[SOLVED] system disk moves from /dev/sda to /dev/sdm

gdevaucorbeil · 03-09-2007, 02:05 PM

Hardware: IBM x3950 with 2 SAS drives configured as hardware raid and an exp3000 filled with 12 disks.

Linux: Redhat Enterprise 4 Update 4

Here is what I did:

I plugged a SAS controler from LSI in a PciX slot.

I installed Linux and used the box for a while without any problems.

Then I shutdown the server and plugged a exp3000 into the server and turned the exp3000 on, then turn the server on.

The server does not boot anymore now. It complains about fsck.ext2 not finding the device.

It seems the system disk is now /dev/sdm instead of /dev/sda.

I tried installing redhat again as a test, and the redhat install sees the system disk as /dev/sdm too (I see it easily because it is the only device that is 36GB, the data disks are 300GB).

both the system disks and data disks are SAS. Is this why the disk device of the system disk changes?

How can I fix this so I can add or remove data disks and Linux still boots?

macemoneta · 03-09-2007, 02:21 PM

You want to use disk labels for booting, not device addresses, which can change as you discovered.

For example, in /etc/grub.conf:

kernel /vmlinuz-x.y.z ro root=LABEL=/ quiet

You can label drives with tune2fs for EXT2/EXT3 (from 'man tune2fs'):

Quote:

-L volume-label
Set the volume label of the filesystem. Ext2 filesystem labels
can be at most 16 characters long; if volume-label is longer
than 16 characters, tune2fs will truncate it and print a warn-
ing. The volume label can be used by mount(8), fsck(8), and
/etc/fstab(5) (and possibly others) by specifying LABEL=vol-
ume_label instead of a block special device name like /dev/hda5.

gdevaucorbeil · 03-10-2007, 08:55 AM

Thanks macemoneta. It almost works. I don't know how it will work for my swap partition.

I tried tune2fs on my ext2 and ext3 partitions.
I modified /etc/fstab accordingly.
And that worked. So I suppose it will work on the real server

But how do I do for the swap partition. This is not a ext2 or ext3 partition of course!

Any good idea for this?

macemoneta · 03-10-2007, 09:17 AM

Similarly, in /etc/fstab, for example:

Code:

LABEL=SWAP-SDA3  swap swap defaults    0 0

You label swap when you initialize it. From 'man mkswap':

Quote:

-L label
Specify a label, to allow swapon by label. (Only for new style
swap areas.)

So on your server, either:

- If swap is critical to operation: boot to run level 1, reinitialize and label the swap areas, and update /etc/fstab, then reboot.
- If you can run without swap for a while: swapoff -a, reinitialize and label the swap areas, and update /etc/fstab, swapon -a

gdevaucorbeil · 03-10-2007, 09:30 AM

Looks clear. Thanks for the prompt answer.
I'll try this on the server.