et aussi dans un chroot http://forums.debian.net/viewtopic.php?t=52283

 mount /dev/sdb1 /media/disk
 mount -o bind /sys /media/disk/sys
 mount -t proc /proc /media/disk/proc
 mount -o bind /dev /media/disk/dev
 chroot /media/disk

run the command, exit chroot, umount all stuff and reboot.