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 systemd switches to the shutdown.target
o systemd starts
/lib/systemd/system/shutdown.target.wants/dracut-shutdown.service
o dracut-shutdown.service executes
/usr/lib/dracut/dracut-initramfs-restore which unpacks the
initramfs to /run/initramfs
o systemd finishes shutdown.target
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 umount 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 04/06/2024 DRACUT-SHUTDOWN.S(8)