[CentOS] CentOS 6 updating policy

Fri Nov 4 14:26:01 UTC 2011
Marko Vojinovic <vvmarko at gmail.com>

On Friday 04 November 2011 13:24:32 David McGiven wrote:
> I am migrating from debian to RHEL (CentOS) and I am wondering how the
> CentOS 6 updating system works.
> Suppose I install CentOS 6.1 now. Suppose in 8 months CentOS 6.2 is
> released.
> Now I issue a yum update, so my system will be updated to CentOS 6.2, or I
> will have an updated 6.1 ?

It would be updated to 6.2.

> What if I have been issuing yum update very day just to be sure there are
> no packages with urgent security bugs ? I am having a very updated 6.1 or
> an almost 6.2 ? Or are they the same thing?

AFAIK, they would be the same thing. I wouldn't know of any major difference 
between a "very updated 6.1" and "almost 6.2".

But I may be wrong here, I'm not a CentOS developer. :-)

> I think that during this time
> I should be using Continous Release repository, right ?

This is more complicated. The story above would be the "usual" way of working, 
and it indeed is for CentOS 4 and 5. They do not have the CR repository.

However, for CentOS 6 there is an additional quirk --- once the upstream (that 
is, Red Hat) releases a new point release (say, 6.1), it naturally stops 
providing updates for the previos point release (say, 6.0), expects everyone 
to just update to 6.1 and receive updates to that from now on.

The problem is that for version 6 CentOS devs have a hard time finishing the 
CentOS rebuild of the new release (6.1), so the CentOS 6 users stay on 6.0, 
and stop receiving any updates for it, because upstream doesn't provide any 
anymore. The CR repo is used for those situations --- it provides updates to 
CentOS 6.0 which were supposed to be updates for CentOS 6.1, if CentOS 6.1 had 
existed at the time of issuing the update.

The bottom line is --- if you use the CR repo, you'll have an up-to-date 
CentOS 6 system as possible, regardless of the minor version number still 
being 0. This is *less* updated than the upstream's 6.1 system, because of the 
mentioned problems with rebuilding certain packages. If you believe these 
missing updates are so very crucial for your system, go buy Red hat and you'll 
be provided with those. Otherwise, use the CR repo and wait for the CentOS 
devs to finish building them.

Eventually, when the 6.1 build of CentOS becomes complete, version numbers 
will be back in sync with what is actually installed on your system (via an 
ordinary yum update), and your syste will be an up-to-date 6.1, regardless of 
whether or not you have used the CR repo in the meantime. The CR repository 
will become empty at that time.

So, yes, you probably want to use the CR repository until 6.1 is finished. 
Maybe there will be a lag for 6.2 release as well, and then there will be the 
CR repo again for the same reasons.

> Also, which is the policy regarding new versions of software, kernel and
> libs ? The bugfixes will be backported or there will be major differences
> between, let’s say, 6.1 and 6.4 ?

AFAIK, most of the software is kept on the single version, but there might be 
some exceptions. For example the kernel version will be fixed throughout the 
6.x releases, and all bugfixes and the rest will be backported.

I don't know exactly about the exceptions, but I think I remember that firefox 
version may be bumped within 6.x releases, or something like that...

> I couldn’t find all of these question properly answered in the FAQs

CentOS follows exactly the release strategy of upstream. You probably want to 
look up the FAQ of RedHat. :-)

HTH, :-)