What is CentOS Linux?
CentOS Linux is a community-supported distribution derived from sources freely provided to the public on Red Hat or CentOS git for Red Hat Enterprise Linux (RHEL). As such, CentOS Linux aims to be functionally compatible with RHEL. The CentOS Project mainly changes packages to remove upstream vendor branding and artwork. CentOS Linux is no-cost and free to redistribute. Each CentOS version is maintained until the equivalent RHEL version goes out of general support. A new CentOS version is made available once a new RHEL version is rebuilt - approximately every 6-12 months for minor point releases and several years for major version bumps. The length of time the rebuild takes varies from weeks for point releases to months for major version bumps. This results in a secure, low-maintenance, reliable, predictable and reproducible Linux environment.
Download CD and DVD images or individual RPM packages.
CentOS originated as a build of CAOS Linux, an RPM-based Linux distribution started by Gregory Kurtzer in 2002. Infiscale described its GravityOS as "[including] the small footprint of Caos", indicating a certain level of influence from the discontinued distribution.
In June 2006, David Parsley, the primary developer of Tao Linux (another RHEL clone), announced the retirement of Tao Linux and its rolling into CentOS development. Tao users migrated to the CentOS release via yum update.
In July 2009, it was reported in an open letter on the CentOS Project web site that CentOS's founder, Lance Davis, had disappeared in 2008. Davis had ceased contribution to the project, but continued to hold the registration for the CentOS domain and PayPal account. In August 2009, the CentOS team reportedly made contact with Davis and obtained the centos.info and centos.org domains.
In July 2010, CentOS overtook Debian to become the most popular Linux distribution for web servers, with almost 30% of all Linux web servers using it. Debian retook the lead in January 2012.
In January 2014, Red Hat announced that it would sponsor the CentOS Project, "helping to establish a platform well-suited to the needs of open source developers that integrate technologies in and around the operating system". As a result of these changes, ownership of CentOS trademarks was transferred to Red Hat, which now employs most of the CentOS head developers; however, they work as part of Red Hat's Open Source and Standards team, which operates separately from the Red Hat Enterprise Linux team. A new CentOS governing board was also established.
On December 8, 2020, the CentOS Project announced that the distribution would be discontinued at the end of 2021. The community's response to this announcement was overwhelmingly negative. Soon thereafter, CentOS founder, Gregory Kurtzer announced a new project to continue the original CentOS focus, which became known as Rocky Linux. On March 30, 2021, Cloud Linux (makers of CloudLinux OS) released the CentOS 8 clone AlmaLinux.
CentOS developers use Red Hat's source code to create a final product very similar to RHEL. Red Hat's branding and logos are changed because Red Hat does not allow them to be redistributed. CentOS is available free of charge. Technical support is primarily provided by the community via official mailing lists, web forums, and chat rooms.
The project is affiliated with Red Hat but aspires to be more public, open, and inclusive. While Red Hat employs most of the CentOS head developers, the CentOS Project itself relies on donations from users and organizational sponsors.
Versioning and releases
CentOS version numbers for releases older than 7.0 have two parts, a major version and a minor version, which correspond to the major version and update set of Red Hat Enterprise Linux (RHEL) used to build a particular CentOS release. For example, CentOS 6.5 is built from the source packages of RHEL 6 update 5 (also known as RHEL version 6.5), which is a so-called "point release" of RHEL 6.
Starting with version 7.0, CentOS version numbers also include a third part that indicates the monthstamp of the source code the release is based on. For example, version number 7.0-1406 still maps this CentOS release to the zeroth update set of RHEL 7, while "1406" indicates that the source code this release is based on dates from June 2014. Using the monthstamp allows installation images to be reissued for (as of July 2014) oncoming container and cloud releases, while maintaining a connection to the related base release version.
Since mid-2006 and starting with RHEL version 4.4, which is formally known as Red Hat Enterprise Linux 4.0 update 4, Red Hat has adopted a version-naming convention identical to that used by CentOS (for example, RHEL 4.5 or RHEL 6.5).
On 10 September 2019 CentOS deferred CentOS 8.1 work for CentOS 7.7 since CentOS 7.x was in production and CentOS 8.x was not in production. Once CentOS 7.7 was released resources moved back to CentOS 8.0.
On 24 September 2019 CentOS officially released CentOS version 8.0.
According to the Red Hat Enterprise Linux (RHEL) life cycle, CentOS 5, 6 and 7 will be "maintained for up to 10 years" as it is based on RHEL. Previously, CentOS 4 had been supported for seven years.
(released 07 Jul 2014, EOL 30 Jun 2024)
(released 10 Jul 2011, EOL 30 Nov 2020)
(released 12 Apr 2007, EOL 31 Mar 2017)
As of version 8, CentOS fully supports x86-64, POWER8 and 64-bit ARM architectures, while the following architectures are not supported:
- IA-32 in all variants, not supported since CentOS 7
- IA-32 without Physical Address Extension (PAE), not supported since CentOS 6
- IA-64 (Intel Itanium architecture), was supported in CentOS 3 and 4
- 32-bit PowerPC (Apple Macintosh and PowerMac running the G3 or G4 PowerPC processor), beta support was available in CentOS 4
- IBM Mainframe (eServer zSeries and S/390), not supported since CentOS 5
- Alpha, support was available in CentOS 4
- SPARC, beta support was available in CentOS 4
As of December 2015, AltArch releases of CentOS 7 are available for the ARMv7hl and AArch64 variants of the ARM architecture, and plans exist for supporting other variants of the ARM architecture. ARM support is a community effort coordinated through the AltArch SIG. AltArch releases of CentOS 7 are also available for the IA-32 architecture and Power ISA (POWER7 and POWER8 chips).
A Live CD version of CentOS is available at mirror.centos.org. A bootable Live USB image of CentOS can be created manually or with UNetbootin.
CentOS images are also available on Amazon's EC2 cloud, in form of prebuilt and already published Amazon Machine Images (AMIs).
There are three primary CentOS repositories (also known as channels), containing software packages that make up the main CentOS distribution:
base: contains packages that form CentOS point releases, and gets updated when the actual point release is formally made available in form of ISO images.
updates: contains packages that serve as security, bugfix or enhancement updates, issued between the regular update sets for point releases. Bugfix and enhancement updates released this way are only those unsuitable to be released through the
CentOS-Fasttrackrepository described below.
addons: provides packages required for building the packages that make up the main CentOS distribution, but are not provided by the upstream.
The CentOS Project provides several additional repositories that contain software packages not provided by the default
updates repositories. Those repositories include the following:
CentOS Extras: contains packages that provide additional functionality to CentOS without breaking its upstream compatibility or updating the base components.
CentOSPlus: contains packages that actually upgrade certain base CentOS components, changing CentOS so that it is not exactly like the upstream provider's content.
CentOS-Testing: serves as a proving ground for packages on their way to
CentOS Extras. Offered packages may or may not replace core CentOS packages, and are not guaranteed to work properly.
CentOS-Fasttrack: contains bugfix and enhancement updates issued from time to time, between the regular update sets for point releases. The packages released this way serve as close candidates for the inclusion into the next point release. This repository does not provide security updates, and does not contain packages unsuitable for uncertain inclusion into point releases.
CR(Continuous Release) : makes generally available packages that will appear in the next point release of CentOS. The packages are made available on a testing and hotfix basis, until the actual point release is formally released in form of ISO images.
debuginfo: Contains packages with debugging symbols generated when the primary packages were built.
contrib: Contains packages contributed by CentOS users that do not overlap with any of the core distribution packages.
Software Collections: Provides versions of software newer than those provided by the base distribution, see above for more details.