DRACUT-SHUTDOWN.S(8)                dracut                DRACUT-SHUTDOWN.S(8)

NAME
       dracut-shutdown.service - unpack the initramfs to /run/initramfs

SYNOPSIS
       dracut-shutdown.service

DESCRIPTION
       This service unpacks the initramfs image to /run/initramfs. systemd
       pivots into /run/initramfs at shutdown, so the root filesystem can be
       safely unmounted.

       The following steps are executed during a shutdown:

       o   The system starts to shut down

       o   ``$prefix/lib/systemd/system/sysinit.target.wants/dracut-shutdown.service``
           gets its ``ExecStop`` target triggered.

       o   ``dracut-shutdown.service`` executes
           ``/usr/lib/dracut/dracut-initramfs-restore`` which unpacks the
           initramfs to ``/run/initramfs``

       o   systemd kills all processes

       o   systemd tries to unmount everything and mounts the remaining
           read-only

       o   systemd checks if there is a ``/run/initramfs/shutdown`` executable

       o   if yes, it does a pivot_root to ``/run/initramfs`` and executes
           ``./shutdown``. The old root is then mounted on ``/oldroot``.
           ``/usr/lib/dracut/modules.d/99shutdown/shutdown.sh`` is the
           shutdown executable.

       o   shutdown will try to unmount every ``/oldroot`` mount and calls the
           various shutdown hooks from the dracut modules

       This ensures, that all devices are disassembled and unmounted cleanly.

       To debug the shutdown process, you can get a shell in the shutdown
       procedure by injecting "rd.break=pre-shutdown rd.shell" or
       "rd.break=shutdown rd.shell".

           # mkdir -p /run/initramfs/etc/cmdline.d
           # echo "rd.break=pre-shutdown rd.shell" > /run/initramfs/etc/cmdline.d/debug.conf
           # touch /run/initramfs/.need_shutdown

       In case the unpack of the initramfs fails,
       dracut-shutdown-onfailure.service executes to make sure switch root
       doesn't happen, since it would result in switching to an incomplete
       initramfs.

AUTHORS
       Harald Hoyer

SEE ALSO
       dracut(8)

dracut                            10/13/2024              DRACUT-SHUTDOWN.S(8)