CentOS

CentOS

Default GNOME desktop in CentOS 7
Developer	The CentOS Project (affiliated with Red Hat)
Written in	{{#property:p277}}
OS family	Unix-like
Working state	Current
Source model	Open source
Initial release	14 May 2004 (2004-05-14)
Latest release	7.2-1511 (14 December 2015 (2015-12-14)) [±] 6.7 (7 August 2015 (2015-08-07)) [±] 5.11 (30 September 2014 (2014-09-30)) [±]
Marketing target	Free computing (desktops, mainframes, servers and workstations)
Update method	Yum (PackageKit)
Package manager	RPM Package Manager
Platforms	x86-64
Kernel type	Monolithic (Linux kernel)
Default user interface	GNOME and KDE Plasma Desktop (user-selectable)
License	Free software (GPL and other licenses)
Official website	www.centos.org

CentOS (abbreviated from Community Enterprise Operating System) is a Linux distribution that attempts to provide a free, enterprise-class, community-supported computing platform which aims to be functionally compatible with its upstream source, Red Hat Enterprise Linux (RHEL). In January 2014, CentOS announced the official joining with Red Hat while staying independent from RHEL, under a new CentOS governing board.

The first CentOS release in May 2004, numbered as CentOS version 2, was forked from RHEL version 2.1AS. Since the release of version 7.0, CentOS officially supports only the x86-64 architecture, while versions older than 7.0-1406 also support IA-32 with Physical Address Extension (PAE), with additional architectures supported in CentOS versions older than 4.7. As of December 2015, AltArch releases of CentOS 7 are available for the IA-32 architecture, Power architecture, and for the ARMv7hl and AArch64 variants of the ARM architecture.

History

Prior to becoming known under its current name, CentOS originated as a build artifact of cAos Linux. At the time, some of the cAos contributors were merely interested in this build artifact for their own use, citing difficulties in collaborating with other noteworthy Red Hat Enterprise Linux (RHEL) clones of the time.

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's 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 the 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 the 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.

Design

RHEL is available only through a paid subscription service that provides access to software updates and varying levels of technical support. The product is largely composed of software packages distributed under free software licenses and the source code for these packages is made public by Red Hat.

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 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).

CentOS version	Architectures	RHEL base	Kernel	CentOS release date	RHEL release date	Delay (days)
2.1	IA-32	2.1	2.4.9	14 May 2004	17 May 2002	728
3.1	IA-32, x86-64, IA-64, s390, s390x	3.1	2.4.21-15	19 March 2004	23 October 2003	148
3.3	IA-32, x86-64, IA-64, s390, s390x	3.3	2.4.21-20	17 September 2004	3 September 2004	14
3.4	IA-32, x86-64, IA-64, s390, s390x	3.4	2.4.21-27	23 January 2005	12 December 2004	42
3.5	IA-32	3.5	2.4.21-32	10 June 2005	18 May 2005	23
3.6	IA-32	3.6	2.4.21-37	1 November 2005	28 September 2005	34
3.7	IA-32, x86-64, IA-64, s390, s390x	3.7	2.4.21-40	10 April 2006	17 March 2006	23
3.8	IA-32, x86-64	3.8	2.4.21-47	25 August 2006	20 July 2006	36
3.9	IA-32, x86-64, IA-64, s390, s390x	3.9	2.4.21-50	26 July 2007	15 June 2007	41
4.0	IA-32, x86-64, various	4.0	2.6.9-5	9 March 2005	14 February 2005	23
4.1	IA-32, IA-64, s390	4.1	2.6.9-11	12 June 2005	8 June 2005	4
4.2	IA-32, x86-64, IA-64, s390, s390x, alpha	4.2	2.6.9-22	13 October 2005	5 October 2005	8
4.3	IA-32, x86-64, IA-64, s390, s390x	4.3	2.6.9-34	21 March 2006	12 March 2006	9
4.4	IA-32, x86-64	4.4	2.6.9-42	30 August 2006	10 August 2006	20
4.5	IA-32, x86-64, IA-64	4.5	2.6.9-55	17 May 2007	1 May 2007	16
4.6	IA-32, x86-64, IA-64, Alpha, s390, s390x, PowerPC (beta), SPARC (beta)	4.6	2.6.9-67	16 December 2007	16 November 2007	30
4.7	IA-32, x86-64	4.7	2.6.9-78	13 September 2008	24 July 2008	51
4.8	IA-32, x86-64	4.8	2.6.9-89	21 August 2009	18 May 2009	95
4.9	IA-32, x86-64	4.9	2.6.9-100	2 March 2011	16 February 2011	14
5.0	IA-32, x86-64	5.0	2.6.18-8	12 April 2007	14 March 2007	28
5.1	IA-32, x86-64	5.1	2.6.18-53	2 December 2007	7 November 2007	25
5.2	IA-32, x86-64	5.2	2.6.18-92	24 June 2008	21 May 2008	34
5.3	IA-32, x86-64	5.3	2.6.18-128	31 March 2009	20 January 2009	69
5.4	IA-32, x86-64	5.4	2.6.18-164	21 October 2009	2 September 2009	49
5.5	IA-32, x86-64	5.5	2.6.18-194	14 May 2010	31 March 2010	44
5.6	IA-32, x86-64	5.6	2.6.18-238	8 April 2011	13 January 2011	85
5.7	IA-32, x86-64	5.7	2.6.18-274	13 September 2011	21 July 2011	54
5.8	IA-32, x86-64	5.8	2.6.18-308	7 March 2012	21 February 2012	15
5.9	IA-32, x86-64	5.9	2.6.18-348	17 January 2013	7 January 2013	10
5.10	IA-32, x86-64	5.10	2.6.18-371	19 October 2013	30 September 2013	19
5.11	IA-32, x86-64	5.11	2.6.18-398	30 September 2014	16 September 2014	14
6.0	IA-32, x86-64	6.0	2.6.32-71	10 July 2011	10 November 2010	242
6.1	IA-32, x86-64	6.1	2.6.32-131	9 December 2011	19 May 2011	204
6.2	IA-32, x86-64	6.2	2.6.32-220	20 December 2011	6 December 2011	14
6.3	IA-32, x86-64	6.3	2.6.32-279	9 July 2012	21 June 2012	18
6.4	IA-32, x86-64	6.4	2.6.32-358	9 March 2013	21 February 2013	15
6.5	IA-32, x86-64	6.5	2.6.32-431	1 December 2013	21 November 2013	10
6.6	IA-32, x86-64	6.6	2.6.32-504	28 October 2014	14 October 2014	14
6.7	IA-32, x86-64	6.7	2.6.32-573	7 August 2015	22 July 2015	16
7.0-1406	x86-64	7.0	3.10.0-123	7 July 2014	10 June 2014	27
7.1-1503	x86-64	7.1	3.10.0-229	31 March 2015	5 March 2015	26
7.2-1511	x86-64	7.2	3.10.0-327	14 December 2015	19 November 2015	25

AltArch releases

AltArch releases are released by the Alternative Architecture Special Interest Group (AltArch SIG) to support architectures that are not supported by the base CentOS releases.

CentOS version	Architectures	RHEL base	CentOS release date
7.1-1503	AArch64	7.1	4 August 2015
	IA-32		12 October 2015
7.2-1511	IA-32	7.2	19 December 2015
	ARMv7hl		19 December 2015
	PowerPC64 (TechPreview)		19 December 2015
	PowerPC8 LE (TechPreview)		19 December 2015

Add-ons releases

Software Collections (SCL) is a CentOS repository that provides a set of dynamic programming languages, database servers, and various related packages. Provided software versions are either more recent than their equivalent versions included in the base CentOS distribution, or are made available as official CentOS packages for the first time. (See also the list of CentOS repositories below.)

Packages available from the SCL do not replace the default system tools provided with CentOS. Instead, a parallel set of tools is installed in the /opt directory, and can be optionally enabled per application by using supplied scl utility. For example, the default versions of Perl or MySQL remain those provided by the base CentOS installation.

Add-on name	Architectures	Base CentOS version	CentOS release date	RHEL release date	Delay (days)
Software Collections (SCL) 1.0	x86-64	6.4, 6.5	19 February 2014	12 September 2013	160
Developer Toolset 2.0	IA-32, x86-64	6.4	N/A	12 September 2013	N/A

End-of-support schedule

In accordance with the Red Hat Enterprise Linux life cycle, CentOS 5, 6 and 7 will also be supported for ten years. Previously, CentOS 4 had been supported for seven years.

CentOS version	Release date	Full updates	Maintenance updates
Old version, no longer supported: 3	19 March 2004	20 July 2006	31 October 2010
Old version, no longer supported: 4	9 March 2005	31 March 2009	29 February 2012
Older version, yet still supported: 5	12 April 2007	Q1 2014	31 March 2017
Older version, yet still supported: 6	10 July 2011	Q2 2017	30 November 2020
Current stable version: 7	7 July 2014	Q4 2020	30 June 2024
Legend: Old version Older version, still supported Latest version Latest preview version Future release

Releases without upstream equivalents

Some of the ISO images released by the CentOS project have no direct upstream equivalents. They are created for specific purposes, such as for providing a live bootable image, or for providing a reduced-size installation media. In addition to those listed below, there are also AltArch releases, which also have no direct upstream equivalents.

LiveCD and LiveDVD images contain a bootable compressed file system, created by a set of custom scripts using a kickstart configuration file. These live images can be also installed to hard disk, thus obtaining a fully functional CentOS installation. The set of packages installed that way on a hard disk can not be adjusted during the installation, as that is a simple transfer of the image existing on CD/DVD, to a hard disk. After booting from hard disk, yum can be used for adding or removing packages.

MinimalCD images contain a minimum of packages required for a functional installation, with no compromises in security or network usability. These minimal images use the standard CentOS installer with all of its regular features minus the selection of packages. Yum can be used after the installation is completed to add or remove packages.

CentOS version	Release name	Architectures	RHEL base	CentOS release date
4.7	Server	IA-32, x86-64	4.7	17 October 2008
5.1	Live CD	IA-32	5.1	18 February 2008
5.2	Live CD	IA-32	5.2	17 July 2008
5.3	Live CD	IA-32	5.3	27 May 2009
5.5	Live CD	IA-32, x86-64	5.5	14 May 2010
5.6	Live CD	IA-32, x86-64	5.6	8 April 2011
6.0	Live CD	IA-32, x86-64	6.0	25 July 2011
	Live DVD			27 July 2011
	Minimal CD			28 July 2011
6.1	Live CD	IA-32, x86-64	6.1	9 December 2011
	Live DVD			9 December 2011
	Minimal CD			9 December 2011
6.2	Live CD	IA-32, x86-64	6.2	20 December 2011
	Live DVD			20 December 2011
	Minimal CD			20 December 2011
6.3	Minimal CD	IA-32, x86-64	6.3	9 July 2012
	Live CD			15 July 2012
	Live DVD			15 July 2012
6.4	Minimal CD	IA-32, x86-64	6.4	9 March 2013
	Live CD			22 May 2013
	Live DVD			22 May 2013
6.5	Minimal CD	IA-32, x86-64	6.5	1 December 2013
	Live CD			1 December 2013
	Live DVD			1 December 2013
6.6	Minimal CD	IA-32, x86-64	6.6	28 October 2014
6.7	Minimal CD	IA-32, x86-64	6.7	7 August 2015
7.0-1406	Live CD	x86-64	7.0	7 July 2014
	Gnome Live			7 July 2014
	KDE Live			7 July 2014
7.1-1503	Live CD	x86-64	7.1	31 March 2015
	Gnome Live			31 March 2015
	KDE Live			31 March 2015
7.2-1511	Gnome Live	x86-64	7.2	14 December 2015
	KDE Live			14 December 2015

Special interest groups

Special interest groups (SIGs) are organized portions of the CentOS community that open paths for building specialized variants of CentOS, which fulfill specific sets of requirements. SIGs have the freedom to modify and enhance CentOS in various ways, including adding more cutting-edge software, rebuilding existing packages depending on the requirements, providing alternative desktop environments, or making CentOS available on otherwise unsupported architectures. Among other things, this provides an opportunity for the community to get the best of both worlds – the overall stability of CentOS and newer technology from various open-source projects.

Architectures

As of version 7, CentOS fully supports only the x86-64 architecture, 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), supported in CentOS 3 and 4
• PowerPC/32 (Apple Macintosh and PowerMac running the G3 or G4 PowerPC processor), beta support available in CentOS 4
• IBM Mainframe (eServer zSeries and S/390), not supported since CentOS 5
• Alpha, support available in CentOS 4
• SPARC, beta support 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 architecture.

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).

Repositories

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-Fasttrack repository 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 base and 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 CentOSPlus and 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

External links

• Official website
• CentOS at DistroWatch
• CentOS.org Wiki: Additional Repositories
• CentOS and Red Hat – LWN.net article, contains a discussion on functional vs. binary compatibility