Comment 8 for bug 1396379

John S. Gruber (jsjgruber) wrote :

I had specifically selected the new efi partition on a removable drive as the place to install the boot loader, yet ubiquity ignored that and installed grub and a grub.cfg file on the computers non-removable hard disk. The newly installed efi/ubuntu/grub.cfg file specifies that the grub menu be loaded from the new removable Ubuntu file system.

This all works OK if the removable drive is not removed. If it is removed then grub (obviously) can't find the newly installed file system and will no longer look for the old one. The result is a "grub> " prompt and a failure to boot.

During the problematic install the old EFI partition was mounted on /boot/efi, as described above.

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If this has happened to a future reader of this bug report, you should be able to boot manually by reinstalling the removable drive, if available.

If it isn't available the grub prompt can be used to find and use the original installs grub menus and boot normally. The grub installed to EFI partitions is quite full featured.

Find the available drives by entering the 'ls' command. Most commonly you will need hd0. Use commands such as 'ls (hd0)' to display the partitions on the various drives, substituting for the '0'. Examine the partitions with the command 'ls (hd0,6)/boot/grub' to find the partition you had been booting Ubuntu from, substituting for the '0' and '6'.

Once found, load its menu with, for example, the command:

configfile (hd0,6)/boot/grub/grub.cfg

and then boot your original Ubuntu installation from your hard disk using the resulting menu.

By the way, drives are numbered starting with 0, partitions are numbered starting with 1.

Once you have been able to boot your old Ubuntu install you should reinstall grub to reinstall the EFI/ubuntu/grub.cfg file to the hard drive EFI partition. Then you should be back where you started (before using Ubiquity to install to the removable disk.)