[CentOS] Upgrading from CentOS 5.6 to 6.0

Sun Jul 24 11:30:25 UTC 2011
Giovanni Tirloni <gtirloni at sysdroid.com>

On Sat, Jul 23, 2011 at 8:58 PM, Thomas Dukes <tdukes at sc.rr.com> wrote:
> Red Hat does not support upgrades between major versions (doesn't necessarily mean it's not possible)
> http://docs.redhat.com/docs/en-US/Red_Hat_Enterprise_Linux/6/html/Installation_Guide/ch-upgrade-x86.html
> http://linsec.ca/blog/2011/02/23/my-adventure-upgrading-rhel5-to-rhel6/
>
> Since when?? I started with slackware 1.0 on a pentinum 1 system from VaResearch back in the mid 90's, change to Redat 2.0, then Fedora, then to Whitebox, then CentOS.. Never had a problem upgrading on an rpm based system.

That's a good question. It seems that since RHEL 4 (2005), Red Hat has
been telling us that upgrading from earlier major versions is not a
good idea.

- RHEL 3 docs say it's possible to upgrade from 2.1 to 3.x (http://goo.gl/8Gwrs)
- RHEL 4 docs don't bother showing the steps and provide a lot of
warnings for 2.x/3.x to 4.x (http://goo.gl/yiRGK)
- RHEL 5 docs explicitly say Red Hat does not support upgrading from
earlier major versions (http://goo.gl/RQABB)
- RHEL 6 docs explicitly say Red Hat does not support upgrading from
earlier major versions (http://goo.gl/H9zBU)

I don't think RPM is the one allowing/disallowing the upgrade between
major versions. The kernel architecture and other major components
changes are more likely to be the culprit. I'd be surprised how you
moved from Slackware 1.0 all the way to CentOS without a reinstall
(because that's what is being discussed here).

Just as reference, starting with Solaris 11, it'll not be possible to
upgrade from earlier major versions either (although binary
compatibility will still be there). Oracle is asking customers to
treat earlier versions as legacy and put them in  containers and/or
virtual machines. Solaris 11 will change so much how things work that
Oracle says it's better not to bother upgrading path from Solaris 10.

My point is that big changes happen in Linux much frequently than in
Solaris and even Solaris sometimes doesn't support these kinds of
upgrades.

--
Giovanni Tirloni