[Malvern] How does linux handle IDE channels

[Keith Edmunds]

On Sat, 2 Apr 2005 19:14:46 +0100
"Robin Wilson" <r.t.wilson at rmplc.co.uk> wrote:

> Haven't tried the disk in that machine with knoppix - but have in another
> machine and it works fine. The disk is absolutley fine - I have used an
> OS  independant disk checking prog and it came out fine.

Hi Robin

Two comments: one, I have (very recently) had a disk that performed
perfectly in every way and passed all the manufacturer's diagnostics - but
I could not get it to boot Linux. So it is possible to have a disk error
that is rather subtle. Second comment: it is inadvisable to say "the disk
is absolutely fine" until you have found exactly what the problem is. Yes,
it may be further down the list of suspects, but don't remove it from that
list yet.

> Does the root partition change? It used to be hda2 - what will it change
> to?  How do I edit the grub config files?

If you move the disk from master on the primary channel (/dev/hda) to
master on the secondary channel (/dev/hdc) then you'll need to edit both
the grub configuration file and /etc/fstab on the disk.

You can edit the grub config file with any text editor. It's
usually /boot/grub/menu.lst, although on older systems it may be
/boot/grub/grub.lst. You need something like:

----------------------------------
title=My Linux system
root (hd2,1)
kernel /boot/bzImage root=/dev/hdc2
----------------------------------

Note that 'hd0' refers to the first disk (/dev/hda typically) and that the
'1' in (hd0,1) refers to the SECOND partition of that disk because grub
numbers partitions from zero (so this would typically refer to /dev/hda2).
The kernel line has the path (on the above partition) to the kernel image,
and may well be a different filename for you, and root= is the name of the
root partition to mount.

HOWEVER: I would not troubleshoot this problem in that way. I would start
by seeing if a recovery disk (I use Gentoo disks, but you can use Knoppix
or similar) boots on that system, and seeing if I could access the hard
disks. I might then download the disk drive manufacturer's diagnostics from
their website and try them. 

Keith

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