GRUB2 install from a chroot environment and a loop device

Question

I created a 10 GB raw .img, formatted it as EXT4 and "rsync'd" my system inside. The plan is to reinstall GRUB2 to its MBR and convert it to .vdi (VirtualBox). I know how to do all that, it's not as difficult as it sounds.
sudo modprobe loop
sudo losetup /dev/loop5 /media/Backup/backup.img
sudo mount -o offset=$((2048 * 512)) /dev/loop5 /mnt
cd /mnt
for i in /proc /sys /dev; do sudo mount -B $i .$i; done
sudo chroot .
sudo grub-install /dev/loop5
sudo grub-mkconfig -o /boot/grub/grub.cfg
(Interesting way to chroot, right?)
...except after converting the .img to .vdi (VBoxManage convertfromraw --format VDI /path/to/backup.img /path/to/backup.vdi), I'm getting:
GRUB loading.
Welcome to GRUB!
error: no such device: 557e19c8-e89b-4661-a1dc-2a3ce3b2064e
Entering rescue mode...
grub rescue> _
However, reinstalling it by hooking up a LiveCD to the VM works:
mount /dev/sda1 /mnt
cd /mnt
for i in /proc /sys /dev; do mount -B $i .$i; done
chroot .
grub-install /dev/sda
grub-mkconfig -o /boot/grub/grub.cfg
It seems to like /dev/sda more than /dev/loop5.
Why is that?
I should mention that the VM's UUID for /dev/sda is the same as /dev/loop5 on the computer.
Last edited by DSpider (2012-07-08 16:14:06)

Answer 1

*bump* I know this thread is older then old, but I have exactly the same problem. It seems that there used to be a workaround (http://superuser.com/questions/130955/h … n-img-file) which has no effect anymore.
The reason I need to do it with loop is, that I'm writing a script for automated virtual-disk creation. So booting a live system is not an option.
Help anybody?