Rettungssytem gebootet, boot gemountet vor chroot:

  /usr/sbin/grub-setup: warning: your core.img is unusually large. It won't fit in the embedding area.
  /usr/sbin/grub-setup: error: embedding is not possible, but this is

Lösung:
  * chroot in zielsystem
  * dann /boot mounten

http://www.imaginaryindustries.com/blog/?p=149