init(1) — Linux manual page

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SYSTEMD(1)                         systemd                        SYSTEMD(1)

NAME         top

       systemd, init - systemd system and service manager

SYNOPSIS         top

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

       init [OPTIONS...] {COMMAND}

DESCRIPTION         top

       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         top

       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         top

       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         top

       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         top

       $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         top

       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 (VT) when it crashes. Defaults to disabled, meaning that
           no such switch is attempted. If set to enabled, the VT the kernel
           messages are written to is selected.

       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         top

       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 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 "Environment, 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 is shown 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         top

       /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         top

       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(5), pkg-config(1), kernel-command-line(7), bootup(7),
       systemd.directives(7)

NOTES         top

        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/

COLOPHON         top

       This page is part of the systemd (systemd system and service manager)
       project.  Information about the project can be found at 
       ⟨http://www.freedesktop.org/wiki/Software/systemd⟩.  If you have a bug
       report for this manual page, see
       ⟨http://www.freedesktop.org/wiki/Software/systemd/#bugreports⟩.  This
       page was obtained from the project's upstream Git repository
       ⟨https://github.com/systemd/systemd.git⟩ on 2020-06-09.  (At that
       time, the date of the most recent commit that was found in the repos‐
       itory was 2020-06-09.)  If you discover any rendering problems in
       this HTML version of the page, or you believe there is a better or
       more up-to-date source for the page, or you have corrections or
       improvements to the information in this COLOPHON (which is not part
       of the original manual page), send a mail to man-pages@man7.org

systemd 245                                                       SYSTEMD(1)

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