Thank you Justus. I appreciate your help.
The .img file contains a partition table and multiple partitions, so you cannot just dd it to a partition. You could try (as root, from the top of my head): # kpartx -a your/image/file ... says something about partitions being found and added # cat /dev/mapper/imagesomehtingp1 >/dev/sdXY Then, re-run update-grub and it should find and detect Debian/Hurd and add a grub entry for it. Justus