About /etc/fstab and LABELs

[Ed Wilts]

On Fri, Oct 07, 2005 at 12:57:03AM +0300, Kostas Sfakiotakis wrote:
> Ed Wilts wrote:
> 
> >Labels can save you from MAJOR problems in a lot of specific situations.
> >Imagine that you have 3 disks, sda, sdb, and sdc.  Now imagine that sdb
> >fails hard.  
> >
> Well the problem is that sdb failled and the DATA whatever
> they were are gone !!! and certainly there is no label trick
> that is going to save someone from that .

No, but you should not lose other data because of it.  Predictability in
system configurations is what keeps us employed. 

> >You reboot and what was sdc is now sdb.  You will mount
> >that filesystem on the wrong mount point and suddenly cause yourself all
> >sorts of grief and possible disk corruption depending on how well
> >behaved your applications are.  Imagine that sdb was your backup drive
> >and you did an rsync --delete from sda to sdb automatically via cron or
> >in rc.local.  Kiss all the data that was on sdc goodbye
> > 
> Well i thought there was a Rescue mode in Linux . Since there is
> a disaster rescue mode can be used to edit the scripts so they
> reflect the current situation .

You're assuming you caught the issue in time.  What if your swap file
was on sdb?  Your system will likely crash, it will hopefully come up
but sdc becomes sdb.  You may come up without swap.

The whole point is to make sure that the system actions are predictable
- what is sdc today will always be sdc - the mount point follows the
physical disk.

The same problem came occur if you add a drive - there's no guarantee
that your system will scan the drives in the same order when you come
up after the drive install.

-- 
Ed Wilts, RHCE
Mounds View, MN, USA
mailto:ewilts at ewilts.org
Member #1, Red Hat Community Ambassador Program