Better yet, learn kickstart 
(http://www.redhat.com/docs/manuals/enterprise/RHEL-5-manual/Installation_Guide-en-US/ch-kickstart2.html) 
and preserve important filesystems with the '--onpart' and '--noformat' 
options. E.g.

part / --fstype ext3 --onpart sda1
part swap --onpart sda2
part /export/d0 --onpart sda3 --noformat

-Jan

On Fri, 25 Jul 2008, Brian Andrus wrote:

> Date: Fri, 25 Jul 2008 13:40:35 -0700
> From: Brian Andrus <[log in to unmask]>
> To: Miguel A. Lerma <[log in to unmask]>
> Cc: [log in to unmask]
> Subject: Re: How to preserve /home while installing 5.2?
> 
> I'd just do a fresh install, but make sure you get to manually handle the 
> partitions. Then make them the same and don't formate /home.
>
> Bada-bing! New install preserving /home
>
> Brian
>
> Miguel A. Lerma wrote:
>> Hi, I have a machine with SL 4.5 and I want to install SL 5.2
>> on it, but without destroying the /home partition. When booting
>> from the installation CD I am given basically only two options:
>> 
>> - Upgrade 4.5 preserving data.
>> 
>> - Install 5.2 destroying all data on the drive.
>> 
>> There is also an option claiming to install only on selected
>> partitions, but when I use it I do not see the current partitions
>> and I cannot select which ones to use for installation and which
>> ones to preserve.
>> 
>> Is there any way to install 5.2 without destroying the home partition?
>> 
>> This is my current layout:
>> 
>> $ df -h
>> Filesystem            Size  Used Avail Use% Mounted on
>> /dev/sda3            1012M  886M   75M  93% /
>> /dev/sda1              99M   74M   21M  79% /boot
>> none                 1009M     0 1009M   0% /dev/shm
>> /dev/sda5              99G   41G   54G  43% /home
>> /dev/sda6             9.9G  374M  9.0G   4% /opt
>> /dev/sda10           1012M   34M  927M   4% /tmp
>> /dev/sda11             94G   73G   16G  83% /u1
>> /dev/sda8             9.9G  4.2G  5.2G  45% /usr
>> /dev/sda7             9.9G  2.3G  7.1G  25% /usr/local
>> /dev/sda9             2.0G  439M  1.5G  23% /var
>> 
>> 
>> # fdisk -l
>> 
>> Disk /dev/sda: 250.0 GB, 250000000000 bytes
>> 255 heads, 63 sectors/track, 30394 cylinders
>> Units = cylinders of 16065 * 512 = 8225280 bytes
>> 
>>    Device Boot      Start         End      Blocks   Id  System
>> /dev/sda1   *           1          13      104391   83  Linux
>> /dev/sda2              14         535     4192965   82  Linux swap
>> /dev/sda3             536         666     1052257+  83  Linux
>> /dev/sda4             667       30394   238790160    5  Extended
>> /dev/sda5             667       13720   104856223+  83  Linux
>> /dev/sda6           13721       15025    10482381   83  Linux
>> /dev/sda7           15026       16330    10482381   83  Linux
>> /dev/sda8           16331       17635    10482381   83  Linux
>> /dev/sda9           17636       17896     2096451   83  Linux
>> /dev/sda10          17897       18027     1052226   83  Linux
>> /dev/sda11          18028       30394    99337896   83  Linux
>> 
>> 
>> I have to do something similar not only on this machine, but on
>> about thirty machines that we have in the department. Installing
>> fresh on each machine and recovering data from backups is going
>> to take forever, if possible I would prefer to install without
>> destroying the user's data.
>> 
>> 
>> Thank you in advance!
>> 
>> 
>> Miguel A. Lerma
>> 
>> --
>>   Miguel A. Lerma
>>   Math Comp Sys Admin
>>   Department of Mathematics  <[log in to unmask]>
>>   Northwestern University    <http://www.math.northwestern.edu/~mlerma/>
>>   2033 Sheridan Road         847-491-8020 (w)
>>   Evanston, IL 60208-2730    847-491-8906 (f)
>>