Manual: systemd-kexec.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)