Provided by: systemd_229-4ubuntu21.31_amd64 bug


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








       systemd-halt.service is a system service that is pulled in by and is
       responsible for the actual system halt. Similarly, systemd-poweroff.service is pulled in
       by, systemd-reboot.service by and systemd-kexec.service by 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, disable
       all remaining swap devices, detach all remaining storage devices and kill all remaining

       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

       Immediately before executing the actual system halt/poweroff/reboot/kexec systemd-shutdown
       will run all executables in /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.


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