systemctl

Commands

Unit Commands

Unit commands are used for introspection and modification.

In unit commands (and unit file commands?), UNIT specifies a (single) unit name while PATTERN… specifies multiple units.

Unit name suffix

The type of the unit is separated from the unit name by a dot. If the type is omitted, systemctl appends a suitable suffix (typically .service but type specific suffixes are possible).

So, the following four commands are equivalent:

systemctl start sshd
systemctl start sshd.service

These two are also equivalent:

systemctl isolate default
systemctl isolate default.target

Absolute path names are converted to device unit names or mount unit names

These two commands are equivalent

systemctl status /dev/sda
systemctl status dev-sda.device

List of commands

`list-units [PATTERN…]`	Compare with `list-unit-files`
`list-automounts [PATTERN…]`
`list-sockets [PATTERN…]`
`list-timers [PATTERN…]`
`is-active PATTERN…`
`is-failed PATTERN…`
`status [PATTERN…\|PID…]]`
`show [PATTERN…\|JOB…]`	Show properties of units, jobs or the manager itself. Compare with `set-property`
`cat PATTERN…`
`help PATTERN…\|PID…`
`list-dependencies [UNIT…]`
`start PATTERN…`	Start the specified units (i. e. activate them)
`stop PATTERN…`
`reload PATTERN…`
`restart PATTERN…`
`try-restart PATTERN…`
`reload-or-restart PATTERN…`
`try-reload-or-restart PATTERN…`
`isolate UNIT`
`kill PATTERN…`
`clean PATTERN…`
`freeze PATTERN…`
`thaw PATTERN…`
`set-property UNIT PROPERTY=VALUE…`	Compare with `show` and the `-p` (or `--property`) options.
`bind UNIT PATH [PATH]`
`mount-image UNIT IMAGE [PATH [PARTITION_NAME:MOUNT_OPTIONS]]`
`service-log-level SERVICE [LEVEL]`
`service-log-target SERVICE [TARGET]`
`reset-failed [PATTERN…]`

Unit File Commands

`list-unit-files [PATTERN…]`	Compare with `list-units`
`enable UNIT…`, `enable PATH…`	Enables the specified units by creating symlinks as specified in the `[Install]` sections of the corresponding unit files.
`disable UNIT…`	Disables the specified unit.
`reenable UNIT…`
`preset UNIT…`
`preset-all`
`is-enabled UNIT…`	Check if a unit is enabled.
`mask UNIT…`
`unmask UNIT…`
`link PATH…`
`revert UNIT…`
`add-wants TARGET UNIT…`, `add-requires TARGET UNIT…`
`edit UNIT…`
`get-default`	Returns the target (unit name `default.target`) into which the system is booted by default. (Apparently, if the Kernel command line contains `single` (and also other words?), the default can be or is overrwritten)
`set-default TARGET`

Machine Commands

There is only one machine command: list-machines [PATTERN…].

Job Commands

`list-jobs [PATTERN…]`
`cancel JOB…`

Environment Commands

systemd supports an environment block that is passed to processes the manager spawns. The names of the variables can contain ASCII letters, digits, and the underscore character. Variable names cannot be empty or start with a digit. In variable values, most characters are allowed, but the whole sequence must be valid UTF-8. (Note that control characters like newline (NL), tab (TAB), or the escape character (ESC), are valid ASCII and thus valid UTF-8). The total length of the environment block is limited to _SC_ARG_MAX value defined by sysconf(3).

`show-environment`
`set-environment VARIABLE=VALUE…`
`unset-environment VARIABLE…`
`import-environment VARIABLE…`

Manager State Commands

`daemon-reload`
`daemon-reexec`
`log-level [LEVEL]`
`log-target [TARGET]`
`service-watchdogs [yes\|no]`

System Commands

`is-system-running`
`default`
`rescue`
`emergency`
`halt`
`poweroff`
`reboot`
`kexec`
`exit [EXIT_CODE]`
`switch-root ROOT [INIT]`
`suspend`	Triggers the target unit `system.target` in order to suspends the system.
`hibernate`	TODO: Requires enough swap space, apparently
`hybrid-sleep`
`suspend-then-hibernate`

Options

`-t`	`--type=`	Restricts command to the indicated (comma separated list) unit type.
	`--state=`
`-p`	`--property=`	See also the `set-property` and `show` commands.
	`-P`
`-a`	`--all`
`-r`	`--recursive`
	`--reverse`
	`--after`
	`--before`
	`--with-dependencies`
`-l`	`--full`
	`--value`
	`--show-types`
	`--job-mode=`
`-T`	`--show-transaction`
	`--fail`
	`--check-inhibitors=`
`-i`		Shortcut for `--check-inhibitors=no`.
	`--dry-run`
`-q`	`--quiet`
	`--no-warn`
	`--no-block`
	`--wait`
	`--user`
	`--system`
	`--failed`
	`--no-wall`
	`--global`
	`--no-reload`
	`--no-ask-password`
	`--kill-whom=`
`-s`	`--signal=`
	`--what=`
`-f`	`--force`
	`--message=`
	`--now`
	`--root=`
	`--image=image`
	`--runtime`
	`--preset-mode=`
`-n`	`--lines=`
`-o`	`--output=`
	`--firmware-setup`
	`--boot-loader-menu=timeout`
	`--boot-loader-entry=ID`
	`--reboot-argument=`
	`--plain`
	`--timestamp=`
	`--mkdir`
	`--marked`
	`--read-only`
`-H`	`--host=`
`-M`	`--machine=`
	`--no-pager`
	`--legend=BOOL`
`-h`	`--help`
	`--version`

name.service files

systemctl reads name.service files. These files define how and when services (daemons) should be started.

These service files are located in /usr/lib/systemd/system. (Possibly also in /run/systemd/system or /etc/systemd/system).

Enabling a service

systemctl enable avahi-daemon.service

Starting a service

systemctl start avahi-daemon.service

Showing the status

Without arguments, systemctl status shows the system status.