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SYSTEMD.SPECIAL(7) | systemd.special | SYSTEMD.SPECIAL(7) |
NAME¶
systemd.special - special systemd unitsSYNOPSIS¶
basic.target, ctrl-alt-del.target, dbus.service, default.target, display-manager.service, emergency.target, exit.service, graphical.target, halt.target, kbrequest.target, local-fs.target, local-fs-pre.target, mail-transfer-agent.target, multi-user.target, network.target, nss-lookup.target, poweroff.target, reboot.target, remote-fs.target, remote-fs-pre.target, rescue.target, rpcbind.target, runlevel2.target, runlevel3.target, runlevel4.target, runlevel5.target, shutdown.target, sigpwr.target, sockets.target, swap.target, sysinit.target, syslog.target, systemd-initctl.service, systemd-initctl.socket, systemd-stdout-syslog-bridge.service, systemd-stdout-syslog-bridge.socket, time-sync.target, umount.targetDESCRIPTION¶
A few units are treated specially by systemd. They have special internal semantics and cannot be renamed.SPECIAL SYSTEM UNITS¶
basic.targetA special target unit covering early boot-up.
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.
Usually this should pull-in all sockets, mount points, swap devices and other
basic initialization necessary for the general purpose daemons. Most normal
daemons should have dependencies of type After and Requires on this
unit.
ctrl-alt-del.target
systemd starts this target whenever
Control+Alt+Del is pressed on the console. Usually this should be aliased
(symlinked) to reboot.target.
dbus.service
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.
default.target
The default unit systemd starts at bootup.
Usually this should be aliased (symlinked) to multi-user.target or
graphical.target.
The default unit systemd starts at bootup can be overridden with the
systemd.unit= kernel command line option.
display-manager.service
The display manager service. Usually this
should be aliased (symlinked) to xdm.service or a similar display manager
service.
systemd automatically adds dependencies of type After for this target unit to
all SysV init script service units with a LSB header referring to the
$x-display-manager facility, for compatibility with Debian.
emergency.target
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 systemd.unit= and has otherwise little use.
graphical.target
A special target unit for setting up a
graphical login screen. This pulls in multi-user.target.
Units that are needed for graphical login shall add Wants dependencies for their
unit to this unit (or multi-user.target) during installation.
halt.target
A special target unit for shutting down and
halting the system.
Applications wanting to halt the system should start this unit.
kbrequest.target
systemd starts this target whenever
Alt+ArrowUp is pressed on the console. This is a good candidate to be aliased
(symlinked) to rescue.target.
local-fs.target
systemd automatically adds dependencies of
type After to all mount units that 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 /etc/fstab that have the auto and
comment=systemd.mount mount options set.
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
$local_fs facility.
local-fs-pre.target
This target unit is automatically ordered
before all local mount points marked with auto (see above). It can be
used to execute certain units before all local mounts.
mail-transfer-agent.target
The mail transfer agent (MTA) service. Usually
this should pull-in all units necessary for sending/receiving mails on the
local host.
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
$mail-transfer-agent or $mail-transport-agent facilities, for compatibility
with Debian.
multi-user.target
A special target unit for setting up a
multi-user system (non-graphical). This is pulled in by graphical.target.
Units that are needed for a multi-user system shall add Wants dependencies to
this unit for their unit during installation.
network.target
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 $network facility.
nss-lookup.target
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 $named facility.
poweroff.target
A special target unit for shutting down and
powering off the system.
Applications wanting to power off the system should start this unit.
runlevel0.target is an alias for this target unit, for compatibility with
SysV.
reboot.target
A special target unit for shutting down and
rebooting the system.
Applications wanting to reboot the system should start this unit.
runlevel6.target is an alias for this target unit, for compatibility with
SysV.
remote-fs.target
Similar to local-fs.target, but for remote
mount points.
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
$remote_fs facility.
remote-fs-pre.target
This target unit is automatically ordered
before all remote mount points marked with auto (see above). It can be
used to execute certain units before all remote mounts.
rescue.target
A special target unit for setting up the base
system and a rescue shell.
runlevel1.target is an alias for this target unit, for compatibility with
SysV.
rpcbind.target
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 $rpcbind facility.
runlevel2.target
This is a target that is called whenever the
SysV compatibility code asks for runlevel 2. It is a good idea to make this an
alias for (i.e. symlink to) multi-user.target.
runlevel3.target
This is a target that is called whenever the
SysV compatibility code asks for runlevel 3. It is a good idea to make this an
alias for (i.e. symlink to) multi-user.target or graphical.target.
runlevel4.target
This is a target that is called whenever the
SysV compatibility code asks for runlevel 4. It is a good idea to make this an
alias for (i.e. symlink to) multi-user.target or graphical.target.
runlevel5.target
This is a target that is called whenever the
SysV compatibility code asks for runlevel 5. It is a good idea to make this an
alias for (i.e. symlink to) multi-user.target or graphical.target.
shutdown.target
A special target unit that terminates the
services on system shutdown.
Services that shall be terminated on system shutdown shall add Conflicts
dependencies to this unit for their service unit, which is implicitly done
when DefaultDependencies=yes is set (the default).
systemd automatically adds dependencies of type Conflicts to this target unit
for all SysV init script service units that shall be terminated in SysV
runlevels 0 or 6.
sigpwr.target
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.
sockets.target
A special target unit that sets up all service
sockets.
Services that can be socket-activated shall add Wants dependencies to this unit
for their socket unit during installation.
swap.target
Similar to local-fs.target, but for swap
partitions and swap files.
sysinit.target
A special target unit covering early boot-up
scripts.
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.
syslog.target
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 $syslog facility.
systemd-initctl.service
This provides compatibility with the SysV
/dev/initctl file system FIFO for communication with the init system.
This is a socket-activated service, see system-initctl.socket.
systemd-initctl.socket
Socket activation unit for
system-initctl.service.
systemd-stdout-syslog-bridge.service
This is internally used by systemd to provide
syslog logging to the processes it maintains.
This is a socket-activated service, see
system-stdout-syslog-bridge.socket.
systemd-stdout-syslog-bridge.socket
Socket activation unit for
system-stdout-syslog-bridge.service. 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.
systemd-shutdownd.service
This is internally used by shutdown(8)
to implement delayed shutdowns.
This is a socket-activated service, see system-shutdownd.socket.
systemd-shutdownd.socket
Socket activation unit for
system-shutdownd.service.
time-sync.target
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 $time facility.
umount.target
A special target unit that umounts all mount
and automount points on system shutdown.
Mounts that shall be unmounted on system shutdown shall add Conflicts
dependencies to this unit for their mount unit, which is implicitly done when
DefaultDependencies=yes is set (the default).
SPECIAL USER UNITS¶
When systemd runs as a user instance, the following special units are available, which have similar definitions as their system counterparts: default.target, local-fs.target, remote-fs.target, shutdown.target, sockets.target, swap.target. In addition the following special unit is understood only when systemd runs as service instance: exit.serviceA special service unit for shutting down the
user service manager.
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.
Normally, this pulls in shutdown.target which in turn should be conflicted by
all units that want to be shut down on user service manager exit.
SEE ALSO¶
AUTHOR¶
Lennart Poettering <lennart@poettering.net>Developer
03/16/2012 | systemd |