Hard drive weirdness.

David Gibb degibb at gmail.com
Wed Jul 23 17:14:38 UTC 2008


Things are getting better! But I'm not quite there yet...

I did:

device (hd0) /dev/sdc
root (hd0,0)
setup (hd0)
quit

And I rebooted. I changed my bios settings to boot from 'IDE-0', and
then I got a grub Error 17:  Cannot mount selected partition...

Oops. Forget to change the menu.lst. I changed root from (hd2,0) to
(hd0,0), rebooted, and it worked ok. The root (pata) drive is at
/dev/sdc. Great!

Now I tried removing both sata drives. It boots ok, but I noticed that
the the root drive is now set to /dev/sda.

When I remove a sata drive, root is set to /dev/sdb, and mdadm
--detail /dev/md0 tells me that the md device does not appear to be
active. I'm just guessing here, but could this be because it's
confused by the fact that one of the raid drives (sdb) is already
mounted as root?

Anyway, I think you see where I'm going here. My problem is that raid
expects the drives to be /dev/sda and /dev/sdb, but that's only the
case when all three drives are running. When a drive goes missing, the
'space' in the lettering is filled by the pata drive, and my raid
device gets all confused.

Thanks again for all your help,
David

On Wed, Jul 23, 2008 at 12:26 PM, Rashkae <ubuntu at tigershaunt.com> wrote:
> David Vincent wrote:
>
>>
>> 2.  in ubuntu install "gparted" in your favorite manner either with
>> synaptic or the add/remove programs app or apt-get or whatever.  open
>> gparted (found under the System menu in Administration) and locate your
>> /dev/sdb drive.  right-click the partition and see what flags are set on
>> it.  click the "boot" flag if it isn't ticked.  click "ok"
>>
>
> This step is... useless. Won't hurt anything, but doesn't achieve
> anything.  It doesn't matter to grub which partition is or is not marked
> bootable.. Unless you are doing something exotic by mixing MS-DOS chain
> loader MTBR with grub, marking partitions as bootable has no effect.
> You would need to setup grub on each device for grub to boot from either
> hard drive.  However, since in this case, the /boot resides outside the
> raid, you can't boot if the root drive is dead anyhow, so there is no
> point in making the raid members bootable.
>
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