systemd.special — Special systemd units
basic.target
,
bluetooth.target
,
ctrl-alt-del.target
,
cryptsetup.target
,
cryptsetup-pre.target
,
dbus.service
,
dbus.socket
,
default.target
,
display-manager.service
,
emergency.target
,
exit.target
,
final.target
,
getty.target
,
graphical.target
,
halt.target
,
hibernate.target
,
hybrid-sleep.target
,
initrd-fs.target
,
kbrequest.target
,
kexec.target
,
local-fs.target
,
local-fs-pre.target
,
multi-user.target
,
network.target
,
network-online.target
,
network-pre.target
,
nss-lookup.target
,
nss-user-lookup.target
,
paths.target
,
poweroff.target
,
printer.target
,
reboot.target
,
remote-fs.target
,
remote-fs-pre.target
,
rescue.target
,
initrd-root-fs.target
,
rpcbind.target
,
runlevel2.target
,
runlevel3.target
,
runlevel4.target
,
runlevel5.target
,
shutdown.target
,
sigpwr.target
,
sleep.target
,
smartcard.target
,
sockets.target
,
sound.target
,
suspend.target
,
swap.target
,
sysinit.target
,
syslog.socket
,
system-update.target
,
time-sync.target
,
timers.target
,
umount.target
,
-.slice
,
system.slice
,
user.slice
,
machine.slice
A few units are treated specially by systemd. They have special internal semantics and cannot be renamed.
basic.target
¶A special target unit covering basic boot-up.
systemd automatically
adds dependencies of the types
Requires=
and After=
for this target unit to all
services (except for those
with
DefaultDependencies=no
).
Usually this should pull-in all mount points, swap devices, sockets, timers, and path units and other basic initialization necessary for general purpose daemons.
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
.
cryptsetup.target
¶A target that pulls in setup services for all encrypted block devices.
dbus.service
¶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.
dbus.socket
¶A special unit for the
D-Bus system bus socket. All
units with
Type=dbus
automatically gain a
dependency on this
unit.
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
gdm.service
or a similar display manager
service.
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.
final.target
¶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.
getty.target
¶A special target unit
that pulls in statically
configured local TTY
getty
instances.
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 logins shall add
Wants=
dependencies for their unit to
this unit (or
multi-user.target
)
during installation. This is
best configured via
WantedBy=graphical.target
in the unit's
"[Install]
"
section.
hibernate.target
¶A special target unit
for hibernating the
system. This pulls in
sleep.target
.
hybrid-sleep.target
¶A special target unit
for hibernating and suspending the
system at the same time. This pulls in
sleep.target
.
halt.target
¶A special target unit
for shutting down and halting
the system. Note that this
target is distinct from
poweroff.target
in that it generally really
just halts the system rather
than powering it down.
Applications wanting to halt the system should start this unit.
initrd-fs.target
¶systemd-fstab-generator(3)
automatically adds
dependencies of type
Before=
to
sysroot-usr.mount
and all mount points found in
/etc/fstab
that have
x-initrd.mount
and not have noauto
mount options set.
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
.
kexec.target
¶A special target unit for shutting down and rebooting the system via kexec.
Applications wanting to reboot the system with kexec should start this unit.
local-fs.target
¶systemd-fstab-generator(3)
automatically adds
dependencies of type
Before=
to
all mount units that refer to
local mount points for this
target unit. In addition, it
adds dependencies of type
Wants=
to
this target unit for those
mounts listed in
/etc/fstab
that have the
auto
mount
option set.
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 for their unit to
this unit during
installation. This is best
configured via
WantedBy=multi-user.target
in the unit's
"[Install]
"
section.
network-online.target
¶Units that strictly
require a configured network
connection should pull in
network-online.target
(via a
Wants=
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.
Note the distinction
between this unit and
network.target
. 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,
network.target
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,
network.target
is part of the boot of most
systems, while
network-online.target
is not, except when at least
one unit requires it. Also see
Running
Services After the Network is
up for more
information.
All mount units for remote network file systems automatically pull in this unit, and order themselves after it. Note that networking daemons that simply provide functionality to other hosts generally do not need to pull this in.
paths.target
¶A special target unit that sets up all path units (see systemd.path(5) for details) that shall be active after boot.
It is recommended that
path units installed by
applications get pulled in via
Wants=
dependencies from this
unit. This is best configured
via a
WantedBy=paths.target
in the path unit's
"[Install]
"
section.
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.
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.
initrd-root-fs.target
¶systemd-fstab-generator(3)
automatically adds
dependencies of type
Before=
to
the
sysroot.mount
unit, which is generated from
the kernel command line.
runlevel2.target
, runlevel3.target
, runlevel4.target
, runlevel5.target
¶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)
multi-user.target
(for runlevel 2) or
graphical.target
(the others).
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).
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.
sleep.target
¶A special target unit
that is pulled in by
suspend.target
,
hibernate.target
and
hybrid-sleep.target
and may be used to hook units
into the sleep state
logic.
sockets.target
¶A special target unit that sets up all socket units.(see systemd.socket(5) for details) that shall be active after boot.
Services that can be
socket-activated shall add
Wants=
dependencies to this unit for
their socket unit during
installation. This is best
configured via a
WantedBy=sockets.target
in the socket unit's
"[Install]
"
section.
suspend.target
¶A special target unit
for suspending the
system. This pulls in
sleep.target
.
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.
syslog.socket
¶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 Syslog Interface document.
system-update.target
¶A special target unit
that is used for off-line
system updates.
systemd-system-update-generator(8)
will redirect the boot process
to this target if
/system-update
exists. For more information
see the System
Updates
Specification.
timers.target
¶A special target unit that sets up all timer units (see systemd.timer(5) for details) that shall be active after boot.
It is recommended that
timer units installed by
applications get pulled in via
Wants=
dependencies from this
unit. This is best configured
via
WantedBy=timers.target
in the timer unit's
"[Install]
"
section.
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).
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.
bluetooth.target
¶This target is started automatically as soon as a Bluetooth controller is plugged in or becomes available at boot.
This may be used to pull in Bluetooth management daemons dynamically when Bluetooth hardware is found.
printer.target
¶This target is started automatically as soon as a printer is plugged in or becomes available at boot.
This may be used to pull in printer management daemons dynamically when printer hardware is found.
smartcard.target
¶This target is started automatically as soon as a smartcard controller is plugged in or becomes available at boot.
This may be used to pull in smartcard management daemons dynamically when smartcard hardware is found.
sound.target
¶This target is started automatically as soon as a sound card is plugged in or becomes available at boot.
This may be used to pull in audio management daemons dynamically when audio hardware is found.
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 passive
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 Wants=
type
dependency).
Note that these passive units cannot be started
manually, i.e. "systemctl start
time-sync.target
" 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.
cryptsetup-pre.target
¶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.
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.
network.target
¶This unit is supposed to
indicate when network
functionality is available,
but it is only very weakly
defined what that is supposed
to mean, with one exception:
at shutdown, a unit that is
ordered after
network.target
will be stopped before the
network -- to whatever level
it might be set up then -- is
shut down. It is hence useful
when writing service files
that require network access on
shutdown, which should order
themselves after this target,
but not pull it in. Also see
Running
Services After the Network is
up for more
information. Also see
network-online.target
described above.
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.
network-pre.target
¶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.
nss-lookup.target
¶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
nss-user-lookup.target
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
After=
for
this target unit to all SysV
init script service units with
an LSB header referring to the
"$named
"
facility.
nss-user-lookup.target
¶A target that should be
used as synchronization point
for all user/group name
service lookups. Note that
this is independent of
host/network name lookups for
which
nss-lookup.target
should be used. All services
for which the availability of
the full user/group database is
essential should be ordered
after this target, but not
pull it in. Note that system
users are always resolvable,
and hence do not require any
special ordering against this
target.
remote-fs-pre.target
¶This target unit is
automatically ordered before
all remote mount point units
(see above). It can be used to
run certain units before the
remote mounts are
established. Note that this
unit is generally not part of
the initial transaction,
unless the unit that wants to
be ordered before all remote
mounts pulls it in via a
Wants=
type
dependency. If the unit wants
to be pulled in by the first
remote mount showing up, it
should use
network-online.target
(see above).
rpcbind.target
¶The portmapper/rpcbind
pulls in this target and
orders itself before it, to
indicate its
availability. systemd
automatically adds
dependencies of type
After=
for
this target unit to all SysV
init script service units with
an LSB header referring to the
"$portmap
"
facility.
time-sync.target
¶Services responsible for
synchronizing the system clock
from a remote source (such as
NTP client implementations)
should pull in this target and
order themselves before
it. All services where correct
time is essential should be
ordered after this unit, but
not pull it in. systemd
automatically adds
dependencies of type
After=
for
this target unit to all SysV
init script service units with
an LSB header referring to the
"$time
"
facility.
When systemd runs as a user instance, the
following special units are available, which have
similar definitions as their system counterparts:
default.target
,
shutdown.target
,
sockets.target
,
timers.target
,
paths.target
,
bluetooth.target
,
printer.target
,
smartcard.target
,
sound.target
.
In addition, the following special unit is understood only when systemd runs as service instance:
exit.target
¶A 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.
There are four ".slice
" units
which form the basis of the hierarchy for assignment
of resources for services, users, and virtual machines
or containers.
-.slice
¶The root slice is the root of the hierarchy. It usually does not contain units directly, but may be used to set defaults for the whole tree.
system.slice
¶By default, all services services started by systemd are found in this slice.
user.slice
¶By default, all user processes and services started on behalf of the user, including the per-user systemd instance are found in this slice.
machine.slice
¶By default, all virtual machines and containers registered with systemd-machined are found in this slice.