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CentOS and Red Hat

CentOS and Red Hat

Posted Apr 20, 2014 15:59 UTC (Sun) by giraffedata (subscriber, #1954)
In reply to: CentOS and Red Hat by hughesjr
Parent article: CentOS and Red Hat

By functional compatibility we mean bug for bug, link the same libraries, the same file lists in the package, etc.


The real issue here is that we now understand that we will never have full binary compatibility

Are you saying there are RPMs that work on RHEL but not CentOS? I.e. there are RPMs with which Red Hat is compatible but CentOS is not? If so, the functional compatibility is limited (because installing and running packages from RPMs is one of the significant functions of an OS), and you really should clarify that whenever you say "functional compatibility."

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CentOS and Red Hat

Posted Apr 21, 2014 2:34 UTC (Mon) by mathstuf (subscriber, #69389) [Link]

I think what they mean is that they compile the same code, but not inexactly the same way. If gcc-4.6-3 is different in CentOS and RHEL because RHEL was compiled with the -2 release (and recompiled because of some bug caught in QA) while CentOS was compiled with -1 since -2 never made it out the door, there's not enough time in the world to track down such differences. In reality, these differences are probably irrelevant, but you never know. If you do find an RPM which works on RHEL but not CentOS, you should file a bug.

CentOS and Red Hat

Posted Apr 22, 2014 14:14 UTC (Tue) by hughesjr (guest, #29949) [Link]

That is exactly what I am saying ... there are always some inherent differences.

However, if something runs on RHEL and not CentOS (and if that is for any other reason than the writer of the program specifically looks at something like /etc/redhat-release and runs only on RHEL and not CentOS on purpose) ... then this is a bug and we will figure out why it is not working and fix it.

So the answer is no, we are not saying anything about any changes in CentOS ... it is the same as it has been with respect to building RHEL sources. We are just telling you what kind of compatibility we have always provided.

Our goal is exactly what you want ... compile the exact sources, with the only changes in the core distribution being changes for branding and artwork.

CentOS and Red Hat

Posted Apr 22, 2014 15:57 UTC (Tue) by giraffedata (subscriber, #1954) [Link]

It sounds like there are people who think "full binary compatibility" means bit for bit identical, thus totally misunderstanding the word "compatibility." If so, it was a good idea for CentOS to stop using the term.

For anyone who is unclear on compatibility: it comes from latin meaning "ability to lie together" and refers to things that can coexist and work together.

We're already taking license with the term when we say two things with the same role are compatible with each other (for example, a classic Dell PC-clone computer being compatible with an IBM PC). In that case what it means is the two things are compatible with the same things.

CentOS and Red Hat

Posted Apr 22, 2014 16:20 UTC (Tue) by mathstuf (subscriber, #69389) [Link]

Well, it depends where you draw the line :) . Typical developers draw it at the linker-level (functions, data structures, call behavior, etc.), but there's a deeper one where you also ensure "compatibility" (I'd call it "binary identical" which reproducible build setups strive to attain) with those doing `sha1sum /usr/bin/ls` and expecting certain values for it. One user of the latter is SecureBoot which can (IIRC) have known-good hashes of binaries whitelisted (rather than public key signatures).

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