<?xml version='1.0'?> <!--*-nxml-*-->
<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
<!--
This file is part of systemd.
Copyright 2010 Lennart Poettering
systemd is free software; you can redistribute it and/or modify it
under the terms of the GNU Lesser General Public License as published by
the Free Software Foundation; either version 2.1 of the License, or
(at your option) any later version.
systemd is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public License
along with systemd; If not, see <http://www.gnu.org/licenses/>.
-->
<refentry id="systemd.special">
<refentryinfo>
<title>systemd.special</title>
<productname>systemd</productname>
<authorgroup>
<author>
<contrib>Developer</contrib>
<firstname>Lennart</firstname>
<surname>Poettering</surname>
<email>lennart@poettering.net</email>
</author>
</authorgroup>
</refentryinfo>
<refmeta>
<refentrytitle>systemd.special</refentrytitle>
<manvolnum>7</manvolnum>
</refmeta>
<refnamediv>
<refname>systemd.special</refname>
<refpurpose>Special systemd units</refpurpose>
</refnamediv>
<refsynopsisdiv>
<para><filename>basic.target</filename>,
<filename>bluetooth.target</filename>,
<filename>ctrl-alt-del.target</filename>,
<filename>cryptsetup.target</filename>,
<filename>dbus.service</filename>,
<filename>dbus.socket</filename>,
<filename>default.target</filename>,
<filename>display-manager.service</filename>,
<filename>emergency.target</filename>,
<filename>exit.target</filename>,
<filename>final.target</filename>,
<filename>getty.target</filename>,
<filename>graphical.target</filename>,
<filename>halt.target</filename>,
<filename>hibernate.target</filename>,
<filename>hybrid-sleep.target</filename>,
<filename>initrd-fs.target</filename>,
<filename>kbrequest.target</filename>,
<filename>kexec.target</filename>,
<filename>local-fs.target</filename>,
<filename>local-fs-pre.target</filename>,
<filename>multi-user.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-fs.target</filename>,
<filename>remote-fs-pre.target</filename>,
<filename>rescue.target</filename>,
<filename>initrd-root-fs.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>smartcard.target</filename>,
<filename>sockets.target</filename>,
<filename>sound.target</filename>,
<filename>suspend.target</filename>,
<filename>swap.target</filename>,
<filename>sysinit.target</filename>,
<filename>syslog.socket</filename>,
<filename>system-update.target</filename>,
<filename>time-sync.target</filename>,
<filename>timers.target</filename>,
<filename>umount.target</filename></para>
</refsynopsisdiv>
<refsect1>
<title>Description</title>
<para>A few units are treated specially by
systemd. They have special internal semantics and
cannot be renamed.</para>
</refsect1>
<refsect1>
<title>Special System Units</title>
<variablelist>
<varlistentry>
<term><filename>basic.target</filename></term>
<listitem>
<para>A special target unit
covering basic boot-up.</para>
<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>Usually this should
pull-in all mount points, swap
devices, sockets, timers, and
path units and other basic
initialization necessary for
general purpose
daemons.</para>
</listitem>
</varlistentry>
<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>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>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>.</para>
<para>The default unit systemd
starts at bootup can be
overridden with the
<varname>systemd.unit=</varname>
kernel command line option.</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 unit is supposed
to be used with the kernel
command line option
<varname>systemd.unit=</varname>
and has otherwise little use.
</para>
</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
<literal>[Install]</literal>
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>
</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 start
this unit.</para>
</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 fround in
<filename>/etc/fstab</filename>
that have the
<option>auto</option> and
<option>x-initrd.mount</option>
mount options set.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><filename>kbrequest.target</filename></term>
<listitem>
<para>systemd starts this
target whenever Alt+ArrowUp is
pressed on the console. This
is a good candidate to be
aliased (symlinked) to
<filename>rescue.target</filename>.</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 with kexec should start
this unit.</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>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>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-uer.target</varname>
in the unit's
<literal>[Install]</literal>
section.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><filename>network.target</filename></term>
<listitem>
<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>$network</literal>
facility.</para>
<para>This unit is supposed to
indicate when the network is
"up", but it is only very
loosely defined what that is
supposed to mean. Also see <ulink
url="http://www.freedesktop.org/wiki/Software/systemd/NetworkTarget">Running
Services After the Network is
up</ulink> for more
information.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><filename>nss-lookup.target</filename></term>
<listitem>
<para>A target that should be
used as synchronization point
for all host/network name
service lookups. Note that
this is independent of
user/group name lookups for
which
<filename>nss-user-lookup.target</filename>
should be used. systemd
automatically adds
dependencies of type
<varname>After=</varname> for
this target unit to all SysV
init script service units with
an LSB header referring to the
<literal>$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. </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
power off the system should start
this unit.</para>
<para><filename>runlevel0.target</filename>
is an alias for this target
unit, for compatibility with SysV.</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>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 start
this unit.</para>
<para><filename>runlevel6.target</filename>
is an alias for this target
unit, for compatibility with SysV.</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>$remote_fs</literal>
facility.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><filename>remote-fs-pre.target</filename></term>
<listitem>
<para>This target unit is
automatically ordered before
all remote mount points marked
with <option>auto</option>
(see above). It can be used to
execute certain units before
all remote mounts.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><filename>rescue.target</filename></term>
<listitem>
<para>A special target unit
for setting up the base system
and a rescue shell.</para>
<para><filename>runlevel1.target</filename>
is an alias for this target
unit, for compatibility with SysV.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><filename>initrd-root-fs.target</filename></term>
<listitem>
<para><citerefentry><refentrytitle>systemd-fstab-generator</refentrytitle><manvolnum>3</manvolnum></citerefentry>
automatically adds
dependencies of type
<varname>Before=</varname> to
the
<filename>sysroot.mount</filename>
unit, which is generated from
the kernel command line.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><filename>rpcbind.target</filename></term>
<listitem>
<para>systemd automatically
adds dependencies of type
<varname>After=</varname> for
this target unit to all SysV
init script service units with
an LSB header referring to the
<literal>$portmap</literal>
facility.</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>multi-user.target</filename>
(for runlevel 2) or
<filename>graphical.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>
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>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 printer management
daemons dynamically when
smartcard hardware is
found.</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>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 printer
hardware is found.</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>A special target unit
covering early boot-up scripts.</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="http://www.freedesktop.org/wiki/Software/systemd/syslog">Syslog
Interface</ulink>
document.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><filename>system-update.target</filename></term>
<listitem>
<para>A special target unit
that is used for off-line
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 the <ulink
url="http://freedesktop.org/wiki/Software/systemd/SystemUpdates">System
Updates
Specification</ulink>.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><filename>time-sync.target</filename></term>
<listitem>
<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>$time</literal>
facility.</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 umounts 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 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>default.target</filename>,
<filename>shutdown.target</filename>,
<filename>sockets.target</filename></para>
<para>In addition the following special unit is
understood only when systemd runs as service instance:</para>
<variablelist>
<varlistentry>
<term><filename>exit.target</filename></term>
<listitem>
<para>A special service unit
for shutting down the
user service manager.</para>
<para>Applications wanting to
terminate the user service
manager should start this
unit. If systemd receives
SIGTERM or SIGINT when running
as user service daemon it will
start this unit.</para>
<para>Normally, this pulls in
<filename>shutdown.target</filename>
which in turn should be
conflicted by all units that
want to be shut down on
user service manager exit.</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>bootup</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
<citerefentry><refentrytitle>systemd-fstab-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>
</para>
</refsect1>
</refentry>