Red Hat Enterprise Linux
Red Hat Enterprise Linux 7's default GNOME 3 desktop
|Developer||Red Hat, Inc.|
|Source model||Open source (with exceptions)|
|Initial release||February 22, 2000|
|Latest release||7.2, 6.8, 5.11 / November 19, 2015, May 10, 2016 , September 16, 2014|
|Marketing target||Commercial market (including for mainframes, servers, supercomputers)|
|Update method||Yum / PackageKit|
|Platforms||IA-32, x86-64; Power Architecture; S/390; z/Architecture|
|Kernel type||Monolithic (Linux)|
|Default user interface||GNOME|
|License||Various free software licenses, plus proprietary binary blobs|
|Preceded by||Red Hat Linux|
Red Hat Enterprise Linux (RHEL) is a Linux distribution developed by Red Hat and targeted toward the commercial market. Red Hat Enterprise Linux is released in server versions for x86, x86-64, Itanium, PowerPC and IBM System z, and desktop versions for x86 and x86-64. All of the Red Hat's official support and training, together with the Red Hat Certification Program, focuses on the Red Hat Enterprise Linux platform. Red Hat Enterprise Linux is often abbreviated to RHEL, although this is not an official designation.
The first version of Red Hat Enterprise Linux to bear the name originally came onto the market as "Red Hat Linux Advanced Server". In 2003 Red Hat rebranded Red Hat Linux Advanced Server to "Red Hat Enterprise Linux AS", and added two more variants, Red Hat Enterprise Linux ES and Red Hat Enterprise Linux WS.
Red Hat uses strict trademark rules to restrict free re-distribution of their officially supported versions of Red Hat Enterprise Linux, but still freely provides its source code. Third-party derivatives can be built and redistributed by stripping away non-free components like Red Hat's trademarks, including community-supported distributions like CentOS and Scientific Linux, and commercial forks like Oracle Linux, which aim to offer 100% binary compatibility with Red Hat Enterprise Linux.
Red Hat Enterprise Linux Server subscription is available at no cost for development purposes. Developers need to register for the Red Hat Developer Program and agree to licensing terms forbidding production use. This free developer subscription was announced on March 31, 2016.
There are also "Academic" editions of the Desktop and Server variants. They are offered to schools and students, are less expensive, and are provided with Red Hat technical support as an optional extra. Web support based on number of customer contacts can be purchased separately.
It is often assumed the branding ES, AS, and WS stand for "Entry-level Server", "Advanced Server" and "Work Station", respectively. The reason for this is that the ES product is indeed the company's base enterprise server product, while AS is the more advanced product. However, nowhere on its site or in its literature does Red Hat say what AS, ES and WS stand for.
- Red Hat Enterprise Linux Advanced Platform (former AS)
- Red Hat Enterprise Linux (former ES) (limited to two CPUs)
- Red Hat Enterprise Linux Desktop with Workstation and Multi-OS option
- Red Hat Enterprise Linux Desktop with Workstation option (former WS)
- Red Hat Enterprise Linux Desktop with Multi-OS option
- Red Hat Enterprise Linux Desktop (former Desktop)
RHEL 4, 3, and prior releases had four variants:
- Red Hat Enterprise Linux AS for mission-critical/enterprise computer systems.
- Red Hat Enterprise Linux ES for supported network servers
- Red Hat Enterprise Linux WS for technical power user enterprise desktops for high-performance computing
- Red Hat Desktop for multiple deployments of single-user desktops for enterprises.
Relationship with Fedora
Originally, Red Hat sold support for versions of Red Hat Linux (Red Hat Linux Enterprise Edition 6.2E was essentially a version of Red Hat Linux 6.2/7 with different support levels.) Starting with RHEL 2.1 AS in 2002, Red Hat sold their first version of RHEL. It was based on Red Hat Linux, but used a much more conservative release cycle. Later versions included technologies from the Red Hat–sponsored Fedora community distribution project. Red Hat Enterprise Linux release schedules do not follow that of Fedora (around 6 months per release) but are more conservative (2 years or more).
Fedora serves as upstream for future versions of RHEL. RHEL trees are forked off the Fedora repository, and released after a substantial stabilization and quality assurance effort. For example, RHEL 6 was forked from Fedora at the end of 2009 (approximately at the time of the Fedora 12 release) and released more or less together with Fedora 14. By the time RHEL 6 was released, many features from Fedora 13 and 14 had already been backported into it. The Fedora Project lists the following lineages for older Red Hat Enterprise releases:
- Red Hat Linux 6.2/7 → Red Hat Linux Enterprise Edition 6.2E
- Red Hat Linux 7.2 → Red Hat Enterprise Linux 2.1
- Red Hat Linux 10 beta 1 → Red Hat Enterprise Linux 3
- Fedora Core 3 → Red Hat Enterprise Linux 4
- Fedora Core 6 → Red Hat Enterprise Linux 5
- Fedora 12, 13 → Red Hat Enterprise Linux 6
- Fedora 19, 20 → Red Hat Enterprise Linux 7
(Note about Fedora Core 1 and Red Hat Enterprise Linux 3: Red Hat released Red Hat Linux 10 beta 1, then took two forks from that codebase to seed both Fedora Core 1 and Red Hat Enterprise Linux 3 beta releases. There was some cross-pollination between the two up until shortly before the first production RHEL 3 release. Therefore, both FC1 and RHEL3 came from a common fork of RHL10beta1.)
In addition, the Fedora project includes Extra Packages for Enterprise Linux (EPEL), a community-provided set of packages for RHEL going beyond the ones that Red Hat selected for inclusion in its supported distribution. The Fedora project provides the following explanation:
Both Fedora and Red Hat Enterprise Linux are open source. Fedora is a free distribution and community project and upstream for Red Hat Enterprise Linux. Fedora is a general purpose system that gives Red Hat and the rest of its contributor community the chance to innovate rapidly with new technologies. Red Hat Enterprise Linux is a commercial enterprise operating system and has its own set of test phases including alpha and beta releases which are separate and distinct from Fedora development.
Originally, Red Hat's enterprise product, then known as Red Hat Linux, was made freely available to anybody who wished to download it, while Red Hat made money from support. Red Hat then moved towards splitting its product line into Red Hat Enterprise Linux which was designed to be stable and with long-term support for enterprise users and Fedora as the community distribution and project sponsored by Red Hat. The use of trademarks prevents verbatim copying of Red Hat Enterprise Linux.
Since Red Hat Enterprise Linux is based completely on free and open source software, Red Hat makes available the complete source code to its enterprise distribution through its FTP site to anybody who wants it. Accordingly, several groups have taken this source code and compiled their own versions of Red Hat Enterprise Linux, typically with the only changes being the removal of any references to Red Hat's trademarks and pointing the update systems to non-Red Hat servers. Groups which have undertaken this include CentOS (the 8th most popular Linux distribution as of November 2011), Oracle Linux, Scientific Linux, White Box Enterprise Linux, StartCom Enterprise Linux, Pie Box Enterprise Linux, X/OS, Lineox, and Bull's XBAS for high-performance computing. All provide a free mechanism for applying updates without paying a service fee to the distributor.
Rebuilds of Red Hat Enterprise Linux are free but do not get any commercial support or consulting services from Red Hat and lack any software, hardware or security certifications. Also, the rebuilds do not get access to Red Hat services like Red Hat Network.
Unusually, Red Hat took steps to obfuscate their changes to the Linux kernel for 6.0 by not publicly providing the patch files for their changes in the source tarball, and only releasing the finished product in source form. Speculation suggested that the move was made to affect Oracle's competing rebuild and support services, which further modifies the distribution. This practice however, still complies with the GNU GPL since source code is defined as "[the] preferred form of the work for making modifications to it", and the distribution still complies with this definition. Red Hat's CTO Brian Stevens later confirmed the change, stating that certain information (such as patch information) would now only be provided to paying customers to make the Red Hat product more competitive against the growing number of companies offering support for products based on RHEL. CentOS developers had no objections to the change since they do not make any changes to the kernel beyond what is provided by Red Hat. Their competitor Oracle announced in November 2012 that they were releasing a RedPatch service, which allows public view of the RHEL kernel changes, broken down by patch.
Related products and add-ons
A number of commercial vendors use Red Hat Enterprise Linux as a base for the operating system in their products. Two of the best known are the Console Operating System in VMware ESX Server and Oracle Linux respin.
Third-party RPM packages for Red Hat Enterprise Linux, CentOS, and Scientific Linux can be downloaded from RepoForge (formerly RPMforge), an alliance of developers who previously had separate distribution sites (similar to the RPM Fusion merger).
- Red Hat Enterprise Linux 2.1 AS (Pensacola), 26 March 2002, uses Linux kernel 2.4.9-e.3
- Update 1, 14 February 2003 (kernel 2.4.9-e.12)
- Update 2, 29 May 2003 (kernel 2.4.9-e.24)
- Update 3, 19 December 2003 (kernel 2.4.9-e.34)
- Update 4, 21 April 2004 (kernel 2.4.9-e.40)
- Update 5, 18 August 2004 (kernel 2.4.9-e.49)
- Update 6, 13 December 2004 (kernel 2.4.9-e.57)
- Update 7, 28 April 2005
- Red Hat Enterprise Linux 2.1 ES (Panama), May 2003
- Red Hat Enterprise Linux 3 (Taroon), 22 October 2003, uses Linux kernel 2.4.21-4
- Update 1, 16 January 2004 (kernel 2.4.21-9)
- Update 2, 12 May 2004 (kernel 2.4.21-15)
- Update 3, 3 September 2004 (kernel 2.4.21-20)
- Update 4, 12 December 2004 (kernel 2.4.21-27)
- Update 5, 18 May 2005 (kernel 2.4.21-32)
- Update 6, 28 September 2005 (kernel 2.4.21-37)
- Update 7, 17 March 2006 (kernel 2.4.21-40)
- Update 8, 20 July 2006 (kernel 2.4.21-47)
- Update 9, 15 June 2007 (kernel 2.4.21-50)
- Red Hat Enterprise Linux 4 (Nahant), 15 February 2005, uses Linux kernel 2.6.9-5
- 4.1, also termed Update 1, 8 June 2005 (kernel 2.6.9-11)
- 4.2, also termed Update 2, 5 October 2005 (kernel 2.6.9-22)
- 4.3, also termed Update 3, 12 March 2006 (kernel 2.6.9-34)
- 4.4, also termed Update 4, 10 August 2006 (kernel 2.6.9-42)
- 4.5, also termed Update 5, 1 May 2007 (kernel 2.6.9-55)
- 4.6, also termed Update 6, 15 November 2007 (kernel 2.6.9-67)
- 4.7, also termed Update 7, 29 July 2008 (kernel 2.6.9-78)
- 4.8, also termed Update 8, 19 May 2009 (kernel 2.6.9-89)
- 4.9, also termed Update 9, 16 February 2011 (kernel 2.6.9-100)
- Red Hat Enterprise Linux 5 (Tikanga), 14 March 2007, uses Linux kernel 2.6.18-8
- 5.1, also termed Update 1, 7 November 2007 (kernel 2.6.18-53)
- 5.2, also termed Update 2, 21 May 2008 (kernel 2.6.18-92)
- 5.3, also termed Update 3, 20 January 2009 (kernel 2.6.18-128)
- 5.4, also termed Update 4, 2 September 2009 (kernel 2.6.18-164)
- 5.5, also termed Update 5, 30 March 2010 (kernel 2.6.18-194)
- 5.6, also termed Update 6, 13 January 2011 (kernel 2.6.18-238)
- 5.7, also termed Update 7, 21 July 2011 (kernel 2.6.18-274)
- 5.8, also termed Update 8, 20 February 2012 (kernel 2.6.18-308)
- 5.9, also termed Update 9, 7 January 2013 (kernel 2.6.18-348)
- 5.10, also termed Update 10, 1 October 2013 (kernel 2.6.18-371)
- 5.11, also termed Update 11, 16 September 2014 (kernel 2.6.18-398)
Red Hat Enterprise Linux 6 was forked from Fedora 12 and contains many backported features from Fedora 13 and 14.
- Red Hat Enterprise Linux 6 (Santiago), 10 November 2010, uses Linux kernel 2.6.32-71
- 6.1, also termed Update 1, 19 May 2011 (kernel 2.6.32-131)
- 6.2, also termed Update 2, 6 December 2011 (kernel 2.6.32-220)
- 6.3, also termed Update 3, 20 June 2012 (kernel 2.6.32-279)
- 6.4, also termed Update 4, 21 February 2013 (kernel 2.6.32-358)
- 6.5, also termed Update 5, 21 November 2013 (kernel 2.6.32-431)
- 6.6, also termed Update 6, 13 October 2014 (kernel 2.6.32-504)
- 6.7, also termed Update 7, 22 July 2015 (kernel 2.6.32-573)
- 6.8, also termed Update 8, 10 May 2016 (kernel 2.6.32-642)
Red Hat Enterprise Linux 7 (Maipo) is based on Fedora 19, upstream Linux kernel 3.10, systemd 208, and GNOME 3.8 (rebased to GNOME 3.14 in RHEL 7.2). The first beta was announced on 11 December 2013, and a release candidate was made available on 15 April 2014. On 10 June 2014 Red Hat Enterprise Linux 7 was officially released.
- Red Hat Enterprise Linux 7.0 (Maipo), 10 June 2014, uses Linux kernel 3.10.0-123
Product life cycle
The life cycle of Red Hat Enterprise Linux is at least seven years for versions 3 and 4, while it spans at least 10 years for more recent versions 5, 6 and 7. The life cycle comprises several phases of varying length with different degrees of support. During the first phase ("Production 1"), Red Hat provides full support and updates software and hardware drivers. In later phases ("Production 2" and "Production 3") only security and other important fixes are provided and support for new hardware is gradually reduced.
In the last years of the support lifecycle (after seven years for the version 4 and earlier, or after 10 years for the version 5 and later), critical and security-related fixes are only provided to customers who pay an additional subscription ("Extended Lifecycle Support Add-On") that is available for versions 3, 4 and 5, and covers a limited number of packages.
|Release date||End of Production 1
|End of Production 2
|End of Production 3
|End of Extended
|Old version, no longer supported: 2.1||26 March 2002 (AS)
1 May 2003 (ES)
|30 November 2004||31 May 2005||31 May 2009||N/A|
|Old version, no longer supported: 3||23 October 2003||20 July 2006||30 June 2007||31 October 2010||30 January 2014|
|Older version, yet still supported: 4||14 February 2005||31 March 2009||16 February 2011||29 February 2012||31 March 2017|
|Older version, yet still supported: 5||15 March 2007||8 January 2013||31 January 2014||31 March 2017||30 November 2020|
|Older version, yet still supported: 6||10 November 2010||10 May 2016||10 May 2017||30 November 2020||N/A|
|Current stable version: 7||10 June 2014||Q4 2019||Q4 2020||30 June 2024||N/A|
To maintain a stable application binary interface (ABI), Red Hat does not update the kernel version, but instead backports new features to the same kernel version with which a particular version of RHEL has been released. New features are backported throughout the Production 1 phase of the RHEL lifecycle. Consequently, RHEL may use a Linux kernel with a dated version number, yet the kernel is up-to-date regarding not only security fixes, but also certain features. One specific example is the SO_REUSEPORT socket option which was added to Linux kernel 3.9, and was subsequently backported and became available since RHEL 6.5, which uses version 2.6.32 of the Linux kernel.
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