[ale] Red Hat upgrades?

[Scott McBrien]

I know there's been a lot of traffic on this thread, but it's morphed into a philosphical discussion, and I wanted a clean slate.

James, you can do an upgrade from 4->5, I haven't checked to see if there's an upgrade option for 5->6, I think there is, but I've not looked for it.

My recommendation would be a fresh install + migrate.  I know you said that wasn't an option, but you're going to be in for a ton of pain if you choose upgrading, more on that later.

If you insist on going the upgrade route, you want to 4->5->6  don't try to go direct from 4->6.

The upgrade installation with RHEL is essentially an rpm -F on all the installed rpms from the install media.  Going from one version to the next, the devels at Red Hat do a lot of work to try and make it a smooth process.  As far as I know, they do not support a 2 version jump with the upgrade installer, and therefore either don't test it at all, or it's very minimal.

The big issue that you run into with upgrade installs is artifacts.  Because your freshening the software based on current install media, what happens to your installed imap RPM when the newer version of RHEL uses dovecot?  You keep your old software in place and you don't get the replacement package.  As for your custom compiled software, it was compiled against a version of GCC and libraries that may no longer exist in the new update.  So they're looking for /lib/foo.2.so and you now have /lib/foo.3.so.  Then there's config files.  With that big if a jump, I'm guessing you'll get a lot of .rpmsave files that you'll have to rectify your modifications to the new vanilla filed dropped by the updated RPM.

I've not even bothered to attempt an upgrade in a number of years after having a very unpleasant experience with it myself.  IMO, it's less of a headache to install fresh and migrate customizations from old to new.  As an added bonus, I can keep the old as a reference and cutover after I've verified it.  If things don't work properly, I can cut back and be no worse for wear.

-Scott

On Jul 1, 2011, at 8:43 AM, James Sumners <james.sumners at gmail.com> wrote:

> I'm going to test upgrading one of my production Virtual Machines. The
> VM is running RHEL4. Can I go from 4 to 6? Or do I need to upgrade to
> 5 before 6?
> 
> -- 
> James Sumners
> http://james.roomfullofmirrors.com/
> 
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> pathological personalities. It is not that power corrupts but that it
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> 
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