In the kernel comments PARTUUID is shown using uppercase A-F:
http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/init/do_mounts.c?id=HEAD#n183
However, dracut tries to use the value of PARTUUID directly in
/dev/disks/by-partuuid/ which expects the hex to be lowercase. This will
cause root to never be found, oops!
Fix dracut so it can, like the Kernel, accept either casing.
Untested but I added a hack on my local system that was similar.
Now init checks that we understood the root= option, and can
act upon it, presenting and error if not. Also, clean up the
generation of udev rules such that we don't require /bin/echo.