<?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.special" xmlns:xi="http://www.w3.org/2001/XInclude">
<refentryinfo>
<title>systemd.special</title>
<productname>systemd</productname>
</refentryinfo>
<refmeta>
<refentrytitle>systemd.special</refentrytitle>
<manvolnum>7</manvolnum>
</refmeta>
<refnamediv>
<refname>systemd.special</refname>
<refpurpose>Special systemd units</refpurpose>
</refnamediv>
<refsynopsisdiv><para>
<!-- sort alphabetically, targets first --><filename>basic.target</filename>,
<filename>bluetooth.target</filename>,
<filename>cryptsetup-pre.target</filename>,
<filename>cryptsetup.target</filename>,
<filename>veritysetup-pre.target</filename>,
<filename>veritysetup.target</filename>,
<filename>ctrl-alt-del.target</filename>,
<filename>blockdev@.target</filename>,
<filename>boot-complete.target</filename>,
<filename>default.target</filename>,
<filename>emergency.target</filename>,
<filename>exit.target</filename>,
<filename>factory-reset.target</filename>,
<filename>final.target</filename>,
<filename>first-boot-complete.target</filename>,
<filename>getty.target</filename>,
<filename>getty-pre.target</filename>,
<filename>graphical.target</filename>,
<filename>halt.target</filename>,
<filename>hibernate.target</filename>,
<filename>hybrid-sleep.target</filename>,
<filename>suspend-then-hibernate.target</filename>,
<filename>initrd.target</filename>,
<filename>initrd-fs.target</filename>,
<filename>initrd-root-device.target</filename>,
<filename>initrd-root-fs.target</filename>,
<filename>initrd-usr-fs.target</filename>,
<filename>integritysetup-pre.target</filename>,
<filename>integritysetup.target</filename>,
<filename>kbrequest.target</filename>,
<filename>kexec.target</filename>,
<filename>local-fs-pre.target</filename>,
<filename>local-fs.target</filename>,
<filename>machines.target</filename>
<filename>multi-user.target</filename>,
<filename>network-online.target</filename>,
<filename>network-pre.target</filename>,
<filename>network.target</filename>,
<filename>nss-lookup.target</filename>,
<filename>nss-user-lookup.target</filename>,
<filename>paths.target</filename>,
<filename>poweroff.target</filename>,
<filename>printer.target</filename>,
<filename>reboot.target</filename>,
<filename>remote-cryptsetup.target</filename>,
<filename>remote-veritysetup.target</filename>,
<filename>remote-fs-pre.target</filename>,
<filename>remote-fs.target</filename>,
<filename>rescue.target</filename>,
<filename>rpcbind.target</filename>,
<filename>runlevel2.target</filename>,
<filename>runlevel3.target</filename>,
<filename>runlevel4.target</filename>,
<filename>runlevel5.target</filename>,
<filename>shutdown.target</filename>,
<filename>sigpwr.target</filename>,
<filename>sleep.target</filename>,
<filename>slices.target</filename>,
<filename>smartcard.target</filename>,
<filename>sockets.target</filename>,
<filename>soft-reboot.target</filename>,
<filename>sound.target</filename>,
<filename>storage-target-mode.target</filename>,
<filename>suspend.target</filename>,
<filename>swap.target</filename>,
<filename>sysinit.target</filename>,
<filename>system-update.target</filename>,
<filename>system-update-pre.target</filename>,
<filename>time-set.target</filename>,
<filename>time-sync.target</filename>,
<filename>timers.target</filename>,
<filename>umount.target</filename>,
<filename>usb-gadget.target</filename>,
<!-- slices --><filename>-.slice</filename>,
<filename>system.slice</filename>,
<filename>user.slice</filename>,
<filename>machine.slice</filename>,
<!-- the rest --><filename>-.mount</filename>,
<filename>dbus.service</filename>,
<filename>dbus.socket</filename>,
<filename>display-manager.service</filename>,
<filename>init.scope</filename>,
<filename>syslog.socket</filename>,
<filename>system-update-cleanup.service</filename>
</para></refsynopsisdiv>
<refsect1>
<title>Description</title>
<para>A few units are treated specially by systemd. Many of them have
special internal semantics and cannot be renamed, while others simply
have a standard meaning and should be present on all systems.</para>
</refsect1>
<refsect1>
<title>Units managed by the system service manager</title>
<refsect2>
<title>Special System Units</title>
<variablelist>
<varlistentry>
<term><filename>-.mount</filename></term>
<listitem>
<para>The root mount point, i.e. the mount unit for the <filename>/</filename>
path. This unit is unconditionally active, during the entire time the system is up, as
this mount point is where the basic userspace is running from.</para>
<xi:include href="version-info.xml" xpointer="v235"/>
</listitem>
</varlistentry>
<varlistentry>
<term><filename>basic.target</filename></term>
<listitem>
<para>A special target unit covering basic boot-up.</para>
<para>systemd automatically adds dependency of the type
<varname>After=</varname> for this target unit to all
services (except for those with
<varname>DefaultDependencies=no</varname>).</para>
<para>Usually, this should pull-in all local mount points plus
<filename>/var/</filename>, <filename>/tmp/</filename> and
<filename>/var/tmp/</filename>, swap devices, sockets, timers,
path units and other basic initialization necessary for general
purpose daemons. The mentioned mount points are special cased
to allow them to be remote.
</para>
<para>This target usually does not pull in any non-target units
directly, but rather does so indirectly via other early boot targets.
It is instead meant as a synchronization point for late boot
services. Refer to
<citerefentry><refentrytitle>bootup</refentrytitle><manvolnum>7</manvolnum></citerefentry>
for details on the targets involved.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><filename>boot-complete.target</filename></term>
<listitem>
<para>This target is intended as generic synchronization point for services that shall determine or act on
whether the boot process completed successfully. Order units that are required to succeed for a boot process
to be considered successful before this unit, and add a <varname>Requires=</varname> dependency from the
target unit to them. Order units that shall only run when the boot process is considered successful after the
target unit and pull in the target from it, also with <varname>Requires=</varname>. Note that by default this
target unit is not part of the initial boot transaction, but is supposed to be pulled in only if required by
units that want to run only on successful boots.</para>
<para>See
<citerefentry><refentrytitle>systemd-boot-check-no-failures.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>
for a service that implements a generic system health check and orders itself before
<filename>boot-complete.target</filename>.</para>
<para>See
<citerefentry><refentrytitle>systemd-bless-boot.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>
for a service that propagates boot success information to the boot loader, and orders itself after
<filename>boot-complete.target</filename>.</para>
<xi:include href="version-info.xml" xpointer="v240"/>
</listitem>
</varlistentry>
<varlistentry>
<term><filename>ctrl-alt-del.target</filename></term>
<listitem>
<para>systemd starts this target whenever Control+Alt+Del is
pressed on the console. Usually, this should be aliased
(symlinked) to <filename>reboot.target</filename>.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><filename>cryptsetup.target</filename></term>
<listitem>
<para>A target that pulls in setup services for all
encrypted block devices.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><filename>veritysetup.target</filename></term>
<listitem>
<para>A target that pulls in setup services for all
verity integrity protected block devices.</para>
<xi:include href="version-info.xml" xpointer="v248"/>
</listitem>
</varlistentry>
<varlistentry>
<term><filename>dbus.service</filename></term>
<listitem>
<para>A special unit for the D-Bus bus daemon. As soon as
this service is fully started up systemd will connect to it
and register its service.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><filename>dbus.socket</filename></term>
<listitem>
<para>A special unit for the D-Bus system bus socket. All
units with <varname>Type=dbus</varname> automatically gain a
dependency on this unit.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><filename>default.target</filename></term>
<listitem>
<para>The default unit systemd starts at bootup. Usually, this should be aliased (symlinked) to
<filename>multi-user.target</filename> or <filename>graphical.target</filename>. See
<citerefentry><refentrytitle>bootup</refentrytitle><manvolnum>7</manvolnum></citerefentry> for
more discussion.</para>
<para>The default unit systemd starts at bootup can be overridden with the
<varname>systemd.unit=</varname> kernel command line option, or more conveniently, with the short
names like <varname>single</varname>, <varname>rescue</varname>, <varname>1</varname>,
<varname>3</varname>, <varname>5</varname>, …; see
<citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><filename>display-manager.service</filename></term>
<listitem>
<para>The display manager service. Usually, this should be
aliased (symlinked) to <filename>gdm.service</filename> or a
similar display manager service.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><filename>emergency.target</filename></term>
<listitem>
<para>A special target unit that starts an emergency shell on the main console. This
target does not pull in other services or mounts. It is the most minimal version of
starting the system in order to acquire an interactive shell; the only processes running
are usually just the system manager (PID 1) and the shell process. This unit may be used
by specifying <varname>emergency</varname> on the kernel command line; it is
also used when a file system check on a required file system fails and boot-up cannot
continue. Compare with <filename>rescue.target</filename>, which serves a similar
purpose, but also starts the most basic services and mounts all file systems.</para>
<para>In many ways booting into <filename>emergency.target</filename> is similar to the
effect of booting with <literal>init=/bin/sh</literal> on the kernel command line,
except that emergency mode provides you with the full system and service manager, and
allows starting individual units in order to continue the boot process in steps.</para>
<para>Note that depending on how <filename>emergency.target</filename> is reached, the root file
system might be mounted read-only or read-write (no remounting is done specially for this
target). For example, the system may boot with root mounted read-only when <varname>ro</varname>
is used on the kernel command line and remain this way for <filename>emergency.target</filename>,
or the system may transition to <filename>emergency.target</filename> after the system has been
partially booted and disks have already been remounted read-write.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><filename>exit.target</filename></term>
<listitem>
<para>A special service unit for shutting down the system or
user service manager. It is equivalent to
<filename>poweroff.target</filename> on non-container
systems, and also works in containers.</para>
<para>systemd will start this unit when it receives the
<constant>SIGTERM</constant> or <constant>SIGINT</constant>
signal when running as user service daemon.</para>
<para>Normally, this (indirectly) pulls in
<filename>shutdown.target</filename>, which in turn should be
conflicted by all units that want to be scheduled for
shutdown when the service manager starts to exit.</para>
<xi:include href="version-info.xml" xpointer="v186"/>
</listitem>
</varlistentry>
<varlistentry>
<term><filename>factory-reset.target</filename></term>
<listitem>
<para>A special target to trigger a factory reset.</para>
<xi:include href="version-info.xml" xpointer="v250"/>
</listitem>
</varlistentry>
<varlistentry>
<term><filename>final.target</filename></term>
<listitem>
<para>A special target unit that is used during the shutdown
logic and may be used to pull in late services after all
normal services are already terminated and all mounts
unmounted.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><filename>getty.target</filename></term>
<listitem>
<para>A special target unit that pulls in statically
configured local TTY <filename>getty</filename> instances.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><filename>graphical.target</filename></term>
<listitem>
<para>A special target unit for setting up a graphical login
screen. This pulls in
<filename>multi-user.target</filename>.</para>
<para>Units that are needed for graphical logins shall add
<varname>Wants=</varname> dependencies for their unit to
this unit (or <filename>multi-user.target</filename>) during
installation. This is best configured via
<varname>WantedBy=graphical.target</varname> in the unit's
[Install] section.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><filename>hibernate.target</filename></term>
<listitem>
<para>A special target unit for hibernating the system. This
pulls in <filename>sleep.target</filename>.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><filename>hybrid-sleep.target</filename></term>
<listitem>
<para>A special target unit for hibernating and suspending
the system at the same time. This pulls in
<filename>sleep.target</filename>.</para>
<xi:include href="version-info.xml" xpointer="v196"/>
</listitem>
</varlistentry>
<varlistentry>
<term><filename>suspend-then-hibernate.target</filename></term>
<listitem>
<para>A special target unit for suspending the system for a period
of time, waking it and putting it into hibernate. This pulls in
<filename>sleep.target</filename>.</para>
<xi:include href="version-info.xml" xpointer="v239"/>
</listitem>
</varlistentry>
<varlistentry>
<term><filename>halt.target</filename></term>
<listitem>
<para>A special target unit for shutting down and halting
the system. Note that this target is distinct from
<filename>poweroff.target</filename> in that it generally
really just halts the system rather than powering it
down.</para>
<para>Applications wanting to halt the system should not start this unit
directly, but should instead execute <command>systemctl halt</command>
(possibly with the <option>--no-block</option> option) or call
<citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>'s
<command>org.freedesktop.systemd1.Manager.Halt</command> D-Bus method
directly.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><filename>init.scope</filename></term>
<listitem>
<para>This scope unit is where the system and service manager (PID 1) itself resides. It
is active as long as the system is running.</para>
<xi:include href="version-info.xml" xpointer="v235"/>
</listitem>
</varlistentry>
<varlistentry>
<term><filename>initrd.target</filename></term>
<listitem>
<para>This is the default target in the initrd, similar to <filename>default.target</filename> in
the main system. It is used to mount the real root and transition to it. See
<citerefentry><refentrytitle>bootup</refentrytitle><manvolnum>7</manvolnum></citerefentry> for
more discussion.</para>
<xi:include href="version-info.xml" xpointer="v245"/>
</listitem>
</varlistentry>
<varlistentry>
<term><filename>initrd-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
<filename>sysroot-usr.mount</filename> and all mount points found in
<filename>/etc/fstab</filename> that have the <option>x-initrd.mount</option> mount option set
and do not have the <option>noauto</option> mount option set. It is also indirectly ordered after
<filename>sysroot.mount</filename>. Thus, once this target is reached the
<filename>/sysroot/</filename> hierarchy is fully set up, in preparation for the transition to
the host OS.</para>
<xi:include href="version-info.xml" xpointer="v199"/>
</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>
<xi:include href="version-info.xml" xpointer="v230"/>
</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's
<varname>root=</varname> setting (or equivalent).</para>
<xi:include href="version-info.xml" xpointer="v199"/>
</listitem>
</varlistentry>
<varlistentry>
<term><filename>initrd-usr-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>sysusr-usr.mount</filename> unit, which is generated from the kernel command line's
<varname>usr=</varname> switch. Services may order themselves after this target unit in order to
run once the <filename>/sysusr/</filename> hierarchy becomes available, on systems that come up
initially without a root file system, but with an initialized <filename>/usr/</filename> and need
to access that before setting up the root file system to ultimately switch to. On systems where
<varname>usr=</varname> is not used this target is ordered after
<filename>sysroot.mount</filename> and thus mostly equivalent to
<filename>initrd-root-fs.target</filename>. In effect on any system once this target is reached
the file system backing <filename>/usr/</filename> is mounted, though possibly at two different
locations, either below the <filename>/sysusr/</filename> or the <filename>/sysroot/</filename>
hierarchies.</para>
<xi:include href="version-info.xml" xpointer="v249"/>
</listitem>
</varlistentry>
<varlistentry>
<term><filename>kbrequest.target</filename></term>
<listitem>
<para>systemd starts this target whenever Alt+ArrowUp is
pressed on the console. Note that any user with physical access
to the machine will be able to do this, without authentication,
so this should be used carefully.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><filename>kexec.target</filename></term>
<listitem>
<para>A special target unit for shutting down and rebooting the system via kexec.</para>
<para>Applications wanting to reboot the system should not start this unit directly, but should
instead execute <command>systemctl kexec</command> (possibly with the
<option>--no-block</option> option) or call
<citerefentry><refentrytitle>systemd-logind</refentrytitle><manvolnum>8</manvolnum></citerefentry>'s
<function>org.freedesktop.login1.Manager.RebootWithFlags()</function> D-Bus method
directly.</para>
<para>See
<citerefentry><refentrytitle>systemd-kexec.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>
for further details of the operation this target pulls in.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><filename>local-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 all mount units that refer to
local mount points for this target unit. In addition, it
adds dependencies of type <varname>Wants=</varname> to this
target unit for those mounts listed in
<filename>/etc/fstab</filename> that have the
<option>auto</option> mount option set.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><filename>machines.target</filename></term>
<listitem>
<para>A standard target unit for starting all the containers
and other virtual machines. See <filename>systemd-nspawn@.service</filename>
for an example.</para>
<xi:include href="version-info.xml" xpointer="v233"/>
</listitem>
</varlistentry>
<varlistentry>
<term><filename>multi-user.target</filename></term>
<listitem>
<para>A special target unit for setting up a multi-user
system (non-graphical). This is pulled in by
<filename>graphical.target</filename>.</para>
<para>Units that are needed for a multi-user system shall
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
[Install] section.</para>
</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> 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 url="https://systemd.io/NETWORK_ONLINE">Running Services After the Network Is
Up</ulink> for more information.</para>
<para>All mount units for remote network file systems automatically pull in this unit, and order
themselves after it. Note that networking daemons that simply <emphasis>provide</emphasis>
functionality to other hosts (as opposed to <emphasis>consume</emphasis> functionality of other
hosts) generally do not need to pull this in.</para>
<para>systemd automatically adds dependencies of type <varname>Wants=</varname> and
<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>
<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>
<xi:include href="version-info.xml" xpointer="v200"/>
</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
[Install] section.</para>
<xi:include href="version-info.xml" xpointer="v199"/>
</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 power off 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
<function>org.freedesktop.login1.Manager.Reboot()</function> D-Bus method directly.</para>
<para>See
<citerefentry><refentrytitle>systemd-reboot.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>
for further details of the operation this target pulls in.</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>
<xi:include href="version-info.xml" xpointer="v235"/>
</listitem>
</varlistentry>
<varlistentry>
<term><filename>remote-veritysetup.target</filename></term>
<listitem>
<para>Similar to <filename>veritysetup.target</filename>, but for verity
integrity protected devices which are accessed over the network. It is used for
<citerefentry><refentrytitle>veritytab</refentrytitle><manvolnum>8</manvolnum></citerefentry>
entries marked with <option>_netdev</option>.</para>
<xi:include href="version-info.xml" xpointer="v248"/>
</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>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 always be active after boot. By default the generic
<filename>system.slice</filename> slice unit as well as the root slice unit
<filename>-.slice</filename> are pulled in and ordered before this unit (see
below).</para>
<para>Adding slice units to <filename>slices.target</filename> is generally not
necessary. Instead, when some unit that uses <varname>Slice=</varname> is started, the
specified slice will be started automatically. Adding
<varname>WantedBy=slices.target</varname> lines to the [Install]
section should only be done for units that need to be always active. In that case care
needs to be taken to avoid creating a loop through the automatic dependencies on
"parent" slices.</para>
<xi:include href="version-info.xml" xpointer="v229"/>
</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 [Install]
section.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><filename>soft-reboot.target</filename></term>
<listitem>
<para>A special target unit for shutting down and rebooting the userspace of the system (leaving
the kernel running).</para>
<para>Applications wanting to reboot the system should not start this unit directly, but should
instead execute <command>systemctl soft-reboot</command> (possibly with the
<option>--no-block</option> option) or call
<citerefentry><refentrytitle>systemd-logind</refentrytitle><manvolnum>8</manvolnum></citerefentry>'s
<function>org.freedesktop.login1.Manager.RebootWithFlags()</function> D-Bus method
directly.</para>
<para>See
<citerefentry><refentrytitle>systemd-soft-reboot.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>
for further details of the operation this target pulls in.</para>
<xi:include href="version-info.xml" xpointer="v254"/>
</listitem>
</varlistentry>
<varlistentry>
<term><filename>storage-target-mode.target</filename></term>
<listitem>
<para>A special target unit that can be booted into that selects the "Storage Target Mode" for
the OS. In this mode all local storage disks are exposed to external systems as block
devices. This invokes
<citerefentry><refentrytitle>systemd-storagetm.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>
which exposes all local disks as NVMe-TCP devices for access over the network. It might as well
invoke other services too that make local disks available via other mechanisms.</para>
<xi:include href="version-info.xml" xpointer="v255"/>
</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-pre.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> or
<filename>/etc/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. The
main units executing the update should order themselves after
<filename>system-update-pre.target</filename> but not pull it in. Services which want to
run during system updates only, but before the actual system update is executed should
order themselves before this unit and pull it in. As a safety measure, if this does not
happen, and <filename>/system-update</filename> or
<filename>/etc/system-update</filename> still exists after
<filename>system-update.target</filename> is reached,
<filename>system-update-cleanup.service</filename> will remove the symlinks and reboot
the machine.</para>
<xi:include href="version-info.xml" xpointer="v186"/>
</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 [Install] section.</para>
<xi:include href="version-info.xml" xpointer="v199"/>
</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>
</refsect2>
<refsect2>
<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>
<varlistentry>
<term><filename>usb-gadget.target</filename></term>
<listitem>
<para>This target is started automatically as soon as a
USB Device Controller becomes available at boot.</para>
<para>This may be used to pull in usb gadget
dynamically when UDC hardware is found.</para>
<xi:include href="version-info.xml" xpointer="v242"/>
</listitem>
</varlistentry>
</variablelist>
</refsect2>
<refsect2>
<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>blockdev@.target</filename></term>
<listitem><para>This template unit is used to order mount units and other consumers of block
devices after services that synthesize these block devices. In particular, this is intended to be
used with storage services (such as
<citerefentry><refentrytitle>systemd-cryptsetup@.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>/
<citerefentry><refentrytitle>systemd-veritysetup@.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>)
that allocate and manage a virtual block device. Storage services are ordered before an instance of
<filename>blockdev@.target</filename>, and the consumer units after it. The ordering is
particularly relevant during shutdown, as it ensures that the mount is deactivated first and the
service backing the mount later. The <filename>blockdev@.target</filename> instance should be
pulled in via a <option>Wants=</option> dependency of the storage daemon and thus generally not be
part of any transaction unless a storage daemon is used. The instance name for instances of this
template unit must be a properly escaped block device node path, e.g.
<filename index="false">blockdev@dev-mapper-foobar.target</filename> for the storage device
<filename index="false">/dev/mapper/foobar</filename>.</para>
<xi:include href="version-info.xml" xpointer="v245"/></listitem>
</varlistentry>
<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>
<xi:include href="version-info.xml" xpointer="v215"/>
</listitem>
</varlistentry>
<varlistentry>
<term><filename>veritysetup-pre.target</filename></term>
<listitem>
<para>This passive target unit may be pulled in by services
that want to run before any verity integrity protected block
device is set up. All verity integrity protected 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 verity integrity
protected block devices are fully stopped.</para>
<xi:include href="version-info.xml" xpointer="v248"/>
</listitem>
</varlistentry>
<varlistentry>
<term><filename>first-boot-complete.target</filename></term>
<listitem>
<para>This passive target is intended as a synchronization point for units that need to run once
during the first boot. Only after all units ordered before this target have finished, will the
<citerefentry><refentrytitle>machine-id</refentrytitle><manvolnum>5</manvolnum></citerefentry>
be committed to disk, marking the first boot as completed. If the boot is aborted at any time
before that, the next boot will re-run any units with <varname>ConditionFirstBoot=yes</varname>.
</para>
<xi:include href="version-info.xml" xpointer="v247"/>
</listitem>
</varlistentry>
<varlistentry>
<term><filename>getty-pre.target</filename></term>
<listitem>
<para>A special passive target unit. Users of this target
are expected to pull it in the boot transaction via
a dependency (e.g. <varname>Wants=</varname>). Order your
unit before this unit if you want to make use of the console
just before <filename>getty</filename> is started.
</para>
<xi:include href="version-info.xml" xpointer="v235"/>
</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. However, the following should apply at
minimum:</para>
<itemizedlist>
<listitem><para>At start-up, any configured synthetic network devices (i.e. not physical ones
that require hardware to show up and be probed, but virtual ones like bridge devices and
similar which are created programmatically) that do not depend on any underlying hardware
should be allocated by the time this target is reached. It is not necessary for these
interfaces to also have completed IP level configuration by the time
<filename>network.target</filename> is reached.</para></listitem>
<listitem><para>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 by 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://systemd.io/NETWORK_ONLINE">Running Services After the Network Is Up</ulink> for
more information.</para></listitem>
</itemizedlist>
<para>It must emphasized that at start-up there's no guarantee that hardware-based devices have
shown up by the time this target is reached, or even acquired complete IP configuration. For that
purpose use <filename>network-online.target</filename> as described above.</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. Also see <ulink
url="https://systemd.io/NETWORK_ONLINE">Running Services After the Network Is Up</ulink> for more
information.</para>
<xi:include href="version-info.xml" xpointer="v214"/>
</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 UNIX 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>$named</literal> facility.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><filename>nss-user-lookup.target</filename></term>
<listitem>
<para>A target that should be used as synchronization point for all regular UNIX
user/group name service lookups. Note that this is independent of host/network name
lookups for which <filename>nss-lookup.target</filename> should be used. All services
for which the availability of the full user/group database is essential should be
ordered after this target, but not pull it in. All services which provide parts of the
user/group database should be ordered before this target, and pull it in. Note that this
unit is only relevant for regular users and groups — system users and groups are
required to be resolvable during earliest boot already, and hence do not need any
special ordering against this target.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><filename>remote-fs-pre.target</filename></term>
<listitem>
<para>This target unit is automatically ordered before all
mount point units (see above) and cryptsetup/veritysetup devices
marked with the <option>_netdev</option>. It can be used to run
certain units before remote encrypted devices and mounts are established.
Note that this unit is generally not part of the initial
transaction, unless the unit that wants to be ordered before
all remote mounts pulls it in via a
<varname>Wants=</varname> type dependency. If the unit wants
to be pulled in by the first remote mount showing up, it
should use <filename>network-online.target</filename> (see
above).</para>
</listitem>
</varlistentry>
<varlistentry>
<term><filename>rpcbind.target</filename></term>
<listitem>
<para>The portmapper/rpcbind pulls in this target and orders
itself before it, to indicate its availability. systemd
automatically adds dependencies of type
<varname>After=</varname> for this target unit to all SysV
init script service units with an LSB header referring to
the <literal>$portmap</literal> facility.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><filename>time-set.target</filename></term>
<listitem>
<para>Services responsible for setting the system clock (<constant>CLOCK_REALTIME</constant>)
from a local source (such as a maintained timestamp file or imprecise real-time clock) should
pull in this target and order themselves before it. Services where approximate, roughly monotonic
time is desired should be ordered after this unit, but not pull it in.</para>
<para>This target does not provide the accuracy guarantees of
<filename>time-sync.target</filename> (see below), however does not depend on remote clock
sources to be reachable, i.e. the target is typically not delayed by network problems and
similar. Use of this target is recommended for services where approximate clock accuracy and
rough monotonicity is desired but activation shall not be delayed for possibly unreliable network
communication.</para>
<para>The service manager automatically adds dependencies of type <varname>After=</varname> for
this target unit to all timer units with at least one <varname>OnCalendar=</varname>
directive.</para>
<para>The
<citerefentry><refentrytitle>systemd-timesyncd.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>
service is a simple daemon that pulls in this target and orders itself before it. Besides
implementing the SNTP network protocol it maintains a timestamp file on disk whose modification
time is regularly updated. At service start-up the local system clock is set from that modification time,
ensuring it increases roughly monotonically.</para>
<para>Note that ordering a unit after <filename>time-set.target</filename> only has effect if
there's actually a service ordered before it that delays it until the clock is adjusted for rough
monotonicity. Otherwise, this target might get reached before the clock is adjusted to be roughly
monotonic. Enable
<citerefentry><refentrytitle>systemd-timesyncd.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
or an alternative NTP implementation to delay the target.</para>
<xi:include href="version-info.xml" xpointer="v242"/>
</listitem>
</varlistentry>
<varlistentry>
<term><filename>time-sync.target</filename></term>
<listitem>
<para>Services indicating completed synchronization of the system clock
(<constant>CLOCK_REALTIME</constant>) to a remote source should pull in this target and order
themselves before it. Services where accurate time is essential should be ordered after this
unit, but not pull it in.</para>
<para>The service manager 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, as well to all timer units with at least one
<varname>OnCalendar=</varname> directive.</para>
<para>This target provides stricter clock accuracy guarantees than
<filename>time-set.target</filename> (see above), but likely requires
network communication and thus introduces unpredictable delays.
Services that require clock accuracy and where network
communication delays are acceptable should use this target. Services that require a less accurate
clock, and only approximate and roughly monotonic clock behaviour should use
<filename>time-set.target</filename> instead.</para>
<para>Note that ordering a unit after <filename>time-sync.target</filename> only has effect if
there's actually a service ordered before it that delays it until clock synchronization is
reached. Otherwise, this target might get reached before the clock is synchronized to any remote
accurate reference clock. When using
<citerefentry><refentrytitle>systemd-timesyncd.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
enable
<citerefentry><refentrytitle>systemd-time-wait-sync.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>
to delay the target; or use an equivalent service for other NTP implementations.</para>
<table>
<title>Comparison</title>
<tgroup cols='2' align='left' colsep='1' rowsep='1'>
<colspec colname="time-set" />
<colspec colname="time-sync" />
<thead>
<row>
<entry><filename>time-set.target</filename></entry>
<entry><filename>time-sync.target</filename></entry>
</row>
</thead>
<tbody>
<row>
<entry>"quick" to reach</entry>
<entry>"slow" to reach</entry>
</row>
<row>
<entry>typically uses local clock sources, boot process not affected by availability of external resources</entry>
<entry>typically uses remote clock sources, inserts dependencies on remote resources into boot process</entry>
</row>
<row>
<entry>reliable, because local</entry>
<entry>unreliable, because typically network involved</entry>
</row>
<row>
<entry>typically guarantees an approximate and roughly monotonic clock only</entry>
<entry>typically guarantees an accurate clock</entry>
</row>
<row>
<entry>implemented by <filename>systemd-timesyncd.service</filename></entry>
<entry>implemented by <filename>systemd-time-wait-sync.service</filename></entry>
</row>
</tbody>
</tgroup>
</table>
</listitem>
</varlistentry>
</variablelist>
</refsect2>
<refsect2>
<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>
<xi:include href="version-info.xml" xpointer="v206"/>
</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>
<xi:include href="version-info.xml" xpointer="v206"/>
</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>
<xi:include href="version-info.xml" xpointer="v206"/>
</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>
<xi:include href="version-info.xml" xpointer="v206"/>
</listitem>
</varlistentry>
</variablelist>
</refsect2>
</refsect1>
<refsect1>
<title>Units managed by the user service manager</title>
<refsect2>
<title>Special User Units</title>
<para>When systemd runs as a user instance, the following special
units are available:</para>
<variablelist>
<varlistentry>
<term><filename>default.target</filename></term>
<listitem>
<para>This is the main target of the user session, started by default. Various services that
compose the normal user session should be pulled into this target. In this regard,
<filename>default.target</filename> is similar to <filename>multi-user.target</filename> in the
system instance, but it is a real unit, not an alias.</para>
<xi:include href="version-info.xml" xpointer="v242"/>
</listitem>
</varlistentry>
</variablelist>
<para>In addition, the following units are available which have definitions similar to their
system counterparts:
<filename>exit.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>
</refsect2>
<refsect2>
<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 [Unit]
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>
<xi:include href="version-info.xml" xpointer="v234"/>
</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>
<xi:include href="version-info.xml" xpointer="v234"/>
</listitem>
</varlistentry>
<varlistentry>
<term><filename>xdg-desktop-autostart.target</filename></term>
<listitem>
<para>The XDG specification defines a way to autostart applications using XDG desktop files.
systemd ships
<citerefentry><refentrytitle>systemd-xdg-autostart-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>
for the XDG desktop files in autostart directories. Desktop Environments can opt-in to use this
service by adding a <varname>Wants=</varname> dependency on
<filename>xdg-desktop-autostart.target</filename>.</para>
<xi:include href="version-info.xml" xpointer="v246"/>
</listitem>
</varlistentry>
</variablelist>
</refsect2>
<refsect2>
<title>Special User Slice Units</title>
<para>There are four <literal>.slice</literal> units which form the basis of the user hierarchy for
assignment of resources for user applications and services. See
<citerefentry><refentrytitle>systemd.slice</refentrytitle><manvolnum>7</manvolnum></citerefentry>
for details about slice units and the documentation about
<ulink url="https://systemd.io/DESKTOP_ENVIRONMENTS">Desktop Environments</ulink>
for further information.</para>
<variablelist>
<varlistentry>
<term><filename>-.slice</filename></term>
<listitem>
<para>The root slice is the root of the user's slice hierarchy.
It usually does not contain units directly, but may be used to set defaults for the whole tree.</para>
<xi:include href="version-info.xml" xpointer="v247"/>
</listitem>
</varlistentry>
<varlistentry>
<term><filename>app.slice</filename></term>
<listitem>
<para>By default, all user services and applications managed by
<command>systemd</command> are found in this slice.
All interactively launched applications like web browsers and text editors
as well as non-critical services should be placed into this slice.</para>
<xi:include href="version-info.xml" xpointer="v247"/>
</listitem>
</varlistentry>
<varlistentry>
<term><filename>session.slice</filename></term>
<listitem>
<para>All essential services and applications required for the
session should use this slice.
These are services that either cannot be restarted easily
or where latency issues may affect the interactivity of the system and applications.
This includes the display server, screen readers and other services such as DBus or XDG portals.
Such services should be configured to be part of this slice by
adding <varname>Slice=session.slice</varname> to their unit files.</para>
<xi:include href="version-info.xml" xpointer="v247"/>
</listitem>
</varlistentry>
<varlistentry>
<term><filename>background.slice</filename></term>
<listitem>
<para>All services running low-priority background tasks should use this slice.
This permits resources to be preferentially assigned to the other slices.
Examples include non-interactive tasks like file indexing or backup operations
where latency is not important.</para>
<xi:include href="version-info.xml" xpointer="v247"/>
</listitem>
</varlistentry>
</variablelist>
</refsect2>
</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>,
<citerefentry><refentrytitle>user@.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>
</para>
</refsect1>
</refentry>