Wily: kernel fails to boot on ppc64el after cloud-init install & reboot

[Brad Figg]

This is an attempted install of Wily via MaaS.

The system times out trying to find a rood device:

Begin: Loading essential drivers ... done.
Begin: Running /scripts/init-premount ... done.
Begin: Mounting root file system ... Begin: Running /scripts/local-top ... Begin: Loading multipath modules ... Success: loaded module dm-multipath.
Failure: failed to load module dm-emc.
done.
Begin: Discovering multipaths ... done.
  Warning: Disk has a valid GPT signature but invalid PMBR.
  Assuming this disk is *not* a GPT disk anymore.
  Use gpt kernel option to override. Use GNU Parted to correct disk.
done.
Begin: Running /scripts/local-premount ... Begin: Waiting for udev to settle (multipath) ... done.
done.
Gave up waiting for root device. Common problems:
 - Boot args (cat /proc/cmdline)
   - Check rootdelay= (did the system wait long enough?)
   - Check root= (did the system wait for the right device?)
 - Missing modules (cat /proc/modules; ls /dev)
ALERT! /dev/mapper/mpath0-part2 does not exist. Dropping to a shell!
[ 220.697138] hidraw: raw HID events driver (C) Jiri Kosina
[ 220.699043] usbcore: registered new interface driver usbhid
[ 220.699089] usbhid: USB HID core driver

BusyBox v1.22.1 (Ubuntu 1:1.22.0-15ubuntu1) built-in shell (ash)
Enter 'help' for a list of built-in commands.

(initramfs)