Re: Debian 6 / Grub 2 problem

.....
On 16/10/11 18:54, cr wrote:
> I've got three hard disks, a 40GB Seagate (which I use for Linux distros), a
> 160GB Seagate for data, and a 500GB WD SATA for data.   The BIOS sees them in
> that order.
Are 40GB and 160GB drives PATA?

>
> And yes, changing my boot sequence in the BIOS found the new Grub2 menu, on
> the 500GB  WD SATA.
>
> Complications persist though -
>
> Debian Lenny sees them as /dev/hda,  /dev/hdc and /dev/sda, whether booted
> from Grub on /hda or Grub2 on sda.
>
> Debian Squeeze, if booted from Grub, sees them as /dev/sda (40GB), /dev/sdb
> (160GB), and /dev/sdc in that order.

IIRC between lenny and squeeze the way PATA/SATA/SCSI drives are 
detected changed so they are all detected as scsi in squeeze (and other 
current distros too) whereas lenny used older detection system, that is 
why the difference I think.

> If booted from Grub2, it sees them as
> /dev/sdb, /dev/sdc and /dev/sda.   I assume Squeeze gets its drive ID's from
> Grub.

You could try (Squeeze from grub1, sda is 40GB sdc is SATA 500GB). Look 
in /boot/grub/device.map to check grub's drive mappings, if necessary 
run grub-install --recheck /dev/sdc to update the mappings then check 
/boot/grub/device.map again. Post back if the mappings are not updated 
correctly as per bios order. You can also manually change drive mappings 
by editing /boot/grub/device.map
If device.map correct run grub-install /dev/sda to activate -- Beware, 
this will replace your current grub1 mbr with grub2, it would pay to 
backup your mbr before running above. You could also test without 
affecting default boot order by installing to /dev/sdc and changing bios 
boot order or select 500GB SATA from bios Boot menu.

> This obviously leads to complications in Squeeze with identifying my data
> partitions in /etc/fstab, since it changes according to which Grub I boot it
> off.   I was hoping to shun UUID's which look like digital garbage.
> I suppose I shall have to bite the bullet and fill my /etc/fstab with UUID's
> (why do they have to be so damn _long_  - I could tolerate 12 digits like MAC
> addresses!).
>   Can somebody confirm, do these UUID's remain the same no matter which drive
> the system was booted from?

They will only change if the filesystem changes, eg you format it. UUIDs 
are the way forward I think so might as well get used to them now.

>
> Then I'll hafta try and get Grub2 installed on the MBR of my 40GB drive (since
> booting a system on one drive off the MBR of another seems like setting up for
> trouble next time I shuffle drives around).
> Which raises the question, why did Debian install the system on one hard drive
> and the Grub boot stage on another anyway?
Debian installed system and grub where it was told to like a good OS 
should. ;)  There should be no problems booting one drive off another's 
mbr that is how the mbr system works, but I think you are right about 
grub2 being part of the solution to this problem (see above).

HTH
Ross.



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