NAME
systemd, init - systemd system and service managerSYNOPSIS
/lib/systemd/systemd
[OPTIONS...]
init
[OPTIONS...] {COMMAND}
DESCRIPTION
systemd is a system and service manager for Linux operating systems. When run as first process on boot (as PID 1), it acts as init system that brings up and maintains userspace services. Separate instances are started for logged-in users to start their services. systemd is usually not invoked directly by the user, but is installed as the /sbin/init symlink and started during early boot. The user manager instances are started automatically through the user@.service(5) service. For compatibility with SysV, if the binary is called as init and is not the first process on the machine (PID is not 1), it will execute telinit and pass all command line arguments unmodified. That means init and telinit are mostly equivalent when invoked from normal login sessions. See telinit(8) for more information. When run as a system instance, systemd interprets the configuration file system.conf and the files in system.conf.d directories; when run as a user instance, systemd interprets the configuration file user.conf and the files in user.conf.d directories. See systemd-system.conf(5) for more information.CONCEPTS
systemd provides a dependency system between various entities called "units" of 11 different types. Units encapsulate various objects that are relevant for system boot-up and maintenance. The majority of units are configured in unit configuration files, whose syntax and basic set of options is described in systemd.unit(5), however some are created automatically from other configuration files, 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.
On first boot, systemd will enable or disable units according to preset
policy. See systemd.preset(5) and "First Boot Semantics" in
machine-id(5).
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
Control Groups v2[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/), 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 Portability and Stability Promise[3].
Units may be generated dynamically at boot and system manager reload time, for
example based on other configuration files or parameters passed on the kernel
command line. For details, see systemd.generator(7).
The D-Bus API of systemd is described in
org.freedesktop.systemd1(5) and org.freedesktop.LogControl1(5).
Systems which invoke systemd in a container or initrd environment should
implement the Container Interface[4] or initrd Interface[5]
specifications, respectively.
DIRECTORIES
System unit directoriesThe 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 /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
SIGTERMUpon 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+25
Upon receiving this signal the systemd manager
will reexecute itself. This is mostly equivalent to systemctl
daemon-reexec except that it will be done asynchronously.
The systemd system manager treats this signal the same way as
SIGTERM.
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
The environment block for the system manager is initially set by the kernel. (In particular, "key=value" assignments on the kernel command line are turned into environment variables for PID 1). For the user manager, the system manager sets the environment as described in the "Environment Variables in Spawned Processes" section of systemd.exec(5). The DefaultEnvironment= setting in the system manager applies to all services including [email protected]. Additional entries may be configured (as for any other service) through the Environment= and EnvironmentFile= settings for [email protected] (see systemd.exec(5)). Also, additional environment variables may be set through the ManagerEnvironment= setting in systemd-system.conf(5) and systemd-user.conf(5). Some of the variables understood by systemd: $SYSTEMD_LOG_LEVELThe maximum log level of emitted messages
(messages with a higher log level, i.e. less important ones, will be
suppressed). Either one of (in order of decreasing importance) emerg,
alert, crit, err, warning, notice,
info, debug, or an integer in the range 0...7. See
syslog(3) for more information.
This can be overridden with --log-level=.
$SYSTEMD_LOG_COLOR
A boolean. If true, messages written to the
tty will be colored according to priority.
This can be overridden with --log-color=.
$SYSTEMD_LOG_TIME
A boolean. If true, console log messages will
be prefixed with a timestamp.
This can be overridden with --log-time=.
$SYSTEMD_LOG_LOCATION
A boolean. If true, messages will be prefixed
with a filename and line number in the source code where the message
originates.
This can be overridden with --log-location=.
$SYSTEMD_LOG_TID
A boolean. If true, messages will be prefixed
with the current numerical thread ID (TID).
$SYSTEMD_LOG_TARGET
The destination for log messages. One of
console (log to the attached tty), console-prefixed (log to the
attached tty but with prefixes encoding the log level and
"facility", see syslog(3), kmsg (log to the kernel
circular log buffer), journal (log to the journal),
journal-or-kmsg (log to the journal if available, and to kmsg
otherwise), auto (determine the appropriate log target automatically,
the default), null (disable log output).
This can be overridden with --log-target=.
$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 paths.
Otherwise, the specified list replaces the usual set of paths.
$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.
Note: if $SYSTEMD_PAGERSECURE is not set, $SYSTEMD_PAGER (as well
as $PAGER) will be silently ignored.
$SYSTEMD_LESS
Override the options passed to less (by
default "FRSXMK").
Users might want to change two options in particular:
K
Note that setting the regular $LESS environment variable has no effect
for less invocations by systemd tools.
See less(1) for more discussion.
$SYSTEMD_LESSCHARSET
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.
Override the charset passed to less (by
default "utf-8", if the invoking terminal is determined to be UTF-8
compatible).
Note that setting the regular $LESSCHARSET environment variable has no
effect for less invocations by systemd tools.
$SYSTEMD_PAGERSECURE
Takes a boolean argument. When true, the
"secure" mode of the pager is enabled; if false, disabled. If
$SYSTEMD_PAGERSECURE is not set at all, secure mode is enabled if the
effective UID is not the same as the owner of the login session, see
geteuid(2) and sd_pid_get_owner_uid(3). In secure mode,
LESSSECURE=1 will be set when invoking the pager, and the pager shall
disable commands that open or create new files or start new subprocesses. When
$SYSTEMD_PAGERSECURE is not set at all, pagers which are not known to
implement secure mode will not be used. (Currently only less(1)
implements secure mode.)
Note: when commands are invoked with elevated privileges, for example under
sudo(8) or pkexec(1), care must be taken to ensure that
unintended interactive features are not enabled. "Secure" mode for
the pager may be enabled automatically as describe above. Setting
SYSTEMD_PAGERSECURE=0 or not removing it from the inherited environment
allows the user to invoke arbitrary commands. Note that if the
$SYSTEMD_PAGER or $PAGER variables are to be honoured,
$SYSTEMD_PAGERSECURE must be set too. It might be reasonable to
completely disable the pager using --no-pager instead.
$SYSTEMD_COLORS
Takes a boolean argument. When true,
systemd and related utilities will use colors in their output,
otherwise the output will be monochrome. Additionally, the variable can take
one of the following special values: "16", "256" to
restrict the use of colors to the base 16 or 256 ANSI colors, respectively.
This can be specified to override the automatic decision based on $TERM
and what the console is connected to.
$SYSTEMD_URLIFY
The value must be a boolean. Controls whether
clickable links should be generated in the output for terminal emulators
supporting this. This can be specified to override the decision that
systemd makes based on $TERM and other conditions.
$LISTEN_PID, $LISTEN_FDS, $LISTEN_FDNAMES
Set by systemd for supervised processes during
socket-based activation. See sd_listen_fds(3) for more
information.
$NOTIFY_SOCKET
Set by systemd for supervised processes for
status and start-up completion notification. See sd_notify(3) for more
information.
For further environment variables understood by systemd and its various
components, see Known Environment Variables[7].
KERNEL COMMAND LINE
When run as the system instance, systemd parses a number of options listed below. They can be specified as kernel command line arguments which are parsed from a number of sources depending on the environment in which systemd is executed. If run inside a Linux container, these options are parsed from the command line arguments passed 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 and from the "SystemdOptions" EFI variable (on EFI systems) instead. Options from /proc/cmdline have higher priority. The 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 initrd, while the one that is not
prefixed only in the main system.
systemd.dump_core
Takes a boolean argument or enables the option
if specified without an argument. If enabled, the systemd manager (PID 1)
dumps core when it crashes. Otherwise, no core dump is created. Defaults to
enabled.
systemd.crash_chvt
Takes a positive integer, or a boolean
argument. Can be also specified without an argument, with the same effect as a
positive boolean. If a positive integer (in the range 1–63) is
specified, the system manager (PID 1) will activate the specified virtual
terminal when it crashes. Defaults to disabled, meaning that no such switch is
attempted. If set to enabled, the virtual terminal the kernel messages are
written to is used instead.
systemd.crash_shell
Takes a boolean argument or enables the option
if specified without an argument. If enabled, the system manager (PID 1)
spawns a shell when it crashes, after a 10s delay. Otherwise, no shell is
spawned. Defaults to disabled, for security reasons, as the shell is not
protected by password authentication.
systemd.crash_reboot
Takes a boolean argument or enables the option
if specified without an argument. If enabled, the system manager (PID 1) will
reboot the machine automatically when it crashes, after a 10s delay.
Otherwise, the system will hang indefinitely. Defaults to disabled, in order
to avoid a reboot loop. If combined with systemd.crash_shell, the
system is rebooted after the shell exits.
systemd.confirm_spawn
Takes a boolean argument or a path to the
virtual console where the confirmation messages should be emitted. Can be also
specified without an argument, with the same effect as a positive boolean. If
enabled, the system manager (PID 1) asks for confirmation when spawning
processes using /dev/console. If a path or a console name (such as
"ttyS0") is provided, the virtual console pointed to by this path or
described by the give name will be used instead. Defaults to disabled.
systemd.service_watchdogs=
Takes a boolean argument. If disabled, all
service runtime watchdogs ( WatchdogSec=) and emergency actions (e.g.
OnFailure= or StartLimitAction=) are ignored by the system
manager (PID 1); see systemd.service(5). Defaults to enabled, i.e.
watchdogs and failure actions are processed normally. The hardware watchdog is
not affected by this option.
systemd.show_status
Takes a boolean argument or the constants
error and auto. Can be also specified without an argument, with
the same effect as a positive boolean. If enabled, the systemd manager (PID 1)
shows terse service status updates on the console during bootup. With
error, only messages about failures are shown, but boot is otherwise
quiet. auto behaves like false until there is a significant
delay in boot. Defaults to enabled, unless quiet is passed as kernel
command line option, in which case it defaults to error. If specified
overrides the system manager configuration file option ShowStatus=, see
systemd-system.conf(5).
systemd.status_unit_format=
Takes name, description or
combined as the value. If name, the system manager will use unit
names in status messages. If combined, the system manager will use unit
names and description in status messages. When 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, systemd.log_tid
Controls log output, with the same effect as
the $SYSTEMD_LOG_COLOR, $SYSTEMD_LOG_LEVEL,
$SYSTEMD_LOG_LOCATION, $SYSTEMD_LOG_TARGET,
$SYSTEMD_LOG_TIME, and $SYSTEMD_LOG_TID environment variables
described above. systemd.log_color, systemd.log_location,
systemd.log_time, and systemd.log_tid= 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.set_credential=
Sets a system credential, which can then be
propagated to system services using the LoadCredential= setting, see
systemd.exec(5) for details. Takes a pair of credential name and value,
separated by a colon. Note that the kernel command line is typically
accessible by unprivileged programs in /proc/cmdline. Thus, this mechanism is
not suitable for transferring sensitive data. Use it only for data that is not
sensitive (e.g. public keys/certificates, rather than private keys), or in
testing/debugging environments.
For further information see System and Service Credentials[8]
documentation.
systemd.import_credentials=
Takes a boolean argument. If false disables
importing credentials from the kernel command line, the DMI/SMBIOS OEM string
table, the qemu_fw_cfg subsystem or the EFI kernel stub.
quiet
Turn off status output at boot, much like
systemd.show_status=no would. Note that this option is also read by the
kernel itself and disables kernel log output. Passing this option hence turns
off the usual output from both the system manager and the kernel.
debug
Turn on debugging output. This is equivalent
to systemd.log_level=debug. Note that this option is also read by the
kernel itself and enables kernel debug output. Passing this option hence turns
on the debug output from both the system manager and the kernel.
emergency, rd.emergency, -b
Boot into emergency mode. This is equivalent
to systemd.unit=emergency.target or
rd.systemd.unit=emergency.target, respectively, and provided for
compatibility reasons and to be easier to type.
rescue, rd.rescue, single, s, S, 1
Boot into rescue mode. This is equivalent to
systemd.unit=rescue.target or rd.systemd.unit=rescue.target,
respectively, and provided for compatibility reasons and to be easier to
type.
2, 3, 4, 5
Boot into the specified legacy SysV runlevel.
These are equivalent to systemd.unit=runlevel2.target,
systemd.unit=runlevel3.target, systemd.unit=runlevel4.target,
and systemd.unit=runlevel5.target, respectively, and provided for
compatibility reasons and to be easier to type.
locale.LANG=, locale.LANGUAGE=, locale.LC_CTYPE=,
locale.LC_NUMERIC=, locale.LC_TIME=, locale.LC_COLLATE=,
locale.LC_MONETARY=, locale.LC_MESSAGES=,
locale.LC_PAPER=, locale.LC_NAME=, locale.LC_ADDRESS=,
locale.LC_TELEPHONE=, locale.LC_MEASUREMENT=,
locale.LC_IDENTIFICATION=
Set the system locale to use. This overrides
the settings in /etc/locale.conf. For more information, see
locale.conf(5) and locale(7).
For other kernel command line parameters understood by components of the core
OS, please refer to kernel-command-line(7).
OPTIONS
systemd is only very rarely invoked directly, since it is started early and is already running by the time users may interact with it. Normally, tools like systemctl(1) are used to give commands to the manager. Since systemd is usually not invoked directly, the options listed below are mostly useful for debugging and special purposes.Introspection and debugging options
Those options are used for testing and introspection, and systemd may be invoked with them at any time: --dump-configuration-itemsDump understood unit configuration items. This
outputs a terse but complete list of configuration items understood in unit
definition files.
--dump-bus-properties
Dump exposed bus properties. This outputs a
terse but complete list of properties exposed on D-Bus.
--test
Determine the initial start-up transaction
(i.e. the list of jobs enqueued at start-up), dump it and exit —
without actually executing any of the determined jobs. This option is useful
for debugging only. Note that during regular service manager start-up
additional units not shown by this operation may be started, because hardware,
socket, bus or other kinds of activation might add additional jobs as the
transaction is executed. Use --system to request the initial
transaction of the system service manager (this is also the implied default),
combine with --user to request the initial transaction of the per-user
service manager instead.
--system, --user
When used in conjunction with --test,
selects whether to calculate the initial transaction for the system instance
or for a per-user instance. These options have no effect when invoked without
--test, as during regular (i.e. non---test) invocations the
service manager will automatically detect whether it shall operate in system
or per-user mode, by checking whether the PID it is run as is 1 or not. Note
that it is not supported booting and maintaining a system with the service
manager running in --system mode but with a PID other than 1.
-h, --help
Print a short help text and exit.
--version
Print a short version string and exit.
Options that duplicate kernel command line settings
Those options correspond directly to options listed above in "Kernel Command Line". Both forms may be used equivalently for the system manager, but it is recommended to use the forms listed above in this context, because they are properly namespaced. When an option is specified both on the kernel command line and as a normal command line argument, the latter has higher precedence. When systemd is used as a user manager, the kernel command line is ignored and only the options described below are understood. Nevertheless, systemd is usually started in this mode through the user@.service(5) service, which is shared between all users. It may be more convenient to use configuration files to modify settings (see systemd-user.conf(5)), or environment variables. See the "Environment" section above for a discussion of how the environment block is set. --unit=Set default unit to activate on startup. If
not specified, defaults to default.target. See systemd.unit=
above.
--dump-core
Enable core dumping on crash. This switch has
no effect when running as user instance. Same as systemd.dump_core=
above.
--crash-vt=VT
Switch to a specific virtual console (VT) on
crash. This switch has no effect when running as user instance. Same as
systemd.crash_chvt= above (but not the different spelling!).
--crash-shell
Run a shell on crash. This switch has no
effect when running as user instance. See systemd.crash_shell=
above.
--crash-reboot
Automatically reboot the system on crash. This
switch has no effect when running as user instance. See
systemd.crash_reboot above.
--confirm-spawn
Ask for confirmation when spawning processes.
This switch has no effect when run as user instance. See
systemd.confirm_spawn above.
--show-status
Show terse unit status information on the
console during boot-up and shutdown. See systemd.show_status
above.
--log-color
Highlight important log messages. See
systemd.log_color above.
--log-level=
Set log level. See systemd.log_level
above.
--log-location
Include code location in log messages. See
systemd.log_location above.
--log-target=
Set log target. See systemd.log_target
above.
--log-time=
Prefix console messages with timestamp. See
systemd.log_time above.
--machine-id=
Override the machine-id set on the hard drive.
See systemd.machine_id= above.
--service-watchdogs
Globally enable/disable all service watchdog
timeouts and emergency actions. See systemd.service_watchdogs
above.
--default-standard-output=, --default-standard-error=
Sets the default output or error output for
all services and sockets, respectively. See
systemd.default_standard_output= and
systemd.default_standard_error= above.
SOCKETS AND FIFOS
/run/systemd/notifyDaemon 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.
HISTORY
systemd 252Kernel command-line arguments
systemd.unified_cgroup_hierarchy and
systemd.legacy_systemd_cgroup_controller were deprecated. Please switch
to the unified cgroup hierarchy.
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), org.freedesktop.systemd1(5), systemd.unit(5), systemd.special(7), pkg-config(1), kernel-command-line(7), bootup(7), systemd.directives(7)NOTES
- 1.
- Control Groups v2
- 2.
- Original Design Document
- 3.
- Interface Portability and Stability Promise
- 4.
- Container Interface
- 5.
- initrd Interface
- 6.
- XDG Base Directory specification
- 7.
- Known Environment Variables
- 8.
- System and Service Credentials
- 9.
- systemd Homepage
systemd 252 |