SYSTEMD-HALT.SERVICE(8) systemd-halt.service SYSTEMD-HALT.SERVICE(8)
NAME
systemd-halt.service, systemd-poweroff.service, systemd-reboot.service, systemd-kexec.service, systemd-
shutdown - System shutdown logic
SYNOPSIS
systemd-halt.service
systemd-poweroff.service
systemd-reboot.service
systemd-kexec.service
/usr/lib/systemd/systemd-shutdown
DESCRIPTION
systemd-halt.service is a system service that is pulled in by halt.target and is responsible for the actual
system halt. Similarly, systemd-poweroff.service is pulled in by poweroff.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 tool
which is then responsible for the actual shutdown. Before shutting down, this binary will try to unmount all
remaining file systems, 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.
Immediately before executing the actual system halt/poweroff/reboot/kexec systemd-shutdown will run all
executables in /usr/lib/systemd/system-shutdown/ and pass one arguments to them: either "halt", "poweroff",
"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 systemd-halt.service (and the related units) should never be executed directly. Instead, trigger
system shutdown with a command such as "systemctl halt" or suchlike.
SEE ALSO
systemd(1), systemctl(1), systemd.special(7), reboot(2), systemd-suspend.service(8)
systemd 219 SYSTEMD-HALT.SERVICE(8)
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