Manual: systemd-sleep

SYSTEMD-SUSPEND.SERVICE(8)			   systemd-suspend.service			  SYSTEMD-SUSPEND.SERVICE(8)

NAME
       systemd-suspend.service, systemd-hibernate.service, systemd-hybrid-sleep.service, systemd-suspend-then-
       hibernate.service, systemd-sleep - System sleep state logic

SYNOPSIS
	   systemd-suspend.service
	   systemd-hibernate.service
	   systemd-hybrid-sleep.service
	   systemd-suspend-then-hibernate.service
	   /usr/lib/systemd/system-sleep

DESCRIPTION
       systemd-suspend.service is a system service that is pulled in by suspend.target and is responsible for the actual
       system suspend. Similarly, systemd-hibernate.service is pulled in by hibernate.target to execute the actual
       hibernation. Finally, systemd-hybrid-sleep.service is pulled in by hybrid-sleep.target to execute hybrid hibernation
       with system suspend and pulled in by suspend-then-hibernate.target to execute system suspend with a timeout that will
       activate hibernate later.

       Immediately before entering system suspend and/or hibernation systemd-suspend.service (and the other mentioned units,
       respectively) will run all executables in /usr/lib/systemd/system-sleep/ and pass two arguments to them. The first
       argument will be "pre", the second either "suspend", "hibernate", "hybrid-sleep", or "suspend-then-hibernate"
       depending on the chosen action. An environment variable called "SYSTEMD_SLEEP_ACTION" will be set and contain the
       sleep action that is processing. This is primarily helpful for "suspend-then-hibernate" where the value of the
       variable will be "suspend", "hibernate", or "suspend-after-failed-hibernate" in cases where hibernation has failed.
       Immediately after leaving system suspend and/or hibernation the same executables are run, but the first argument is
       now "post". All executables in this directory are executed in parallel, and execution of the action is not continued
       until all executables have finished. Note that user.slice will be frozen while the executables are running, so they
       should not attempt to communicate with any user services expecting a reply.

       Note that scripts or binaries dropped in /usr/lib/systemd/system-sleep/ are intended for local use only and should be
       considered hacks. If applications want to react to system suspend/hibernation and resume, they should rather use the
       Inhibitor Locks[1].

       Note that systemd-suspend.service, systemd-hibernate.service, systemd-hybrid-sleep.service, and
       systemd-suspend-then-hibernate.service should never be executed directly. Instead, trigger system sleep with a
       command such as systemctl suspend or systemctl hibernate.

       Internally, this service will echo a string like "mem" into /sys/power/state, to trigger the actual system suspend.
       What exactly is written where can be configured in the [Sleep] section of /etc/systemd/sleep.conf or a sleep.conf.d
       file. See systemd-sleep.conf(5).

       Note that by default these services freeze user.slice while they run. This prevents the execution of any process in
       any of the user sessions while the system is entering into and resuming from sleep. Thus, this prevents the hooks in
       /usr/lib/systemd/system-sleep/, or any other process for that matter, from communicating with any user session
       process during sleep.

OPTIONS
       systemd-sleep understands the following commands:

       -h, --help
	   Print a short help text and exit.

       --version
	   Print a short version string and exit.

       suspend, hibernate, suspend-then-hibernate, hybrid-sleep
	   Suspend, hibernate, suspend then hibernate, or put the system to hybrid sleep.

	   Added in version 203.

SEE ALSO
       systemd-sleep.conf(5), systemd(1), systemctl(1), systemd.special(7), systemd-halt.service(8)

NOTES
	1. Inhibitor Locks
	   https://systemd.io/INHIBITOR_LOCKS

systemd 259.5											  SYSTEMD-SUSPEND.SERVICE(8)