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HTML rendering created 2025-09-06 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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NAME | SYNOPSIS | DESCRIPTION | SEE ALSO | COLOPHON |
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SYSTEMD-P...F.SERVICE(8) systemd-poweroff.serviceSYSTEMD-P...F.SERVICE(8)
systemd-poweroff.service, systemd-halt.service, systemd-
reboot.service, systemd-kexec.service, systemd-shutdown - System
shutdown logic
systemd-poweroff.service
systemd-halt.service
systemd-reboot.service
systemd-kexec.service
/usr/lib/systemd/systemd-shutdown
/usr/lib/systemd/system-shutdown/
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.
systemd(1), systemctl(1), systemd.special(7), reboot(2),
systemd-suspend.service(8), systemd-soft-reboot.service(8),
bootup(7)
This page is part of the systemd (systemd system and service
manager) project. Information about the project can be found at
⟨http://www.freedesktop.org/wiki/Software/systemd⟩. If you have a
bug report for this manual page, see
⟨http://www.freedesktop.org/wiki/Software/systemd/#bugreports⟩.
This page was obtained from the project's upstream Git repository
⟨https://github.com/systemd/systemd.git⟩ on 2025-08-11. (At that
time, the date of the most recent commit that was found in the
repository was 2025-08-11.) If you discover any rendering
problems in this HTML version of the page, or you believe there is
a better or more up-to-date source for the page, or you have
corrections or improvements to the information in this COLOPHON
(which is not part of the original manual page), send a mail to
man-pages@man7.org
systemd 258~rc2 SYSTEMD-P...F.SERVICE(8)
Pages that refer to this page: bootup(7), systemd.directives(7), systemd.index(7), systemd.special(7), systemd-soft-reboot.service(8), systemd-suspend.service(8)
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HTML rendering created 2025-09-06 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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