Ext2/Ext3 partition label abuse

Hi!

I have a RedHat 7.2 machine installed from scratch. Recently I installed RedHat 7.2 on another machine that has two harddisks (/dev/hda and /dev/hdc) The second is in a removable bay.
Linux was installed on /dev/hdc.

My main machine also has a hdd bay (/dev/hdc) and I have put the new machine's removable hdd into the main one and booted up. (I had to copy some files and no network between the machines.)

On boot I had strange errors that said that this and that partitions cannot be found. I observed the following.

The / partition contains the main machine's data from /dev/hda2 although the mount command lists / as mounted from /dev/hdcX. Every other partitions are mounted from /dev/hdc.

The problem is that /etc/fstab as used by RedHat, lists the partition by LABEL=/mountpoint which labels can be found on both /dev/hda and /dev/hdc.

The /proc/partitions "file" lists the partitions in disk-reversed order, e.g.:

/dev/hdc1 ....
...
/dev/hdc10 ...
/dev/hda1 ...
...
/dev/hda9 ...

Is there a way to fix this? Yes there is: vendors should not use LABEL=XXX method in /etc/fstab. Either use the proper device/partition or the UUID. The downside is that fsck messages would not be as pretty-printed as now. Or maybe the partitions should not be registered in disk-reversed order...

Best regards,
Zoltán Böszörményi

On Fri, Mar 08, 2002 at 10:49:00AM +0100, Boszormenyi Zoltan wrote:

[I had two disks with the same labels on one machine and that caused problems with booting]

Yes, if you have an fstab file that says: mount the filesystem with label "ROOTDISK" on /, and then come with two filesystems that both are labeled "ROOTDISK", then it is hardly surprising when problems arise. The same will happen if you use UUID instead of label but created the other disk by copying the first using dd.

You can change fstab for example with an editor. You can change labels for example with the e2label utility.

Labels have an advantage for example when you add or remove a SCSI disk:
the label stays the same but the disks are renumbered.
Also when you add or remove partitions, causing a renumbering. Using UUID is slightly more stable, slightly less user-friendly.

Attaching a significance to the order of items in /proc/partitions is a bad idea.

It would be nice if the raid code could do that with drive serial numbers...

Followup to:  <[email protected]>
By author:    Boszormenyi Zoltan <[email protected]>
In newsgroup: linux.dev.kernel

Or maybe mount(8) should signal an error if a label is ambiguous instead of mounting a random partition.

-hpa

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"Unix gives you enough rope to shoot yourself in the foot."
http://www.zytor.com/~hpa/puzzle.txt	<[email protected]>