Working With Disk Labels in RHEL

When you install RHEL, the filesystems are labeled for you. Usually you won’t have to mess with it anymore, but on occasion, you may want to change them to more accurately represent the data that is stored on that partition. If, for instance, you used to have all of your database files on a partition labeled “/database”, but you have now moved them somewhere else, and you now wish to house your user account data there, it would make sense to change the label to something like “/users”.

Labels are, of course, arbitrary, so there is no technical need to do this, and you could, instead simply change the mount point in the fstab file, mounting the partition by device name rather than label, but it is usually cleaner to change the label. Here is how you do it:

First, let’s figure out what the partition is currently labeled as:

[root@calvin /]# /sbin/e2label /dev/hda4
[root@calvin /]#

It’s current label is “/database”, and, since we have moved the database data somewhere else, we now want to store our user account data here, we need to change it to “/users”.

[root@calvin /]# /sbin/e2label /dev/hda4 /users
[root@calvin /]#

That’s all there is to it, now we check to make sure we have done what we think we have done.

[root@calvin /]# /sbin/e2label /dev/hda4
[root@calvin /]#

Sure enough, it’s now labeled “/users” and the data on the disk remains intact. Now all we have to do is change the appropriate entry in the “/etc/fstab” file to represent the change.

Change this:

LABEL=/database       /databases            ext3    defaults        1 2

To this:

LABEL=/users          /users                ext3    defaults        1 2

And you’re all set to go. Make sure you have unmounted “/databases” before making the change.

Now, just run:
[root@calvin /]# mount /users
[root@calvin /]#

And you’re all set to go. As always, change the values here to represent those in your environment.

Changing Linux Mount Points

If you’re familiar with UNIX, you know that changing mount points is really pretty easy. All you have to do is go into “/etc/fstab”, “/etc/vfstab” (or whatever your flavor of UNIX happens to call its filesystem table) and change the mount directory.

If, for instance, you had a Solaris box, and you wanted to make the disk currently mounted as “/data” be mounted as “/database”, all you would have to do is the following:

# umount /data
# mv /data /database
Change this line in “/etc/vfstab” from something like this:
/dev/dsk/c1d0s6 /dev/rdsk/c1d0s6 /data ufs 1 yes –
to something like this:
/dev/dsk/c1d0s6 /dev/rdsk/c1d0s6 /database ufs 1 yes –
and remount it as “/database”.
# mount /database

With Linux, however, it’s not quite so clear anymore… It’s still easy, but it’s just not so clear what you have to do since they have now taken to mounting filesystems using the volume label. Rather than pointing directly to the disk device, Linux points to the label, and “/etc/fstab” look more like this:

LABEL=/data /data ext3 defaults 1 2

You can always simply change the disk label, but if you don’t care, you can just tell linux where the raw device is, bypassing the need to worry about the label. The easiest way to do this is simply to replace the “LABEL=/data” value to the “/dev” entry of the disk itself. Then, simply change “/data” to “/database” and you’re all set.

Here is an example of what you would do to change the mountpoint of “/data” to /database”:

# umount /data
# mv /data /database
Change this line in “/etc/fstab” from this:
LABEL=/data /data ext3 defaults 1 2
to this:
/dev/sda6 /database ext3 defaults 1 2
and remount it as /database
# mount /database

Remembering to change the example values here with those required for your situation.