Upgrade RHEL3 to RHEL4, upgrade or clean install?

[nilesh vaghela]

Hi,

One more helpful doc from Redhat Kbase.

http://kbase.redhat.com/faq/FAQ_80_4451.shtm

Article ID: 4451
Last update: 12-03-04

Issue: Should I upgrade my existing Red Hat Enterprise Linux system to the
next version or should I do a clean install of the later version?
Resolution:

It is technically possible to do an upgrade of an existing Red Hat
Enterprise Linux system to the next version of the operating system in the
case where the new operating system is the same class (AS, ES, or WS) as the
existing one. In other words, ES 3 can be upgraded to ES 4, AS 2.1 can be
upgraded to AS 3, etc.

It is definitely *not* recommended to upgrade across two versions, e.g: AS
2.1 to AS 4.

There are risks and drawbacks to either approach, as well as potential
relative advantages. In the case where an upgrade is performed, there may be
complications due to changed configuration file formats in newer versions of
component software packages, incompatible versions of libraries, and so on.
In some cases, people have upgraded their system for years successfully
across many different releases and have not experienced problems. In other
cases, people have spent more time reconfiguring the system to fix it after
an unsuccessful upgrade than they would have spent on a reinstall.

In the case of the reinstall there is the necessity to restore data from
backup and reconfigure services and settings. In either case, it is
imperative to have a backup of all data in case something goes wrong.

Both options require work. How much work is involved in the reinstall
depends on the number of services you have configured on the machine and
their complexity.

Upgrading has the potential of saving time and effort if it is successful.
In the case that it is not, it then becomes a question of whether you wish
to invest time troubleshooting and fixing any complications or cut your
losses and go for the reinstall before you spend too much time. In either
case, it is a wise idea to prepare a strategy for doing a reinstall ahead of
time, just in case.

In the case of a reinstall, you should back everything up, then make a list
of services that the machine handles, and copy all the necessary
configuration files. Preparing a strategy ahead of time will enable you to
work faster and minimize downtime and possible errors.

You may also consider executing your planned approach in a test environment
first.

Nilesh