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SYSTEMD(1)				     systemd				       SYSTEMD(1)

NAME
       systemd, init - systemd system and service manager

SYNOPSIS
       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.

       For compatibility with SysV, if systemd is called as init and a PID that 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 system instance, systemd interprets the configuration file system.conf,
       otherwise user.conf. See systemd-system.conf(5) for more information.

OPTIONS
       The following options are understood:

       -h, --help
	   Prints a short help text and exits.

       --version
	   Prints a systemd version identifier and exits.

       --test
	   Determine startup sequence, dump it and exit. This is an option useful for debugging
	   only.

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

       --introspect=
	   Extract D-Bus interface introspection data. This is mostly useful at install time to
	   generate data suitable for the D-Bus interfaces repository. Optionally the interface
	   name for the introspection data may be specified. If omitted, the introspection data
	   for all interfaces is dumped.

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

       --system, --user
	   For --system, tell systemd to run a system instance, even if the process ID is not 1,
	   i.e. systemd is not run as init process.  --user does the opposite, running a user
	   instance even if the process ID is 1. Normally it should not be necessary to pass
	   these options, as systemd automatically detects the mode it is started in. These
	   options are hence of little use except for debugging. Note that it is not supported
	   booting and maintaining a full system with systemd running in --system mode, but PID
	   not 1. In practice, passing --system explicitly is only useful in conjunction with
	   --test.

       --dump-core
	   Dump core on crash. This switch has no effect when run as user instance.

       --crash-shell
	   Run shell on crash. This switch has no effect when run as user instance.

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

       --show-status=
	   Show terse service status information while booting. This switch has no effect when
	   run as user instance. Takes a boolean argument which may be omitted which is
	   interpreted as true.

       --log-target=
	   Set log target. Argument must be one of console, journal, syslog, kmsg,
	   journal-or-kmsg, syslog-or-kmsg, null.

       --log-level=
	   Set log level. As argument this accepts a numerical log level or the well-known
	   syslog(3) symbolic names (lowercase): emerg, alert, crit, err, warning, notice, info,
	   debug.

       --log-color=
	   Highlight important log messages. Argument is a boolean value. If the argument is
	   omitted, it defaults to true.

       --log-location=
	   Include code location in log messages. This is mostly relevant for debugging purposes.
	   Argument is a boolean value. If the argument is omitted it defaults to true.

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

CONCEPTS
       systemd provides a dependency system between various entities called "units" of 12
       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, or an operation timed
       out). 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. Snapshot units can be used to temporarily save the state of the set of systemd units,
	   which later may be restored by activating the saved snapshot unit. For more
	   information see systemd.snapshot(5).

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

	9. 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).

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

       11. 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).

       12. 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.

       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 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.

       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 the Generators Specification[4].

       Systems which invoke systemd in a container or initrd environment should implement the
       Container Interface[5] or initrd Interface[6] 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[7] 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.

       SIGINT
	   Upon receiving this signal the systemd system manager will start the
	   ctrl-alt-del.target unit. This is mostly equivalent to systemctl start
	   ctl-alt-del.target.

	   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 systemctl 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 start 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.

       SIGRTMIN+4
	   Powers off the machine, starts the poweroff.target unit. This is mostly equivalent to
	   systemctl start poweroff.target.

       SIGRTMIN+5
	   Reboots the machine, starts the reboot.target unit. This is mostly equivalent to
	   systemctl start reboot.target.

       SIGRTMIN+6
	   Reboots the machine via kexec, starts the kexec.target unit. This is mostly equivalent
	   to systemctl start kexec.target.

       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, SIGRTMIN+23
	   Sets the log level to "debug" (or "info" on SIGRTMIN+23), as controlled via
	   systemd.log_level=debug (or systemd.log_level=info on SIGRTMIN+23) on the kernel
	   command line.

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

       SIGRTMIN+26, SIGRTMIN+27, SIGRTMIN+28, SIGRTMIN+29
	   Sets the log level to "journal-or-kmsg" (or "console" on SIGRTMIN+27, "kmsg" on
	   SIGRTMIN+28, or "syslog-or-kmsg" on SIGRTMIN+29), as controlled via
	   systemd.log_target=journal-or-kmsg (or systemd.log_target=console on SIGRTMIN+27,
	   systemd.log_target=kmsg on SIGRTMIN+28, or systemd.log_target=syslog-or-kmsg on
	   SIGRTMIN+29) on the kernel command line.

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

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

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

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

       $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[7] to find its configuration.

       $SYSTEMD_UNIT_PATH
	   Controls where systemd looks for unit files.

       $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.

       $LISTEN_PID, $LISTEN_FDS
	   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.

KERNEL COMMAND LINE
       When run as system instance systemd parses a number of kernel command line arguments[8]:

       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. If true, systemd dumps core when it crashes. Otherwise, no
	   core dump is created. Defaults to true.

       systemd.crash_shell=
	   Takes a boolean argument. If true, systemd spawns a shell when it crashes. Otherwise,
	   no shell is spawned. Defaults to false, for security reasons, as the shell is not
	   protected by any password authentication.

       systemd.crash_chvt=
	   Takes an integer argument. If positive systemd activates the specified virtual
	   terminal when it crashes. Defaults to -1.

       systemd.confirm_spawn=
	   Takes a boolean argument. If true, asks for confirmation when spawning processes.
	   Defaults to false.

       systemd.show_status=
	   Takes a boolean argument. If true, shows terse service status updates on the console
	   during bootup. Defaults to true, unless quiet is passed as kernel command line option
	   in which case it defaults to false.

       systemd.log_target=, systemd.log_level=, systemd.log_color=, systemd.log_location=
	   Controls log output, with the same effect as the $SYSTEMD_LOG_TARGET,
	   $SYSTEMD_LOG_LEVEL, $SYSTEMD_LOG_COLOR, $SYSTEMD_LOG_LOCATION environment variables
	   described above.

       systemd.default_standard_output=, systemd.default_standard_error=
	   Controls default standard output and error output for services, with the same effect
	   as the --default-standard-output= and --default-standard-error= command line arguments
	   described above, respectively.

       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.

       quiet
	   Turn off status output at boot, much like systemd.show_status=false 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.

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

       single, s, S, 1
	   Boot into rescue mode. This is equivalent to systemd.unit=rescue.target 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).

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/shutdownd
	   Used internally by the shutdown(8) tool to implement delayed shutdowns. This is an
	   AF_UNIX datagram socket.

       /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[9], systemd-system.conf(5), locale.conf(5), systemctl(1),
       journalctl(1), systemd-notify(1), daemon(7), sd-daemon(3), systemd.unit(5),
       systemd.special(5), pkg-config(1), kernel-command-line(7), bootup(7),
       systemd.directives(7)

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

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

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

	4. Generators Specification
	   http://www.freedesktop.org/wiki/Software/systemd/Generators

	5. Container Interface
	   http://www.freedesktop.org/wiki/Software/systemd/ContainerInterface

	6. initrd Interface
	   http://www.freedesktop.org/wiki/Software/systemd/InitrdInterface

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

	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. systemd Homepage
	   http://www.freedesktop.org/wiki/Software/systemd/

systemd 208									       SYSTEMD(1)
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