[CentOS] update from 4.8 to 5.4?

At Fri, 4 Jun 2010 15:16:05 -0400 CentOS mailing list <centos at centos.org> wrote:

> 
> I have searched the list, and don't see this covered or didn't search for the 
> right words.
> 
> I'm running CentOS 4.8 and have some DVD's for 5.4. I have a lot of customized 
> and additional software installed and would like to avoid starting over with 
> a scratch install. After the upgrade from the DVD I would do a yum upgrade to 
> 5.5. 
> 
> Is this a workable (and safe) thing to do? What should I look out for? 
> 
> I plan to build a clone of the boot disk in case there is a problem so I can 
> swap it back in to the hba1 position (as soon as I find a way to make a clone 
> of a disk with LVM ).
> 
> Here is some info on the system:
> 
> [root at hat /]# cat /etc/redhat-release
> CentOS release 4.8 (Final)
> [root at hat  /]# uname -a
> Linux hat.rbt.net 2.6.9-89.0.25.ELsmp #1 SMP Thu May 6 12:28:03 EDT 2010 i686 
> athlon i386 GNU/Linux[root at hat .spamassassin]# df -h
> Filesystem                           Size      Used  Avail   Use%   Mounted on
> /dev/mapper/VG00-LV00     2.0G     695M   1.2G   37%   /
> /dev/hda1                            494M    25M    444M     6%   /boot
> none                                    1013M  0       1013M     0%   /dev/shm
> /dev/mapper/VG00-LV04     9.9G     5.4G    4.0G   58%    /home
> /dev/mapper/VG00-LV05     1008M  34M    924M    4%    /opt
> /dev/mapper/VG00-LV03     4.0G     41M     3.7G     2%    /tmp
> /dev/mapper/VG00-LV01     7.9G     4.2G    3.4G   56%   /usr
> /dev/mapper/VG00-LV02     4.0G     929M   2.9G   25%   /var
> 
> Thanks in advance for any help with this....

What I did was carve out fresh /, /usr, and /var file systems out of my
VG (I had enough free space) and did a fresh install, using the
*existing* /boot file system.  I thus created a dual boot system: 4.8 AND
5.4.  I then mounted the 4.8 system file systems read-only on the 5.4
system and 'migrated' the various configuration files.  In some cases I
could just copy them, in other cases they needed various sorts of
updating. Things like dumping the LDAP database and reloading it in the
new system.  Ditto with the SVN data.  Since I had already upgraded both
MySQL and PostgreSQL to the newer versions via the CentOS Plus packages,
I could actually just copy the databases over (I might have done a
dump/restore of the PostgreSQL database).  I did things one-by-one,
checking to be sure things were sane at each step.

I would recomend *against* trying to do a direct upgrade -- it is too
likely to leave some cruft behind, which could cause all many of
problems later on.


> 
> Bob
> 
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>                                                                    

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