[CentOS] Migrate CentOS 3 to 4 to 5?

[Chris Mauritz]

David Christopher Zentgraf wrote:
> Hi,
>
> After the previous debacle with PHP and MySQL it has been decided that 
> we think about an upgrade from CentOS 3 to 5, since that would solve 
> our problem, if successful. I tried finding information on how to best 
> attempt this, but thanks to a plethora of contradictory information my 
> head is now spinning with a few rpm (rounds per minute).
>
> The situation is as follows: Remote box at our host who offers CentOS 
> 3 as the most up-to-date OS, unless you pay them an unholy amount of 
> money for RHEL or Windows licences. Popping in a CD for an upgrade 
> does not work for us. We can and will have the OS restored to a clean 
> post-install state prior to updating. I have little intimate knowledge 
> with CentOS, RPMs or yum, but general good UNIX experience. I know 
> "live" yum migrations are greatly discouraged, but it seems to work 
> for people.
>
> The most detailed instructions I seemed to be able to find are here: 
> http://www.centos.org/modules/newbb/viewtopic.php?topic_id=382
> Can anybody confirm this to work, is there anything else that's 
> implied but not spelled out?
> Another, differing approach seems to be this: 
> http://levine.sscnet.ucla.edu/general/software/tc1000/rmredhat.htm
> Any ideas about it?
>
> Any hints, or rather detailed steps, would be greatly appreciated.

I tried it and failed pretty miserably.  The box wedged after the 
"upgrade" and would not boot after being power cycled.  I didn't really 
do a detailed "WTF" analysis afterwards since we do have physical access 
to the machine.  So I had someone pop in a CentOS 5 DVD and pave over 
the system and walked them through which options to check during the 
install.  Once it was back up and reachable from the net, I selectively 
restored bits I needed from the backup I did before the experiment.  
This was a CentOS 3 machine on a pretty vanilla dual Opteron box and was 
patched "up to the minute" as of the day the upgrade was attempted.  If 
you manage to sort things out, I'll be curious to know how you did it.

Best,