1SYSTEMD(1) systemd SYSTEMD(1)
2
6 systemd, init - systemd system and service manager
7
9 /usr/lib/systemd/systemd [OPTIONS...]
10 init [OPTIONS...] {COMMAND}
12
14 systemd is a system and service manager for Linux operating systems.
15 When run as first process on boot (as PID 1), it acts as init system
16 that brings up and maintains userspace services. Separate instances are
17 started for logged-in users to start their services.
18 systemd is usually not invoked directly by the user, but is installed
20 as the /sbin/init symlink and started during early boot. The user
21 manager instances are started automatically through the
22 user@.service(5) service.
23 For compatibility with SysV, if the binary is called as init and is not
25 the first process on the machine (PID is not 1), it will execute
26 telinit and pass all command line arguments unmodified. That means init
27 and telinit are mostly equivalent when invoked from normal login
28 sessions. See telinit(8) for more information.
29 When run as a system instance, systemd interprets the configuration
31 file system.conf and the files in system.conf.d directories; when run
32 as a user instance, systemd interprets the configuration file user.conf
33 and the files in user.conf.d directories. See systemd-system.conf(5)
34 for more information.
35
37 systemd provides a dependency system between various entities called
38 "units" of 11 different types. Units encapsulate various objects that
39 are relevant for system boot-up and maintenance. The majority of units
40 are configured in unit configuration files, whose syntax and basic set
41 of options is described in systemd.unit(5), however some are created
42 automatically from other configuration files, dynamically from system
43 state or programmatically at runtime. Units may be "active" (meaning
44 started, bound, plugged in, ..., depending on the unit type, see
45 below), or "inactive" (meaning stopped, unbound, unplugged, ...), as
46 well as in the process of being activated or deactivated, i.e. between
47 the two states (these states are called "activating", "deactivating").
48 A special "failed" state is available as well, which is very similar to
49 "inactive" and is entered when the service failed in some way (process
50 returned error code on exit, or crashed, an operation timed out, or
51 after too many restarts). If this state is entered, the cause will be
52 logged, for later reference. Note that the various unit types may have
53 a number of additional substates, which are mapped to the five
54 generalized unit states described here.
55 The following unit types are available:
57 1. Service units, which start and control daemons and the processes
59 they consist of. For details, see systemd.service(5).
60 2. Socket units, which encapsulate local IPC or network sockets in the
62 system, useful for socket-based activation. For details about
63 socket units, see systemd.socket(5), for details on socket-based
64 activation and other forms of activation, see daemon(7).
65 3. Target units are useful to group units, or provide well-known
67 synchronization points during boot-up, see systemd.target(5).
68 4. Device units expose kernel devices in systemd and may be used to
70 implement device-based activation. For details, see
71 systemd.device(5).
72 5. Mount units control mount points in the file system, for details
74 see systemd.mount(5).
75 6. Automount units provide automount capabilities, for on-demand
77 mounting of file systems as well as parallelized boot-up. See
78 systemd.automount(5).
79 7. Timer units are useful for triggering activation of other units
81 based on timers. You may find details in systemd.timer(5).
82 8. Swap units are very similar to mount units and encapsulate memory
84 swap partitions or files of the operating system. They are
85 described in systemd.swap(5).
86 9. Path units may be used to activate other services when file system
88 objects change or are modified. See systemd.path(5).
89 10. Slice units may be used to group units which manage system
91 processes (such as service and scope units) in a hierarchical tree
92 for resource management purposes. See systemd.slice(5).
93 11. Scope units are similar to service units, but manage foreign
95 processes instead of starting them as well. See systemd.scope(5).
96 Units are named as their configuration files. Some units have special
98 semantics. A detailed list is available in systemd.special(7).
99 systemd knows various kinds of dependencies, including positive and
101 negative requirement dependencies (i.e. Requires= and Conflicts=) as
102 well as ordering dependencies (After= and Before=). NB: ordering and
103 requirement dependencies are orthogonal. If only a requirement
104 dependency exists between two units (e.g. foo.service requires
105 bar.service), but no ordering dependency (e.g. foo.service after
106 bar.service) and both are requested to start, they will be started in
107 parallel. It is a common pattern that both requirement and ordering
108 dependencies are placed between two units. Also note that the majority
109 of dependencies are implicitly created and maintained by systemd. In
110 most cases, it should be unnecessary to declare additional dependencies
111 manually, however it is possible to do this.
112 Application programs and units (via dependencies) may request state
114 changes of units. In systemd, these requests are encapsulated as 'jobs'
115 and maintained in a job queue. Jobs may succeed or can fail, their
116 execution is ordered based on the ordering dependencies of the units
117 they have been scheduled for.
118 On boot systemd activates the target unit default.target whose job is
120 to activate on-boot services and other on-boot units by pulling them in
121 via dependencies. Usually, the unit name is just an alias (symlink) for
122 either graphical.target (for fully-featured boots into the UI) or
123 multi-user.target (for limited console-only boots for use in embedded
124 or server environments, or similar; a subset of graphical.target).
125 However, it is at the discretion of the administrator to configure it
126 as an alias to any other target unit. See systemd.special(7) for
127 details about these target units.
128 On first boot, systemd will enable or disable units according to preset
130 policy. See systemd.preset(5) and "First Boot Semantics" in machine-
131 id(5).
132 systemd only keeps a minimal set of units loaded into memory.
134 Specifically, the only units that are kept loaded into memory are those
135 for which at least one of the following conditions is true:
136 1. It is in an active, activating, deactivating or failed state (i.e.
138 in any unit state except for "inactive")
139 2. It has a job queued for it
141 3. It is a dependency of at least one other unit that is loaded into
143 memory
144 4. It has some form of resource still allocated (e.g. a service unit
146 that is inactive but for which a process is still lingering that
147 ignored the request to be terminated)
148 5. It has been pinned into memory programmatically by a D-Bus call
150 systemd will automatically and implicitly load units from disk — if
152 they are not loaded yet — as soon as operations are requested for them.
153 Thus, in many respects, the fact whether a unit is loaded or not is
154 invisible to clients. Use systemctl list-units --all to comprehensively
155 list all units currently loaded. Any unit for which none of the
156 conditions above applies is promptly unloaded. Note that when a unit is
157 unloaded from memory its accounting data is flushed out too. However,
158 this data is generally not lost, as a journal log record is generated
159 declaring the consumed resources whenever a unit shuts down.
160 Processes systemd spawns are placed in individual Linux control groups
162 named after the unit which they belong to in the private systemd
163 hierarchy. (see Control Groups v2[1] for more information about control
164 groups, or short "cgroups"). systemd uses this to effectively keep
165 track of processes. Control group information is maintained in the
166 kernel, and is accessible via the file system hierarchy (beneath
167 /sys/fs/cgroup/), or in tools such as systemd-cgls(1) or ps(1) (ps xawf
168 -eo pid,user,cgroup,args is particularly useful to list all processes
169 and the systemd units they belong to.).
170 systemd is compatible with the SysV init system to a large degree: SysV
172 init scripts are supported and simply read as an alternative (though
173 limited) configuration file format. The SysV /dev/initctl interface is
174 provided, and compatibility implementations of the various SysV client
175 tools are available. In addition to that, various established Unix
176 functionality such as /etc/fstab or the utmp database are supported.
177 systemd has a minimal transaction system: if a unit is requested to
179 start up or shut down it will add it and all its dependencies to a
180 temporary transaction. Then, it will verify if the transaction is
181 consistent (i.e. whether the ordering of all units is cycle-free). If
182 it is not, systemd will try to fix it up, and removes non-essential
183 jobs from the transaction that might remove the loop. Also, systemd
184 tries to suppress non-essential jobs in the transaction that would stop
185 a running service. Finally it is checked whether the jobs of the
186 transaction contradict jobs that have already been queued, and
187 optionally the transaction is aborted then. If all worked out and the
188 transaction is consistent and minimized in its impact it is merged with
189 all already outstanding jobs and added to the run queue. Effectively
190 this means that before executing a requested operation, systemd will
191 verify that it makes sense, fixing it if possible, and only failing if
192 it really cannot work.
193 Note that transactions are generated independently of a unit's state at
195 runtime, hence, for example, if a start job is requested on an already
196 started unit, it will still generate a transaction and wake up any
197 inactive dependencies (and cause propagation of other jobs as per the
198 defined relationships). This is because the enqueued job is at the time
199 of execution compared to the target unit's state and is marked
200 successful and complete when both satisfy. However, this job also pulls
201 in other dependencies due to the defined relationships and thus leads
202 to, in our example, start jobs for any of those inactive units getting
203 queued as well.
204 systemd contains native implementations of various tasks that need to
206 be executed as part of the boot process. For example, it sets the
207 hostname or configures the loopback network device. It also sets up and
208 mounts various API file systems, such as /sys/ or /proc/.
209 For more information about the concepts and ideas behind systemd,
211 please refer to the Original Design Document[2].
212 Note that some but not all interfaces provided by systemd are covered
214 by the Interface Portability and Stability Promise[3].
215 Units may be generated dynamically at boot and system manager reload
217 time, for example based on other configuration files or parameters
218 passed on the kernel command line. For details, see
219 systemd.generator(7).
220 The D-Bus API of systemd is described in org.freedesktop.systemd1(5)
222 and org.freedesktop.LogControl1(5).
223 Systems which invoke systemd in a container or initrd environment
225 should implement the Container Interface[4] or initrd Interface[5]
226 specifications, respectively.
227
229 System unit directories
230 The systemd system manager reads unit configuration from various
231 directories. Packages that want to install unit files shall place
232 them in the directory returned by pkg-config systemd
233 --variable=systemdsystemunitdir. Other directories checked are
234 /usr/local/lib/systemd/system and /usr/lib/systemd/system. User
235 configuration always takes precedence. pkg-config systemd
236 --variable=systemdsystemconfdir returns the path of the system
237 configuration directory. Packages should alter the content of these
238 directories only with the enable and disable commands of the
239 systemctl(1) tool. Full list of directories is provided in
240 systemd.unit(5).
241 User unit directories
243 Similar rules apply for the user unit directories. However, here
244 the XDG Base Directory specification[6] is followed to find units.
245 Applications should place their unit files in the directory
246 returned by pkg-config systemd --variable=systemduserunitdir.
247 Global configuration is done in the directory reported by
248 pkg-config systemd --variable=systemduserconfdir. The enable and
249 disable commands of the systemctl(1) tool can handle both global
250 (i.e. for all users) and private (for one user) enabling/disabling
251 of units. Full list of directories is provided in systemd.unit(5).
252 SysV init scripts directory
254 The location of the SysV init script directory varies between
255 distributions. If systemd cannot find a native unit file for a
256 requested service, it will look for a SysV init script of the same
257 name (with the .service suffix removed).
258 SysV runlevel link farm directory
260 The location of the SysV runlevel link farm directory varies
261 between distributions. systemd will take the link farm into account
262 when figuring out whether a service shall be enabled. Note that a
263 service unit with a native unit configuration file cannot be
264 started by activating it in the SysV runlevel link farm.
265
267 SIGTERM
268 Upon receiving this signal the systemd system manager serializes
269 its state, reexecutes itself and deserializes the saved state
270 again. This is mostly equivalent to systemctl daemon-reexec.
271 systemd user managers will start the exit.target unit when this
273 signal is received. This is mostly equivalent to systemctl --user
274 start exit.target --job-mode=replace-irreversibly.
275 SIGINT
277 Upon receiving this signal the systemd system manager will start
278 the ctrl-alt-del.target unit. This is mostly equivalent to
279 systemctl start ctrl-alt-del.target
280 --job-mode=replace-irreversibly. If this signal is received more
281 than 7 times per 2s, an immediate reboot is triggered. Note that
282 pressing Ctrl+Alt+Del on the console will trigger this signal.
283 Hence, if a reboot is hanging, pressing Ctrl+Alt+Del more than 7
284 times in 2 seconds is a relatively safe way to trigger an immediate
285 reboot.
286 systemd user managers treat this signal the same way as SIGTERM.
288 SIGWINCH
290 When this signal is received the systemd system manager will start
291 the kbrequest.target unit. This is mostly equivalent to systemctl
292 start kbrequest.target.
293 This signal is ignored by systemd user managers.
295 SIGPWR
297 When this signal is received the systemd manager will start the
298 sigpwr.target unit. This is mostly equivalent to systemctl start
299 sigpwr.target.
300 SIGUSR1
302 When this signal is received the systemd manager will try to
303 reconnect to the D-Bus bus.
304 SIGUSR2
306 When this signal is received the systemd manager will log its
307 complete state in human-readable form. The data logged is the same
308 as printed by systemd-analyze dump.
309 SIGHUP
311 Reloads the complete daemon configuration. This is mostly
312 equivalent to systemctl daemon-reload.
313 SIGRTMIN+0
315 Enters default mode, starts the default.target unit. This is mostly
316 equivalent to systemctl isolate default.target.
317 SIGRTMIN+1
319 Enters rescue mode, starts the rescue.target unit. This is mostly
320 equivalent to systemctl isolate rescue.target.
321 SIGRTMIN+2
323 Enters emergency mode, starts the emergency.service unit. This is
324 mostly equivalent to systemctl isolate emergency.service.
325 SIGRTMIN+3
327 Halts the machine, starts the halt.target unit. This is mostly
328 equivalent to systemctl start halt.target
329 --job-mode=replace-irreversibly.
330 SIGRTMIN+4
332 Powers off the machine, starts the poweroff.target unit. This is
333 mostly equivalent to systemctl start poweroff.target
334 --job-mode=replace-irreversibly.
335 SIGRTMIN+5
337 Reboots the machine, starts the reboot.target unit. This is mostly
338 equivalent to systemctl start reboot.target
339 --job-mode=replace-irreversibly.
340 SIGRTMIN+6
342 Reboots the machine via kexec, starts the kexec.target unit. This
343 is mostly equivalent to systemctl start kexec.target
344 --job-mode=replace-irreversibly.
345 SIGRTMIN+13
347 Immediately halts the machine.
348 SIGRTMIN+14
350 Immediately powers off the machine.
351 SIGRTMIN+15
353 Immediately reboots the machine.
354 SIGRTMIN+16
356 Immediately reboots the machine with kexec.
357 SIGRTMIN+20
359 Enables display of status messages on the console, as controlled
360 via systemd.show_status=1 on the kernel command line.
361 SIGRTMIN+21
363 Disables display of status messages on the console, as controlled
364 via systemd.show_status=0 on the kernel command line.
365 SIGRTMIN+22
367 Sets the service manager's log level to "debug", in a fashion
368 equivalent to systemd.log_level=debug on the kernel command line.
369 SIGRTMIN+23
371 Restores the log level to its configured value. The configured
372 value is derived from – in order of priority – the value specified
373 with systemd.log-level= on the kernel command line, or the value
374 specified with LogLevel= in the configuration file, or the built-in
375 default of "info".
376 SIGRTMIN+24
378 Immediately exits the manager (only available for --user
379 instances).
380 SIGRTMIN+25
382 Upon receiving this signal the systemd manager will reexecute
383 itself. This is mostly equivalent to systemctl daemon-reexec except
384 that it will be done asynchronously.
385 The systemd system manager treats this signal the same way as
387 SIGTERM.
388 SIGRTMIN+26
390 Restores the log target to its configured value. The configured
391 value is derived from – in order of priority – the value specified
392 with systemd.log-target= on the kernel command line, or the value
393 specified with LogTarget= in the configuration file, or the
394 built-in default.
395 SIGRTMIN+27, SIGRTMIN+28
397 Sets the log target to "console" on SIGRTMIN+27 (or "kmsg" on
398 SIGRTMIN+28), in a fashion equivalent to systemd.log_target=console
399 (or systemd.log_target=kmsg on SIGRTMIN+28) on the kernel command
400 line.
401
403 The environment block for the system manager is initially set by the
404 kernel. (In particular, "key=value" assignments on the kernel command
405 line are turned into environment variables for PID 1). For the user
406 manager, the system manager sets the environment as described in the
407 "Environment Variables in Spawned Processes" section of
408 systemd.exec(5). The DefaultEnvironment= setting in the system manager
409 applies to all services including user@.service. Additional entries may
410 be configured (as for any other service) through the Environment= and
411 EnvironmentFile= settings for user@.service (see systemd.exec(5)).
412 Also, additional environment variables may be set through the
413 ManagerEnvironment= setting in systemd-system.conf(5) and systemd-
414 user.conf(5).
415 Some of the variables understood by systemd:
417 $SYSTEMD_LOG_LEVEL
419 The maximum log level of emitted messages (messages with a higher
420 log level, i.e. less important ones, will be suppressed). Either
421 one of (in order of decreasing importance) emerg, alert, crit, err,
422 warning, notice, info, debug, or an integer in the range 0...7. See
423 syslog(3) for more information.
424 This can be overridden with --log-level=.
426 $SYSTEMD_LOG_COLOR
428 A boolean. If true, messages written to the tty will be colored
429 according to priority.
430 This can be overridden with --log-color=.
432 $SYSTEMD_LOG_TIME
434 A boolean. If true, console log messages will be prefixed with a
435 timestamp.
436 This can be overridden with --log-time=.
438 $SYSTEMD_LOG_LOCATION
440 A boolean. If true, messages will be prefixed with a filename and
441 line number in the source code where the message originates.
442 This can be overridden with --log-location=.
444 $SYSTEMD_LOG_TID
446 A boolean. If true, messages will be prefixed with the current
447 numerical thread ID (TID).
448 $SYSTEMD_LOG_TARGET
450 The destination for log messages. One of console (log to the
451 attached tty), console-prefixed (log to the attached tty but with
452 prefixes encoding the log level and "facility", see syslog(3), kmsg
453 (log to the kernel circular log buffer), journal (log to the
454 journal), journal-or-kmsg (log to the journal if available, and to
455 kmsg otherwise), auto (determine the appropriate log target
456 automatically, the default), null (disable log output).
457 This can be overridden with --log-target=.
459 $XDG_CONFIG_HOME, $XDG_CONFIG_DIRS, $XDG_DATA_HOME, $XDG_DATA_DIRS
461 The systemd user manager uses these variables in accordance to the
462 XDG Base Directory specification[6] to find its configuration.
463 $SYSTEMD_UNIT_PATH, $SYSTEMD_GENERATOR_PATH,
465 $SYSTEMD_ENVIRONMENT_GENERATOR_PATH
466 Controls where systemd looks for unit files and generators.
467 These variables may contain a list of paths, separated by colons
469 (":"). When set, if the list ends with an empty component ("...:"),
470 this list is prepended to the usual set of paths. Otherwise, the
471 specified list replaces the usual set of paths.
472 $SYSTEMD_PAGER
474 Pager to use when --no-pager is not given; overrides $PAGER. If
475 neither $SYSTEMD_PAGER nor $PAGER are set, a set of well-known
476 pager implementations are tried in turn, including less(1) and
477 more(1), until one is found. If no pager implementation is
478 discovered no pager is invoked. Setting this environment variable
479 to an empty string or the value "cat" is equivalent to passing
480 --no-pager.
481 Note: if $SYSTEMD_PAGERSECURE is not set, $SYSTEMD_PAGER (as well
483 as $PAGER) will be silently ignored.
484 $SYSTEMD_LESS
486 Override the options passed to less (by default "FRSXMK").
487 Users might want to change two options in particular:
489 K
491 This option instructs the pager to exit immediately when Ctrl+C
492 is pressed. To allow less to handle Ctrl+C itself to switch
493 back to the pager command prompt, unset this option.
494 If the value of $SYSTEMD_LESS does not include "K", and the
496 pager that is invoked is less, Ctrl+C will be ignored by the
497 executable, and needs to be handled by the pager.
498 X
500 This option instructs the pager to not send termcap
501 initialization and deinitialization strings to the terminal. It
502 is set by default to allow command output to remain visible in
503 the terminal even after the pager exits. Nevertheless, this
504 prevents some pager functionality from working, in particular
505 paged output cannot be scrolled with the mouse.
506 See less(1) for more discussion.
508 $SYSTEMD_LESSCHARSET
510 Override the charset passed to less (by default "utf-8", if the
511 invoking terminal is determined to be UTF-8 compatible).
512 $SYSTEMD_PAGERSECURE
514 Takes a boolean argument. When true, the "secure" mode of the pager
515 is enabled; if false, disabled. If $SYSTEMD_PAGERSECURE is not set
516 at all, secure mode is enabled if the effective UID is not the same
517 as the owner of the login session, see geteuid(2) and
518 sd_pid_get_owner_uid(3). In secure mode, LESSSECURE=1 will be set
519 when invoking the pager, and the pager shall disable commands that
520 open or create new files or start new subprocesses. When
521 $SYSTEMD_PAGERSECURE is not set at all, pagers which are not known
522 to implement secure mode will not be used. (Currently only less(1)
523 implements secure mode.)
524 Note: when commands are invoked with elevated privileges, for
526 example under sudo(8) or pkexec(1), care must be taken to ensure
527 that unintended interactive features are not enabled. "Secure" mode
528 for the pager may be enabled automatically as describe above.
529 Setting SYSTEMD_PAGERSECURE=0 or not removing it from the inherited
530 environment allows the user to invoke arbitrary commands. Note that
531 if the $SYSTEMD_PAGER or $PAGER variables are to be honoured,
532 $SYSTEMD_PAGERSECURE must be set too. It might be reasonable to
533 completely disable the pager using --no-pager instead.
534 $SYSTEMD_COLORS
536 Takes a boolean argument. When true, systemd and related utilities
537 will use colors in their output, otherwise the output will be
538 monochrome. Additionally, the variable can take one of the
539 following special values: "16", "256" to restrict the use of colors
540 to the base 16 or 256 ANSI colors, respectively. This can be
541 specified to override the automatic decision based on $TERM and
542 what the console is connected to.
543 $SYSTEMD_URLIFY
545 The value must be a boolean. Controls whether clickable links
546 should be generated in the output for terminal emulators supporting
547 this. This can be specified to override the decision that systemd
548 makes based on $TERM and other conditions.
549 $LISTEN_PID, $LISTEN_FDS, $LISTEN_FDNAMES
551 Set by systemd for supervised processes during socket-based
552 activation. See sd_listen_fds(3) for more information.
553 $NOTIFY_SOCKET
555 Set by systemd for supervised processes for status and start-up
556 completion notification. See sd_notify(3) for more information.
557 For further environment variables understood by systemd and its various
559 components, see Known Environment Variables[7].
560
562 When run as the system instance, systemd parses a number of options
563 listed below. They can be specified as kernel command line arguments
564 which are parsed from a number of sources depending on the environment
565 in which systemd is executed. If run inside a Linux container, these
566 options are parsed from the command line arguments passed to systemd
567 itself, next to any of the command line options listed in the Options
568 section above. If run outside of Linux containers, these arguments are
569 parsed from /proc/cmdline and from the "SystemdOptions" EFI variable
570 (on EFI systems) instead. Options from /proc/cmdline have higher
571 priority. The following variables are understood:
572 systemd.unit=, rd.systemd.unit=
574 Overrides the unit to activate on boot. Defaults to default.target.
575 This may be used to temporarily boot into a different boot unit,
576 for example rescue.target or emergency.service. See
577 systemd.special(7) for details about these units. The option
578 prefixed with "rd." is honored only in the initrd, while the one
579 that is not prefixed only in the main system.
580 systemd.dump_core
582 Takes a boolean argument or enables the option if specified without
583 an argument. If enabled, the systemd manager (PID 1) dumps core
584 when it crashes. Otherwise, no core dump is created. Defaults to
585 enabled.
586 systemd.crash_chvt
588 Takes a positive integer, or a boolean argument. Can be also
589 specified without an argument, with the same effect as a positive
590 boolean. If a positive integer (in the range 1–63) is specified,
591 the system manager (PID 1) will activate the specified virtual
592 terminal when it crashes. Defaults to disabled, meaning that no
593 such switch is attempted. If set to enabled, the virtual terminal
594 the kernel messages are written to is used instead.
595 systemd.crash_shell
597 Takes a boolean argument or enables the option if specified without
598 an argument. If enabled, the system manager (PID 1) spawns a shell
599 when it crashes, after a 10s delay. Otherwise, no shell is spawned.
600 Defaults to disabled, for security reasons, as the shell is not
601 protected by password authentication.
602 systemd.crash_reboot
604 Takes a boolean argument or enables the option if specified without
605 an argument. If enabled, the system manager (PID 1) will reboot the
606 machine automatically when it crashes, after a 10s delay.
607 Otherwise, the system will hang indefinitely. Defaults to disabled,
608 in order to avoid a reboot loop. If combined with
609 systemd.crash_shell, the system is rebooted after the shell exits.
610 systemd.confirm_spawn
612 Takes a boolean argument or a path to the virtual console where the
613 confirmation messages should be emitted. Can be also specified
614 without an argument, with the same effect as a positive boolean. If
615 enabled, the system manager (PID 1) asks for confirmation when
616 spawning processes using /dev/console. If a path or a console name
617 (such as "ttyS0") is provided, the virtual console pointed to by
618 this path or described by the give name will be used instead.
619 Defaults to disabled.
620 systemd.service_watchdogs=
622 Takes a boolean argument. If disabled, all service runtime
623 watchdogs (WatchdogSec=) and emergency actions (e.g. OnFailure= or
624 StartLimitAction=) are ignored by the system manager (PID 1); see
625 systemd.service(5). Defaults to enabled, i.e. watchdogs and failure
626 actions are processed normally. The hardware watchdog is not
627 affected by this option.
628 systemd.show_status
630 Takes a boolean argument or the constants error and auto. Can be
631 also specified without an argument, with the same effect as a
632 positive boolean. If enabled, the systemd manager (PID 1) shows
633 terse service status updates on the console during bootup. With
634 error, only messages about failures are shown, but boot is
635 otherwise quiet. auto behaves like false until there is a
636 significant delay in boot. Defaults to enabled, unless quiet is
637 passed as kernel command line option, in which case it defaults to
638 error. If specified overrides the system manager configuration file
639 option ShowStatus=, see systemd-system.conf(5).
640 systemd.status_unit_format=
642 Takes name, description or combined as the value. If name, the
643 system manager will use unit names in status messages. If combined,
644 the system manager will use unit names and description in status
645 messages. When specified, overrides the system manager
646 configuration file option StatusUnitFormat=, see systemd-
647 system.conf(5).
648 systemd.log_color, systemd.log_level=, systemd.log_location,
650 systemd.log_target=, systemd.log_time, systemd.log_tid
651 Controls log output, with the same effect as the
652 $SYSTEMD_LOG_COLOR, $SYSTEMD_LOG_LEVEL, $SYSTEMD_LOG_LOCATION,
653 $SYSTEMD_LOG_TARGET, $SYSTEMD_LOG_TIME, and $SYSTEMD_LOG_TID
654 environment variables described above. systemd.log_color,
655 systemd.log_location, systemd.log_time, and systemd.log_tid= can be
656 specified without an argument, with the same effect as a positive
657 boolean.
658 systemd.default_standard_output=, systemd.default_standard_error=
660 Controls default standard output and error output for services and
661 sockets. That is, controls the default for StandardOutput= and
662 StandardError= (see systemd.exec(5) for details). Takes one of
663 inherit, null, tty, journal, journal+console, kmsg, kmsg+console.
664 If the argument is omitted systemd.default-standard-output=
665 defaults to journal and systemd.default-standard-error= to inherit.
666 systemd.setenv=
668 Takes a string argument in the form VARIABLE=VALUE. May be used to
669 set default environment variables to add to forked child processes.
670 May be used more than once to set multiple variables.
671 systemd.machine_id=
673 Takes a 32 character hex value to be used for setting the
674 machine-id. Intended mostly for network booting where the same
675 machine-id is desired for every boot.
676 systemd.set_credential=
678 Sets a system credential, which can then be propagated to system
679 services using the LoadCredential= setting, see systemd.exec(5) for
680 details. Takes a pair of credential name and value, separated by a
681 colon. Note that the kernel command line is typically accessible by
682 unprivileged programs in /proc/cmdline. Thus, this mechanism is not
683 suitable for transferring sensitive data. Use it only for data that
684 is not sensitive (e.g. public keys/certificates, rather than
685 private keys), or in testing/debugging environments.
686 For further information see System and Service Credentials[8]
688 documentation.
689 systemd.import_credentials=
691 Takes a boolean argument. If false disables importing credentials
692 from the kernel command line, the DMI/SMBIOS OEM string table, the
693 qemu_fw_cfg subsystem or the EFI kernel stub.
694 quiet
696 Turn off status output at boot, much like systemd.show_status=no
697 would. Note that this option is also read by the kernel itself and
698 disables kernel log output. Passing this option hence turns off the
699 usual output from both the system manager and the kernel.
700 debug
702 Turn on debugging output. This is equivalent to
703 systemd.log_level=debug. Note that this option is also read by the
704 kernel itself and enables kernel debug output. Passing this option
705 hence turns on the debug output from both the system manager and
706 the kernel.
707 emergency, rd.emergency, -b
709 Boot into emergency mode. This is equivalent to
710 systemd.unit=emergency.target or rd.systemd.unit=emergency.target,
711 respectively, and provided for compatibility reasons and to be
712 easier to type.
713 rescue, rd.rescue, single, s, S, 1
715 Boot into rescue mode. This is equivalent to
716 systemd.unit=rescue.target or rd.systemd.unit=rescue.target,
717 respectively, and provided for compatibility reasons and to be
718 easier to type.
719 2, 3, 4, 5
721 Boot into the specified legacy SysV runlevel. These are equivalent
722 to systemd.unit=runlevel2.target, systemd.unit=runlevel3.target,
723 systemd.unit=runlevel4.target, and systemd.unit=runlevel5.target,
724 respectively, and provided for compatibility reasons and to be
725 easier to type.
726 locale.LANG=, locale.LANGUAGE=, locale.LC_CTYPE=, locale.LC_NUMERIC=,
728 locale.LC_TIME=, locale.LC_COLLATE=, locale.LC_MONETARY=,
729 locale.LC_MESSAGES=, locale.LC_PAPER=, locale.LC_NAME=,
730 locale.LC_ADDRESS=, locale.LC_TELEPHONE=, locale.LC_MEASUREMENT=,
731 locale.LC_IDENTIFICATION=
732 Set the system locale to use. This overrides the settings in
733 /etc/locale.conf. For more information, see locale.conf(5) and
734 locale(7).
735 For other kernel command line parameters understood by components of
737 the core OS, please refer to kernel-command-line(7).
738
740 systemd is only very rarely invoked directly, since it is started early
741 and is already running by the time users may interact with it.
742 Normally, tools like systemctl(1) are used to give commands to the
743 manager. Since systemd is usually not invoked directly, the options
744 listed below are mostly useful for debugging and special purposes.
745 Introspection and debugging options
747 Those options are used for testing and introspection, and systemd may
748 be invoked with them at any time:
749 --dump-configuration-items
751 Dump understood unit configuration items. This outputs a terse but
752 complete list of configuration items understood in unit definition
753 files.
754 --dump-bus-properties
756 Dump exposed bus properties. This outputs a terse but complete list
757 of properties exposed on D-Bus.
758 --test
760 Determine the initial start-up transaction (i.e. the list of jobs
761 enqueued at start-up), dump it and exit — without actually
762 executing any of the determined jobs. This option is useful for
763 debugging only. Note that during regular service manager start-up
764 additional units not shown by this operation may be started,
765 because hardware, socket, bus or other kinds of activation might
766 add additional jobs as the transaction is executed. Use --system to
767 request the initial transaction of the system service manager (this
768 is also the implied default), combine with --user to request the
769 initial transaction of the per-user service manager instead.
770 --system, --user
772 When used in conjunction with --test, selects whether to calculate
773 the initial transaction for the system instance or for a per-user
774 instance. These options have no effect when invoked without --test,
775 as during regular (i.e. non---test) invocations the service manager
776 will automatically detect whether it shall operate in system or
777 per-user mode, by checking whether the PID it is run as is 1 or
778 not. Note that it is not supported booting and maintaining a system
779 with the service manager running in --system mode but with a PID
780 other than 1.
781 -h, --help
783 Print a short help text and exit.
784 --version
786 Print a short version string and exit.
787 Options that duplicate kernel command line settings
789 Those options correspond directly to options listed above in "Kernel
790 Command Line". Both forms may be used equivalently for the system
791 manager, but it is recommended to use the forms listed above in this
792 context, because they are properly namespaced. When an option is
793 specified both on the kernel command line and as a normal command line
794 argument, the latter has higher precedence.
795 When systemd is used as a user manager, the kernel command line is
797 ignored and only the options described below are understood.
798 Nevertheless, systemd is usually started in this mode through the
799 user@.service(5) service, which is shared between all users. It may be
800 more convenient to use configuration files to modify settings (see
801 systemd-user.conf(5)), or environment variables. See the "Environment"
802 section above for a discussion of how the environment block is set.
803 --unit=
805 Set default unit to activate on startup. If not specified, defaults
806 to default.target. See systemd.unit= above.
807 --dump-core
809 Enable core dumping on crash. This switch has no effect when
810 running as user instance. Same as systemd.dump_core= above.
811 --crash-vt=VT
813 Switch to a specific virtual console (VT) on crash. This switch has
814 no effect when running as user instance. Same as
815 systemd.crash_chvt= above (but not the different spelling!).
816 --crash-shell
818 Run a shell on crash. This switch has no effect when running as
819 user instance. See systemd.crash_shell= above.
820 --crash-reboot
822 Automatically reboot the system on crash. This switch has no effect
823 when running as user instance. See systemd.crash_reboot above.
824 --confirm-spawn
826 Ask for confirmation when spawning processes. This switch has no
827 effect when run as user instance. See systemd.confirm_spawn above.
828 --show-status
830 Show terse unit status information on the console during boot-up
831 and shutdown. See systemd.show_status above.
832 --log-color
834 Highlight important log messages. See systemd.log_color above.
835 --log-level=
837 Set log level. See systemd.log_level above.
838 --log-location
840 Include code location in log messages. See systemd.log_location
841 above.
842 --log-target=
844 Set log target. See systemd.log_target above.
845 --log-time=
847 Prefix console messages with timestamp. See systemd.log_time above.
848 --machine-id=
850 Override the machine-id set on the hard drive. See
851 systemd.machine_id= above.
852 --service-watchdogs
854 Globally enable/disable all service watchdog timeouts and emergency
855 actions. See systemd.service_watchdogs above.
856 --default-standard-output=, --default-standard-error=
858 Sets the default output or error output for all services and
859 sockets, respectively. See systemd.default_standard_output= and
860 systemd.default_standard_error= above.
861
863 /run/systemd/notify
864 Daemon status notification socket. This is an AF_UNIX datagram
865 socket and is used to implement the daemon notification logic as
866 implemented by sd_notify(3).
867 /run/systemd/private
869 Used internally as communication channel between systemctl(1) and
870 the systemd process. This is an AF_UNIX stream socket. This
871 interface is private to systemd and should not be used in external
872 projects.
873 /dev/initctl
875 Limited compatibility support for the SysV client interface, as
876 implemented by the systemd-initctl.service unit. This is a named
877 pipe in the file system. This interface is obsolete and should not
878 be used in new applications.
879
881 systemd 252
882 Kernel command-line arguments systemd.unified_cgroup_hierarchy and
883 systemd.legacy_systemd_cgroup_controller were deprecated. Please
884 switch to the unified cgroup hierarchy.
885
887 The systemd Homepage[9], systemd-system.conf(5), locale.conf(5),
888 systemctl(1), journalctl(1), systemd-notify(1), daemon(7), sd-
889 daemon(3), org.freedesktop.systemd1(5), systemd.unit(5),
890 systemd.special(7), pkg-config(1), kernel-command-line(7), bootup(7),
891 systemd.directives(7)
892
894 1. Control Groups v2
895 https://docs.kernel.org/admin-guide/cgroup-v2.html
896 2. Original Design Document
898 https://0pointer.de/blog/projects/systemd.html
899 3. Interface Portability and Stability Promise
901 https://systemd.io/PORTABILITY_AND_STABILITY/
902 4. Container Interface
904 https://systemd.io/CONTAINER_INTERFACE
905 5. initrd Interface
907 https://systemd.io/INITRD_INTERFACE/
908 6. XDG Base Directory specification
910 https://standards.freedesktop.org/basedir-spec/basedir-spec-latest.html
911 7. Known Environment Variables
913 https://systemd.io/ENVIRONMENT
914 8. System and Service Credentials
916 https://systemd.io/CREDENTIALS
917 9. systemd Homepage
919 https://systemd.io/
920systemd 253 SYSTEMD(1)