The response from Pat technically is correct.  However, we have faced 
this problem and have a work around that still involves a fresh install.

To do this install, the only viable solution we have found is to use 
partitions, not true logical volumes, as the fresh install will not 
damage any partitions but those assigned to

/  (root)

/boot

/usr

/bin

/etc

and will not overwrite /home if specified not to do so.

We keep as separate partitions /opt , /usr1 , /usr/local , /lib-back and 
within /usr1 , /usr1/etc-back , /usr1/share-back, /usr1/lib-back, and 
the like (1.1 copy from the untouched old disk the contents of the above 
partitions and
so that vital configuration files such as passwd and shadow are not 
touched and do not need to be re-created).  We keep a hardcopy of the IP 
address, DNS name of the node, gateway IP address, and similar network 
information for the node upon which we are installing.

thus, one has two choices:

1.  install a blank harddrive, install partitions including the above 
using a manual disk layout, install SLNx (N being 6 now, and soon 7). 
One then uses dd from the old partition to the new blank partition (tar, 
cp -PR, and other methods probably will work as well)

2.  Assuming that the overwritten partitions on the existing disk are 
large enough, simply allow the install to overwrite (smash) these, but 
do not allow the "saved" partitions to be touched by the install.  Then 
one simply makes certain that entries fro the mount table in the saved 
etc-back directory tree is edited into the current mount table from the 
new install.

Does anyone know how to do the above with the logical volume management 
(lvm) or other replacements for partitions that is the currently 
recommended layout for a disk?

Yasha Karant

On 07/23/2013 11:17 AM, Pat Riehecky wrote:
> It is not possible to upgrade from the 5x branch to the 6x branch.  A
> fresh install is required.
>
> Pat
>
> On 07/23/2013 01:02 PM, Jeffrey Anderson wrote:
>> I hope this is an appropriate place for this question.
>>
>> I have a box running the CERN variant of SL 5.  I want to upgrade it
>> to SLC6.  When I boot from the install media it fails to find the old
>> installation and only gives me the option to do a fresh install.  Is
>> it possible to upgrade SLC5 to SLC6?
>>
>> Thanks,
>> Jeff
>> --
>> --------------------------------------------------------------

>> Jeffrey Anderson                        | [log in to unmask]
>> <mailto:[log in to unmask]>
>> Lawrence Berkeley National Laboratory   |
>> Office: 50A-5104E                       | Mailstop 50A-5101
>> Phone: 510 486-4208                     | Fax: 510 486-4204
>
>
> --
> Pat Riehecky
>
> Scientific Linux developer
> http://www.scientificlinux.org/
>