UUIDs in fstab

[John Summerfield]

Scott Robbins wrote:
> On Wed, Apr 30, 2008 at 12:35:41AM -0400, Christopher L Tubbs II wrote:
> 
>> Has anybody noticed that F9-pre installer creates an /etc/fstab file based on 
>> UUIDs instead of LABELs? I seem to remember everybody all worked up about 
>> LABELs instead of the traditional /dev/sda2 type identifiers, in order to 
>> simplify changes to hard drive configuration. But now, all of a sudden I've got 
>> this 32-character long UUID that makes everything complicated again.
>>
> 
> This was discussed awhile back on the list.  Take a quick look through
> the archives--probably last month.  

I think there's been discussion on the anaconda list too.

> 
> There are reasons for it.  Whether they're really good reasons or not is
> beyond my knowledge, so I made no comments.  

Labels are inherently broken, as others have noted. At one time, on one 
system, I was multibooting two RHEL betas, opensuse 10, sles10 and 
Fedora Core 6.

SCSI disks tend to change their names too, depending on the order 
they're recognised and (maybe) whether they're hotplugged.

I discovered my HP DC7700 got thoroughly confused about its disks when I 
added a second SATA drive; the BIOS tried to boot the wrong drive. I 
don't know whether it was me, the BIOS or the documents, I just shuffled 
cables to positions that worked.

I don't much liked UUIDs either (I had problems duplicating disks when 
RH introduced labels) and UUIDs don't solve the problems I had. And they 
may introduce new problems: try cloning a disk thus:

fdisk -l /dev/sda
fdisk /dev/sdb # create a suitable new partition layout
mke2fs /dev/sdb1 # etc
mount ...
tar clC <source mount> . | tar xpC <target mount>
etc

If the intent is to clone the system on sda, then the partitions on sdb 
have different UUIDs (as they should) and the fstab needs to be updated.

If, as is possible with a little fiddling, one copies with dd, then the 
UUIDs are duplicated, and if one then reboots _I_ don't know which gets 
mounted, but it's likely it's the wrong one!






-- 

Cheers
John

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