Re: Grub rescue

[David WE Roberts]

On Tue, 26 Mar 2013 12:07:59 -0700, Jordan Uggla wrote:

> On Tue, Mar 26, 2013 at 6:50 AM, David WE Roberts
> <address@hidden> wrote:
>>
>> Test #3
>>
>> Installed Ubuntu 12.04 64 bit to the partition on the GPT drive where
>> it was previously installed.
>>
>> Nominated MBR drive as boot drive.
>>
>> Same failure as Test #2.
>>
>> Now, of course, I can't boot anything because when I revert back to a
>> full MBR configuration core.img is set up for GPT partitions so can't
>> see the MBR partitions, although it can see both MBR discs.
>>
>> About to rerun Test #2 on the MBR configuration to reset core.img (I
>> hope).
> 
> I am very confused about what you're trying to accomplish, and even more
> confused about what you've done up to this point. There is no reason
> that you should need to get stuck at a grub rescue shell when
> transitioning from an msdos label to a GPT label if you run grub-install
> properly (meaning, passing the device whose boot sector your BIOS is
> going to load, and if needed a proper --boot-directory argument, no
> --modules argument should ever be necessary) after making any
> partitioning changes. Please re-run grub-install (without --modules) and
> note down the exact command you ran, as well as the output of "mount"
> when you ran grub-install, and post both. If after that grub-install
> command you're still not able to boot, please run boot info script
> http://bootinfoscript.sourceforge.net/ from a LiveCD/USB or other
> working GNU/Linux installation and post the RESULTS.txt that it
> produces.

Please read back up thread (a few words added to hopefully clarify).

"Boot from Ubuntu 12.04 Live CD into the 'Try Ubuntu' option.

start up Terminal

within the terminal window:

sudo bash

mount /dev/sdb2/ /mnt/

[ls to confirm correct filestore mounted]

grub-install --boot-directory=/mnt/boot /dev/sda

[I believe this meets your requirements for running 'grub-install' without 
a --modules argument.]

reboot, and get

error: no such device: 28ba1903-0731-40e2*8ce2-55e5597293c2

*Then at the grub rescue prompt *

$ set

prefix=(hd0,2)/boot/grub

root=hd0,2

$ ls

(hd0)
"

Please not that I have run grub-install on an ext2 partition on a GPT disc.

This (as you have already described) has built core.img with module 
'part_gpt' instead of 'part_msdos'.

The result is that grub cannot see any partitions (although it does still 
recognise the MBR disc ).

>From this I deduce that grub does not recognise the GPT disc.

With 'part_gpt' in use, the MBR disc is seen but not the partitions.
With 'part_msdos' in use, the MBR disc and the partitions are seen, but 
still no sign of the GPT disc.

This suggests that the basic problem is that grub just can't see the GPT 
disc and so has no chance of identifying partitions on the disc.

Hope this is becoming clear.

David