Comment 3 for bug 1352038

For other users encountering this issue on Ubuntu 14.04.2 the workaround is pretty much identical to the Xubuntu commands posted in the initial description. I've pasted them below for reference:

sudo -i
mount /dev/mapper/ubuntu--vg-root /mnt
cp /boot/* /mnt/boot
umount /mnt
ltsp-update-image -c /
exit