1081 lines
49 KiB
XML
1081 lines
49 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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SPDX-License-Identifier: LGPL-2.1+
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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.special">
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<refentryinfo>
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<title>systemd.special</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.special</refentrytitle>
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<manvolnum>7</manvolnum>
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</refmeta>
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<refnamediv>
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<refname>systemd.special</refname>
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<refpurpose>Special systemd units</refpurpose>
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</refnamediv>
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<refsynopsisdiv><para>
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<!-- sort alphabetically, targets first --><filename>basic.target</filename>,
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<filename>bluetooth.target</filename>,
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<filename>cryptsetup-pre.target</filename>,
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<filename>cryptsetup.target</filename>,
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<filename>ctrl-alt-del.target</filename>,
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<filename>default.target</filename>,
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<filename>emergency.target</filename>,
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<filename>exit.target</filename>,
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<filename>final.target</filename>,
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<filename>getty.target</filename>,
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<filename>getty-pre.target</filename>,
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<filename>graphical.target</filename>,
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<filename>halt.target</filename>,
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<filename>hibernate.target</filename>,
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<filename>hybrid-sleep.target</filename>,
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<filename>initrd-fs.target</filename>,
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<filename>initrd-root-device.target</filename>,
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<filename>initrd-root-fs.target</filename>,
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<filename>kbrequest.target</filename>,
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<filename>kexec.target</filename>,
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<filename>local-fs-pre.target</filename>,
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<filename>local-fs.target</filename>,
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<filename>machines.target</filename>
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<filename>multi-user.target</filename>,
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<filename>network-online.target</filename>,
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<filename>network-pre.target</filename>,
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<filename>network.target</filename>,
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<filename>nss-lookup.target</filename>,
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<filename>nss-user-lookup.target</filename>,
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<filename>paths.target</filename>,
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<filename>poweroff.target</filename>,
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<filename>printer.target</filename>,
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<filename>reboot.target</filename>,
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<filename>remote-cryptsetup.target</filename>,
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<filename>remote-fs-pre.target</filename>,
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<filename>remote-fs.target</filename>,
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<filename>rescue.target</filename>,
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<filename>rpcbind.target</filename>,
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<filename>runlevel2.target</filename>,
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<filename>runlevel3.target</filename>,
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<filename>runlevel4.target</filename>,
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<filename>runlevel5.target</filename>,
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<filename>shutdown.target</filename>,
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<filename>sigpwr.target</filename>,
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<filename>sleep.target</filename>,
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<filename>slices.target</filename>,
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<filename>smartcard.target</filename>,
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<filename>sockets.target</filename>,
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<filename>sound.target</filename>,
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<filename>suspend.target</filename>,
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<filename>swap.target</filename>,
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<filename>sysinit.target</filename>,
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<filename>system-update.target</filename>,
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<filename>time-sync.target</filename>,
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<filename>timers.target</filename>,
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<filename>umount.target</filename>,
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<!-- slices --><filename>-.slice</filename>,
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<filename>system.slice</filename>,
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<filename>user.slice</filename>,
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<filename>machine.slice</filename>,
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<!-- the rest --><filename>-.mount</filename>,
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<filename>dbus.service</filename>,
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<filename>dbus.socket</filename>,
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<filename>display-manager.service</filename>,
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<filename>init.scope</filename>,
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<filename>syslog.socket</filename>,
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<filename>system-update-cleanup.service</filename>
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</para></refsynopsisdiv>
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<refsect1>
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<title>Description</title>
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<para>A few units are treated specially by systemd. Many of them have
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special internal semantics and cannot be renamed, while others simply
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have a standard meaning and should be present on all systems.</para>
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</refsect1>
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<refsect1>
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<title>Special System Units</title>
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<variablelist>
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<varlistentry>
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<term><filename>-.mount</filename></term>
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<listitem>
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<para>The root mount point, i.e. the mount unit for the <filename>/</filename> path. This unit is
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unconditionally active, during the entire time the system is up, as this mount point is where the basic
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userspace is running from.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><filename>basic.target</filename></term>
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<listitem>
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<para>A special target unit covering basic boot-up.</para>
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<para>systemd automatically adds dependency of the type
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<varname>After=</varname> for this target unit to all
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services (except for those with
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<varname>DefaultDependencies=no</varname>).</para>
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<para>Usually, this should pull-in all local mount points plus
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<filename>/var</filename>, <filename>/tmp</filename> and
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<filename>/var/tmp</filename>, swap devices, sockets, timers,
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path units and other basic initialization necessary for general
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purpose daemons. The mentioned mount points are special cased
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to allow them to be remote.
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</para>
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<para>This target usually does not pull in any non-target units
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directly, but rather does so indirectly via other early boot targets.
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It is instead meant as a synchronization point for late boot
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services. Refer to
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<citerefentry><refentrytitle>bootup</refentrytitle><manvolnum>7</manvolnum></citerefentry>
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for details on the targets involved.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><filename>ctrl-alt-del.target</filename></term>
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<listitem>
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<para>systemd starts this target whenever Control+Alt+Del is
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pressed on the console. Usually, this should be aliased
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(symlinked) to <filename>reboot.target</filename>.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><filename>cryptsetup.target</filename></term>
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<listitem>
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<para>A target that pulls in setup services for all
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encrypted block devices.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><filename>dbus.service</filename></term>
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<listitem>
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<para>A special unit for the D-Bus bus daemon. As soon as
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this service is fully started up systemd will connect to it
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and register its service.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><filename>dbus.socket</filename></term>
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<listitem>
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<para>A special unit for the D-Bus system bus socket. All
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units with <varname>Type=dbus</varname> automatically gain a
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dependency on this unit.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><filename>default.target</filename></term>
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<listitem>
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<para>The default unit systemd starts at bootup. Usually,
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this should be aliased (symlinked) to
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<filename>multi-user.target</filename> or
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<filename>graphical.target</filename>.</para>
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<para>The default unit systemd starts at bootup can be
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overridden with the <varname>systemd.unit=</varname> kernel
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command line option.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><filename>display-manager.service</filename></term>
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<listitem>
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<para>The display manager service. Usually, this should be
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aliased (symlinked) to <filename>gdm.service</filename> or a
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similar display manager service.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><filename>emergency.target</filename></term>
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<listitem>
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<para>A special target unit that starts an emergency shell on the main console. This target does not pull in
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any services or mounts. It is the most minimal version of starting the system in order to acquire an
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interactive shell; the only processes running are usually just the system manager (PID 1) and the shell
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process. This unit is supposed to be used with the kernel command line option
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<varname>systemd.unit=</varname>; it is also used when a file system check on a required file system fails,
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and boot-up cannot continue. Compare with <filename>rescue.target</filename>, which serves a similar purpose,
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but also starts the most basic services and mounts all file systems.</para>
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<para>Use the <literal>systemd.unit=emergency.target</literal> kernel command line option to boot into this
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mode. A short alias for this kernel command line option is <literal>emergency</literal>, for compatibility
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with SysV.</para>
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<para>In many ways booting into <filename>emergency.target</filename> is similar to the effect of booting
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with <literal>init=/bin/sh</literal> on the kernel command line, except that emergency mode provides you with
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the full system and service manager, and allows starting individual units in order to continue the boot
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process in steps.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><filename>exit.target</filename></term>
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<listitem>
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<para>A special service unit for shutting down the system or
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user service manager. It is equivalent to
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<filename>poweroff.target</filename> on non-container
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systems, and also works in containers.</para>
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<para>systemd will start this unit when it receives the
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<constant>SIGTERM</constant> or <constant>SIGINT</constant>
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signal when running as user service daemon.</para>
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<para>Normally, this (indirectly) pulls in
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<filename>shutdown.target</filename>, which in turn should be
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conflicted by all units that want to be scheduled for
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shutdown when the service manager starts to exit.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><filename>final.target</filename></term>
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<listitem>
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<para>A special target unit that is used during the shutdown
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logic and may be used to pull in late services after all
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normal services are already terminated and all mounts
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unmounted.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><filename>getty.target</filename></term>
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<listitem>
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<para>A special target unit that pulls in statically
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configured local TTY <filename>getty</filename> instances.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><filename>getty-pre.target</filename></term>
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<listitem>
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<para>A special passive target unit. Users of this target
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are expected to pull it in the boot transaction via
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a dependency (e.g. <varname>Wants=</varname>). Order your
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unit before this unit if you want to make use of the console
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just before <filename>getty</filename> is started.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><filename>graphical.target</filename></term>
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<listitem>
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<para>A special target unit for setting up a graphical login
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screen. This pulls in
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<filename>multi-user.target</filename>.</para>
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<para>Units that are needed for graphical logins shall add
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<varname>Wants=</varname> dependencies for their unit to
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this unit (or <filename>multi-user.target</filename>) during
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installation. This is best configured via
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<varname>WantedBy=graphical.target</varname> in the unit's
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<literal>[Install]</literal> section.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><filename>hibernate.target</filename></term>
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<listitem>
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<para>A special target unit for hibernating the system. This
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pulls in <filename>sleep.target</filename>.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><filename>hybrid-sleep.target</filename></term>
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<listitem>
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<para>A special target unit for hibernating and suspending
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the system at the same time. This pulls in
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<filename>sleep.target</filename>.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><filename>halt.target</filename></term>
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<listitem>
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<para>A special target unit for shutting down and halting
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the system. Note that this target is distinct from
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<filename>poweroff.target</filename> in that it generally
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really just halts the system rather than powering it
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down.</para>
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<para>Applications wanting to halt the system should not start this unit
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directly, but should instead execute <command>systemctl halt</command>
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(possibly with the <option>--no-block</option> option) or call
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<citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>'s
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<command>org.freedesktop.systemd1.Manager.Halt</command> D-Bus method
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directly.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><filename>init.scope</filename></term>
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<listitem>
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<para>This scope unit is where the system and service manager (PID 1) itself resides. It is active as long as
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the system is running.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><filename>initrd-fs.target</filename></term>
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<listitem>
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<para><citerefentry><refentrytitle>systemd-fstab-generator</refentrytitle><manvolnum>3</manvolnum></citerefentry>
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automatically adds dependencies of type
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<varname>Before=</varname> to
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<filename>sysroot-usr.mount</filename> and all mount points
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found in <filename>/etc/fstab</filename> that have
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<option>x-initrd.mount</option> and not have
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<option>noauto</option> mount options set.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><filename>kbrequest.target</filename></term>
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<listitem>
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<para>systemd starts this target whenever Alt+ArrowUp is
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pressed on the console. Note that any user with physical access
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to the machine will be able to do this, without authentication,
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so this should be used carefully.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><filename>kexec.target</filename></term>
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<listitem>
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<para>A special target unit for shutting down and rebooting
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the system via kexec.</para>
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<para>Applications wanting to reboot the system should not start this unit
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directly, but should instead execute <command>systemctl kexec</command>
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(possibly with the <option>--no-block</option> option) or call
|
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<citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>'s
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<command>org.freedesktop.systemd1.Manager.KExec</command> D-Bus method
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directly.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><filename>local-fs.target</filename></term>
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<listitem>
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<para><citerefentry><refentrytitle>systemd-fstab-generator</refentrytitle><manvolnum>3</manvolnum></citerefentry>
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automatically adds dependencies of type
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<varname>Before=</varname> to all mount units that refer to
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local mount points for this target unit. In addition, it
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|
adds dependencies of type <varname>Wants=</varname> to this
|
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target unit for those mounts listed in
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<filename>/etc/fstab</filename> that have the
|
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<option>auto</option> mount option set.</para>
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</listitem>
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</varlistentry>
|
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<varlistentry>
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<term><filename>machines.target</filename></term>
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<listitem>
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<para>A standard target unit for starting all the containers
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and other virtual machines. See <filename>systemd-nspawn@.service</filename>
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for an example.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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|
<term><filename>multi-user.target</filename></term>
|
|
<listitem>
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<para>A special target unit for setting up a multi-user
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|
system (non-graphical). This is pulled in by
|
|
<filename>graphical.target</filename>.</para>
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|
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|
<para>Units that are needed for a multi-user system shall
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|
add <varname>Wants=</varname> dependencies for their unit to
|
|
this unit during installation. This is best configured via
|
|
<varname>WantedBy=multi-user.target</varname> in the unit's
|
|
<literal>[Install]</literal> section.</para>
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|
</listitem>
|
|
</varlistentry>
|
|
<varlistentry>
|
|
<term><filename>network-online.target</filename></term>
|
|
<listitem>
|
|
<para>Units that strictly require a configured network
|
|
connection should pull in
|
|
<filename>network-online.target</filename> (via a
|
|
<varname>Wants=</varname> type dependency) and order
|
|
themselves after it. This target unit is intended to pull in
|
|
a service that delays further execution until the network is
|
|
sufficiently set up. What precisely this requires is left to
|
|
the implementation of the network managing service.</para>
|
|
|
|
<para>Note the distinction between this unit and
|
|
<filename>network.target</filename>. This unit is an active
|
|
unit (i.e. pulled in by the consumer rather than the
|
|
provider of this functionality) and pulls in a service which
|
|
possibly adds substantial delays to further execution. In
|
|
contrast, <filename>network.target</filename> is a passive
|
|
unit (i.e. pulled in by the provider of the functionality,
|
|
rather than the consumer) that usually does not delay
|
|
execution much. Usually, <filename>network.target</filename>
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|
is part of the boot of most systems, while
|
|
<filename>network-online.target</filename> is not, except
|
|
when at least one unit requires it. Also see <ulink
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|
url="https://www.freedesktop.org/wiki/Software/systemd/NetworkTarget">Running
|
|
Services After the Network is up</ulink> for more
|
|
information.</para>
|
|
|
|
<para>All mount units for remote network file systems
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|
automatically pull in this unit, and order themselves after
|
|
it. Note that networking daemons that simply provide
|
|
functionality to other hosts generally do not need to pull
|
|
this in.</para>
|
|
|
|
<para>Note that this unit is only useful during the original system start-up logic. After the system has
|
|
completed booting up, it will not track the online state of the system anymore. Due to this it cannot be used
|
|
as a network connection monitor concept, it is purely a one-time system start-up concept.</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
<varlistentry>
|
|
<term><filename>paths.target</filename></term>
|
|
<listitem>
|
|
<para>A special target unit that sets up all path units (see
|
|
<citerefentry><refentrytitle>systemd.path</refentrytitle><manvolnum>5</manvolnum></citerefentry>
|
|
for details) that shall be active after boot.</para>
|
|
|
|
<para>It is recommended that path units installed by
|
|
applications get pulled in via <varname>Wants=</varname>
|
|
dependencies from this unit. This is best configured via a
|
|
<varname>WantedBy=paths.target</varname> in the path unit's
|
|
<literal>[Install]</literal> section.</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
<varlistentry>
|
|
<term><filename>poweroff.target</filename></term>
|
|
<listitem>
|
|
<para>A special target unit for shutting down and powering
|
|
off the system.</para>
|
|
|
|
<para>Applications wanting to reboot the system should not start this unit
|
|
directly, but should instead execute <command>systemctl poweroff</command>
|
|
(possibly with the <option>--no-block</option> option) or call
|
|
<citerefentry><refentrytitle>systemd-logind</refentrytitle><manvolnum>8</manvolnum></citerefentry>'s
|
|
<command>org.freedesktop.login1.Manager.PowerOff</command> D-Bus method
|
|
directly.</para>
|
|
|
|
<para><filename>runlevel0.target</filename> is an alias for
|
|
this target unit, for compatibility with SysV.</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
<varlistentry>
|
|
<term><filename>reboot.target</filename></term>
|
|
<listitem>
|
|
<para>A special target unit for shutting down and rebooting
|
|
the system.</para>
|
|
|
|
<para>Applications wanting to reboot the system should not start this unit
|
|
directly, but should instead execute <command>systemctl reboot</command>
|
|
(possibly with the <option>--no-block</option> option) or call
|
|
<citerefentry><refentrytitle>systemd-logind</refentrytitle><manvolnum>8</manvolnum></citerefentry>'s
|
|
<command>org.freedesktop.login1.Manager.Reboot</command> D-Bus method
|
|
directly.</para>
|
|
|
|
<para><filename>runlevel6.target</filename> is an alias for
|
|
this target unit, for compatibility with SysV.</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
<varlistentry>
|
|
<term><filename>remote-cryptsetup.target</filename></term>
|
|
<listitem>
|
|
<para>Similar to <filename>cryptsetup.target</filename>, but for encrypted
|
|
devices which are accessed over the network. It is used for
|
|
<citerefentry><refentrytitle>crypttab</refentrytitle><manvolnum>8</manvolnum></citerefentry>
|
|
entries marked with <option>_netdev</option>.</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
<varlistentry>
|
|
<term><filename>remote-fs.target</filename></term>
|
|
<listitem>
|
|
<para>Similar to <filename>local-fs.target</filename>, but
|
|
for remote mount points.</para>
|
|
|
|
<para>systemd automatically adds dependencies of type
|
|
<varname>After=</varname> for this target unit to all SysV
|
|
init script service units with an LSB header referring to
|
|
the <literal>$remote_fs</literal> facility.</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
<varlistentry>
|
|
<term><filename>rescue.target</filename></term>
|
|
<listitem>
|
|
<para>A special target unit that pulls in the base system (including system mounts) and spawns a rescue
|
|
shell. Isolate to this target in order to administer the system in single-user mode with all file systems
|
|
mounted but with no services running, except for the most basic. Compare with
|
|
<filename>emergency.target</filename>, which is much more reduced and does not provide the file systems or
|
|
most basic services. Compare with <filename>multi-user.target</filename>, this target could be seen as
|
|
<filename>single-user.target</filename>.</para>
|
|
|
|
<para><filename>runlevel1.target</filename> is an alias for this target unit, for compatibility with
|
|
SysV.</para>
|
|
|
|
<para>Use the <literal>systemd.unit=rescue.target</literal> kernel command line option to boot into this
|
|
mode. A short alias for this kernel command line option is <literal>1</literal>, for compatibility with
|
|
SysV.</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
<varlistentry>
|
|
<term><filename>initrd-root-device.target</filename></term>
|
|
<listitem>
|
|
<para>A special initrd target unit that is reached when the root filesystem device is available, but before
|
|
it has been mounted.
|
|
<citerefentry><refentrytitle>systemd-fstab-generator</refentrytitle><manvolnum>3</manvolnum></citerefentry>
|
|
and
|
|
<citerefentry><refentrytitle>systemd-gpt-auto-generator</refentrytitle><manvolnum>3</manvolnum></citerefentry>
|
|
automatically setup the appropriate dependencies to make this happen.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
<varlistentry>
|
|
<term><filename>initrd-root-fs.target</filename></term>
|
|
<listitem>
|
|
<para><citerefentry><refentrytitle>systemd-fstab-generator</refentrytitle><manvolnum>3</manvolnum></citerefentry>
|
|
automatically adds dependencies of type
|
|
<varname>Before=</varname> to the
|
|
<filename>sysroot.mount</filename> unit, which is generated
|
|
from the kernel command line.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
<varlistentry>
|
|
<term><filename>runlevel2.target</filename></term>
|
|
<term><filename>runlevel3.target</filename></term>
|
|
<term><filename>runlevel4.target</filename></term>
|
|
<term><filename>runlevel5.target</filename></term>
|
|
<listitem>
|
|
<para>These are targets that are called whenever the SysV
|
|
compatibility code asks for runlevel 2, 3, 4, 5,
|
|
respectively. It is a good idea to make this an alias for
|
|
(i.e. symlink to) <filename>graphical.target</filename>
|
|
(for runlevel 5) or <filename>multi-user.target</filename>
|
|
(the others).</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
<varlistentry>
|
|
<term><filename>shutdown.target</filename></term>
|
|
<listitem>
|
|
<para>A special target unit that terminates the services on
|
|
system shutdown.</para>
|
|
|
|
<para>Services that shall be terminated on system shutdown
|
|
shall add <varname>Conflicts=</varname> and
|
|
<varname>Before=</varname> dependencies to this unit for
|
|
their service unit, which is implicitly done when
|
|
<varname>DefaultDependencies=yes</varname> is set (the
|
|
default).</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
<varlistentry>
|
|
<term><filename>sigpwr.target</filename></term>
|
|
<listitem>
|
|
<para>A special target that is started when systemd receives
|
|
the SIGPWR process signal, which is normally sent by the
|
|
kernel or UPS daemons when power fails.</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
<varlistentry>
|
|
<term><filename>sleep.target</filename></term>
|
|
<listitem>
|
|
<para>A special target unit that is pulled in by
|
|
<filename>suspend.target</filename>,
|
|
<filename>hibernate.target</filename> and
|
|
<filename>hybrid-sleep.target</filename> and may be used to
|
|
hook units into the sleep state logic.</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
<varlistentry>
|
|
<term><filename>slices.target</filename></term>
|
|
<listitem>
|
|
<para>A special target unit that sets up all slice units (see
|
|
<citerefentry><refentrytitle>systemd.slice</refentrytitle><manvolnum>5</manvolnum></citerefentry> for
|
|
details) that shall be active after boot. By default the generic <filename>system.slice</filename>
|
|
slice unit, as well as the root slice unit <filename>-.slice</filename>, is pulled in and ordered before
|
|
this unit (see below).</para>
|
|
|
|
<para>It's a good idea to add <varname>WantedBy=slices.target</varname> lines to the <literal>[Install]</literal>
|
|
section of all slices units that may be installed dynamically.</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
<varlistentry>
|
|
<term><filename>sockets.target</filename></term>
|
|
<listitem>
|
|
<para>A special target unit that sets up all socket
|
|
units (see
|
|
<citerefentry><refentrytitle>systemd.socket</refentrytitle><manvolnum>5</manvolnum></citerefentry>
|
|
for details) that shall be active after boot.</para>
|
|
|
|
<para>Services that can be socket-activated shall add
|
|
<varname>Wants=</varname> dependencies to this unit for
|
|
their socket unit during installation. This is best
|
|
configured via a <varname>WantedBy=sockets.target</varname>
|
|
in the socket unit's <literal>[Install]</literal>
|
|
section.</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
<varlistentry>
|
|
<term><filename>suspend.target</filename></term>
|
|
<listitem>
|
|
<para>A special target unit for suspending the system. This
|
|
pulls in <filename>sleep.target</filename>.</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
<varlistentry>
|
|
<term><filename>swap.target</filename></term>
|
|
<listitem>
|
|
<para>Similar to <filename>local-fs.target</filename>, but
|
|
for swap partitions and swap files.</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
<varlistentry>
|
|
<term><filename>sysinit.target</filename></term>
|
|
<listitem>
|
|
<para>systemd automatically adds dependencies of the types
|
|
<varname>Requires=</varname> and <varname>After=</varname>
|
|
for this target unit to all services (except for those with
|
|
<varname>DefaultDependencies=no</varname>).</para>
|
|
|
|
<para>This target pulls in the services required for system
|
|
initialization. System services pulled in by this target should
|
|
declare <varname>DefaultDependencies=no</varname> and specify
|
|
all their dependencies manually, including access to anything
|
|
more than a read only root filesystem. For details on the
|
|
dependencies of this target, refer to
|
|
<citerefentry><refentrytitle>bootup</refentrytitle><manvolnum>7</manvolnum></citerefentry>.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
<varlistentry>
|
|
<term><filename>syslog.socket</filename></term>
|
|
<listitem>
|
|
<para>The socket unit syslog implementations should listen
|
|
on. All userspace log messages will be made available on
|
|
this socket. For more information about syslog integration,
|
|
please consult the <ulink
|
|
url="https://www.freedesktop.org/wiki/Software/systemd/syslog">Syslog
|
|
Interface</ulink> document.</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
<varlistentry>
|
|
<term><filename>system-update.target</filename></term>
|
|
<term><filename>system-update-cleanup.service</filename></term>
|
|
<listitem>
|
|
<para>A special target unit that is used for offline system updates.
|
|
<citerefentry><refentrytitle>systemd-system-update-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>
|
|
will redirect the boot process to this target if <filename>/system-update</filename>
|
|
exists. For more information see
|
|
<citerefentry><refentrytitle>systemd.offline-updates</refentrytitle><manvolnum>7</manvolnum></citerefentry>.
|
|
</para>
|
|
|
|
<para>Updates should happen before the <filename>system-update.target</filename> is
|
|
reached, and the services which implement them should cause the machine to reboot. As
|
|
a safety measure, if this does not happen, and <filename>/system-update</filename>
|
|
still exists after <filename>system-update.target</filename> is reached,
|
|
<filename>system-update-cleanup.service</filename> will remove this symlink and
|
|
reboot the machine.</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
<varlistentry>
|
|
<term><filename>timers.target</filename></term>
|
|
<listitem>
|
|
<para>A special target unit that sets up all timer units
|
|
(see
|
|
<citerefentry><refentrytitle>systemd.timer</refentrytitle><manvolnum>5</manvolnum></citerefentry>
|
|
for details) that shall be active after boot.</para>
|
|
|
|
<para>It is recommended that timer units installed by
|
|
applications get pulled in via <varname>Wants=</varname>
|
|
dependencies from this unit. This is best configured via
|
|
<varname>WantedBy=timers.target</varname> in the timer
|
|
unit's <literal>[Install]</literal> section.</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
<varlistentry>
|
|
<term><filename>umount.target</filename></term>
|
|
<listitem>
|
|
<para>A special target unit that unmounts all mount and
|
|
automount points on system shutdown.</para>
|
|
|
|
<para>Mounts that shall be unmounted on system shutdown
|
|
shall add Conflicts dependencies to this unit for their
|
|
mount unit, which is implicitly done when
|
|
<varname>DefaultDependencies=yes</varname> is set (the
|
|
default).</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
</variablelist>
|
|
</refsect1>
|
|
|
|
<refsect1>
|
|
<title>Special System Units for Devices</title>
|
|
|
|
<para>Some target units are automatically pulled in as devices of
|
|
certain kinds show up in the system. These may be used to
|
|
automatically activate various services based on the specific type
|
|
of the available hardware.</para>
|
|
|
|
<variablelist>
|
|
<varlistentry>
|
|
<term><filename>bluetooth.target</filename></term>
|
|
<listitem>
|
|
<para>This target is started automatically as soon as a
|
|
Bluetooth controller is plugged in or becomes available at
|
|
boot.</para>
|
|
|
|
<para>This may be used to pull in Bluetooth management
|
|
daemons dynamically when Bluetooth hardware is found.</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
<varlistentry>
|
|
<term><filename>printer.target</filename></term>
|
|
<listitem>
|
|
<para>This target is started automatically as soon as a
|
|
printer is plugged in or becomes available at boot.</para>
|
|
|
|
<para>This may be used to pull in printer management daemons
|
|
dynamically when printer hardware is found.</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
<varlistentry>
|
|
<term><filename>smartcard.target</filename></term>
|
|
<listitem>
|
|
<para>This target is started automatically as soon as a
|
|
smartcard controller is plugged in or becomes available at
|
|
boot.</para>
|
|
|
|
<para>This may be used to pull in smartcard management
|
|
daemons dynamically when smartcard hardware is found.</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
<varlistentry>
|
|
<term><filename>sound.target</filename></term>
|
|
<listitem>
|
|
<para>This target is started automatically as soon as a
|
|
sound card is plugged in or becomes available at
|
|
boot.</para>
|
|
|
|
<para>This may be used to pull in audio management daemons
|
|
dynamically when audio hardware is found.</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
</variablelist>
|
|
</refsect1>
|
|
|
|
<refsect1>
|
|
<title>Special Passive System Units </title>
|
|
|
|
<para>A number of special system targets are defined that can be
|
|
used to properly order boot-up of optional services. These targets
|
|
are generally not part of the initial boot transaction, unless
|
|
they are explicitly pulled in by one of the implementing services.
|
|
Note specifically that these <emphasis>passive</emphasis> target
|
|
units are generally not pulled in by the consumer of a service,
|
|
but by the provider of the service. This means: a consuming
|
|
service should order itself after these targets (as appropriate),
|
|
but not pull it in. A providing service should order itself before
|
|
these targets (as appropriate) and pull it in (via a
|
|
<varname>Wants=</varname> type dependency).</para>
|
|
|
|
<para>Note that these passive units cannot be started manually,
|
|
i.e. <literal>systemctl start time-sync.target</literal> will fail
|
|
with an error. They can only be pulled in by dependency. This is
|
|
enforced since they exist for ordering purposes only and thus are
|
|
not useful as only unit within a transaction.</para>
|
|
|
|
<variablelist>
|
|
<varlistentry>
|
|
<term><filename>cryptsetup-pre.target</filename></term>
|
|
<listitem>
|
|
<para>This passive target unit may be pulled in by services
|
|
that want to run before any encrypted block device is set
|
|
up. All encrypted block devices are set up after this target
|
|
has been reached. Since the shutdown order is implicitly the
|
|
reverse start-up order between units, this target is
|
|
particularly useful to ensure that a service is shut down
|
|
only after all encrypted block devices are fully
|
|
stopped.</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
<varlistentry>
|
|
<term><filename>local-fs-pre.target</filename></term>
|
|
<listitem>
|
|
<para>This target unit is
|
|
automatically ordered before
|
|
all local mount points marked
|
|
with <option>auto</option>
|
|
(see above). It can be used to
|
|
execute certain units before
|
|
all local mounts.</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
<varlistentry>
|
|
<term><filename>network.target</filename></term>
|
|
<listitem>
|
|
<para>This unit is supposed to indicate when network
|
|
functionality is available, but it is only very weakly
|
|
defined what that is supposed to mean, with one exception:
|
|
at shutdown, a unit that is ordered after
|
|
<filename>network.target</filename> will be stopped before
|
|
the network — to whatever level it might be set up then —
|
|
is shut down. It is hence useful when writing service files
|
|
that require network access on shutdown, which should order
|
|
themselves after this target, but not pull it in. Also see
|
|
<ulink url="https://www.freedesktop.org/wiki/Software/systemd/NetworkTarget">Running
|
|
Services After the Network is up</ulink> for more
|
|
information. Also see
|
|
<filename>network-online.target</filename> described
|
|
above.</para>
|
|
|
|
<para>systemd automatically adds dependencies of type
|
|
<varname>After=</varname> for this target unit to all SysV
|
|
init script service units with an LSB header referring to
|
|
the <literal>$network</literal> facility.</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
<varlistentry>
|
|
<term><filename>network-pre.target</filename></term>
|
|
<listitem>
|
|
<para>This passive target unit may be pulled in by services
|
|
that want to run before any network is set up, for example
|
|
for the purpose of setting up a firewall. All network
|
|
management software orders itself after this target, but
|
|
does not pull it in.</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
<varlistentry>
|
|
<term><filename>nss-lookup.target</filename></term>
|
|
<listitem>
|
|
<para>A target that should be used as synchronization point
|
|
for all host/network name service lookups. Note that this is
|
|
independent of user/group name lookups for which
|
|
<filename>nss-user-lookup.target</filename> should be used.
|
|
All services for which the availability of full host/network
|
|
name resolution is essential should be ordered after this
|
|
target, but not pull it in. systemd automatically adds
|
|
dependencies of type <varname>After=</varname> for this
|
|
target unit to all SysV init script service units with an
|
|
LSB header referring to the <literal>$named</literal>
|
|
facility.</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
<varlistentry>
|
|
<term><filename>nss-user-lookup.target</filename></term>
|
|
<listitem>
|
|
<para>A target that should be used as synchronization point
|
|
for all user/group name service lookups. Note that this is
|
|
independent of host/network name lookups for which
|
|
<filename>nss-lookup.target</filename> should be used. All
|
|
services for which the availability of the full user/group
|
|
database is essential should be ordered after this target,
|
|
but not pull it in. Note that system users are always
|
|
resolvable, and hence do not require any special ordering
|
|
against this target.</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
<varlistentry>
|
|
<term><filename>remote-fs-pre.target</filename></term>
|
|
<listitem>
|
|
<para>This target unit is automatically ordered before all
|
|
mount point units (see above) and cryptsetup devices
|
|
marked with the <option>_netdev</option>. It can be used to run
|
|
certain units before remote encrypted devices and mounts are established.
|
|
Note that this unit is generally not part of the initial
|
|
transaction, unless the unit that wants to be ordered before
|
|
all remote mounts pulls it in via a
|
|
<varname>Wants=</varname> type dependency. If the unit wants
|
|
to be pulled in by the first remote mount showing up, it
|
|
should use <filename>network-online.target</filename> (see
|
|
above).</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
<varlistentry>
|
|
<term><filename>rpcbind.target</filename></term>
|
|
<listitem>
|
|
<para>The portmapper/rpcbind pulls in this target and orders
|
|
itself before it, to indicate its availability. systemd
|
|
automatically adds dependencies of type
|
|
<varname>After=</varname> for this target unit to all SysV
|
|
init script service units with an LSB header referring to
|
|
the <literal>$portmap</literal> facility.</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
<varlistentry>
|
|
<term><filename>time-sync.target</filename></term>
|
|
<listitem>
|
|
<para>Services responsible for synchronizing the system
|
|
clock from a remote source (such as NTP client
|
|
implementations) should pull in this target and order
|
|
themselves before it. All services where correct time is
|
|
essential should be ordered after this unit, but not pull it
|
|
in. systemd automatically adds dependencies of type
|
|
<varname>After=</varname> for this target unit to all SysV
|
|
init script service units with an LSB header referring to
|
|
the <literal>$time</literal> facility. </para>
|
|
</listitem>
|
|
</varlistentry>
|
|
</variablelist>
|
|
</refsect1>
|
|
|
|
<refsect1>
|
|
<title>Special User Units</title>
|
|
|
|
<para>When systemd runs as a user instance, the following special
|
|
units are available, which have similar definitions as their
|
|
system counterparts:
|
|
<filename>exit.target</filename>,
|
|
<filename>default.target</filename>,
|
|
<filename>shutdown.target</filename>,
|
|
<filename>sockets.target</filename>,
|
|
<filename>timers.target</filename>,
|
|
<filename>paths.target</filename>,
|
|
<filename>bluetooth.target</filename>,
|
|
<filename>printer.target</filename>,
|
|
<filename>smartcard.target</filename>,
|
|
<filename>sound.target</filename>.</para>
|
|
</refsect1>
|
|
|
|
<refsect1>
|
|
<title>Special Passive User Units</title>
|
|
|
|
<variablelist>
|
|
<varlistentry>
|
|
<term><filename>graphical-session.target</filename></term>
|
|
<listitem>
|
|
<para>This target is active whenever any graphical session is running. It is used to stop user services which
|
|
only apply to a graphical (X, Wayland, etc.) session when the session is terminated. Such services should
|
|
have <literal>PartOf=graphical-session.target</literal> in their <literal>[Unit]</literal> section. A target
|
|
for a particular session (e. g. <filename>gnome-session.target</filename>) starts and stops
|
|
<literal>graphical-session.target</literal> with <literal>BindsTo=graphical-session.target</literal>.</para>
|
|
|
|
<para>Which services are started by a session target is determined by the <literal>Wants=</literal> and
|
|
<literal>Requires=</literal> dependencies. For services that can be enabled independently, symlinks in
|
|
<literal>.wants/</literal> and <literal>.requires/</literal> should be used, see
|
|
<citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>. Those
|
|
symlinks should either be shipped in packages, or should be added dynamically after installation, for example
|
|
using <literal>systemctl add-wants</literal>, see
|
|
<citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>.
|
|
</para>
|
|
|
|
<example>
|
|
<title>Nautilus as part of a GNOME session</title>
|
|
|
|
<para><literal>gnome-session.target</literal> pulls in Nautilus as top-level service:</para>
|
|
|
|
<programlisting>[Unit]
|
|
Description=User systemd services for GNOME graphical session
|
|
Wants=nautilus.service
|
|
BindsTo=graphical-session.target</programlisting>
|
|
|
|
<para><literal>nautilus.service</literal> gets stopped when the session stops:</para>
|
|
|
|
<programlisting>[Unit]
|
|
Description=Render the desktop icons with Nautilus
|
|
PartOf=graphical-session.target
|
|
|
|
[Service]
|
|
…</programlisting>
|
|
</example>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><filename>graphical-session-pre.target</filename></term>
|
|
<listitem>
|
|
<para>This target contains services which set up the environment or global configuration of a graphical
|
|
session, such as SSH/GPG agents (which need to export an environment variable into all desktop processes) or
|
|
migration of obsolete d-conf keys after an OS upgrade (which needs to happen before starting any process that
|
|
might use them). This target must be started before starting a graphical session like
|
|
<filename>gnome-session.target</filename>.</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
</variablelist>
|
|
|
|
</refsect1>
|
|
|
|
<refsect1>
|
|
<title>Special Slice Units</title>
|
|
|
|
<para>There are four <literal>.slice</literal> units which form the basis of the hierarchy for assignment of
|
|
resources for services, users, and virtual machines or containers. See
|
|
<citerefentry><refentrytitle>systemd.slice</refentrytitle><manvolnum>7</manvolnum></citerefentry> for details about slice
|
|
units.</para>
|
|
|
|
<variablelist>
|
|
<varlistentry>
|
|
<term><filename>-.slice</filename></term>
|
|
<listitem>
|
|
<para>The root slice is the root of the slice hierarchy. It usually does not contain units directly, but may
|
|
be used to set defaults for the whole tree.</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><filename>system.slice</filename></term>
|
|
<listitem>
|
|
<para>By default, all system services started by
|
|
<command>systemd</command> are found in this slice.</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><filename>user.slice</filename></term>
|
|
<listitem>
|
|
<para>By default, all user processes and services started on
|
|
behalf of the user, including the per-user systemd instance
|
|
are found in this slice. This is pulled in by
|
|
<filename>systemd-logind.service</filename></para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><filename>machine.slice</filename></term>
|
|
<listitem>
|
|
<para>By default, all virtual machines and containers
|
|
registered with <command>systemd-machined</command> are
|
|
found in this slice. This is pulled in by
|
|
<filename>systemd-machined.service</filename></para>
|
|
</listitem>
|
|
</varlistentry>
|
|
</variablelist>
|
|
</refsect1>
|
|
|
|
<refsect1>
|
|
<title>See Also</title>
|
|
<para>
|
|
<citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
|
|
<citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
|
|
<citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
|
|
<citerefentry><refentrytitle>systemd.socket</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
|
|
<citerefentry><refentrytitle>systemd.target</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
|
|
<citerefentry><refentrytitle>systemd.slice</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
|
|
<citerefentry><refentrytitle>bootup</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
|
|
<citerefentry><refentrytitle>systemd-fstab-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>
|
|
</para>
|
|
</refsect1>
|
|
|
|
</refentry>
|