update-grub help

[Tom H]

On Fri, May 28, 2010 at 4:25 PM, Goh Lip <g.lip at gmx.com> wrote:
> On Sat, 29 May 2010 03:55:01 +0800
> Goh Lip <g.lip at gmx.com> wrote:
>> On Fri, 28 May 2010 14:58:29 -0400
>> Tom H <tomh0665 at gmail.com> wrote:
>>
>> Tom, you can try this out, edit one of the grub entry, as an example
>> in the following lines...
>>
>> set root='(hd0,5)'
>> search --no-floppy --fs-uuid --set xxxxxxxxxxxxxx
>>
>> edit it to.....
>> set root='(hd0,x)'           {where x is any other number, not 5}
>> search --no-floppy --fs-uuid --set xxxxxxxxxxxxxx {this line
>> unchanged}
>>
>>
>> You will still be able to boot okay as though there had been no
>> changes. This is because the 2nd line, search --no-floppy xxxxxx,
>> will set the partition specified by the uuid to root, which in this
>> example, (hd0,5). whatever the first line says.


> Further to this...
> If you remove the 2nd line and leave only the first line, then
> set root='(hd0,x)'
> will set (hd0,x) to 'root' (not /) and if (hd0,x) is wrong then it will
> not boot.

In "set root...", root is /boot/grub (and the grub developers should
have called it groot or grubroot to differentiate it from the "root="
in the linux line!)

To go back to the OP (who seems to have disappeared), it will be
vaguely/mildly interesting to see whether Suse/OpenSuse submit a patch
to grub2's search to be able to search by disk id or whether they will
do the search by uuid and then use the disk id in the linux line.
There's a one-to-one relationship between the two so uuid's uniqueness
aspect would be preserved.


> You can leave out the first line totally and just have the
> search --no-floppy --fs-uuid --set xxxxxxxxxxxxxx    to boot.
>
> You  have noted this yourself in one of your earlier messages in another
> thread.

I remember that post! I must have understood "search --set" for a
little while... :)