systemd

SYSTEMD(1)                           systemd                          SYSTEMD(1)



NAME
       systemd, init - systemd system and service manager

SYNOPSIS
       /usr/lib/systemd/systemd [OPTIONS...]

       init [OPTIONS...] {COMMAND}

DESCRIPTION
       systemd is a system and service manager for Linux operating systems. When
       run as first process on boot (as PID 1), it acts as init system that
       brings up and maintains userspace services. Separate instances are
       started for logged-in users to start their services.

       systemd is usually not invoked directly by the user, but is installed as
       the /sbin/init symlink and started during early boot. The user manager
       instances are started automatically through the user@.service(5) service.

       For compatibility with SysV, if the binary is called as init and is not
       the first process on the machine (PID is not 1), it will execute telinit
       and pass all command line arguments unmodified. That means init and
       telinit are mostly equivalent when invoked from normal login sessions.
       See telinit(8) for more information.

       When run as a system instance, systemd interprets the configuration file
       system.conf and the files in system.conf.d directories; when run as a
       user instance, systemd interprets the configuration file user.conf and
       the files in user.conf.d directories. See systemd-system.conf(5) for more
       information.

CONCEPTS
       systemd provides a dependency system between various entities called
       "units" of 11 different types. Units encapsulate various objects that are
       relevant for system boot-up and maintenance. The majority of units are
       configured in unit configuration files, whose syntax and basic set of
       options is described in systemd.unit(5), however some are created
       automatically from other configuration, dynamically from system state or
       programmatically at runtime. Units may be "active" (meaning started,
       bound, plugged in, ..., depending on the unit type, see below), or
       "inactive" (meaning stopped, unbound, unplugged, ...), as well as in the
       process of being activated or deactivated, i.e. between the two states
       (these states are called "activating", "deactivating"). A special
       "failed" state is available as well, which is very similar to "inactive"
       and is entered when the service failed in some way (process returned
       error code on exit, or crashed, an operation timed out, or after too many
       restarts). If this state is entered, the cause will be logged, for later
       reference. Note that the various unit types may have a number of
       additional substates, which are mapped to the five generalized unit
       states described here.

       The following unit types are available:

        1. Service units, which start and control daemons and the processes they
           consist of. For details, see systemd.service(5).

        2. Socket units, which encapsulate local IPC or network sockets in the
           system, useful for socket-based activation. For details about socket
           units, see systemd.socket(5), for details on socket-based activation
           and other forms of activation, see daemon(7).

        3. Target units are useful to group units, or provide well-known
           synchronization points during boot-up, see systemd.target(5).

        4. Device units expose kernel devices in systemd and may be used to
           implement device-based activation. For details, see
           systemd.device(5).

        5. Mount units control mount points in the file system, for details see
           systemd.mount(5).

        6. Automount units provide automount capabilities, for on-demand
           mounting of file systems as well as parallelized boot-up. See
           systemd.automount(5).

        7. Timer units are useful for triggering activation of other units based
           on timers. You may find details in systemd.timer(5).

        8. Swap units are very similar to mount units and encapsulate memory
           swap partitions or files of the operating system. They are described
           in systemd.swap(5).

        9. Path units may be used to activate other services when file system
           objects change or are modified. See systemd.path(5).

       10. Slice units may be used to group units which manage system processes
           (such as service and scope units) in a hierarchical tree for resource
           management purposes. See systemd.slice(5).

       11. Scope units are similar to service units, but manage foreign
           processes instead of starting them as well. See systemd.scope(5).

       Units are named as their configuration files. Some units have special
       semantics. A detailed list is available in systemd.special(7).

       systemd knows various kinds of dependencies, including positive and
       negative requirement dependencies (i.e.  Requires= and Conflicts=) as
       well as ordering dependencies (After= and Before=). NB: ordering and
       requirement dependencies are orthogonal. If only a requirement dependency
       exists between two units (e.g.  foo.service requires bar.service), but no
       ordering dependency (e.g.  foo.service after bar.service) and both are
       requested to start, they will be started in parallel. It is a common
       pattern that both requirement and ordering dependencies are placed
       between two units. Also note that the majority of dependencies are
       implicitly created and maintained by systemd. In most cases, it should be
       unnecessary to declare additional dependencies manually, however it is
       possible to do this.

       Application programs and units (via dependencies) may request state
       changes of units. In systemd, these requests are encapsulated as 'jobs'
       and maintained in a job queue. Jobs may succeed or can fail, their
       execution is ordered based on the ordering dependencies of the units they
       have been scheduled for.

       On boot systemd activates the target unit default.target whose job is to
       activate on-boot services and other on-boot units by pulling them in via
       dependencies. Usually, the unit name is just an alias (symlink) for
       either graphical.target (for fully-featured boots into the UI) or
       multi-user.target (for limited console-only boots for use in embedded or
       server environments, or similar; a subset of graphical.target). However,
       it is at the discretion of the administrator to configure it as an alias
       to any other target unit. See systemd.special(7) for details about these
       target units.

       systemd only keeps a minimal set of units loaded into memory.
       Specifically, the only units that are kept loaded into memory are those
       for which at least one of the following conditions is true:

        1. It is in an active, activating, deactivating or failed state (i.e. in
           any unit state except for "inactive")

        2. It has a job queued for it

        3. It is a dependency of at least one other unit that is loaded into
           memory

        4. It has some form of resource still allocated (e.g. a service unit
           that is inactive but for which a process is still lingering that
           ignored the request to be terminated)

        5. It has been pinned into memory programmatically by a D-Bus call

       systemd will automatically and implicitly load units from disk — if they
       are not loaded yet — as soon as operations are requested for them. Thus,
       in many respects, the fact whether a unit is loaded or not is invisible
       to clients. Use systemctl list-units --all to comprehensively list all
       units currently loaded. Any unit for which none of the conditions above
       applies is promptly unloaded. Note that when a unit is unloaded from
       memory its accounting data is flushed out too. However, this data is
       generally not lost, as a journal log record is generated declaring the
       consumed resources whenever a unit shuts down.

       Processes systemd spawns are placed in individual Linux control groups
       named after the unit which they belong to in the private systemd
       hierarchy. (see cgroups.txt[1] for more information about control groups,
       or short "cgroups"). systemd uses this to effectively keep track of
       processes. Control group information is maintained in the kernel, and is
       accessible via the file system hierarchy (beneath
       /sys/fs/cgroup/systemd/), or in tools such as systemd-cgls(1) or ps(1)
       (ps xawf -eo pid,user,cgroup,args is particularly useful to list all
       processes and the systemd units they belong to.).

       systemd is compatible with the SysV init system to a large degree: SysV
       init scripts are supported and simply read as an alternative (though
       limited) configuration file format. The SysV /dev/initctl interface is
       provided, and compatibility implementations of the various SysV client
       tools are available. In addition to that, various established Unix
       functionality such as /etc/fstab or the utmp database are supported.

       systemd has a minimal transaction system: if a unit is requested to start
       up or shut down it will add it and all its dependencies to a temporary
       transaction. Then, it will verify if the transaction is consistent (i.e.
       whether the ordering of all units is cycle-free). If it is not, systemd
       will try to fix it up, and removes non-essential jobs from the
       transaction that might remove the loop. Also, systemd tries to suppress
       non-essential jobs in the transaction that would stop a running service.
       Finally it is checked whether the jobs of the transaction contradict jobs
       that have already been queued, and optionally the transaction is aborted
       then. If all worked out and the transaction is consistent and minimized
       in its impact it is merged with all already outstanding jobs and added to
       the run queue. Effectively this means that before executing a requested
       operation, systemd will verify that it makes sense, fixing it if
       possible, and only failing if it really cannot work.

       Note that transactions are generated independently of a unit's state at
       runtime, hence, for example, if a start job is requested on an already
       started unit, it will still generate a transaction and wake up any
       inactive dependencies (and cause propagation of other jobs as per the
       defined relationships). This is because the enqueued job is at the time
       of execution compared to the target unit's state and is marked successful
       and complete when both satisfy. However, this job also pulls in other
       dependencies due to the defined relationships and thus leads to, in our
       example, start jobs for any of those inactive units getting queued as
       well.

       systemd contains native implementations of various tasks that need to be
       executed as part of the boot process. For example, it sets the hostname
       or configures the loopback network device. It also sets up and mounts
       various API file systems, such as /sys or /proc.

       For more information about the concepts and ideas behind systemd, please
       refer to the Original Design Document[2].

       Note that some but not all interfaces provided by systemd are covered by
       the Interface Stability Promise[3].

       Units may be generated dynamically at boot and system manager reload
       time, for example based on other configuration files or parameters passed
       on the kernel command line. For details, see systemd.generator(7).

       The D-Bus API of systemd is described in org.freedesktop.systemd1(5) and
       org.freedesktop.LogControl1(5).

       Systems which invoke systemd in a container or initrd environment should
       implement the Container Interface[4] or initrd Interface[5]
       specifications, respectively.

DIRECTORIES
       System unit directories
           The systemd system manager reads unit configuration from various
           directories. Packages that want to install unit files shall place
           them in the directory returned by pkg-config systemd
           --variable=systemdsystemunitdir. Other directories checked are
           /usr/local/lib/systemd/system and /usr/lib/systemd/system. User
           configuration always takes precedence.  pkg-config systemd
           --variable=systemdsystemconfdir returns the path of the system
           configuration directory. Packages should alter the content of these
           directories only with the enable and disable commands of the
           systemctl(1) tool. Full list of directories is provided in
           systemd.unit(5).

       User unit directories
           Similar rules apply for the user unit directories. However, here the
           XDG Base Directory specification[6] is followed to find units.
           Applications should place their unit files in the directory returned
           by pkg-config systemd --variable=systemduserunitdir. Global
           configuration is done in the directory reported by pkg-config systemd
           --variable=systemduserconfdir. The enable and disable commands of the
           systemctl(1) tool can handle both global (i.e. for all users) and
           private (for one user) enabling/disabling of units. Full list of
           directories is provided in systemd.unit(5).

       SysV init scripts directory
           The location of the SysV init script directory varies between
           distributions. If systemd cannot find a native unit file for a
           requested service, it will look for a SysV init script of the same
           name (with the .service suffix removed).

       SysV runlevel link farm directory
           The location of the SysV runlevel link farm directory varies between
           distributions. systemd will take the link farm into account when
           figuring out whether a service shall be enabled. Note that a service
           unit with a native unit configuration file cannot be started by
           activating it in the SysV runlevel link farm.

SIGNALS
       SIGTERM
           Upon receiving this signal the systemd system manager serializes its
           state, reexecutes itself and deserializes the saved state again. This
           is mostly equivalent to systemctl daemon-reexec.

           systemd user managers will start the exit.target unit when this
           signal is received. This is mostly equivalent to systemctl --user
           start exit.target --job-mode=replace-irreversibly.

       SIGINT
           Upon receiving this signal the systemd system manager will start the
           ctrl-alt-del.target unit. This is mostly equivalent to systemctl
           start ctrl-alt-del.target --job-mode=replace-irreversibly. If this
           signal is received more than 7 times per 2s, an immediate reboot is
           triggered. Note that pressing Ctrl+Alt+Del on the console will
           trigger this signal. Hence, if a reboot is hanging, pressing
           Ctrl+Alt+Del more than 7 times in 2 seconds is a relatively safe way
           to trigger an immediate reboot.

           systemd user managers treat this signal the same way as SIGTERM.

       SIGWINCH
           When this signal is received the systemd system manager will start
           the kbrequest.target unit. This is mostly equivalent to systemctl
           start kbrequest.target.

           This signal is ignored by systemd user managers.

       SIGPWR
           When this signal is received the systemd manager will start the
           sigpwr.target unit. This is mostly equivalent to systemctl start
           sigpwr.target.

       SIGUSR1
           When this signal is received the systemd manager will try to
           reconnect to the D-Bus bus.

       SIGUSR2
           When this signal is received the systemd manager will log its
           complete state in human-readable form. The data logged is the same as
           printed by systemd-analyze dump.

       SIGHUP
           Reloads the complete daemon configuration. This is mostly equivalent
           to systemctl daemon-reload.

       SIGRTMIN+0
           Enters default mode, starts the default.target unit. This is mostly
           equivalent to systemctl isolate default.target.

       SIGRTMIN+1
           Enters rescue mode, starts the rescue.target unit. This is mostly
           equivalent to systemctl isolate rescue.target.

       SIGRTMIN+2
           Enters emergency mode, starts the emergency.service unit. This is
           mostly equivalent to systemctl isolate emergency.service.

       SIGRTMIN+3
           Halts the machine, starts the halt.target unit. This is mostly
           equivalent to systemctl start halt.target
           --job-mode=replace-irreversibly.

       SIGRTMIN+4
           Powers off the machine, starts the poweroff.target unit. This is
           mostly equivalent to systemctl start poweroff.target
           --job-mode=replace-irreversibly.

       SIGRTMIN+5
           Reboots the machine, starts the reboot.target unit. This is mostly
           equivalent to systemctl start reboot.target
           --job-mode=replace-irreversibly.

       SIGRTMIN+6
           Reboots the machine via kexec, starts the kexec.target unit. This is
           mostly equivalent to systemctl start kexec.target
           --job-mode=replace-irreversibly.

       SIGRTMIN+13
           Immediately halts the machine.

       SIGRTMIN+14
           Immediately powers off the machine.

       SIGRTMIN+15
           Immediately reboots the machine.

       SIGRTMIN+16
           Immediately reboots the machine with kexec.

       SIGRTMIN+20
           Enables display of status messages on the console, as controlled via
           systemd.show_status=1 on the kernel command line.

       SIGRTMIN+21
           Disables display of status messages on the console, as controlled via
           systemd.show_status=0 on the kernel command line.

       SIGRTMIN+22
           Sets the service manager's log level to "debug", in a fashion
           equivalent to systemd.log_level=debug on the kernel command line.

       SIGRTMIN+23
           Restores the log level to its configured value. The configured value
           is derived from – in order of priority – the value specified with
           systemd.log-level= on the kernel command line, or the value specified
           with LogLevel= in the configuration file, or the built-in default of
           "info".

       SIGRTMIN+24
           Immediately exits the manager (only available for --user instances).

       SIGRTMIN+26
           Restores the log target to its configured value. The configured value
           is derived from – in order of priority – the value specified with
           systemd.log-target= on the kernel command line, or the value
           specified with LogTarget= in the configuration file, or the built-in
           default.

       SIGRTMIN+27, SIGRTMIN+28
           Sets the log target to "console" on SIGRTMIN+27 (or "kmsg" on
           SIGRTMIN+28), in a fashion equivalent to systemd.log_target=console
           (or systemd.log_target=kmsg on SIGRTMIN+28) on the kernel command
           line.

ENVIRONMENT
       $SYSTEMD_LOG_COLOR
           Controls whether systemd highlights important log messages. This can
           be overridden with --log-color.

       $SYSTEMD_LOG_LEVEL
           systemd reads the log level from this environment variable. This can
           be overridden with --log-level=.

       $SYSTEMD_LOG_LOCATION
           Controls whether systemd prints the code location along with log
           messages. This can be overridden with --log-location.

       $SYSTEMD_LOG_TARGET
           systemd reads the log target from this environment variable. This can
           be overridden with --log-target=.

       $SYSTEMD_LOG_TIME
           Controls whether systemd prefixes log messages with the current time.
           This can be overridden with --log-time=.

       $XDG_CONFIG_HOME, $XDG_CONFIG_DIRS, $XDG_DATA_HOME, $XDG_DATA_DIRS
           The systemd user manager uses these variables in accordance to the
           XDG Base Directory specification[6] to find its configuration.

       $SYSTEMD_UNIT_PATH, $SYSTEMD_GENERATOR_PATH,
       $SYSTEMD_ENVIRONMENT_GENERATOR_PATH
           Controls where systemd looks for unit files and generators.

           These variables may contain a list of paths, separated by colons
           (":"). When set, if the list ends with an empty component ("...:"),
           this list is prepended to the usual set of of paths. Otherwise, the
           specified list replaces the usual set of paths.

       $SYSTEMD_SYSVINIT_PATH
           Controls where systemd looks for SysV init scripts.

       $SYSTEMD_SYSVRCND_PATH
           Controls where systemd looks for SysV init script runlevel link
           farms.

       $SYSTEMD_PAGER
           Pager to use when --no-pager is not given; overrides $PAGER. If
           neither $SYSTEMD_PAGER nor $PAGER are set, a set of well-known pager
           implementations are tried in turn, including less(1) and more(1),
           until one is found. If no pager implementation is discovered no pager
           is invoked. Setting this environment variable to an empty string or
           the value "cat" is equivalent to passing --no-pager.

       $SYSTEMD_LESS
           Override the options passed to less (by default "FRSXMK").

           Users might want to change two options in particular:

           K
               This option instructs the pager to exit immediately when Ctrl+C
               is pressed. To allow less to handle Ctrl+C itself to switch back
               to the pager command prompt, unset this option.

               If the value of $SYSTEMD_LESS does not include "K", and the pager
               that is invoked is less, Ctrl+C will be ignored by the
               executable, and needs to be handled by the pager.

           X
               This option instructs the pager to not send termcap
               initialization and deinitialization strings to the terminal. It
               is set by default to allow command output to remain visible in
               the terminal even after the pager exits. Nevertheless, this
               prevents some pager functionality from working, in particular
               paged output cannot be scrolled with the mouse.

           See less(1) for more discussion.

       $SYSTEMD_LESSCHARSET
           Override the charset passed to less (by default "utf-8", if the
           invoking terminal is determined to be UTF-8 compatible).

       $SYSTEMD_COLORS
           The value must be a boolean. Controls whether colorized output should
           be generated. This can be specified to override the decision that
           systemd makes based on $TERM and what the console is connected to.

       $SYSTEMD_URLIFY
           The value must be a boolean. Controls whether clickable links should
           be generated in the output for terminal emulators supporting this.
           This can be specified to override the decision that systemd makes
           based on $TERM and other conditions.

       $LISTEN_PID, $LISTEN_FDS, $LISTEN_FDNAMES
           Set by systemd for supervised processes during socket-based
           activation. See sd_listen_fds(3) for more information.

       $NOTIFY_SOCKET
           Set by systemd for supervised processes for status and start-up
           completion notification. See sd_notify(3) for more information.

       For further environment variables understood by systemd and its various
       components, see Known Environment Variables[7].

KERNEL COMMAND LINE
       When run as the system instance systemd parses a number of options listed
       below. They can be specified as kernel command line arguments[8], or
       through the "SystemdOptions" EFI variable (on EFI systems). The kernel
       command line has higher priority. Following variables are understood:

       systemd.unit=, rd.systemd.unit=
           Overrides the unit to activate on boot. Defaults to default.target.
           This may be used to temporarily boot into a different boot unit, for
           example rescue.target or emergency.service. See systemd.special(7)
           for details about these units. The option prefixed with "rd."  is
           honored only in the initial RAM disk (initrd), while the one that is
           not prefixed only in the main system.

       systemd.dump_core
           Takes a boolean argument or enables the option if specified without
           an argument. If enabled, the systemd manager (PID 1) dumps core when
           it crashes. Otherwise, no core dump is created. Defaults to enabled.

       systemd.crash_chvt
           Takes a positive integer, or a boolean argument. Can be also
           specified without an argument, with the same effect as a positive
           boolean. If a positive integer (in the range 1–63) is specified, the
           system manager (PID 1) will activate the specified virtual terminal
           when it crashes. Defaults to disabled, meaning that no such switch is
           attempted. If set to enabled, the virtual terminal the kernel
           messages are written to is used instead.

       systemd.crash_shell
           Takes a boolean argument or enables the option if specified without
           an argument. If enabled, the system manager (PID 1) spawns a shell
           when it crashes, after a 10s delay. Otherwise, no shell is spawned.
           Defaults to disabled, for security reasons, as the shell is not
           protected by password authentication.

       systemd.crash_reboot
           Takes a boolean argument or enables the option if specified without
           an argument. If enabled, the system manager (PID 1) will reboot the
           machine automatically when it crashes, after a 10s delay. Otherwise,
           the system will hang indefinitely. Defaults to disabled, in order to
           avoid a reboot loop. If combined with systemd.crash_shell, the system
           is rebooted after the shell exits.

       systemd.confirm_spawn
           Takes a boolean argument or a path to the virtual console where the
           confirmation messages should be emitted. Can be also specified
           without an argument, with the same effect as a positive boolean. If
           enabled, the system manager (PID 1) asks for confirmation when
           spawning processes using /dev/console. If a path or a console name
           (such as "ttyS0") is provided, the virtual console pointed to by this
           path or described by the give name will be used instead. Defaults to
           disabled.

       systemd.service_watchdogs=
           Takes a boolean argument. If disabled, all service runtime watchdogs
           (WatchdogSec=) and emergency actions (e.g.  OnFailure= or
           StartLimitAction=) are ignored by the system manager (PID 1); see
           systemd.service(5). Defaults to enabled, i.e. watchdogs and failure
           actions are processed normally. The hardware watchdog is not affected
           by this option.

       systemd.show_status
           Takes a boolean argument or the constants error and auto. Can be also
           specified without an argument, with the same effect as a positive
           boolean. If enabled, the systemd manager (PID 1) shows terse service
           status updates on the console during bootup. With error, only
           messages about failures are shown, but boot is otherwise quiet.  auto
           behaves like false until there is a significant delay in boot.
           Defaults to enabled, unless quiet is passed as kernel command line
           option, in which case it defaults to error. If specified overrides
           the system manager configuration file option ShowStatus=, see
           systemd-system.conf(5).

       systemd.status_unit_format=
           Takes either name or description as the value. If name, the system
           manager will use unit names in status messages. If specified,
           overrides the system manager configuration file option
           StatusUnitFormat=, see systemd-system.conf(5).

       systemd.log_color, systemd.log_level=, systemd.log_location,
       systemd.log_target=, systemd.log_time
           Controls log output, with the same effect as the $SYSTEMD_LOG_COLOR,
           $SYSTEMD_LOG_LEVEL, $SYSTEMD_LOG_LOCATION, $SYSTEMD_LOG_TARGET,
           $SYSTEMD_LOG_TIME, environment variables described above.
           systemd.log_color, systemd.log_location, and systemd.log_time can be
           specified without an argument, with the same effect as a positive
           boolean.

       systemd.default_standard_output=, systemd.default_standard_error=
           Controls default standard output and error output for services and
           sockets. That is, controls the default for StandardOutput= and
           StandardError= (see systemd.exec(5) for details). Takes one of
           inherit, null, tty, journal, journal+console, kmsg, kmsg+console. If
           the argument is omitted systemd.default-standard-output= defaults to
           journal and systemd.default-standard-error= to inherit.

       systemd.setenv=
           Takes a string argument in the form VARIABLE=VALUE. May be used to
           set default environment variables to add to forked child processes.
           May be used more than once to set multiple variables.

       systemd.machine_id=
           Takes a 32 character hex value to be used for setting the machine-id.
           Intended mostly for network booting where the same machine-id is
           desired for every boot.

       systemd.unified_cgroup_hierarchy
           When specified without an argument or with a true argument, enables
           the usage of unified cgroup hierarchy[9] (a.k.a. cgroups-v2). When
           specified with a false argument, fall back to hybrid or full legacy
           cgroup hierarchy.

           If this option is not specified, the default behaviour is determined
           during compilation (the -Ddefault-hierarchy= meson option). If the
           kernel does not support unified cgroup hierarchy, the legacy
           hierarchy will be used even if this option is specified.

       systemd.legacy_systemd_cgroup_controller
           Takes effect if the full unified cgroup hierarchy is not used (see
           previous option). When specified without an argument or with a true
           argument, disables the use of "hybrid" cgroup hierarchy (i.e. a
           cgroups-v2 tree used for systemd, and legacy cgroup hierarchy[10],
           a.k.a. cgroups-v1, for other controllers), and forces a full "legacy"
           mode. When specified with a false argument, enables the use of
           "hybrid" hierarchy.

           If this option is not specified, the default behaviour is determined
           during compilation (the -Ddefault-hierarchy= meson option). If the
           kernel does not support unified cgroup hierarchy, the legacy
           hierarchy will be used even if this option is specified.

       quiet
           Turn off status output at boot, much like systemd.show_status=no
           would. Note that this option is also read by the kernel itself and
           disables kernel log output. Passing this option hence turns off the
           usual output from both the system manager and the kernel.

       debug
           Turn on debugging output. This is equivalent to
           systemd.log_level=debug. Note that this option is also read by the
           kernel itself and enables kernel debug output. Passing this option
           hence turns on the debug output from both the system manager and the
           kernel.

       emergency, rd.emergency, -b
           Boot into emergency mode. This is equivalent to
           systemd.unit=emergency.target or rd.systemd.unit=emergency.target,
           respectively, and provided for compatibility reasons and to be easier
           to type.

       rescue, rd.rescue, single, s, S, 1
           Boot into rescue mode. This is equivalent to
           systemd.unit=rescue.target or rd.systemd.unit=rescue.target,
           respectively, and provided for compatibility reasons and to be easier
           to type.

       2, 3, 4, 5
           Boot into the specified legacy SysV runlevel. These are equivalent to
           systemd.unit=runlevel2.target, systemd.unit=runlevel3.target,
           systemd.unit=runlevel4.target, and systemd.unit=runlevel5.target,
           respectively, and provided for compatibility reasons and to be easier
           to type.

       locale.LANG=, locale.LANGUAGE=, locale.LC_CTYPE=, locale.LC_NUMERIC=,
       locale.LC_TIME=, locale.LC_COLLATE=, locale.LC_MONETARY=,
       locale.LC_MESSAGES=, locale.LC_PAPER=, locale.LC_NAME=,
       locale.LC_ADDRESS=, locale.LC_TELEPHONE=, locale.LC_MEASUREMENT=,
       locale.LC_IDENTIFICATION=
           Set the system locale to use. This overrides the settings in
           /etc/locale.conf. For more information, see locale.conf(5) and
           locale(7).

       For other kernel command line parameters understood by components of the
       core OS, please refer to kernel-command-line(7).

OPTIONS
       systemd is only very rarely invoked directly, since it is started early
       and is already running by the time users may interact with it. Normally,
       tools like systemctl(1) are used to give commands to the manager. Since
       systemd is usually not invoked directly, the options listed below are
       mostly useful for debugging and special purposes.

   Introspection and debugging options
       Those options are used for testing and introspection, and systemd may be
       invoked with them at any time:

       --dump-configuration-items
           Dump understood unit configuration items. This outputs a terse but
           complete list of configuration items understood in unit definition
           files.

       --dump-bus-properties
           Dump exposed bus properties. This outputs a terse but complete list
           of properties exposed on D-Bus.

       --test
           Determine the initial start-up transaction (i.e. the list of jobs
           enqueued at start-up), dump it and exit — without actually executing
           any of the determined jobs. This option is useful for debugging only.
           Note that during regular service manager start-up additional units
           not shown by this operation may be started, because hardware, socket,
           bus or other kinds of activation might add additional jobs as the
           transaction is executed. Use --system to request the initial
           transaction of the system service manager (this is also the implied
           default), combine with --user to request the initial transaction of
           the per-user service manager instead.

       --system, --user
           When used in conjunction with --test, selects whether to calculate
           the initial transaction for the system instance or for a per-user
           instance. These options have no effect when invoked without --test,
           as during regular (i.e. non---test) invocations the service manager
           will automatically detect whether it shall operate in system or
           per-user mode, by checking whether the PID it is run as is 1 or not.
           Note that it is not supported booting and maintaining a system with
           the service manager running in --system mode but with a PID other
           than 1.

       -h, --help
           Print a short help text and exit.

       --version
           Print a short version string and exit.

   Options that duplicate kernel command line settings
       Those options correspond directly to options listed above in "Kernel
       Command Line". Both forms may be used equivalently for the system
       manager, but it is recommended to use the forms listed above in this
       context, because they are properly namespaced. When an option is
       specified both on the kernel command line, and as a normal command line
       argument, the latter has higher precedence.

       When systemd is used as a user manager, the kernel command line is
       ignored and the options described are understood. Nevertheless, systemd
       is usually started in this mode through the user@.service(5) service,
       which is shared between all users, and it may be more convenient to use
       configuration files to modify settings, see systemd-user.conf(5), or a
       drop-in that specifies one of the environment variables listed above in
       the Environment section, see systemd.unit(5).

       --unit=
           Set default unit to activate on startup. If not specified, defaults
           to default.target. See systemd.unit= above.

       --dump-core
           Enable core dumping on crash. This switch has no effect when running
           as user instance. Same as systemd.dump_core= above.

       --crash-vt=VT
           Switch to a specific virtual console (VT) on crash. This switch has
           no effect when running as user instance. Same as systemd.crash_chvt=
           above (but not the different spelling!).

       --crash-shell
           Run a shell on crash. This switch has no effect when running as user
           instance. See systemd.crash_shell= above.

       --crash-reboot
           Automatically reboot the system on crash. This switch has no effect
           when running as user instance. See systemd.crash_reboot above.

       --confirm-spawn
           Ask for confirmation when spawning processes. This switch has no
           effect when run as user instance. See systemd.confirm_spawn above.

       --show-status
           Show terse unit status information on the console during boot-up and
           shutdown. See systemd.show_status above.

       --log-color
           Highlight important log messages. See systemd.log_color above.

       --log-level=
           Set log level. See systemd.log_level above.

       --log-location
           Include code location in log messages. See systemd.log_location
           above.

       --log-target=
           Set log target. See systemd.log_target above.

       --log-time=
           Prefix messages with timestamp. See systemd.log_time above.

       --machine-id=
           Override the machine-id set on the hard drive. See
           systemd.machine_id= above.

       --service-watchdogs
           Globally enable/disable all service watchdog timeouts and emergency
           actions. See systemd.service_watchdogs above.

       --default-standard-output=, --default-standard-error=
           Sets the default output or error output for all services and sockets,
           respectively. See systemd.default_standard_output= and
           systemd.default_standard_error= above.

SOCKETS AND FIFOS
       /run/systemd/notify
           Daemon status notification socket. This is an AF_UNIX datagram socket
           and is used to implement the daemon notification logic as implemented
           by sd_notify(3).

       /run/systemd/private
           Used internally as communication channel between systemctl(1) and the
           systemd process. This is an AF_UNIX stream socket. This interface is
           private to systemd and should not be used in external projects.

       /dev/initctl
           Limited compatibility support for the SysV client interface, as
           implemented by the systemd-initctl.service unit. This is a named pipe
           in the file system. This interface is obsolete and should not be used
           in new applications.

SEE ALSO
       The systemd Homepage[11], systemd-system.conf(5), locale.conf(5),
       systemctl(1), journalctl(1), systemd-notify(1), daemon(7), sd-daemon(3),
       org.freedesktop.systemd1(5), systemd.unit(5), systemd.special(7), pkg-
       config(1), kernel-command-line(7), bootup(7), systemd.directives(7)

NOTES
        1. cgroups.txt
           https://www.kernel.org/doc/Documentation/cgroup-v1/cgroups.txt

        2. Original Design Document
           http://0pointer.de/blog/projects/systemd.html

        3. Interface Stability Promise
           https://www.freedesktop.org/wiki/Software/systemd/InterfaceStabilityPromise

        4. Container Interface
           https://systemd.io/CONTAINER_INTERFACE

        5. initrd Interface
           https://www.freedesktop.org/wiki/Software/systemd/InitrdInterface

        6. XDG Base Directory specification
           http://standards.freedesktop.org/basedir-spec/basedir-spec-latest.html

        7. Known Environment Variables
           https://systemd.io/ENVIRONMENT

        8. If run inside a Linux container these arguments may be passed as
           command line arguments to systemd itself, next to any of the command
           line options listed in the Options section above. If run outside of
           Linux containers, these arguments are parsed from /proc/cmdline
           instead.

        9. unified cgroup hierarchy
           https://www.kernel.org/doc/html/latest/admin-guide/cgroup-v2.html

       10. legacy cgroup hierarchy
           https://www.kernel.org/doc/Documentation/cgroup-v1/

       11. systemd Homepage
           https://www.freedesktop.org/wiki/Software/systemd/



systemd 246                                                           SYSTEMD(1)