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authorDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-10 20:49:52 +0000
committerDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-10 20:49:52 +0000
commit55944e5e40b1be2afc4855d8d2baf4b73d1876b5 (patch)
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Adding upstream version 255.4.upstream/255.4
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
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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.target">
+ <refentryinfo>
+ <title>systemd.target</title>
+ <productname>systemd</productname>
+ </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. Target units are used to group units and to set synchronization points for
+ ordering dependencies with other unit files.</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 merely group units, allowing a single target name to be used in <varname>Wants=</varname>
+ and <varname>Requires=</varname> settings to establish a dependency on a set of units defined by the
+ target, and in <varname>Before=</varname> and <varname>After=</varname> settings to establish ordering.
+ Targets establish standardized names for synchronization points during boot and shutdown. Importantly,
+ see <citerefentry><refentrytitle>systemd.special</refentrytitle><manvolnum>7</manvolnum></citerefentry>
+ for examples and descriptions of standard systemd targets.</para>
+
+ <para>Target units provide a more flexible replacement for SysV runlevels in the classic SysV init
+ system. 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>Note that a target unit file must not be empty, lest it be considered a masked unit. It is
+ recommended to provide a [Unit] section which includes informative <varname>Description=</varname> and
+ <varname>Documentation=</varname> options.</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.</para>
+
+ <para>Note that the reverse is not true. For example, defining <option>Wants=that.target</option> in
+ <filename index='false'>some.service</filename> will not automatically add the
+ <option>After=that.target</option> ordering dependency for <filename>some.service</filename>.
+ Instead, <filename>some.service</filename> should use the primary synchronization function of target
+ type units, by setting a specific <option>After=that.target</option> or
+ <option>Before=that.target</option> ordering dependency in its .service unit file.
+ </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>Options</title>
+
+ <para>Target unit files may include [Unit] and [Install] sections, which are described in
+ <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
+ No options specific to this file type are supported.</para>
+ </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>