David McGiven wrote:

I am migrating from debian to RHEL (CentOS) and I am wondering how the CentOS 6 updating system works.

Welcome, then.

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 ?

6.2 Yum does subreleases without a hitch (mostly). <snip> mark

Vreme: 11/04/2011 02:24 PM, David McGiven piše:

I am migrating from debian to RHEL (CentOS) and I am wondering how the CentOS 6 updating system works.

Welcome.

In first part I will explain normal process, without CR repository (which changes things).

Suppose I install CentOS 6.1 now. Suppose in 8 months CentOS 6.2 is released.

Yum update is continuous process. So far (or at present) only way is that you will be upgraded to latest minor point-release (.1, .2,...).

Now I issue a yum update, so my system will be updated to CentOS 6.2, or I will have an updated 6.1 ?

In your example, you would have 6.2 when yum update is finished. Sometimes "yum upgrade" is recommended, but only if you are advised in Release Notes for given point release.

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

There are normal updates against every point release, like updates against 6.0 until 6.1 is released, then updates until 6.2, etc. So just "very updated 6.1" in your example.

Point releases are mostly used to bring new kernel/hardware support (drivers), new versions of core packages (rarely), or new technologies. Updates between point releases will only (in most cases) contain bugfixes.

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 ?

Upstream changes (mostly) versions of packages only if there is compelling reason to do so. Whole point is to have unchanged system that will behave the same as previous point releases. Of course, there are deviations from this policy, but as small and as rare as possible.

So short answer is backported bugfixes (even in kernel) and as small changes as possible, unless gains are overwhelming and do not brake anything.

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, :-) Marko