suggestions to upgrade RHEL3 to RHEL4

hey experts,

I'm planning to upgrade my Red hat enterprise ltd 3 system to RHEL4 ..(need some suggestions)

Could the upgrade option in the cds really work ?? or what are the chances of system upgrading to RHEL 4 without any hassle???

Is it necessary to backup all the necessary stuff before upgrading??

please let me know the problems that I may face in the process of upgrading ....

Any more suggestions are welcomed..

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I don 't really have experience in using RHEL however I do use Fedora which is used as testing grounds for RHEL. What I can say is that upgrading between versions of Fedora worked nicely w/o any hitches so I'd say it should be ok to upgrade from RHEL3 to RHEL4.

You *can* upgrade from RHEL3 to RHEL4, however you will get a better, cleaner result by doing a fresh install.

You should *always* perform a backup before doing any upgrade.

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Just one other thought.

I you have non-redhat installed software, they may have kernel/library version dependencies, so you'll need to keep that in mind.
Upgrade option does work!...**BUT** there are a number of problem areas:

1.    RHEL4 Kernel has dropped some drivers (including the SCSI MegaRAID!), and this may cause problems with certain hardware, in that it will no longer be recognised and therefore not work, unless you decide to compile a customised kernel - possible, but hassle!

2.    RHEL4 uses the Xorg X libraries instead of XFree86. This causes problems with some none Redhat binaries that try to do some fancy display orientated things.

3.    RHEL4 by default mounts CDROMs and other media under the directory /media, rather than under /mnt. This causes problems with some applications where the path is hard coded (copyright protection etc tend to fall foul of this, but it can often be rectified with symbolic links).

4.    As suggested libraries change, and you may be able to solve these problems with symbolic links to the newer libraries.

5.    RHEL4 comes with SEL (Security Enhanced Linux). It is enabled by default! On first login, I took over 10 minutes to work out how to access my CDROM! SEL is not for the faint hearted, and is administration intensive. The security implications of this are that for every piece of software, you have from a 3rd party, you may have to configure its access permissions! I personally thing that SEL does have a use in a risky environment..particularly if the server is exposed to the internet. You need to decide that. However, I feel that in most circumstances, you will find it easier to completely disable SEL during the upgrade/install process.

However, why do you need to do this? RHEL3 is still in the supported part of the release cycle and will be for some time. Upgrading will inevitably cause a few 'niggles and glitches', and if this is a production system, I'd say leave well alone, unless you have a very good reason. Server software such as the RHEL series have extended support widows after the release in order to minimise disruption to commercial organisations. If you're going to change your server software sytem every 2 years when a new version comes out, then you might as well save yourself the cost of your rhn subscription because you are wasting one of the most valuable support elements that it provides - i.e. the extented support period in the release cycle!

If you do decide to upgrade/install, then set up a test server first!...and check!!
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