update-grub help

[Goh Lip]

On Fri, 28 May 2010 14:58:29 -0400
Tom H <tomh0665 at gmail.com> wrote:

> On Wed, May 26, 2010 at 11:37 PM, Goh Lip <g.lip at gmx.com> wrote:
> > On 05/27/2010 11:03 AM, Tom H wrote:
> >> On Wed, May 26, 2010 at 10:48 PM, Goh Lip<g.lip at gmx.com>  wrote:
> >>> On 05/27/2010 03:23 AM, Goh Lip wrote:

> >
> > Yes, understood. Got it. But when Dave deletes the "search xxxxxx
> > set xxx", this means using the set root=(hdx,y) which is unreliable
> > and will set that as the root. Even if he specify kernel
> > correctly,as in "linux /boot/vmlinuz-xxx xxxxx
> > root=/dev/disk/by-id/xxxxxx", his "root partition" may be wrong and
> > will not boot.
> 
> If the "set root=(hdx,y)" is unreliable, then the "search ..." is
> unreliable too because it only sets a uuid to the first partition that
> it finds, 

"sets" means setting that partition as root, not setting the uuid and
therefore means setting the partition specified by that uuid.


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.

Hope this is clear. 
Appreciate your query - makes both of us better.

Regards - Goh Lip