Re: Grub rescue

[David WE Roberts]

On Tue, 26 Mar 2013 12:38:51 +0000, David WE Roberts wrote:

> On Tue, 26 Mar 2013 11:46:41 +0000, David WE Roberts wrote:
> 
>> On Sun, 24 Mar 2013 23:47:24 +0400, Andrey Borzenkov wrote:
>> 
>>> В Sun, 24 Mar 2013 16:58:55 +0000 (UTC)
>>> David WE Roberts <address@hidden> пишет:
>>> 
>>>> On Sun, 24 Mar 2013 16:14:48 +0000, David WE Roberts wrote:
>>>> 
>>>> > Should grub rescue started from an MBR disc be able to see GPT
>>>> > partitions?
>> 
>> <snip>
>> 
>>> If you still can boot in original configuration, reinstall grub while
>>> explicitly adding part_gpt:
>>> 
>>> grub-install --modules=part_gpt ...
>>> 
>>> If you cannot return to original configuration - just follow boot
>>> recovery procedure for your distro.
>> 
>> Done that.
>> 
>> When I disconnect the original MBR data drive and connect the new GPT
>> data drive and boot grub of the MBR disc and go into grub rescue
>> 
>> I still find that 'ls' can only see one drive, the one with the MSDOS
>> partitions on.
>> 
>> If I 'insmod part_gpt' it does not complain, but still can't see the
>> GPT drive.
>> 
>> Not enough in core.img to chain load Windows either.
> 
> Test #2
> 
> Boot from Ubuntu 12.04 Live CD into 'Try'
> 
> startup Terminal
> 
> sudo bash
> 
> mount /dev/sdb2/ /mnt/
> 
> [ls to confirm correct filestore mounted]
> 
> grub-install --boot-directory=/mnt/boot /dev/sda
> 
> reboot, and get
> 
> error: no such device: 28ba1903-0731-40e2*8ce2-55e5597293c2
> 
>  >set
> 
> prefix=(hd0,2)/boot/grub
> 
> root=hd0,2
> 
>>ls
> 
> (hd0)
> 
> 
> So as far as I can see grub-install has installed grub on /dev/sda and
> set up core.img to cope with a GPT disc and correctly identified the
> disc and that /boot/grub and /root are on partition 2 of the disc.
> 
> When the initial bit of grub starts to load, it is unable to see the GPT
> disc (no such device:) and reverts to the only disc it can see, the MBR
> disc.
> 
> However it hasn't got the module 'part_msdos' included so it can't even
> see the partitions on the MBR disc.
> 
> [I checked this - at the grub rescue> prompt insmode part_gpt worked,
> insmod part_msdos failed.]
> 
> So I think this is a bug not a feature.
> 
> It looks as though currently the only way that I can get my GPT disc up
> and running using grub2 from an MBR disc is to have /boot/grub in a
> separate mini-partition on the MBR disc. Assuming even that works.
> 
> I will try a full install of Ubuntu 12.04 onto the GPT disc, nominating
> the MBR disc as the location for grub, and see what happens.
> However I fully expect the same failure.
> 
> Bug: grub 2 on initial boot does not correctly support GPT discs with
> the module 'part_gpt'.
> It fails to recognise the disc or the partitions.
> 
> Note that the discs are configured in AHCI mode.

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).

Cheers

Dave R