systemd.special

SYSTEMD.SPECIAL(7)               systemd.special              SYSTEMD.SPECIAL(7)



NAME
       systemd.special - Special systemd units

SYNOPSIS
       basic.target, bluetooth.target, cryptsetup-pre.target, cryptsetup.target,
       ctrl-alt-del.target, blockdev@.target, boot-complete.target,
       default.target, emergency.target, exit.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, 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-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, sound.target, suspend.target,
       swap.target, sysinit.target, system-update.target,
       system-update-pre.target, time-set.target, time-sync.target,
       timers.target, umount.target, usb-gadget.target, -.slice, system.slice,
       user.slice, machine.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.

       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.

       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. 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).

       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.

       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.

       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.

       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.

       initrd.target
           This is the default target in the initramfs, 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.

       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.

       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(3) and systemd-gpt-auto-generator(3) automatically setup
           the appropriate dependencies to make this happen.

       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.

       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(1)'s
           org.freedesktop.systemd1.Manager.KExec D-Bus method directly.

       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.

       machines.target
           A standard target unit for starting all the containers and other
           virtual machines. See systemd-nspawn@.service for an example.

       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 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.

       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 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.

           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(8) entries marked
           with _netdev.

       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.

       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
           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 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
           still exists after system-update.target is reached,
           system-update-cleanup.service will remove this symlink and reboot the
           machine.

       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 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.

   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)) 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.

       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.

       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.

       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.

       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[1] for more information.
           Also see network-online.target 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.

       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 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.

       time-set.target
           Services responsible for setting the system clock 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 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.

       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.

   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(7) 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.

       system.slice
           By default, all system 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. This is pulled in by systemd-logind.service.

       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.

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 session, started by default.
           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.

       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]
               ...

       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.

       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".

   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(7) 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.

       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.

       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.

       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.

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://www.freedesktop.org/wiki/Software/systemd/NetworkTarget

        2. Syslog Interface
           https://www.freedesktop.org/wiki/Software/systemd/syslog

        3. Desktop Environments
           https://systemd.io/DESKTOP_ENVIRONMENTS



systemd 247                                                   SYSTEMD.SPECIAL(7)