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The last few days I'm itching to change the distribution I'm using for years, Debian. Since stability is of major importance for me and I'm not interested in bleeding edge features, I've decided to play around with RHEL. Considering it's not free and being aware of CentOS, I've decided also to make some further investigation to the issue.

While searching, I've found an interesting comment from user Christopher in this question, which says the following (among other things):

"Yeah... recompiled sources. But, only Red Hat has the "secret sauce" to compile them correctly. CentOS 6 is 85% different in terms of binary compatibility with RHEL 6."

Which gave further boost to my initial wondering "Red Hat is investing a lot on their OS. Can it be THAT similar with the CentOS? Is there nothing that they can do to make things a little bit more "closed source"? "

And the actual question:

CentOS is considered to be binary compatible with RHEL, but what is the difference from the "real thing"? Is it possible by using different compile configurations to produce an entirely different OS?

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  • "Yet another..." is a meaningless title, please make it specific to your question. – jasonwryan Feb 23 '16 at 17:32
  • I have itching to change to FreeBSD. – Rui F Ribeiro Feb 23 '16 at 17:42
  • @RuiFRibeiro Been there, done that. Nice system, but too grumpy for my taste... – Arkoudinos Feb 23 '16 at 17:45
  • I left RH for too many years to count now, well because of exactly the same kind of things that seems to be reaching Debian lately. I was born in HP/UX/Ultrix, and did not use FreeBSD because of package management issues. But I am tempted to try it again, with new tools. – Rui F Ribeiro Feb 23 '16 at 18:02
  • @RuiFRibeiro What kind of "things"? – Faheem Mitha Feb 23 '16 at 18:05
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Redhat is investing a lot on their OS. [...] Is there nothing that they can do to make things a little bit more "closed source"? "

Not sure why you phrase it that (as if being closed source would be a good thing). RH does develop more FOSS than any other distro company but they're far from the only one and there's a large amount of involvement from the community at large. So yeah, RH "loses" their work but they also gain the work others contribute underneath the same set of restrictions.

CentOS is considered to be binary compatible with RHEL

More or less, yeah. I've never seen something designed for RHEL fail on CentOS. You typically buy RHEL subscriptions for the support and because updates are pushed out to RHEL a lot sooner than they are to CentOS.

Is it possible by using different compile options to produce an entirely different OS?

There's a lot of variation possible with compile-time decisions, but I don't think RH's "secret sauce" is going to be that magical. A large part of what actually differentiates distros is this exact thing (along with some package selection stuff and package release management).

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    I would also add that Red Hat is a major partner with CentOS in the development of their variant: redhat.com/en/about/press-releases/… – Thomas N Feb 23 '16 at 17:32
  • I phrase it in that way, because for a company producing software and making profit from it, the ideal would be that software to be closed-source. Also, even with open-source code they always could include their own proprietary "blobs" without ever mentioning them to anyone, which might be another profitable strategy. – Arkoudinos Feb 23 '16 at 17:32
  • @Arkoudinos From my understanding most Red Hat packages were open source before Red hat began using them, so while they are free to develop them, if they do they have to continue to be open source, so RHEL wouldn't have a choice to close source them. – Centimane Feb 23 '16 at 17:38
  • @Arkoudinos Again, though they lose all the contributions that people outside RH make that would never be made if people thought RH would be the only company profiting from it. For example, RH is the largest contributor to the Linux kernel (as far as distros go) but if the kernel were closed source EMC would just tell RH to develop their own HBA drivers. Since it's vendor neutral, EMC can contribute their code upstream and RH benefits. Also, like Dave said, there's a healthy mix of stuff that RH didn't develop initially and they had to either re-write it or abide by the author's terms. – Bratchley Feb 23 '16 at 17:50
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From my understanding CentOS is simply another build of the same source code used for RHEL, which is open source (this is also stated in CentOS FAQ).

Using different compile options shouldn't have too much impact on the behavior of the OS.

The largest difference between the two is the speed at which new versions are released. Because CentOS is essentially a branch of RHEL they are always slower to release updates (because RHEL has to be updated first before CentOS can branch the changes). According to their FAQ CentOS is committed to updating packages within 72 hours of RHEL updating them, though I know when RHEL 7 came out it was a few months before CentOS 7 was released.

You can dig deeper in the CentOS FAQ to get more insight on this (https://wiki.centos.org/FAQ/General) and as well search for your question again on SE Unix & Linux + Google

Is CentOS exactly the same as RHEL?

https://danielmiessler.com/study/fedora_redhat_centos/

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