Current Differences Between CentOS and Red Hat Enterprise Linux

centosdockerlinuxrhel

What is current the difference between CentOS and Red Hat Enterprise Linux (as of 2017)?

When you develop software targeting Red Hat, users and support staff inevitably ask why can't they just use CentOS instead as "CentOS is the same as Red Hat".

I often find myself in a position of having to explain the costs vs benefits of using one or the other as "Free" does not mean there is not a cost somewhere.
Someone has to pay the cost of covering the risk that there is a significant difference.

What practical differences can we point to, to explain the difference?

How do they differ in terms of targeting them as a development platform?

The question of how CentOS and Red Hat differ is old.
However, I think some things may be different in 2017 from what they have been previously.

I've added my own answer as a community wiki. Please chip in if you can improve on it.

Best Answer

Each platform you support comes with an associated cost. Typically you require:

  • A build environment
  • A separate test environment (for example, not having the development tools installed)
  • Additional time to build and test new releases
  • Additional resources to support each platform

CentOS aims to be binary compatible with Red Hat which lessens the need for a separate build environment. However, if you don't also have access to a CentOS environment, at least for testing, you might get caught out by subtle differences. Theoretically you might be unable to reproduce an issue that occurs on a user's CentOS installation on your Red Hat installation.

You might also have to provide different installation instructions for dependencies due to the different repository organisation.

Repository Organisation

Red Hat as of RHEL 7 has split things up into many more repositories:

  • atomic host
  • server
  • workstation
  • optional variants of the above
  • supplementary repos for the above
  • beta repos for the above

In fact I count no less than 85 (as follows):

>yum repolist all | grep rhel | wc -l
85

This does not seem to be the case for CentOS 7 (please correct me if I'm wrong)

Moreover things available in one RHEL repository are not compatible with some of the others. For example, docker from atomichost does not play well on my workstation install.

Java

This post from 2016 mentions that (Oracle) Java cannot be installed directly on CentOS:

Red Hat has a contract with Oracle to redistribute Oracle Java SE binaries (including the JDK and JRE) and to support those products as part of a RHEL subscriptions. CentOS does not ship Oracle Java SE; CentOS users who wish to use Oracle Java SE must download and install it directly from Oracle.

Security Patches

Security patches are generally applied to CentOS very quickly:

  1. How long after Red Hat publishes a fix does it take for CentOS to publish a fix?

Our goal is to have individual RPM packages available on the mirrors within 72 hours of their release, and normally they are available within 24 hours. Occasionally packages are delayed for various reasons. On rare occasions packages may be built and pushed to the mirrors but not available via yum. (This is because yum-arch has not been run on the master mirror. This may happen when issues with upstream packages are discovered shortly after their release, and if releasing the package would break it's functionality.)

Red Hat provide extended life-cycle support for older versions (at additional cost). This means that you can get patches for critical CVEs for RHEL 5 while CentOS can simply write off CentOS 5 as no longer supported. Notably there have been several critical CVEs affecting RHEL 5 since it (and CentOS 5) reached end of life.

See also Is CentOS exactly the same as RHEL?

Docker

With the rise of Docker we have a new difference:

Docker Community Edition (Docker CE) is not supported on Red Hat Enterprise Linux.

You must instead buy Docker EE license. You can install Docker-CE on RHEL using the CentOS repositories. See install Docker CE 17.03 on RHEL7

But this is obviously an unsupported configuration.

This is an odd one as that decision is made by the Docker team and not Red Hat. So presumably Red Hat could decide to support Docker CE if they wanted to?

The essential difference between them is still the same:

If you want commercial support and certification you need to pay for it (use Red Hat) If you don't want it you can use CentOS.

Direction

From the CentOS FAQ:

Red Hat and the CentOS Project are building a new CentOS, capable of driving forward development and adoption of next-generation open source projects.

This is corporate blurb but it could be taken as meaning Red Hat want RHEL to diverge from CentOS in some interesting but unspecified way.

Update: Dec-2020

The direction for CentOS is now clearer:

  • CentOS 8 is to be end of lifed early (2021).
  • CentOS 7 support continues until 2024.
  • RedHat (now owned by IBM) will no longer provide a CentOS that competes with RHEL.
  • They now have "CentOS stream" which is upstream from RedHat and acts a bit like a beta.

The best summary is probably - https://hackaday.com/2020/12/09/centos-is-dead-long-live-centos/

See also:

The eagle eyed may note that Fedora is an upstream version of RedHat. So where does CentOS stream fit? To explain the difference lwn says:

“If the distros were wooden furniture, RHEL would be a finished desk, Stream would be the unpainted and unsanded desk, and Fedora would be the tree.”

A further explanation and more positive spin on the split is given by:

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