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+ SPDX-License-Identifier: LGPL-2.1+
+
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/>.
-->
<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>
- <refentrytitle>systemd.target</refentrytitle>
- <manvolnum>5</manvolnum>
- </refmeta>
-
- <refnamediv>
- <refname>systemd.target</refname>
- <refpurpose>Target unit configuration</refpurpose>
- </refnamediv>
-
- <refsynopsisdiv>
- <para><filename>systemd.target</filename></para>
- </refsynopsisdiv>
-
- <refsect1>
- <title>Description</title>
-
- <para>A unit configuration file whose name ends in
- <filename>.target</filename> encodes information about
- a target unit of systemd, which is used for grouping
- units and as well-known synchronization points during
- start-up.</para>
-
- <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, since no
- target-specific options may be configured.</para>
-
- <para>Target units do not offer any additional
- functionality on top of the generic functionality
- provided by units. They exist merely to group units via dependencies
- (useful as boot targets), and to establish
- standardized names for synchronization points used in
- dependencies between units. Among other things, target
- units are a more flexible replacement for SysV
- runlevels in the classic SysV init system. (And for
- compatibility reasons special
- target units such as
- <filename>runlevel3.target</filename> exist which are used by
- the SysV runlevel compatibility code in systemd. See
- <citerefentry><refentrytitle>systemd.special</refentrytitle><manvolnum>7</manvolnum></citerefentry>
- for details).</para>
-
- <para>Unless <varname>DefaultDependencies=</varname>
- is set to <option>false</option>, target units will
- implicitly complement all configured dependencies of
- type <varname>Wants=</varname>,
- <varname>Requires=</varname>,
- <varname>RequiresOverridable=</varname> with
- dependencies of type <varname>After=</varname> if the
- units in question also have
- <varname>DefaultDependencies=true</varname>.
- </para>
- </refsect1>
-
- <refsect1>
- <title>See Also</title>
- <para>
- <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
- <citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
- <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
- <citerefentry><refentrytitle>systemd.special</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
- <citerefentry><refentrytitle>systemd.directives</refentrytitle><manvolnum>7</manvolnum></citerefentry>
- </para>
- </refsect1>
+ <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>
+ <refentrytitle>systemd.target</refentrytitle>
+ <manvolnum>5</manvolnum>
+ </refmeta>
+
+ <refnamediv>
+ <refname>systemd.target</refname>
+ <refpurpose>Target unit configuration</refpurpose>
+ </refnamediv>
+
+ <refsynopsisdiv>
+ <para><filename><replaceable>target</replaceable>.target</filename></para>
+ </refsynopsisdiv>
+
+ <refsect1>
+ <title>Description</title>
+
+ <para>A unit configuration file whose name ends in
+ <literal>.target</literal> encodes information about a target unit
+ of systemd, which is used for grouping units and as well-known
+ synchronization points during start-up.</para>
+
+ <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,
+ since no target-specific options may be configured.</para>
+
+ <para>Target units do not offer any additional functionality on
+ top of the generic functionality provided by units. They exist
+ merely to group units via dependencies (useful as boot targets),
+ and to establish standardized names for synchronization points
+ used in dependencies between units. Among other things, target
+ units are a more flexible replacement for SysV runlevels in the
+ classic SysV init system. (And for compatibility reasons special
+ target units such as <filename>runlevel3.target</filename> exist
+ which are used by the SysV runlevel compatibility code in systemd.
+ See
+ <citerefentry><refentrytitle>systemd.special</refentrytitle><manvolnum>7</manvolnum></citerefentry>
+ for details).</para>
+ </refsect1>
+
+ <refsect1>
+ <title>Automatic Dependencies</title>
+
+ <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>
+ dependency 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>
+ <title>See Also</title>
+ <para>
+ <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>systemd.special</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>systemd.directives</refentrytitle><manvolnum>7</manvolnum></citerefentry>
+ </para>
+ </refsect1>
</refentry>
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