SYSTEMD.SPECIAL(7)                             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

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              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.

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          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

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              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.

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              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

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              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 m[blue]Running
              Services After the Network is upm[][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.

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              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

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              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.

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          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

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              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 m[blue]Syslog
              Interfacem[][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

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          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

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          (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

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              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 m[blue]Running Services After the Network is
              upm[][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

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              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

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              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

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              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 m[blue]Desktop
          Environmentsm[][3] for further information.

          -.slice
              The root slice is the root of the user's slice
              hierarchy. It usually does not contain units directly,

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              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

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