Comment 18 for bug 47768

I think I have found the cause of the issue. It seems that the udev persistent storage rules that should be found in the initrd under the directory {initrd}/etc/udev/rules.d/65-persistent-storage.rules don't exist for some unknown reason. It is my belief that since grub only passes a UUID to indicate the root storage device, the kernel is unable to make the correlation with out this file in it's initrd.

I checked to verify that the appropriate statement existed in /usr/share/initramfs-tools/hooks/udev to copy that file into the initrd and it does. It may not have when my machine made the initrd originally, I have no idea.

A simple `sudo apt-get --reinstall install linux-generic` should do the trick of fixing this problem.

attached is the initrd cpio archive that contains the missing edev rule set