[Novalug] RHEL In-place [Pre-]Upgrade (very different from FedUp) -- WAS: Bad upgrade to Fedora 22 with fedup (LONG)

Bryan J Smith b.j.smith@ieee.org
Tue Aug 18 19:35:16 EDT 2015


Bryan J Smith wrote:
> The "in-place Upgrade" means full upgrade to RHEL7 from RHEL6, with
> possible breakage at points.  It requires you to use the separate
> "Upgrade Tool" and not just "yum."

To put it another way ...

A RHEL (or CentOS) 6 to 7 "in-place [Major Version] Upgrade" -- of
which Red Hat is only offering for the very first time with RHEL 7 --
is almost exactly like upgrading from ...

from Fedora 13
to Fedora 20

You're literally jumping 4 years newer.  ;)

Most corporations _never_ do this (long story), because Oracle and
other software isn't going to like the fact that the LibC and
LibStdC++ and other things change overnight.  Even with the
Compat-libs (of which Red Hat goes all the way back to '00 and ECGS
1.1.2/GCC 2.91.66 and GCC 2.96, and every ABI since), there is often
going to be some library incompatibilities that aren't provided as
Compat-libs.

They just do the Updates (e.g., RHEL 6 Update 7 aka RHEL 6.7, from
Update 6, 6.6, etc...), and don't jump major version, but "migrate."

That said ... if you did do a CentOS 6.6 to 7.1, and not just to 6.7,
I'd _love_ to hear your experiences.  Because I worked with a number
of partners on doing the "in-place [Major Version] Upgrade" back in
2014.  Because most of them want Red Hat to "solve" the issues of
Oracle and ISVs with Upgrades, which is outside of Red Hat's control.

I.e., if you just use the base OS, the Upgrade usually works, with a
few caveats.
But if you use ISV software, then it usually breaks or has issues --
although the Pre-Upgrade Tool warns you what libraries and other
things change.

But the irony here is this ...

If you're just a corporation using the OS, and no add-on ISV software,
it's _cake_ to re-deploy a new RHEL system with Kickstart, and push
down all required configuration changes, to come close to what you had
with the prior version.

But if you're running ISV software, which usually isn't packaged as
RPM, it's a total PITA.  Hence the desire for the "in-place [Major
Version] Upgrade."  And yet, it's that software that's most likely to
break when all those libraries change.  ;)

-- bjs

-- 
Bryan J Smith - http://www.linkedin.com/in/bjsmith



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