Any script placed in /pre-udev will be sourced just before udev starts
device scanning and loading.
Any script placed in /pre-mount will be sourced just before we try to
mount a root filesystem.
Any script placed in /pre-pivot will be sourced just before we switch to the
new root filesystem.
These hooks should be the minimum needed to add back plymouth and deal with
more advanced filesysem mounting needs (multipath, iscsi, nfs, nbd, etc.)
This is for tasks that should run after device discovery, but before
mounting the new rootfs. Things like cryptoroot and resume from hibernate
should go here.
Hooks are sourced, not executed as separate scripts.