[CentOS] Upgrading CentOS from 7 to 8

Thu Sep 30 10:49:05 UTC 2021
Simon Matter <simon.matter at invoca.ch>

> On 9/29/21 3:24 PM, Gestió Servidors wrote:
>> Hi,
>> I'm doing some tests of upgrading CentOS from 7 to 8 reading this
>> step-by-step guide:
>> https://netshopisp.medium.com/how-to-upgrade-linux-servecentos-7-to-centos-8-ec2db96a189b
>> I'm trying this upgrade in a VM, so I can save "snapshots" and restart
>> in a past saved point. However, all my test ends wrong, exacly in Step 4
>> when I run "rpm -e `rpm -q kernel`". Then, systems says that some
>> packages are kernel dependencies. After I remove that dependencies, I
>> can't remove kernel...

One problem which could show up here is that kernel packages have
changed/splitted and therefore things are more complicated. At least
that's what has happened in the past, don't know about 7->8.

> That specific step is probably useless.
> Installing new kernels for Centos8 will sooner or later remove older
> kernels coming form C7.
> If you really want to do this manually you could specify the version on
> your "rpm -e" command.
> If you are not ready to tweak the process a bit while upgrading and just
> expect
> a straightforward list of commands, well, as others have explained, there
> is no guaranteed
> script or method.
> If instead you have enough familiarity with the system to work around the
> obstacles,
> "impossible" things can often be done: for example, years ago I've managed
> to upgrade
> a Fedora 16 from i386 to x86_64, and everybody was swearing it was
> impossible to do.

I can confirm that because I also migrated a server from i386 to x86_64 in
place. That was with an old RHEL release.

I don't remember exactly how I did it but I think I only used rpm for it,
no yum.

Unfortunately upgrading complex systems is still a lot of work these days,
no matter what all the cloud experts try to tell you :-)