dracut-shutdown.service.8

DRACUT−SHUTDOWN.S

NAME
SYNOPSIS
DESCRIPTION
AUTHORS
SEE ALSO

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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)

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