NAME

       systemd-poweroff.service, systemd-halt.service, systemd-reboot.service, systemd-
       kexec.service, systemd-shutdown - System shutdown logic

SYNOPSIS

       systemd-poweroff.service

       systemd-halt.service

       systemd-reboot.service

       systemd-kexec.service

       /lib/systemd/systemd-shutdown

       /lib/systemd/system-shutdown/

DESCRIPTION

       systemd-poweroff.service is a system service that is pulled in by poweroff.target and is
       responsible for the actual system power-off operation. Similarly, systemd-halt.service is
       pulled in by halt.target, systemd-reboot.service by reboot.target and
       systemd-kexec.service by kexec.target to execute the respective actions.

       When these services are run, they ensure that PID 1 is replaced by the
       /lib/systemd/systemd-shutdown tool which is then responsible for the actual shutdown.
       Before shutting down, this binary will try to unmount all remaining file systems (or at
       least remount them read-only), disable all remaining swap devices, detach all remaining
       storage devices and kill all remaining processes.

       It is necessary to have this code in a separate binary because otherwise rebooting after
       an upgrade might be broken — the running PID 1 could still depend on libraries which are
       not available any more, thus keeping the file system busy, which then cannot be re-mounted
       read-only.

       Shortly before executing the actual system power-off/halt/reboot/kexec systemd-shutdown
       will run all executables in /lib/systemd/system-shutdown/ and pass one arguments to them:
       either "poweroff", "halt", "reboot", or "kexec", depending on the chosen action. All
       executables in this directory are executed in parallel, and execution of the action is not
       continued before all executables finished. Note that these executables are run after all
       services have been shut down, and after most mounts have been detached (the root file
       system as well as /run/ and various API file systems are still around though). This means
       any programs dropped into this directory must be prepared to run in such a limited
       execution environment and not rely on external services or hierarchies such as /var/ to be
       around (or writable).

       Note that systemd-poweroff.service (and the related units) should never be executed
       directly. Instead, trigger system shutdown with a command such as "systemctl poweroff".

SEE ALSO

       systemd(1), systemctl(1), systemd.special(7), reboot(2), systemd-suspend.service(8),
       bootup(7)