My setup has Ubuntu Precise on sda4 (an SSD).
I am backing up to sdb2 (an HD) and would like it to be bootable (as a rescue system).
After copying the files (rsync) i chroot and update-grub. But the
grub.cfg has no entries for the ORIGINAL system (sda4) until i really boot into the rescue system and do the update-grub THERE. Whereas update-grub on the ORIGINAL system always has entries for both systems (which is expected).
This effectively relies on grub-install to sda and if i happen to lose the MBR (or the dr, i would have to resort do some CD booting life. But i DO HAVE grub2 installed to sdb (even a bios-grub partition there) and want to be independent of sda (just in case).
I tried copying
/$chroot/etc/mtab but that did not help. Also read the internet, tried on my own, lost DAYS but not success. What am i missing in the chroot environment?