I’m sure this question has been asked again and again elsewhere (I did not find anything specific to CentOS vs RHEL in SE), but I would still like to ask and confirm a few specific points.
I am well aware that CentOS removes all RH trademarks, logos, etc. and is based on the same codes with packages built by the community.
- Are the packages built for CentOS exactly the same? Will the contents of the packages and the behavior of the programs be identical to those found on RHEL?
- What is RHN other than a medium for license registration? What is it to CentOS?
I’m an Ubuntu desktop user. Attended a RH299 course which did not really touch anything about the support aspect (i.e. RHN). Other than that I’ve no professional Linux knowledge or experience.
EDIT
I did read the CentOS 6.2 release notes, but I found the details unsatisfactory. The release notes mentions packages modified, removed or added to upstream. But it neither explains nor links to any document detailing what exactly is different in the modified packages. Granted the branding packages are self-explanatory, but it mentions packages like kernel, ntp, anaconda, etc. which have nothing to do with branding as far as I’m aware.
Answers:
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Method 1
CentOS is very close to being RHEL without the branding and support. In particular, the library versions are the same, so binaries that work on one will work on the other. The administration tools are the same and configured in similar ways. However, there are a few differences, as the two distributions sometimes apply different minor patches. For example, in this question, it was apparent that RHEL 5 and CentOS 5 apply different rules to identify files under /etc/cron.d.
In other words, at the level of your course, you can treat CentOS and RHEL as interchangeable. But if you needed to look up the precise behavior of a program in a corner of the man page, you may encounter differences.
Method 2
This may answer your question. Here’s an excerpt from the page.
CentOS is a free operating system distribution based upon the Linux kernel. It is derived entirely from the Red Hat Enterprise Linux (RHEL) distribution. CentOS exists to provide a free enterprise class computing platform and strives to maintain 100% binary compatibility with its upstream source, Red Hat.[2] CentOS stands for Community ENTerprise Operating System.
CentOS is the most popular Linux distribution for web servers with almost 30% of all Linux web servers using it
Method 3
No. Although it’s close. There are some key differences.
- CentOS lacks certified cryptographic protection required on government networks.
- CVEs (Common Vulnerabilities and Exposures) are not tested on CentOS, and it is expensive to test them properly.
Method 4
For all intents and purposes, CentOS is RedHat. CentOS, however is more flexible in what they can do.
From the CentOS website:
CentOS is developed by a small but growing team of core developers. In turn the core developers are supported by an active user community including system administrators, network administrators, enterprise users, managers, core Linux contributors and Linux enthusiasts from around the world.
CentOS has numerous advantages over some of the other clone projects including: an active and growing user community, quickly rebuilt, tested, and QA’ed errata packages, an extensive mirror network, developers who are contactable and responsive, multiple free support avenues including IRC Chat, Mailing Lists, Forums, a dynamic FAQ.
In a nutshell, CentOS is a community version of RedHat. You use Ubuntu, so you may understand this analogy a bit better: CentOS is to RedHat as Linux Mint is to Ubuntu.
Method 5
With RHEL you pay RedHat for support.
With CentOS you do not get commercial support from RedHat.
Most updates are first available for RedHat, then for CentOS.
Other than that they are the same.
See this for further reference: CentOS vs RHEL.
Method 6
Look at the release-notes on the CentOS-pages. There is a list of rpms that are added/different from RH. These are about branding or about the update mechanism (which requires a license in RH).
Method 7
Read the Centos FAQ one question that has the answer:
How is CentOS different from Red Hat Enterprise Linux?
CentOS is a community project that is developed, maintained, and supported by and for its users and contributors. Red Hat Enterprise Linux is a subscription product that is developed, maintained, and supported by Red Hat for its subscribers.
While CentOS is derived from the Red Hat Enterprise Linux codebase, CentOS and Red Hat Enterprise Linux are distinguished by divergent build environments, QA processes, and, in some editions, different kernels and other open source components. For this reason, the CentOS binaries are not the same as the Red Hat Enterprise Linux binaries.
The two also have very different focuses. While CentOS delivers a distribution with strong community support, Red Hat Enterprise Linux provides a stable enterprise platform with a focus on security, reliability, and performance as well as hardware, software, and government certifications for production deployments. Red Hat also delivers training, and an entire support organization ready to fix problems and deliver future flexibility by getting features worked into new versions.
Once in use, the operating systems often diverge further, as users selectively install patches to address bugs and security vulnerabilities to maintain their respective installs. In addition, the CentOS Project maintains code repositories of software that are not part of the Red Hat Enterprise Linux codebase. This includes feature changes selected by the CentOS Project. These are available as extra/additional packages and environments for CentOS users.
Method 8
I did read the CentOS 6.2 release notes, but I found the details
unsatisfactory. The release notes mentions packages modified,
removed or added to upstream. But it neither explains nor
links to any document detailing what exactly is different in the
modified packages. Granted the branding packages are self-explanatory,
but it mentions packages likekernel,ntp,anaconda, etc. which
have nothing to do with branding as far as I’m aware.
If you are curious about the differences between the RHEL and CentOS versions of a particular package (ntp, for example), you should compare the source RPMs:
- http://ftp.redhat.com/pub/redhat/linux/enterprise/6Server/en/os/SRPMS/
- http://vault.centos.org/6.0/os/SRPMS/Packages/
Method 9
Please read the below note form CentOS.
It clearly says:
CentOS is an Enterprise-class Linux Distribution derived from sources
freely provided to the public by Red Hat1.CentOS conforms fully with
Red Hat’s redistribution policy and aims to have full functional
compatibility with the upstream product. CentOS mainly changes
packages to remove Red Hat’s branding and artwork.
So I believe this clears all your doubts.
Method 10
- CentOS is the same of Redhat but without cost of support.
- CentOS is community driven, Redhat it supported by Redhat themselves.
So, ideally CentOS is a perfect choice for poor Redhat lovers 🙂
Method 11
Technically, they are the same in the sense that Red Hat Enterprise Linux makes use of the GPL, meaning that the source code must be made available and that the CentOS project uses that source code to make CentOS.
However, this is a simplification. Red Hat Enterprise Linux is tied to Red Hat’s business model. CentOS is a community project.
To be honest, I regret getting the subscription. Not that it isn’t a good product. It is. However, for the home user there’s no added value over CentOS and CentOS is less restrictive. I now run CentOS and consider the RHEL subscription a sunk cost.
Method 12
In 2019 RedHat announces CentOS Stream and in 2020 killed CentOS 8 as a stable release, leaving only rolling release. So the answer what is CentOS has changes since drastically ))
- https://www.redhat.com/en/topics/linux/what-is-centos
- https://en.wikipedia.org/wiki/CentOS
- https://almalinux.org/ – reincarnation of CentOS from community (funded by company producing CPanel)
- https://rockylinux.org/ – reincarnation of CentOS from main dev
All methods was sourced from stackoverflow.com or stackexchange.com, is licensed under cc by-sa 2.5, cc by-sa 3.0 and cc by-sa 4.0