Manual: systemd-poweroff.service

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

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 259.5											 SYSTEMD-POWEROFF.SERVICE(8)