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<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 >
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<para > <filename > basic.target</filename> ,
<filename > ctrl-alt-del.target</filename> ,
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<filename > dbus.service</filename> ,
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<filename > dbus.target</filename> ,
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<filename > default.target</filename> ,
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<filename > display-manager.service</filename> ,
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<filename > emergency.target</filename> ,
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<filename > exit.service</filename> ,
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<filename > graphical.target</filename> ,
<filename > halt.target</filename> ,
<filename > kbrequest.target</filename> ,
<filename > local-fs.target</filename> ,
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<filename > mail-transfer-agent.target</filename> ,
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<filename > multi-user.target</filename> ,
<filename > network.target</filename> ,
<filename > nss-lookup.target</filename> ,
<filename > poweroff.target</filename> ,
<filename > reboot.target</filename> ,
<filename > remote-fs.target</filename> ,
<filename > rescue.target</filename> ,
<filename > rpcbind.target</filename> ,
<filename > rtc-set.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 > sockets.target</filename> ,
<filename > swap.target</filename> ,
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<filename > sysinit.target</filename> ,
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<filename > @SPECIAL_SYSLOG_SERVICE@</filename> ,
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<filename > syslog.target</filename> ,
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<filename > systemd-initctl.service</filename> ,
<filename > systemd-initctl.socket</filename> ,
<filename > systemd-logger.service</filename> ,
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<filename > systemd-logger.socket</filename> ,
<filename > umount.target</filename> </para>
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</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 >
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<varlistentry >
<term > <filename > basic.target</filename> </term>
<listitem >
<para > A special target unit
covering early boot-up.</para>
<para > systemd automatically
adds dependencies of the types
Requires and After for this
target unit to all SysV
service units configured for
runlevel 1 to 5.</para>
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<para > Usually this should pull-in
all sockets, mount points,
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swap devices and other basic
initialization necessary for
the general purpose
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daemons. Most normal daemons
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should have dependencies of
type After and Requires on
this unit.</para>
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</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>
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<varlistentry >
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<term > <filename > dbus.service</filename> </term>
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<listitem >
<para > A special unit for the
D-Bus system bus. As soon as
this service is fully started
up systemd will connect to it
and register its
service.</para>
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<para > Units should generally
avoid depending on this unit
directly and instead refer to
the
<filename > dbus.target</filename>
unit instead, which pulls this
one in directly or indirectly
via socket-based activation.</para>
</listitem>
</varlistentry>
<varlistentry >
<term > <filename > dbus.target</filename> </term>
<listitem >
<para > Administrators should
ensure that this target pulls
in a service unit with the
name or alias of
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<filename > dbus.service</filename>
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(or a socket unit that
activates this
service).</para>
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</listitem>
</varlistentry>
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<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
overriden with the
<varname > systemd.default=</varname>
kernel command line option.</para>
</listitem>
</varlistentry>
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<varlistentry >
<term > <filename > display-manager.service</filename> </term>
<listitem >
<para > The display manager
service. Usually this should
be aliased (symlinked) to
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<filename > xdm.service</filename>
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or a similar display manager
service.</para>
<para > systemd automatically
adds dependencies of type
After for this target unit to
all SysV init script service
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units with a LSB header
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referring to the
<literal > $x-display-manager</literal>
facility, for compatibility
with Debian.</para>
</listitem>
</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
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that starts an emergency
shell on the main
console. This unit is supposed
to be used with the kernel
command line option
<varname > systemd.default=</varname>
and has otherwise little use.
</para>
</listitem>
</varlistentry>
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<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 login shall add
Wants dependencies for their
unit to this unit (or
<filename > multi-user.target</filename> )
during installation.</para>
</listitem>
</varlistentry>
<varlistentry >
<term > <filename > halt.target</filename> </term>
<listitem >
<para > A special target unit
for shutting down and halting the system.</para>
<para > Applications wanting to
halt the system should start
this unit.</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>
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<varlistentry >
<term > <filename > local-fs.target</filename> </term>
<listitem >
<para > systemd automatically
adds dependencies of type
After to all mount units that
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refer to local mount points
for this target unit. In
addition, systemd adds
dependencies of type Wants to
this 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> and
<option > comment=systemd.mount</option>
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mount options set.</para>
<para > systemd automatically
adds dependencies of type
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After for this target unit to
all SysV init script service
units with an LSB header
referring to the
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<literal > $local_fs</literal>
facility.</para>
</listitem>
</varlistentry>
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<varlistentry >
<term > <filename > mail-transfer-agent.target</filename> </term>
<listitem >
<para > The mail transfer agent
(MTA) service. Usually this
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should pull-in all units
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necessary for
sending/receiving mails on the
local host.</para>
<para > systemd automatically
adds dependencies of type
After for this target unit to
all SysV init script service
units with an LSB header
referring to the
<literal > $mail-transfer-argent</literal>
or
<literal > $mail-transport-agent</literal>
facilities, for compatibility
with Debian.</para>
</listitem>
</varlistentry>
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<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 Wants dependencies to
this unit for their unit during
installation.</para>
</listitem>
</varlistentry>
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<varlistentry >
<term > <filename > network.target</filename> </term>
<listitem >
<para > systemd automatically
adds dependencies of type
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After for this target unit to
all SysV init script service
units with an LSB header
referring to the
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<literal > $network</literal>
facility.</para>
</listitem>
</varlistentry>
<varlistentry >
<term > <filename > nss-lookup.target</filename> </term>
<listitem >
<para > systemd automatically
adds dependencies of type
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After for this target unit to
all SysV init script service
units with an LSB header
referring to the
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<literal > $named</literal>
facility.</para>
</listitem>
</varlistentry>
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<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 > 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>
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<varlistentry >
<term > <filename > remote-fs.target</filename> </term>
<listitem >
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<para > Similar to
<filename > local-fs.target</filename> ,
but for remote mount
points.</para>
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<para > systemd automatically
adds dependencies of type
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After for this target unit to
all SysV init script service
units with an LSB header
referring to the
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<literal > $remote_fs</literal>
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facility.</para>
</listitem>
</varlistentry>
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<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>
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<varlistentry >
<term > <filename > rpcbind.target</filename> </term>
<listitem >
<para > systemd automatically
adds dependencies of type
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After for this target unit to
all SysV init script service
units with an LSB header
referring to the
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<literal > $rpcbind</literal>
facility.</para>
</listitem>
</varlistentry>
<varlistentry >
<term > <filename > rtc-set.target</filename> </term>
<listitem >
<para > systemd automatically
adds dependencies of type
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After for this target unit to
all SysV init script service
units with an LSB header
referring to the
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<literal > $time</literal>
facility.</para>
</listitem>
</varlistentry>
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<varlistentry >
<term > <filename > runlevel2.target</filename> </term>
<listitem >
<para > This is a target that is
called whever the SysV
compatibility code asks for
runlevel 2. It is a good idea
to make this an alias for
(i.e. symlink to)
<filename > multi-user.target</filename> .</para>
</listitem>
</varlistentry>
<varlistentry >
<term > <filename > runlevel3.target</filename> </term>
<listitem >
<para > This is a target that is
called whever the SysV
compatibility code asks for
runlevel 3. It is a good idea
to make this an alias for
(i.e. symlink to)
<filename > multi-user.target</filename>
or
<filename > graphical.target</filename> .</para>
</listitem>
</varlistentry>
<varlistentry >
<term > <filename > runlevel4.target</filename> </term>
<listitem >
<para > This is a target that is
called whever the SysV
compatibility code asks for
runlevel 4. It is a good idea
to make this an alias for
(i.e. symlink to)
<filename > multi-user.target</filename>
or
<filename > graphical.target</filename> .</para>
</listitem>
</varlistentry>
<varlistentry >
<term > <filename > runlevel5.target</filename> </term>
<listitem >
<para > This is a target that is
called whever the SysV
compatibility code asks for
runlevel 5. It is a good idea
to make this an alias for
(i.e. symlink to)
<filename > multi-user.target</filename>
or
<filename > graphical.target</filename> .</para>
</listitem>
</varlistentry>
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<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
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shall add Conflicts
dependencies to this unit for
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their service unit, which is
implicitly done when
<varname > DefaultDependencies=yes</varname>
is set (the default).</para>
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<para > systemd automatically
adds dependencies of type
Conflicts to this target unit
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for all SysV init script
service units that shall be
terminated in SysV runlevels 0
or 6.</para>
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</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
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kernel or UPS daemons when
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power fails.</para>
</listitem>
</varlistentry>
<varlistentry >
<term > <filename > sockets.target</filename> </term>
<listitem >
<para > A special target unit
that sets up all service
sockets.</para>
<para > Services that can be
socket-activated shall add
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Wants dependencies to this
unit for their socket unit
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during installation.</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>
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<varlistentry >
<term > <filename > sysinit.target</filename> </term>
<listitem >
<para > A special target unit
covering early boot-up scripts.</para>
<para > systemd automatically
adds dependencies of the types
Wants and After for all
SysV service units configured
for runlevels that are not 0
to 6 to this target unit.
This covers the special
boot-up runlevels some
distributions have, such as S
or b.</para>
</listitem>
</varlistentry>
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<varlistentry >
<term > <filename > @SPECIAL_SYSLOG_SERVICE@</filename> </term>
<listitem >
<para > A special unit for the
syslog daemon. As soon as
this service is fully started
up systemd will connect to it
and use it for logging if it
has been configured for
that.</para>
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<para > Units should generally
avoid depending on this unit
directly and instead refer to
the
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<filename > syslog.target</filename>
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unit instead, which pulls this
one in directly or indirectly
via socket-based activation.</para>
</listitem>
</varlistentry>
<varlistentry >
<term > <filename > syslog.target</filename> </term>
<listitem >
<para > systemd automatically
adds dependencies of type
After for this target unit to
all SysV init script service
units with an LSB header
referring to the
<literal > $syslog</literal>
facility.</para>
<para > Administrators should
ensure that this target pulls
in a service unit with the
name or alias of
<filename > @SPECIAL_SYSLOG_SERVICE@</filename>
(or a socket unit that
activates this
service).</para>
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</listitem>
</varlistentry>
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<varlistentry >
<term > <filename > systemd-initctl.service</filename> </term>
<listitem >
<para > This provides
compatibility with the SysV
/dev/initctl file system FIFO
for communication with the
init system.</para>
<para > This is a
socket-activated service, see
<filename > system-initctl.socket</filename> .</para>
</listitem>
</varlistentry>
<varlistentry >
<term > <filename > systemd-initctl.socket</filename> </term>
<listitem >
<para > Socket activation unit
for
<filename > system-initctl.service</filename> .</para>
</listitem>
</varlistentry>
<varlistentry >
<term > <filename > systemd-logger.service</filename> </term>
<listitem >
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<para > This is internally used
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by systemd to provide syslog
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logging to the processes it
maintains.</para>
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<para > This is a
socket-activated service, see
<filename > system-logger.socket</filename> .</para>
</listitem>
</varlistentry>
<varlistentry >
<term > <filename > systemd-logger.socket</filename> </term>
<listitem >
<para > Socket activation unit
for
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<filename > system-logger.service</filename> . systemd
will automatically add
dependencies of types Requires
and After to all units that
have been configured for
stdout or stderr to be
connected to syslog or the
kernel log buffer.</para>
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</listitem>
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</varlistentry>
<varlistentry >
<term > <filename > systemd-shutdownd.service</filename> </term>
<listitem >
<para > This is internally used
by
<citerefentry > <refentrytitle > shutdown</refentrytitle> <manvolnum > 8</manvolnum> </citerefentry>
to implement delayed shutdowns.</para>
<para > This is a
socket-activated service, see
<filename > system-shutdownd.socket</filename> .</para>
</listitem>
</varlistentry>
<varlistentry >
<term > <filename > systemd-shutdownd.socket</filename> </term>
<listitem >
<para > Socket activation unit
for
<filename > system-shutdownd.service</filename> .</para>
</listitem>
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</varlistentry>
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<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>
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</variablelist>
</refsect1>
<refsect1 >
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<title > Special User Units</title>
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<para > When systemd runs as a user instance, the
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following special units are available, which have
similar definitions as their system counterparts:
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<filename > default.target</filename> ,
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<filename > local-fs.target</filename> ,
<filename > remote-fs.target</filename> ,
<filename > shutdown.target</filename> ,
<filename > sockets.target</filename> ,
<filename > swap.target</filename> .</para>
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<para > In addition the following special unit is
understood only when systemd runs as service instance:</para>
<variablelist >
<varlistentry >
<term > <filename > exit.service</filename> </term>
<listitem >
<para > A special service unit
for shutting down the
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user service manager.</para>
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<para > Applications wanting to
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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>
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<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
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user service manager exit.</para>
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</listitem>
</varlistentry>
</variablelist>
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</refsect1>
<refsect1 >
<title > See Also</title>
<para >
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<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> ,
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<citerefentry > <refentrytitle > systemd.target</refentrytitle> <manvolnum > 5</manvolnum> </citerefentry>
</para>
</refsect1>
</refentry>
