, and compatibility implementations of the
|
|
various SysV client tools are available. In addition to
|
|
that, various established Unix functionality such as
|
|
<filename>/etc/fstab</filename> or the
|
|
<filename>utmp</filename> database are
|
|
supported.</para>
|
|
|
|
<para>systemd has a minimal transaction system: if a
|
|
unit is requested to start up or shut down it will add
|
|
it and all its dependencies to a temporary
|
|
transaction. Then, it will verify if the transaction
|
|
is consistent (i.e. whether the ordering of all units
|
|
is cycle-free). If it is not, systemd will try to fix
|
|
it up, and removes non-essential jobs from the
|
|
transaction that might remove the loop. Also, systemd
|
|
tries to suppress non-essential jobs in the
|
|
transaction that would stop a running service. Finally
|
|
it is checked whether the jobs of the transaction
|
|
contradict jobs that have already been queued, and
|
|
optionally the transaction is aborted then. If all
|
|
worked out and the transaction is consistent and
|
|
minimized in its impact it is merged with all already
|
|
outstanding jobs and added to the run
|
|
queue. Effectively this means that before executing a
|
|
requested operation, systemd will verify that it makes
|
|
sense, fixing it if possible, and only failing if it
|
|
really cannot work.</para>
|
|
|
|
<para>Systemd contains native implementations of
|
|
various tasks that need to be executed as part of the
|
|
boot process. For example, it sets the host name or
|
|
configures the loopback network device. It also sets
|
|
up and mounts various API file systems, such as
|
|
<filename>/sys</filename> or
|
|
<filename>/proc</filename>.</para>
|
|
|
|
<para>For more information about the concepts and
|
|
ideas behind systemd please refer to the <ulink
|
|
url="http://0pointer.de/blog/projects/systemd.html">Original
|
|
Design Document</ulink>.</para>
|
|
|
|
<para>Note that some but not all interfaces provided
|
|
by systemd are covered by the <ulink
|
|
url="http://www.freedesktop.org/wiki/Software/systemd/InterfaceStabilityPromise">Interface
|
|
Stability Promise</ulink>.</para>
|
|
</refsect1>
|
|
|
|
<refsect1>
|
|
<title>Directories</title>
|
|
|
|
<variablelist>
|
|
<varlistentry>
|
|
<term>System unit directories</term>
|
|
|
|
<listitem><para>The systemd system
|
|
manager reads unit configuration from
|
|
various directories. Packages that
|
|
want to install unit files shall place
|
|
them in the directory returned by
|
|
<command>pkg-config systemd
|
|
--variable=systemdsystemunitdir</command>. Other
|
|
directories checked are
|
|
<filename>/usr/local/lib/systemd/system</filename>
|
|
and
|
|
<filename>/usr/lib/systemd/system</filename>. User
|
|
configuration always takes
|
|
precedence. <command>pkg-config
|
|
systemd
|
|
--variable=systemdsystemconfdir</command>
|
|
returns the path of the system
|
|
configuration directory. Packages
|
|
should alter the content of these
|
|
directories only with the
|
|
<command>enable</command> and
|
|
<command>disable</command> commands of
|
|
the
|
|
<citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>
|
|
tool.</para></listitem>
|
|
</varlistentry>
|
|
</variablelist>
|
|
|
|
<variablelist>
|
|
<varlistentry>
|
|
<term>User unit directories</term>
|
|
|
|
<listitem><para>Similar rules apply
|
|
for the user unit
|
|
directories. However, here the <ulink
|
|
url="http://standards.freedesktop.org/basedir-spec/basedir-spec-latest.html">XDG
|
|
Base Directory specification</ulink>
|
|
is followed to find
|
|
units. Applications should place their
|
|
unit files in the directory returned
|
|
by <command>pkg-config systemd
|
|
--variable=systemduserunitdir</command>. Global
|
|
configuration is done in the directory
|
|
reported by <command>pkg-config
|
|
systemd
|
|
--variable=systemduserconfdir</command>. The
|
|
<command>enable</command> and
|
|
<command>disable</command> commands of
|
|
the
|
|
<citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>
|
|
tool can handle both global (i.e. for
|
|
all users) and private (for one user)
|
|
enabling/disabling of
|
|
units.</para></listitem>
|
|
</varlistentry>
|
|
</variablelist>
|
|
|
|
<variablelist>
|
|
<varlistentry>
|
|
<term>SysV init scripts directory</term>
|
|
|
|
<listitem><para>The location of the
|
|
SysV init script directory varies
|
|
between distributions. If systemd
|
|
cannot find a native unit file for a
|
|
requested service, it will look for a
|
|
SysV init script of the same name
|
|
(with the
|
|
<filename>.service</filename> suffix
|
|
removed).</para></listitem>
|
|
</varlistentry>
|
|
</variablelist>
|
|
|
|
<variablelist>
|
|
<varlistentry>
|
|
<term>SysV runlevel link farm directory</term>
|
|
|
|
<listitem><para>The location of the
|
|
SysV runlevel link farm directory
|
|
varies between distributions. systemd
|
|
will take the link farm into account
|
|
when figuring out whether a service
|
|
shall be enabled. Note that a service
|
|
unit with a native unit configuration
|
|
file cannot be started by activating it
|
|
in the SysV runlevel link
|
|
farm.</para></listitem>
|
|
</varlistentry>
|
|
</variablelist>
|
|
</refsect1>
|
|
|
|
<refsect1>
|
|
<title>Signals</title>
|
|
|
|
<variablelist>
|
|
<varlistentry>
|
|
<term>SIGTERM</term>
|
|
|
|
<listitem><para>Upon receiving this
|
|
signal the systemd system manager
|
|
serializes its state, reexecutes
|
|
itself and deserializes the saved
|
|
state again. This is mostly equivalent
|
|
to <command>systemctl
|
|
daemon-reexec</command>.</para>
|
|
|
|
<para>systemd user managers will
|
|
start the
|
|
<filename>exit.target</filename> unit
|
|
when this signal is received. This is
|
|
mostly equivalent to
|
|
<command>systemctl --user start
|
|
exit.target</command>.</para></listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term>SIGINT</term>
|
|
|
|
<listitem><para>Upon receiving this
|
|
signal the systemd system manager will
|
|
start the
|
|
<filename>ctrl-alt-del.target</filename> unit. This
|
|
is mostly equivalent to
|
|
<command>systemctl start
|
|
ctl-alt-del.target</command>.</para>
|
|
|
|
<para>systemd user managers
|
|
treat this signal the same way as
|
|
SIGTERM.</para></listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term>SIGWINCH</term>
|
|
|
|
<listitem><para>When this signal is
|
|
received the systemd system manager
|
|
will start the
|
|
<filename>kbrequest.target</filename>
|
|
unit. This is mostly equivalent to
|
|
<command>systemctl start
|
|
kbrequest.target</command>.</para>
|
|
|
|
<para>This signal is ignored by
|
|
systemd user
|
|
managers.</para></listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term>SIGPWR</term>
|
|
|
|
<listitem><para>When this signal is
|
|
received the systemd manager
|
|
will start the
|
|
<filename>sigpwr.target</filename>
|
|
unit. This is mostly equivalent to
|
|
<command>systemctl start
|
|
sigpwr.target</command>.</para></listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term>SIGUSR1</term>
|
|
|
|
<listitem><para>When this signal is
|
|
received the systemd manager will try
|
|
to reconnect to the D-Bus
|
|
bus.</para></listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term>SIGUSR2</term>
|
|
|
|
<listitem><para>When this signal is
|
|
received the systemd manager will log
|
|
its complete state in human readable
|
|
form. The data logged is the same as
|
|
printed by <command>systemctl
|
|
dump</command>.</para></listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term>SIGHUP</term>
|
|
|
|
<listitem><para>Reloads the complete
|
|
daemon configuration. This is mostly
|
|
equivalent to <command>systemctl
|
|
daemon-reload</command>.</para></listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term>SIGRTMIN+0</term>
|
|
|
|
<listitem><para>Enters default mode, starts the
|
|
<filename>default.target</filename>
|
|
unit. This is mostly equivalent to
|
|
<command>systemctl start
|
|
default.target</command>.</para></listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term>SIGRTMIN+1</term>
|
|
|
|
<listitem><para>Enters rescue mode,
|
|
starts the
|
|
<filename>rescue.target</filename>
|
|
unit. This is mostly equivalent to
|
|
<command>systemctl isolate
|
|
rescue.target</command>.</para></listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term>SIGRTMIN+2</term>
|
|
|
|
<listitem><para>Enters emergency mode,
|
|
starts the
|
|
<filename>emergency.service</filename>
|
|
unit. This is mostly equivalent to
|
|
<command>systemctl isolate
|
|
emergency.service</command>.</para></listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term>SIGRTMIN+3</term>
|
|
|
|
<listitem><para>Halts the machine,
|
|
starts the
|
|
<filename>halt.target</filename>
|
|
unit. This is mostly equivalent to
|
|
<command>systemctl start
|
|
halt.target</command>.</para></listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term>SIGRTMIN+4</term>
|
|
|
|
<listitem><para>Powers off the machine,
|
|
starts the
|
|
<filename>poweroff.target</filename>
|
|
unit. This is mostly equivalent to
|
|
<command>systemctl start
|
|
poweroff.target</command>.</para></listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term>SIGRTMIN+5</term>
|
|
|
|
<listitem><para>Reboots the machine,
|
|
starts the
|
|
<filename>reboot.target</filename>
|
|
unit. This is mostly equivalent to
|
|
<command>systemctl start
|
|
reboot.target</command>.</para></listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term>SIGRTMIN+6</term>
|
|
|
|
<listitem><para>Reboots the machine via kexec,
|
|
starts the
|
|
<filename>kexec.target</filename>
|
|
unit. This is mostly equivalent to
|
|
<command>systemctl start
|
|
kexec.target</command>.</para></listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term>SIGRTMIN+13</term>
|
|
|
|
<listitem><para>Immediately halts the machine.</para></listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term>SIGRTMIN+14</term>
|
|
|
|
<listitem><para>Immediately powers off the machine.</para></listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term>SIGRTMIN+15</term>
|
|
|
|
<listitem><para>Immediately reboots the machine.</para></listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term>SIGRTMIN+16</term>
|
|
|
|
<listitem><para>Immediately reboots the machine with kexec.</para></listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term>SIGRTMIN+20</term>
|
|
|
|
<listitem><para>Enables display of
|
|
status messages on the console, as
|
|
controlled via
|
|
<varname>systemd.show_status=1</varname>
|
|
on the kernel command
|
|
line.</para></listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term>SIGRTMIN+21</term>
|
|
|
|
<listitem><para>Disables display of
|
|
status messages on the console, as
|
|
controlled via
|
|
<varname>systemd.show_status=0</varname>
|
|
on the kernel command
|
|
line.</para></listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term>SIGRTMIN+22</term>
|
|
<term>SIGRTMIN+23</term>
|
|
|
|
<listitem><para>Sets the log level to
|
|
<literal>debug</literal>
|
|
(resp. <literal>info</literal> on
|
|
<literal>SIGRTMIN+23</literal>), as
|
|
controlled via
|
|
<varname>systemd.log_level=debug</varname>
|
|
(resp. <varname>systemd.log_level=info</varname>
|
|
on <literal>SIGRTMIN+23</literal>) on
|
|
the kernel command
|
|
line.</para></listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term>SIGRTMIN+26</term>
|
|
<term>SIGRTMIN+27</term>
|
|
<term>SIGRTMIN+28</term>
|
|
<term>SIGRTMIN+29</term>
|
|
|
|
<listitem><para>Sets the log level to
|
|
<literal>journal-or-kmsg</literal>
|
|
(resp. <literal>console</literal> on
|
|
<literal>SIGRTMIN+27</literal>;
|
|
resp. <literal>kmsg</literal> on
|
|
<literal>SIGRTMIN+28</literal>;
|
|
resp. <literal>syslog-or-kmsg</literal>
|
|
on <literal>SIGRTMIN+29</literal>), as
|
|
controlled via
|
|
<varname>systemd.log_target=journal-or-kmsg</varname>
|
|
(resp. <varname>systemd.log_target=console</varname>
|
|
on <literal>SIGRTMIN+27</literal>;
|
|
resp. <varname>systemd.log_target=kmsg</varname>
|
|
on <literal>SIGRTMIN+28</literal>;
|
|
resp
|
|
<varname>systemd.log_target=syslog-or-kmsg</varname>
|
|
on <literal>SIGRTMIN+29</literal>) on
|
|
the kernel command
|
|
line.</para></listitem>
|
|
</varlistentry>
|
|
</variablelist>
|
|
</refsect1>
|
|
|
|
<refsect1>
|
|
<title>Environment</title>
|
|
|
|
<variablelist>
|
|
<varlistentry>
|
|
<term><varname>$SYSTEMD_LOG_LEVEL</varname></term>
|
|
<listitem><para>systemd reads the
|
|
log level from this environment
|
|
variable. This can be overridden with
|
|
<option>--log-level=</option>.</para></listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><varname>$SYSTEMD_LOG_TARGET</varname></term>
|
|
<listitem><para>systemd reads the
|
|
log target from this environment
|
|
variable. This can be overridden with
|
|
<option>--log-target=</option>.</para></listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><varname>$SYSTEMD_LOG_COLOR</varname></term>
|
|
<listitem><para>Controls whether
|
|
systemd highlights important log
|
|
messages. This can be overridden with
|
|
<option>--log-color=</option>.</para></listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><varname>$SYSTEMD_LOG_LOCATION</varname></term>
|
|
<listitem><para>Controls whether
|
|
systemd prints the code location along
|
|
with log messages. This can be
|
|
overridden with
|
|
<option>--log-location=</option>.</para></listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><varname>$XDG_CONFIG_HOME</varname></term>
|
|
<term><varname>$XDG_CONFIG_DIRS</varname></term>
|
|
<term><varname>$XDG_DATA_HOME</varname></term>
|
|
<term><varname>$XDG_DATA_DIRS</varname></term>
|
|
|
|
<listitem><para>The systemd user
|
|
manager uses these variables in
|
|
accordance to the <ulink
|
|
url="http://standards.freedesktop.org/basedir-spec/basedir-spec-latest.html">XDG
|
|
Base Directory specification</ulink>
|
|
to find its configuration.</para></listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><varname>$SYSTEMD_UNIT_PATH</varname></term>
|
|
|
|
<listitem><para>Controls where systemd
|
|
looks for unit
|
|
files.</para></listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><varname>$SYSTEMD_SYSVINIT_PATH</varname></term>
|
|
|
|
<listitem><para>Controls where systemd
|
|
looks for SysV init scripts.</para></listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><varname>$SYSTEMD_SYSVRCND_PATH</varname></term>
|
|
|
|
<listitem><para>Controls where systemd
|
|
looks for SysV init script runlevel link
|
|
farms.</para></listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><varname>$LISTEN_PID</varname></term>
|
|
<term><varname>$LISTEN_FDS</varname></term>
|
|
|
|
<listitem><para>Set by systemd for
|
|
supervised processes during
|
|
socket-based activation. See
|
|
<citerefentry><refentrytitle>sd_listen_fds</refentrytitle><manvolnum>3</manvolnum></citerefentry>
|
|
for more information.
|
|
</para></listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><varname>$NOTIFY_SOCKET</varname></term>
|
|
|
|
<listitem><para>Set by systemd for
|
|
supervised processes for status and
|
|
start-up completion notification. See
|
|
<citerefentry><refentrytitle>sd_notify</refentrytitle><manvolnum>3</manvolnum></citerefentry>
|
|
for more information.
|
|
</para></listitem>
|
|
</varlistentry>
|
|
</variablelist>
|
|
</refsect1>
|
|
|
|
<refsect1>
|
|
<title>Kernel Command Line</title>
|
|
|
|
<para>When run as system instance systemd parses a
|
|
number of kernel command line
|
|
arguments<footnote><para>If run inside a Linux
|
|
container these arguments may be passed as command
|
|
line arguments to systemd itself, next to any of the
|
|
command line options listed in the Options section
|
|
above. If run outside of Linux containers, these
|
|
arguments are parsed from
|
|
<filename>/proc/cmdline</filename>
|
|
instead.</para></footnote>:</para>
|
|
|
|
<variablelist>
|
|
<varlistentry>
|
|
<term><varname>systemd.unit=</varname></term>
|
|
|
|
<listitem><para>Overrides the unit to
|
|
activate on boot. Defaults to
|
|
<filename>default.target</filename>. This
|
|
may be used to temporarily boot into a
|
|
different boot unit, for example
|
|
<filename>rescue.target</filename> or
|
|
<filename>emergency.service</filename>. See
|
|
<citerefentry><refentrytitle>systemd.special</refentrytitle><manvolnum>7</manvolnum></citerefentry>
|
|
for details about these
|
|
units.</para></listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><varname>systemd.dump_core=</varname></term>
|
|
|
|
<listitem><para>Takes a boolean
|
|
argument. If <option>true</option>
|
|
systemd dumps core when it
|
|
crashes. Otherwise no core dump is
|
|
created. Defaults to
|
|
<option>true</option>.</para></listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><varname>systemd.crash_shell=</varname></term>
|
|
|
|
<listitem><para>Takes a boolean
|
|
argument. If <option>true</option>
|
|
systemd spawns a shell when it
|
|
crashes. Otherwise no shell is
|
|
spawned. Defaults to
|
|
<option>false</option>, for security
|
|
reasons, as the shell is not protected
|
|
by any password
|
|
authentication.</para></listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><varname>systemd.crash_chvt=</varname></term>
|
|
|
|
<listitem><para>Takes an integer
|
|
argument. If positive systemd
|
|
activates the specified virtual
|
|
terminal when it crashes. Defaults to
|
|
<literal>-1</literal>.</para></listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><varname>systemd.confirm_spawn=</varname></term>
|
|
|
|
<listitem><para>Takes a boolean
|
|
argument. If <option>true</option>
|
|
asks for confirmation when spawning
|
|
processes. Defaults to
|
|
<option>false</option>.</para></listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><varname>systemd.show_status=</varname></term>
|
|
|
|
<listitem><para>Takes a boolean
|
|
argument. If <option>true</option>
|
|
shows terse service status updates on
|
|
the console during bootup. Defaults to
|
|
<option>true</option>.</para></listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><varname>systemd.sysv_console=</varname></term>
|
|
|
|
<listitem><para>Takes a boolean
|
|
argument. If <option>true</option>
|
|
output of SysV init scripts will be
|
|
directed to the console. Defaults to
|
|
<option>true</option>, unless
|
|
<option>quiet</option> is passed as
|
|
kernel command line option in which
|
|
case it defaults to
|
|
<option>false</option>.</para></listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><varname>systemd.log_target=</varname></term>
|
|
<term><varname>systemd.log_level=</varname></term>
|
|
<term><varname>systemd.log_color=</varname></term>
|
|
<term><varname>systemd.log_location=</varname></term>
|
|
|
|
<listitem><para>Controls log output,
|
|
with the same effect as the
|
|
<varname>$SYSTEMD_LOG_TARGET</varname>, <varname>$SYSTEMD_LOG_LEVEL</varname>, <varname>$SYSTEMD_LOG_COLOR</varname>, <varname>$SYSTEMD_LOG_LOCATION</varname>
|
|
environment variables described above.</para></listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><varname>systemd.default_standard_output=</varname></term>
|
|
<term><varname>systemd.default_standard_error=</varname></term>
|
|
<listitem><para>Controls default
|
|
standard output/error output for
|
|
services, with the same effect as the
|
|
<option>--default-standard-output=</option>
|
|
resp. <option>--default-standard-error=</option>
|
|
command line arguments described
|
|
above.</para></listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><varname>systemd.setenv=</varname></term>
|
|
|
|
<listitem><para>Takes a string
|
|
argument in the form
|
|
VARIABLE=VALUE. May be used to set
|
|
environment variables for the init
|
|
process and all its children at boot
|
|
time. May be used more than once to
|
|
set multiple variables. If the equal
|
|
sign and variable are missing unsets
|
|
an environment variable which might be
|
|
passed in from the initial ram
|
|
disk.</para></listitem>
|
|
</varlistentry>
|
|
|
|
</variablelist>
|
|
</refsect1>
|
|
|
|
<refsect1>
|
|
<title>Sockets and FIFOs</title>
|
|
|
|
<variablelist>
|
|
<varlistentry>
|
|
<term><filename>/run/systemd/notify</filename></term>
|
|
|
|
<listitem><para>Daemon status
|
|
notification socket. This is an
|
|
AF_UNIX datagram socket and is used to
|
|
implement the daemon notification
|
|
logic as implemented by
|
|
<citerefentry><refentrytitle>sd_notify</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para></listitem>
|
|
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><filename>/run/systemd/shutdownd</filename></term>
|
|
|
|
<listitem><para>Used internally by the
|
|
<citerefentry><refentrytitle>shutdown</refentrytitle><manvolnum>8</manvolnum></citerefentry>
|
|
tool to implement delayed
|
|
shutdowns. This is an AF_UNIX datagram
|
|
socket.</para></listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><filename>/run/systemd/private</filename></term>
|
|
|
|
<listitem><para>Used internally as
|
|
communication channel between
|
|
<citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>
|
|
and the systemd process. This is an
|
|
AF_UNIX stream socket. This interface
|
|
is private to systemd and should not
|
|
be used in external
|
|
projects.</para></listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><filename>/dev/initctl</filename></term>
|
|
|
|
<listitem><para>Limited compatibility
|
|
support for the SysV client interface,
|
|
as implemented by the
|
|
<filename>systemd-initctl.service</filename>
|
|
unit. This is a named pipe in the file
|
|
system. This interface is obsolete and
|
|
should not be used in new
|
|
applications.</para></listitem>
|
|
</varlistentry>
|
|
</variablelist>
|
|
</refsect1>
|
|
|
|
<refsect1>
|
|
<title>See Also</title>
|
|
<para>
|
|
<citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
|
|
<citerefentry><refentrytitle>systemadm</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
|
|
<citerefentry><refentrytitle>systemd-notify</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
|
|
<citerefentry><refentrytitle>daemon</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
|
|
<citerefentry><refentrytitle>sd-daemon</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
|
|
<citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
|
|
<citerefentry><refentrytitle>systemd.special</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
|
|
<citerefentry><refentrytitle>pkg-config</refentrytitle><manvolnum>1</manvolnum></citerefentry>
|
|
</para>
|
|
</refsect1>
|
|
|
|
</refentry>
|