SYSTEMD-POWEROFF.SERVICE(8)			      systemd-poweroff.service

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

       /usr/lib/systemd/systemd-shutdown

       /usr/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
       /usr/lib/systemd/systemd-shutdown binary 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
       /usr/lib/systemd/system-shutdown/. Those executables are called with
       one argument: 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. (A safety timeout of 90s is applied
       however.) Note that these executables are run after all services have
       been shut down, and after most mounts have been unmounted (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".

       Another form of shutdown is provided by the systemd-soft-
       reboot.service(8) functionality. It reboots only the OS userspace,
       leaving the kernel, firmware, and hardware as it is.

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

systemd 258					   SYSTEMD-POWEROFF.SERVICE(8)