<?xml version='1.0'?> <!--*-nxml-*-->
-<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
+<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
-
-<!--
- This file is part of systemd.
-
- Copyright 2010 Lennart Poettering
-
- systemd is free software; you can redistribute it and/or modify it
- under the terms of the GNU Lesser General Public License as published by
- the Free Software Foundation; either version 2.1 of the License, or
- (at your option) any later version.
-
- systemd is distributed in the hope that it will be useful, but
- WITHOUT ANY WARRANTY; without even the implied warranty of
- MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
- Lesser General Public License for more details.
-
- You should have received a copy of the GNU Lesser General Public License
- along with systemd; If not, see <http://www.gnu.org/licenses/>.
--->
+<!-- SPDX-License-Identifier: LGPL-2.1+ -->
<refentry id="systemd.target">
<refentryinfo>
<title>systemd.target</title>
<productname>systemd</productname>
-
- <authorgroup>
- <author>
- <contrib>Developer</contrib>
- <firstname>Lennart</firstname>
- <surname>Poettering</surname>
- <email>lennart@poettering.net</email>
- </author>
- </authorgroup>
</refentryinfo>
<refmeta>
<para>This unit type has no specific options. See
<citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>
for the common options of all unit configuration files. The common
- configuration items are configured in the generic [Unit] and
- [Install] sections. A separate [Target] section does not exist,
+ configuration items are configured in the generic <literal>[Unit]</literal> and
+ <literal>[Install]</literal> sections. A separate <literal>[Target]</literal> section does not exist,
since no target-specific options may be configured.</para>
<para>Target units do not offer any additional functionality on
<refsect1>
<title>Automatic Dependencies</title>
- <para>Unless <varname>DefaultDependencies=</varname> is set to
- <option>no</option>, target units will implicitly complement all
- configured dependencies of type <varname>Wants=</varname>,
- <varname>Requires=</varname> with dependencies of type
- <varname>After=</varname>, unless an ordering dependency of any
- kind between the target and the respective other unit is already
- in place. Note that this behaviour is disabled if either unit has
- <varname>DefaultDependencies=no</varname>.</para>
+ <refsect2>
+ <title>Implicit Dependencies</title>
+
+ <para>There are no implicit dependencies for target units.</para>
+ </refsect2>
+
+ <refsect2>
+ <title>Default Dependencies</title>
+
+ <para>The following dependencies are added unless
+ <varname>DefaultDependencies=no</varname> is set:</para>
+
+ <itemizedlist>
+ <listitem><para>Target units will automatically complement all
+ configured dependencies of type <varname>Wants=</varname> or
+ <varname>Requires=</varname> with dependencies of type
+ <varname>After=</varname> unless <varname>DefaultDependencies=no</varname>
+ is set in the specified units. Note that <varname>Wants=</varname> or
+ <varname>Requires=</varname> must be defined in the target unit itself — if
+ you for example define <varname>Wants=</varname>some.target in
+ some.service, the automatic ordering will not be added.</para></listitem>
+
+ <listitem><para>Target units automatically gain <varname>Conflicts=</varname>
+ and <varname>Before=</varname> dependencies against
+ <filename>shutdown.target</filename>.</para></listitem>
+ </itemizedlist>
+ </refsect2>
+ </refsect1>
+
+ <refsect1>
+ <title>Example</title>
+
+ <example>
+ <title>Simple standalone target</title>
+
+ <programlisting># emergency-net.target
+
+[Unit]
+Description=Emergency Mode with Networking
+Requires=emergency.target systemd-networkd.service
+After=emergency.target systemd-networkd.service
+AllowIsolate=yes</programlisting>
+
+ <para>When adding dependencies to other units, it's important to check if they set
+ <varname>DefaultDependencies=</varname>. Service units, unless they set
+ <varname>DefaultDependencies=no</varname>, automatically get a dependency on
+ <filename>sysinit.target</filename>. In this case, both
+ <filename>emergency.target</filename> and <filename>systemd-networkd.service</filename>
+ have <varname>DefaultDependencies=no</varname>, so they are suitable for use
+ in this target, and do not pull in <filename>sysinit.target</filename>.</para>
+
+ <para>You can now switch into this emergency mode by running <varname>systemctl
+ isolate emergency-net.target</varname> or by passing the option
+ <varname>systemd.unit=emergency-net.target</varname> on the kernel command
+ line.</para>
+
+ <para>Other units can have <varname>WantedBy=emergency-net.target</varname> in the
+ <varname>[Install]</varname> section. After they are enabled using
+ <command>systemctl enable</command>, they will be started before
+ <varname>emergency-net.target</varname> is started. It is also possible to add
+ arbitrary units as dependencies of <filename>emergency.target</filename> without
+ modifying them by using <command>systemctl add-wants</command>.
+ </para>
+ </example>
</refsect1>
<refsect1>
projects / thirdparty / systemd.git / blobdiff