Several months ago I installed Ubuntu in an external 500MB USB disk (and on an old MacBook4,1). with a GPT Partition table and partitioned as following:
- an unique ext4 partition for Ubuntu
- one NTFS partition for datas
Everything worked fine with Grub on sda (a 500MB disk with standard osx installation and partitions).
Some days ago I installed another distro in another USB disk, also with GPT:
- a couple NTFS partitions
- unformatted 12 MB flagged as bios_grub
and installed this Grub in the external disk. Both installations does not rely on EFI to boot.
When I tried to boot the new installation a message always complained about the lack of the other partition (Ubuntu) so I did a backup and cleared the MBR.
sudo dd if=/dev/zero of=/dev/sda bs=446 count=1
Short story, after clearing (and also after restoring) the MBR I am not anymore able to boot Ubuntu and when trying to reinstall Grub from the LIVE CD I get the following message:
/usr/bin/grub-setup: warn: This GPT partition label has no BIOS Boot Partition, embedding won't be possible. /usr/bin/grub-setup: error: embedding is not possible, but this is required fro cross-disk install.
Well, how Grub installed originally at Ubuntu installation time? There is something different from grub-install procedure?
Both Ubuntu (I've installed a Grub also in it) and the other distro boot fine on another computer, but after reading a lot of posts here and there nothing worked for me and I am really confused:
how can I restore the Grub and let both disk to boot?
Without to say that I am afraid that trying the EFI way would produce nasty effects.