CentOS

CentOS was a free and open-source Linux distribution that worked very well with another popular system called Red Hat Enterprise Linux. It was made for people who wanted a stable operating system to use on their computers and servers without paying for it.

The first version of CentOS came out in May 2004. It was created from an earlier version of Red Hat, and it kept getting better over the years. By the time it reached version 8, CentOS could run on many different types of computer processors.

In December 2020, the company behind Red Hat decided to stop working on CentOS and started a new system called CentOS Stream instead. But some people still wanted CentOS to keep going, so new projects like AlmaLinux and Rocky Linux were created to carry on the CentOS mission.

History

CentOS started as a version of CAOS Linux, a type of computer system created by Gregory Kurtzer in 2002. Over time, CentOS grew and became very popular.

In 2014, Red Hat, a big company that makes computer software, began supporting CentOS. This helped CentOS grow even more. However, in December 2020, the CentOS team announced they would stop making the original CentOS. This made many people unhappy. After this news, two new projects started: Rocky Linux and AlmaLinux. These were created to keep the spirit of CentOS alive.

Design

CentOS developers used code from Red Hat to make a product that works much like Red Hat's system. They changed Red Hat's branding and logos because Red Hat does not allow them to share these. CentOS is free to use. Help with technical issues comes mostly from other users through mailing lists, web forums, and chat rooms.

Though the project works closely with Red Hat, it aims to be open and welcoming to everyone. Even though Red Hat employs many of the main CentOS developers, the CentOS Project depends on gifts from users and support from organizations.

Versioning and releases

CentOS releases

CentOS used to have version numbers with two parts for releases before 7.0. These parts matched the major version and updates of Red Hat Enterprise Linux (RHEL). For example, CentOS 6.5 came from RHEL 6 update 5.

Starting with version 7.0, CentOS added a third part to the version number. This part showed the month the source code was from. For example, version 7.0-1406 linked to the first update of RHEL 7, with "1406" meaning the code was from June 2014. This helped when new versions were needed for containers and clouds.

Since mid-2006, Red Hat began using the same naming as CentOS. For example, RHEL 4.5 or RHEL 6.5.

On September 10, 2019, CentOS delayed work on CentOS 8.1 to focus on CentOS 7.7 because CentOS 7 was being used more. After CentOS 7.7 came out, work went back to CentOS 8.0.

CentOS officially released version 8.0 on September 24, 2019. Because CentOS stopped in late 2021, its last version was 8.5, released on November 16, 2021. Meanwhile, RHEL kept going and reached version 8.10 by September 2024.

End-of-support schedule

CentOS versions 5, 6, and 7 were supported for up to 10 years because they were based on RHEL. Before that, CentOS 4 was supported for seven years.

Older version information

CentOS version 7

Latest version information

CentOS version 8

AltArch releases

AltArch releases are made by the Alternative Architecture Special Interest Group (AltArch SIG). They support types of computers that the main CentOS versions do not.

Add-ons releases

Software Collections (SCL) is a CentOS collection that offers newer versions of programming languages, database servers, and other packages. These do not replace the regular tools in CentOS. Instead, they are installed in a separate place and can be chosen when needed. For example, the regular versions of Perl or MySQL stay the same.

Releases without upstream equivalents

Some CentOS images have special purposes and no matching versions from Red Hat.

LiveCD and LiveDVD images can boot a computer from a CD or DVD and can also be installed on a hard drive. The set of packages cannot be changed during installation.

MinimalCD images have only the needed packages for installation and use the regular CentOS installer without package choices. More packages can be added after installation using yum.

Main article: CentOS repositories

Special interest groups

Special interest groups, or SIGs, are groups within the CentOS community. They help create special versions of CentOS that meet specific needs. These groups can change and improve CentOS in many ways. They might add newer software, change existing parts to fit certain needs, offer different desktop options, or make CentOS work on systems it didn’t support before.

Architectures

Since version 8, CentOS works well with x86-64, POWER8, and 64-bit ARM computers. Some older types of computers, like those using IA-32, are no longer supported.

As of December 2015, CentOS also offered versions for ARMv7hl and AArch64 types of ARM computers. There were plans to support more types of ARM computers in the future. You can find CentOS versions on Amazon's EC2 cloud as pre-made images called Amazon Machine Images (AMIs).

Repositories

CentOS had three main repositories (also called channels) with software packages that made up the main CentOS system:

• base: held packages that formed CentOS updates, changing when new updates were released as ISO images.
• updates: held packages for security, bug fixes, or improvements, released between regular updates.
• addons: provided packages needed to build the main CentOS packages but not supplied by the source.

The CentOS Project also offered extra repositories with software not in the default base and updates repositories. These included:

• CentOS Extras: held packages adding features to CentOS without changing its compatibility.
• CentOSPlus: held packages that updated some base CentOS parts, making CentOS different from the source.
• CentOS-Testing: tested packages before they moved to CentOSPlus and CentOS Extras. These packages might not work properly.
• CentOS-Fasttrack: held bug fixes and improvements released between updates. These were possible candidates for the next update but did not include security updates.
• CR (Continuous Release): made packages available that would appear in the next CentOS update. These were shared for testing until the update was released.
• debuginfo: held packages with symbols for finding problems when packages were built.
• contrib: held packages added by CentOS users that did not match the main distribution packages.
• Software Collections: offered newer software versions than those in the base distribution, see above for more information.

CentOS Stream

CentOS Stream is a type of operating system that changes often and follows the development of Red Hat Enterprise Linux (RHEL). It is meant for people who want to help and work together in the RHEL community.

Before CentOS Stream, older versions of CentOS were based directly on RHEL. But CentOS Stream is different. It sits between the fast-changing Fedora Linux and the more stable RHEL. CentOS Stream 9 and RHEL 9 started from the same basic code, so CentOS Stream is often closer to RHEL than Fedora is. The first version, CentOS Stream 8, came out on September 24, 2019, at the same time as CentOS 8. When CentOS 8 stopped getting updates, the CentOS Project made it easy to change from CentOS Linux 8 to CentOS Stream 8.