RHEL upgrade from 4u9 to 6

[ggigk]

Hi,

I want to upgrade RHEL 4u9 to 6.1:

Please send me the comparison issues between the versions and the applications compatibility along with their file system compatibility.

[Irithori]

That is a bit much to ask.
But thankfully RedHat maintains release notes for every new version:

Red Hat Enterprise Linux 5.0 Release Notes
Red Hat Enterprise Linux 5.1 Release Notes
Red Hat Enterprise Linux 5.2 Release Notes
5.3 Release Notes
5.4 Release Notes
5.5 Release Notes
5.6 Release Notes
5.7 Release Notes

6.0 Release Notes
6.1 Release Notes
6.2 Release Notes


And also technical notes:
http://docs.redhat.com/docs/en-US/Re...tes/index.html
http://docs.redhat.com/docs/en-US/Re...tes/index.html
http://docs.redhat.com/docs/en-US/Re...tes/index.html
http://docs.redhat.com/docs/en-US/Re...tes/index.html
http://docs.redhat.com/docs/en-US/Re...tes/index.html
http://docs.redhat.com/docs/en-US/Re...tes/index.html
http://docs.redhat.com/docs/en-US/Re...tes/index.html

http://docs.redhat.com/docs/en-US/Re...tes/index.html
http://docs.redhat.com/docs/en-US/Re...tes/index.html



In general I would advise to
1) backup
- configs
- data
- logs

2) Then install the newest redhat available (6.2) on a new machine in parallel.
3) Migrate the server configs.
4) Then import the data
5) Test
6) Automate the deploy
7) Document the deploy
Test
9) Switch over to the new setup

These are of course milestones, the detailed and actual workflow depends on your specific setup/data.

[Rubberman]

Irithori gave you some great links, but the short story is that an upgrade from 4.x to 6.x is not straight-forward. It is HIGHLY recommended that you do a clean installation of 6.x, reinstall all standard packages you need, and then rebuild ALL of your custom applications. Finally, you need to do a LOT of testing to find where stuff is still going to break. As an analogy, going from 4.x to 6.x is kind of like upgrading your personal transportation from horse&buggy to a BMW 700 series roadster. There will be a lot of changes. So, keep your 4.x system running and install 6.x on another box, or in a virtual machine, until you are satisfied that you have dotted all of the i's and crossed all of the t's.

FWIW, I moved last year from 5.x to 6.x, and there are still some things that don't work like I'd prefer... All in all, however, the upgrade was waaay worth the pain and suffering. Better hardware support is just the start, but also better support for newer applications that I wanted to use.