логика выключения системы (System shutdown logic)
Имя (Name)
systemd-halt.service, systemd-poweroff.service, systemd-
reboot.service, systemd-kexec.service, systemd-shutdown - System
shutdown logic
Синопсис (Synopsis)
systemd-halt.service
systemd-poweroff.service
systemd-reboot.service
systemd-kexec.service
/usr/lib/systemd/systemd-shutdown
/usr/lib/systemd/system-shutdown/
Описание (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.
Смотри также (See also)
systemd(1), systemctl(1), systemd.special(7), reboot(2),
systemd-suspend.service(8), bootup(7)
