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