SYSTEMD.SPECIAL(7) systemd.special SYSTEMD.SPECIAL(7)
NAME
systemd.special - Special systemd units
SYNOPSIS
basic.target, bluetooth.target, cryptsetup-pre.target,
cryptsetup.target, veritysetup-pre.target, veritysetup.target,
ctrl-alt-del.target, blockdev@.target, boot-complete.target,
default.target, emergency.target, exit.target, factory-reset.target,
final.target, first-boot-complete.target, getty.target,
getty-pre.target, graphical.target, halt.target, hibernate.target,
hybrid-sleep.target, suspend-then-hibernate.target, initrd.target,
initrd-fs.target, initrd-root-device.target, initrd-root-fs.target,
initrd-usr-fs.target, integritysetup-pre.target, integritysetup.target,
kbrequest.target, kexec.target, local-fs-pre.target, local-fs.target,
machines.target, multi-user.target, network-online.target,
network-pre.target, network.target, nss-lookup.target,
nss-user-lookup.target, paths.target, poweroff.target, printer.target,
reboot.target, remote-cryptsetup.target, remote-veritysetup.target,
remote-fs-pre.target, remote-fs.target, rescue.target, rpcbind.target,
runlevel2.target, runlevel3.target, runlevel4.target, runlevel5.target,
shutdown.target, sigpwr.target, sleep.target, slices.target,
smartcard.target, sockets.target, soft-reboot.target, sound.target,
ssh-access.target, storage-target-mode.target, suspend.target,
swap.target, sysinit.target, system-update.target,
system-update-pre.target, time-set.target, time-sync.target,
timers.target, tpm2.target, umount.target, usb-gadget.target, -.slice,
capsule.slice, machine.slice, system.slice, user.slice, -.mount,
dbus.service, dbus.socket, display-manager.service, init.scope,
syslog.socket, system-update-cleanup.service
DESCRIPTION
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.
UNITS MANAGED BY THE SYSTEM SERVICE MANAGER
Special System Units
-.mount
The root mount point, i.e. the mount unit for the / 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.
Added in version 235.
basic.target
A special target unit covering basic boot-up.
systemd automatically adds dependency of the type After= for this
target unit to all services (except for those with
DefaultDependencies=no).
Usually, this should pull-in all local mount points plus /var/,
/tmp/ and /var/tmp/, 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.
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 bootup(7) for details on the targets involved.
boot-complete.target
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 Requires= 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
Requires=. 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.
See systemd-boot-check-no-failures.service(8) for a service that
implements a generic system health check and orders itself before
boot-complete.target.
See systemd-bless-boot.service(8) for a service that propagates boot
success information to the boot loader, and orders itself after
boot-complete.target.
Added in version 240.
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.
veritysetup.target
A target that pulls in setup services for all verity integrity
protected block devices.
Added in version 248.
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. See
bootup(7) for more discussion.
The default unit systemd starts at bootup can be overridden with the
systemd.unit= kernel command line option, or more conveniently, with
the short names like single, rescue, 1, 3, 5, ...; see systemd(1).
For typical unit files please set "WantedBy=" to a regular target
(like multi-user.target or graphical.target), instead of
default.target, since such a service will also be run on special
boots like on system update, emergency boot...
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 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 emergency 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 rescue.target, which
serves a similar purpose, but also starts the most basic services
and mounts all file systems.
In many ways booting into emergency.target is similar to the effect
of booting with "init=/bin/sh" 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.
Note that depending on how emergency.target 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 ro is used on the kernel command
line and remain this way for emergency.target, or the system may
transition to emergency.target after the system has been partially
booted and disks have already been remounted read-write.
exit.target
A special service unit for shutting down the system or user service
manager. It is equivalent to poweroff.target on non-container
systems, and also works in containers.
systemd will start this unit when it receives the SIGTERM or SIGINT
signal when running as user service daemon.
Normally, this (indirectly) pulls in shutdown.target, which in turn
should be conflicted by all units that want to be scheduled for
shutdown when the service manager starts to exit.
Added in version 186.
factory-reset.target
A special target to trigger a factory reset.
Added in version 250.
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.
Added in version 196.
suspend-then-hibernate.target
A special target unit for suspending the system for a period of
time, waking it and putting it into hibernate. This pulls in
sleep.target.
Added in version 239.
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 not start this unit
directly, but should instead execute systemctl halt (possibly with
the --no-block option) or call systemd(1)'s
org.freedesktop.systemd1.Manager.Halt D-Bus method directly.
init.scope
This scope unit is where the system and service manager (PID 1)
itself resides. It is active as long as the system is running.
Added in version 235.
initrd.target
This is the default target in the initrd, similar to default.target
in the main system. It is used to mount the real root and transition
to it. See bootup(7) for more discussion.
Added in version 245.
initrd-fs.target
systemd-fstab-generator(8) automatically adds dependencies of type
Before= to sysroot-usr.mount and all mount points found in
/etc/fstab that have the x-initrd.mount mount option set and do not
have the noauto mount option set. It is also indirectly ordered
after sysroot.mount. Thus, once this target is reached the /sysroot/
hierarchy is fully set up, in preparation for the transition to the
host OS.
Added in version 199.
initrd-root-device.target
A special initrd target unit that is reached when the root
filesystem device is available, but before it has been mounted.
systemd-fstab-generator(8) and systemd-gpt-auto-generator(8)
automatically set up the appropriate dependencies to make this
happen.
Added in version 230.
initrd-root-fs.target
systemd-fstab-generator(8) automatically adds dependencies of type
Before= to the sysroot.mount unit, which is generated from the
kernel command line's root= setting (or equivalent).
Added in version 199.
initrd-usr-fs.target
systemd-fstab-generator(8) automatically adds dependencies of type
Before= to the sysusr-usr.mount unit, which is generated from the
kernel command line's usr= switch. Services may order themselves
after this target unit in order to run once the /sysusr/ hierarchy
becomes available, on systems that come up initially without a root
file system, but with an initialized /usr/ and need to access that
before setting up the root file system to ultimately switch to. On
systems where usr= is not used this target is ordered after
sysroot.mount and thus mostly equivalent to initrd-root-fs.target.
In effect on any system once this target is reached the file system
backing /usr/ is mounted, though possibly at two different
locations, either below the /sysusr/ or the /sysroot/ hierarchies.
Added in version 249.
kbrequest.target
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.
kexec.target
A special target unit for shutting down and rebooting the system via
kexec.
Applications wanting to reboot the system should not start this unit
directly, but should instead execute systemctl kexec (possibly with
the --no-block option) or call systemd-logind(8)'s
org.freedesktop.login1.Manager.RebootWithFlags() D-Bus method
directly.
See systemd-kexec.service(8) for further details of the operation
this target pulls in.
local-fs.target
systemd-fstab-generator(8) 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.
machines.target
A standard target unit for starting all the containers and other
virtual machines. See systemd-nspawn@.service for an example.
Added in version 233.
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[1] 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 (as opposed
to consume functionality of other hosts) generally do not need to
pull this in.
systemd automatically adds dependencies of type Wants= and After=
for this target unit to all SysV init script service units with an
LSB header referring to the "$network" facility.
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.
Added in version 200.
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.
Added in version 199.
poweroff.target
A special target unit for shutting down and powering off the system.
Applications wanting to power off the system should not start this
unit directly, but should instead execute systemctl poweroff
(possibly with the --no-block option) or call systemd-logind(8)'s
org.freedesktop.login1.Manager.PowerOff D-Bus method directly.
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 not start this unit
directly, but should instead execute systemctl reboot (possibly with
the --no-block option) or call systemd-logind(8)'s
org.freedesktop.login1.Manager.Reboot() D-Bus method directly.
See systemd-reboot.service(8) for further details of the operation
this target pulls in.
runlevel6.target is an alias for this target unit, for compatibility
with SysV.
remote-cryptsetup.target
Similar to cryptsetup.target, but for encrypted devices which are
accessed over the network. It is used for crypttab(5) entries marked
with _netdev.
Added in version 235.
remote-veritysetup.target
Similar to veritysetup.target, but for verity integrity protected
devices which are accessed over the network. It is used for
veritytab(5) entries marked with _netdev.
Added in version 248.
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 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 emergency.target, which is much more reduced and
does not provide the file systems or most basic services. Compare
with multi-user.target, this target could be seen as
single-user.target.
runlevel1.target is an alias for this target unit, for compatibility
with SysV.
Use the "systemd.unit=rescue.target" kernel command line option to
boot into this mode. A short alias for this kernel command line
option is "1", for compatibility with SysV.
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) graphical.target (for
runlevel 5) or multi-user.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= and Before= 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.
slices.target
A special target unit that sets up all slice units (see
systemd.slice(5) for details) that shall always be active after
boot. By default, the generic system.slice slice unit as well as the
root slice unit -.slice are pulled in and ordered before this unit
(see below).
Adding slice units to slices.target is generally not necessary.
Instead, when some unit that uses Slice= is started, the specified
slice will be started automatically. Adding WantedBy=slices.target
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.
Added in version 229.
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.
soft-reboot.target
A special target unit for shutting down and rebooting the userspace
of the system (leaving the kernel running).
Applications wanting to reboot the system should not start this unit
directly, but should instead execute systemctl soft-reboot (possibly
with the --no-block option) or call systemd-logind(8)'s
org.freedesktop.login1.Manager.RebootWithFlags() D-Bus method
directly.
See systemd-soft-reboot.service(8) for further details of the
operation this target pulls in.
Added in version 254.
storage-target-mode.target
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
systemd-storagetm.service(8) 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.
Added in version 255.
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
systemd automatically adds dependencies of the types Requires= and
After= for this target unit to all services (except for those with
DefaultDependencies=no).
This target pulls in the services required for system
initialization. System services pulled in by this target should
declare DefaultDependencies=no 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
bootup(7).
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[2] document.
system-update.target, system-update-pre.target,
system-update-cleanup.service
A special target unit that is used for offline system updates.
systemd-system-update-generator(8) will redirect the boot process to
this target if /system-update or /etc/system-update exists. For more
information see systemd.offline-updates(7).
Updates should happen before the system-update.target is reached,
and the services which implement them should cause the machine to
reboot. The main units executing the update should order themselves
after system-update-pre.target 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
/system-update or /etc/system-update still exists after
system-update.target is reached, system-update-cleanup.service will
remove the symlinks and reboot the machine.
Added in version 186.
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.
Added in version 199.
umount.target
A special target unit that unmounts 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 System Units for Devices
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.
usb-gadget.target
This target is started automatically as soon as a USB Device
Controller becomes available at boot.
This may be used to pull in usb gadget dynamically when UDC hardware
is found.
Added in version 242.
tpm2.target
This target is started automatically if a TPM2 device is discovered,
either by the OS or by the firmware. It acts as synchronization
point for services that require TPM2 device access. The target unit
is enqueued by systemd-tpm2-generator(8) if it detects that the
firmware has discovered a TPM2 device but the OS kernel has not
activated a driver for it yet. It is also pulled in whenever
systemd-udevd.service(8) discovers a TPM2 device. The target unit is
ordered after the /dev/tpmrm0 device node, so that it only becomes
active once the TPM2 device is actually accessible. Early boot
programs that intend to access the TPM2 device should hence order
themselves after this target unit, but not pull it in.
Added in version 256.
Special Passive System Units
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.
blockdev@.target
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 systemd-cryptsetup@.service(5)/ systemd-
veritysetup@.service(8)) that allocate and manage a virtual block
device. Storage services are ordered before an instance of
blockdev@.target, 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
blockdev@.target instance should be pulled in via a Wants=
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. blockdev@dev-mapper-foobar.target for the
storage device /dev/mapper/foobar.
Added in version 245.
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.
Added in version 215.
veritysetup-pre.target
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.
Added in version 248.
first-boot-complete.target
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 machine-id(5) 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 ConditionFirstBoot=yes.
Added in version 247.
getty-pre.target
A special passive target unit. Users of this target are expected to
pull it in the boot transaction via a dependency (e.g. Wants=).
Order your unit before this unit if you want to make use of the
console just before getty is started.
Added in version 235.
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. However, the following should apply at minimum:
• 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 network.target is reached.
• At shutdown, a unit that is ordered after network.target 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 Running Services After the Network Is Up[1] for more
information.
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 network-online.target as described above.
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. Also see Running
Services After the Network Is Up[1] for more information.
Added in version 214.
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
UNIX 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 "$named"
facility.
nss-user-lookup.target
A target that should be used as synchronization point for all
regular UNIX user/group name service lookups. Note that this is
independent of host/network name lookups for which nss-lookup.target
should be used. All services for which the availability of the full
user/group database is essential should be ordered after this
target, but not pull it in. All services which provide parts of the
user/group database should be ordered before this target, and pull
it in. Note that this unit is only relevant for regular users and
groups — system users and groups are required to be resolvable
during earliest boot already, and hence do not need any special
ordering against this target.
remote-fs-pre.target
This target unit is automatically ordered before all mount point
units (see above) and cryptsetup/veritysetup devices marked with the
_netdev. It can be used to run certain units before remote encrypted
devices and mounts are established. Note that this unit is generally
not part of the initial transaction, unless the unit that wants to
be ordered before all remote mounts pulls it in via a Wants= type
dependency. If the unit wants to be pulled in by the first remote
mount showing up, it should use network-online.target (see above).
rpcbind.target
The portmapper/rpcbind pulls in this target and orders itself before
it, to indicate its availability. systemd automatically adds
dependencies of type After= for this target unit to all SysV init
script service units with an LSB header referring to the "$portmap"
facility.
ssh-access.target
Service and socket units that provide remote SSH secure shell access
to the local system should pull in this unit and order themselves
before this unit. It's supposed to act as a milestone indicating if
and when SSH access into the system is available. It should only
become active when an SSH port is bound for remote clients (i.e. if
SSH is used as a local privilege escalation mechanism, it should not
involve this target unit), regardless of the protocol choices, i.e.
regardless if IPv4, IPv6 or AF_VSOCK is used.
Added in version 256.
time-set.target
Services responsible for setting the system clock (CLOCK_REALTIME)
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.
This target does not provide the accuracy guarantees of
time-sync.target (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.
The service manager automatically adds dependencies of type After=
for this target unit to all timer units with at least one
OnCalendar= directive.
The systemd-timesyncd.service(8) 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.
Note that ordering a unit after time-set.target 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 systemd-timesyncd.service(8), or an alternative
NTP implementation to delay the target.
Added in version 242.
time-sync.target
Services indicating completed synchronization of the system clock
(CLOCK_REALTIME) 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.
The service manager 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, as well to all timer
units with at least one OnCalendar= directive.
This target provides stricter clock accuracy guarantees than
time-set.target (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 time-set.target instead.
Note that ordering a unit after time-sync.target 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 systemd-timesyncd.service(8), enable
systemd-time-wait-sync.service(8) to delay the target; or use an
equivalent service for other NTP implementations.
Table 1. Comparison
┌────────────────────────────┬────────────────────────────────┐
│ time-set.target │ time-sync.target │
├────────────────────────────┼────────────────────────────────┤
│ "quick" to reach │ "slow" to reach │
├────────────────────────────┼────────────────────────────────┤
│ typically uses local clock │ typically uses remote │
│ sources, boot process not │ clock sources, inserts │
│ affected by availability │ dependencies on remote │
│ of external resources │ resources into boot │
│ │ process │
├────────────────────────────┼────────────────────────────────┤
│ reliable, because local │ unreliable, because │
│ │ typically network involved │
├────────────────────────────┼────────────────────────────────┤
│ typically guarantees an │ typically guarantees an │
│ approximate and roughly │ accurate clock │
│ monotonic clock only │ │
├────────────────────────────┼────────────────────────────────┤
│ implemented by │ implemented by │
│ systemd-timesyncd.service │ systemd-time-wait-sync.service │
└────────────────────────────┴────────────────────────────────┘
Special Slice Units
There are four ".slice" units which form the basis of the hierarchy for
assignment of resources for services, users, and virtual machines or
containers. See systemd.slice(5) for details about slice units.
-.slice
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.
Added in version 206.
machine.slice
By default, all virtual machines and containers registered with
systemd-machined are found in this slice. This is pulled in by
systemd-machined.service.
Added in version 206.
capsule.slice
By default, all capsules encapsulated in capsule@.service are found
in this slice.
Added in version 255.
system.slice
By default, all system services started by systemd are found in this
slice.
Added in version 206.
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. This is pulled in by systemd-logind.service.
Added in version 206.
UNITS MANAGED BY THE USER SERVICE MANAGER
Special User Units
When systemd runs as a user instance, the following special units are
available:
default.target
This is the main target of the user service manager, started by
default when the service manager is invoked. Various services that
compose the normal user session should be pulled into this target.
In this regard, default.target is similar to multi-user.target in
the system instance, but it is a real unit, not an alias.
Added in version 242.
capsule@.target
This is the main target of capsule service managers, started by
default, instantiated with the capsule name. This may be used to
define different sets of units that are started for different
capsules via generic unit definitions. For details about capsules
see capsule@.service(5).
Added in version 255.
In addition, the following units are available which have definitions
similar to their system counterparts: exit.target, shutdown.target,
sockets.target, timers.target, paths.target, bluetooth.target,
printer.target, smartcard.target, sound.target.
Special Passive User Units
graphical-session.target
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 "PartOf=graphical-session.target" in their [Unit]
section. A target for a particular session (e. g.
gnome-session.target) starts and stops "graphical-session.target"
with "BindsTo=graphical-session.target".
Which services are started by a session target is determined by the
"Wants=" and "Requires=" dependencies. For services that can be
enabled independently, symlinks in ".wants/" and ".requires/" should
be used, see systemd.unit(5). Those symlinks should either be
shipped in packages, or should be added dynamically after
installation, for example using "systemctl add-wants", see
systemctl(1).
Example 1. Nautilus as part of a GNOME session
"gnome-session.target" pulls in Nautilus as top-level service:
[Unit]
Description=User systemd services for GNOME graphical session
Wants=nautilus.service
BindsTo=graphical-session.target
"nautilus.service" gets stopped when the session stops:
[Unit]
Description=Render the desktop icons with Nautilus
PartOf=graphical-session.target
[Service]
...
Added in version 234.
graphical-session-pre.target
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
gnome-session.target.
Added in version 234.
xdg-desktop-autostart.target
The XDG specification defines a way to autostart applications using
XDG desktop files. systemd ships systemd-xdg-autostart-generator(8)
for the XDG desktop files in autostart directories. Desktop
Environments can opt-in to use this service by adding a Wants=
dependency on xdg-desktop-autostart.target.
Added in version 246.
Special User Slice Units
There are four ".slice" units which form the basis of the user hierarchy
for assignment of resources for user applications and services. See
systemd.slice(5) for details about slice units and the documentation
about Desktop Environments[3] for further information.
-.slice
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.
Added in version 247.
app.slice
By default, all user services and applications managed by systemd
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.
Added in version 247.
session.slice
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 Slice=session.slice to their unit files.
Added in version 247.
background.slice
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.
Added in version 247.
SEE ALSO
systemd(1), systemd.unit(5), systemd.service(5), systemd.socket(5),
systemd.target(5), systemd.slice(5), bootup(7), systemd-fstab-
generator(8), user@.service(5)
NOTES
1. Running Services After the Network Is Up
https://systemd.io/NETWORK_ONLINE
2. Syslog Interface
https://systemd.io/SYSLOG
3. Desktop Environments
https://systemd.io/DESKTOP_ENVIRONMENTS
systemd 257.9 SYSTEMD.SPECIAL(7)
Generated by dwww version 1.16 on Tue Dec 16 04:00:01 CET 2025.