Serious GRUB booting problem after install Ubuntu 9.10beta for testing it.

[Tom H]

Luis Maceira <luis_a_maceira at yahoo.com> wrote:

> I installed 9.10 beta for testing it on an external
> USB HDD partition (/dev/sdb7), and I have 9.04 on
> /dev/sdb5 (where the default GRUB stage2 is), I
> also have 9.04 on the internal SSD drive (partition
> /dev/sda3). Now I am not able to boot Ubuntu 9.04
> on my internal SSD drive.

> When I disconnect my external USB HDD the booting
> process gives me:

> GRUB loading...
> error: no such disk
> grub rescue>_

> When the external USB HDD is connected and I call
> the GRUB menu and it appears, the system (9.04) on
> the internal SSD appears normally on the GRUB menu
> (I think everything is OK) choose booting the SSD
> but then the warning:

> Error 17 : cannot mount selected partition
> Press any key to continue...
> (and return back to GRUB menu)

> From my working systems 9.04 and 9.10 on the USB
> HDD I mount the filesystem on the internal SSD and
> everything appears OK even the /boot/grub directory,
> so in my opinion the installer of Ubuntu 9.10 beta
> messed up with GRUB stage 1 on the MBR of the internal
> SSD and the way to the right partition /dev/sda3 is
> lost.

> Any way to revert this? without installing Ubuntu
> from scratch on the internal SSD.

Since you are at the "grub rescue" prompt when you try to boot from
your internal SSD and no external HD connected, you must have grub2
installed on your SSD.

grub rescue> ls

It should list your disk and its partitions.

grub rescue> root (hd0,X)
Where X is your "/" partition (or your "/boot" partition, if it is separate).

grub rescue> ls /boot
To confirm that you have "rooted" the correct partition.
If you have, you should see your kernel, initrd, etc and the grub directory.
If not, do another "root (hd0,X)" and try again.

Once you have the correct "root (hd0,X)".

grub rescue> insmod /boot/grub/normal.mod
To go to the normal grub prompt.

grub> insmod /boot/grub/ext2.mod
To load ext2 module.

grub> ls /boot
If you cannot see the output of the previous "ls /boot" and cannot
remember the file names of the kernel and initrd.

grub> linux /boot/vmlinuz-2.6.31-13-generic root=/dev/sda3 ro
To load the kernel.

grub> initrd /boot/initrd.img-2.6.31-13-generic
To load the initrd.

grub> boot
To boot.

You should boot into your SSD install.

Once booted, you should run "grub-install /dev/sda" to ensure that
your SSD's grub.cfg is updated/corrected and you should then check it.

Then connect the HDD and run "update-grub" to add the two HDD installs
to the SSD's grub.cfg.

(I would also check that the device.map and grub.cfg disk references
correspond.)