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:

       •   The system starts to shut down

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

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

       •   systemd kills all processes

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

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

       •   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.

       •   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)