[CentOS] Door not hitting me on my way out

Mon Apr 4 17:36:33 UTC 2011
Ljubomir Ljubojevic <office at plnet.rs>

Marko Vojinovic wrote:
> On Monday 04 April 2011 12:25:06 Mister IT Guru wrote:
>> Maybe it's my curiosity, but my brain tells me that Fedora is the
>> forerunner for RHEL. And the Fedora code is out there. CentOS is built
>> from the RHEL code, with all RHEL specific items removed. Ergo - If I
>> replicate the build environment on some of my machines,
> Herein lies the main problem: *there* *is* *no* *build* *environment* yet. In 
> other words --- the Fedora environment is far too 
> big/generic/unsuitable/whatever (am I right here?), and RedHat is not 
> interested in giving details about their build environment.

Better explanation is that CentOS project is not building packages, it 
is *re*building/repackaging packages that Red Hat already built, and 
they have to be *100%* binary compatible. Fedora environment, "koji", 
and any other environment are meant for tracking and changing packages. 
CentOS does not change packages (other then ~5% of .centos. ones), so 
such environment is practically useless.

> So the main problem that CentOS team has to solve with each major release is 
> to construct a build environment that will produce binaries that are bit-by-
> bit equivalent to official RHEL (up to trademarks, branding and some other 
> stuff).
>>From my naive understanding, this boils down to the proper order in which 
> packages are supposed to be built. There is more than one possible ordering, 
> and only one will give binary equivalent set of packages.
> I am probably oversimplifying things, but it roughly goes as follows:
> 1) start from some build environment
> 2) compile the whole distro
> 3) compare the result bit-by-bit with RHEL binaries
> 4) if it matches you're done; if it doesn't match, modify the build 
> environment and go back to 1).
> AFAIU, the CentOS devs are currently in the above loop. Once they are done, 
> testing will begin and CentOS 6 will probably be released shortly thereafter.
> However, nobody knows how much time is it going to take to finish the loop. Not 
> even the devs can estimate that, so better don't ask them! ;-)

Reverse engineering that is taking place in CentOS project is somewhat 
stabbing in the dark, trying to find what version of dependency was used 
to compile the original, and some dependencies used are even from Fedora 
6! Try compiling package that could use only one dependency for every 
package version (and it's every update) from Fedora 6 to 14, and you 
will get the idea.

For those saying that CentOS devs are slow, take notice that Scientific 
Linux released SL 6.0, *but* SL 5.6 is still in it's *ALPHA* stage. If 
too separate teams are close with results, then there is no room for 
accusations or wondering...