Red Hat Enterprise Linux

Red Hat Enterprise Linux
GNOME 3 on RHEL 7
Developer Red Hat, Inc.
OS family Linux
Working state Current
Source model Open source (with exceptions)[1]
Initial release February 22, 2000 (2000-02-22)[2]
Latest release 7.5, 6.10, 5.11 / April 10, 2018 (2018-04-10), June 19, 2018 (2018-06-19), September 16, 2014 (2014-09-16)
Latest preview 7.6 Beta[3][4] / August 22, 2018 (2018-08-22)
Marketing target Commercial market (including for mainframes, servers, supercomputers)
Available in Multilingual
Update method Long-term support (LTS)
Package manager
  • Yum (command-line front-end), yumex (graphical front-end)
  • PackageKit (graphical front-ends)
  • RPM (package format)
Platforms ARM64,[5] x86-32, x86-64; Power Architecture; S/390; z/Architecture[6]
Kernel type Monolithic (Linux)
Userland GNU
Default user interface GNOME
License Various free software licenses, plus proprietary binary blobs[1]
Preceded by Red Hat Linux
Official website www.redhat.com/rhel

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.[7]

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,[8] 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. Examples include community-supported distributions like CentOS and Scientific Linux, and commercial forks like Oracle Linux, which does not offer 100% binary compatibility with Red Hat Enterprise Linux, because Oracle uses a non-standard process to clear the Red Hat brand.

Variants

Red Hat Enterprise Linux Server subscription is available at no cost for development purposes.[9] 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.[10]

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.

In Red Hat Enterprise Linux 5 there are new editions that substitute former Red Hat Enterprise Linux AS/ES/WS/Desktop:[11][12]

  • 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)

Red Hat had also announced its Red Hat Global Desktop Linux edition "for emerging markets".[13]

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.)[14] 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.[15] 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:[15]

  • 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[15]
  • Fedora 19, 20 → Red Hat Enterprise Linux 7[16]

(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:[17]

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.

Rebuilds

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),[18] 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.[19] 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.[20] 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.[21] 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.[22][23]

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.

Version history and timeline

RHEL 7

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 3.26 in RHEL 7.5).[24] The first beta was announced on 11 December 2013,[16][25] and a release candidate was made available on 15 April 2014.[26] On June 10, 2014 Red Hat Enterprise Linux 7 was officially released.[27]

  • Red Hat Enterprise Linux 7.0 (Maipo), June 10, 2014, uses Linux kernel 3.10.0-123[28]
    • 7.1, also termed Update 1, March 5, 2015 (kernel 3.10.0-229)[29]
    • 7.2, also termed Update 2, November 19, 2015 (kernel 3.10.0-327)[30]
    • 7.3, also termed Update 3, November 3, 2016 (kernel 3.10.0-514)[31]
    • 7.4, also termed Update 4, August 1, 2017 (kernel 3.10.0-693)[32]
    • 7.5, also termed Update 5, April 10, 2018 (kernel 3.10.0-862)[33]
    • 7.6, currently in beta (kernel 3.10.0-933)

RHEL 6

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), November 10, 2010, uses Linux kernel 2.6.32-71[28]
    • 6.1, also termed Update 1, May 19, 2011 (kernel 2.6.32-131)
    • 6.2, also termed Update 2, December 6, 2011 (kernel 2.6.32-220)
    • 6.3, also termed Update 3, June 20, 2012 (kernel 2.6.32-279)
    • 6.4, also termed Update 4, February 21, 2013 (kernel 2.6.32-358)
    • 6.5, also termed Update 5, November 21, 2013 (kernel 2.6.32-431)
    • 6.6, also termed Update 6, October 13, 2014 (kernel 2.6.32-504)
    • 6.7, also termed Update 7, July 22, 2015 (kernel 2.6.32-573)
    • 6.8, also termed Update 8, May 10, 2016 (kernel 2.6.32-642)
    • 6.9, also termed Update 9, March 21, 2017 (kernel 2.6.32-696)
    • 6.10, also termed Update 10, June 19, 2018 (kernel 2.6.32-754)
    • 6 ELS +, Extended Life-cycle Support (ELS) Start Date November 30, 2020
      • aka added ELS entitlement until ELS end Date June 30, 2024

    RHEL 5

    • Red Hat Enterprise Linux 5 (Tikanga), March 15, 2007, uses Linux kernel 2.6.18-8[28]
      • 5.1, also termed Update 1, November 7, 2007 (kernel 2.6.18-53)
      • 5.2, also termed Update 2, May 21, 2008 (kernel 2.6.18-92)
      • 5.3, also termed Update 3, January 20, 2009 (kernel 2.6.18-128)
      • 5.4, also termed Update 4, September 2, 2009 (kernel 2.6.18-164)
      • 5.5, also termed Update 5, March 30, 2010 (kernel 2.6.18-194)
      • 5.6, also termed Update 6, January 13, 2011 (kernel 2.6.18-238)
      • 5.7, also termed Update 7, July 21, 2011 (kernel 2.6.18-274)
      • 5.8, also termed Update 8, February 20, 2012 (kernel 2.6.18-308)
      • 5.9, also termed Update 9, January 7, 2013 (kernel 2.6.18-348)
      • 5.10, also termed Update 10, October 1, 2013 (kernel 2.6.18-371)
      • 5.11, also termed Update 11, September 16, 2014 (kernel 2.6.18-398)
      • 5.11+, Extended Life-cycle Support (ELS) Start Date March 31, 2017
        • aka added ELS entitlement until ELS end Date November 30, 2020

    RHEL 4

    • Red Hat Enterprise Linux 4 (Nahant), February 15, 2005, uses Linux kernel 2.6.9-5[28]
      • 4.1, also termed Update 1, June 8, 2005 (kernel 2.6.9-11)
      • 4.2, also termed Update 2, October 5, 2005 (kernel 2.6.9-22)
      • 4.3, also termed Update 3, March 12, 2006 (kernel 2.6.9-34)
      • 4.4, also termed Update 4, August 10, 2006 (kernel 2.6.9-42)
      • 4.5, also termed Update 5, May 1, 2007 (kernel 2.6.9-55)
      • 4.6, also termed Update 6, November 15, 2007 (kernel 2.6.9-67)
      • 4.7, also termed Update 7, July 29, 2008 (kernel 2.6.9-78)
      • 4.8, also termed Update 8, May 19, 2009 (kernel 2.6.9-89)
      • 4.9, also termed Update 9, February 16, 2011 (kernel 2.6.9-100)

    RHEL 3

    • Red Hat Enterprise Linux 3 (Taroon), October 22, 2003, uses Linux kernel 2.4.21-4[28]
      • Update 1, January 16, 2004 (kernel 2.4.21-9)
      • Update 2, May 12, 2004 (kernel 2.4.21-15)
      • Update 3, September 3, 2004 (kernel 2.4.21-20)
      • Update 4, December 12, 2004 (kernel 2.4.21-27)
      • Update 5, May 18, 2005 (kernel 2.4.21-32)
      • Update 6, September 28, 2005 (kernel 2.4.21-37)
      • Update 7, March 17, 2006 (kernel 2.4.21-40)
      • Update 8, July 20, 2006 (kernel 2.4.21-47)
      • Update 9, June 15, 2007 (kernel 2.4.21-50)

    RHEL 2.1

    • Red Hat Enterprise Linux 2.1 AS (Pensacola), March 26, 2002, uses Linux kernel 2.4.9-e.3[28]
      • Update 1, February 14, 2003 (kernel 2.4.9-e.12)
      • Update 2, May 29, 2003 (kernel 2.4.9-e.24)
      • Update 3, December 19, 2003 (kernel 2.4.9-e.34)
      • Update 4, April 21, 2004 (kernel 2.4.9-e.40)
      • Update 5, August 18, 2004 (kernel 2.4.9-e.49)
      • Update 6, December 13, 2004 (kernel 2.4.9-e.57)
      • Update 7, April 28, 2005[34]
      • Red Hat Enterprise Linux 2.1 ES (Panama), May 2003

    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.[35]

    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.[36]

    RHEL
    Version    		Release dateEnd of Production 1
    phase    		End of Production 2
    phase    		End of Production 3
    phase    		End of Extended
    Lifecycle Support    		Last Minor Release
    Old version, no longer supported: 2.1 26 March 2002 (AS)
    1 May 2003 (ES)    		 30 November 2004 31 May 2005 31 May 2009[37] N/A
    Old version, no longer supported: 3 23 October 2003 20 July 2006 30 June 2007 31 October 2010[38] 30 January 2014
    Old version, no longer supported: 4 14 February 2005 31 March 2009 16 February 2011 29 February 2012 31 March 2017 4.9
    Older version, yet still supported: 5 15 March 2007 8 January 2013 31 January 2014 31 March 2017 30 November 2020 5.11
    Older version, yet still supported: 6 10 November 2010 10 May 2016 10 May 2017 30 November 2020 30 June 2024 6.10
    Current stable version: 7 10 June 2014[39] Q4 2019 Q4 2020 30 June 2024 N/A 7.5
    Legend:
    Old version
    Older version, still supported
    Latest version
    Latest preview version
    Future release

    Kernel backporting

    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.[40] 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.[41] 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.[42][43][44]

    Extended Update Support (EUS) / Z Tree

    The Extended Update Support (EUS) allows an organization / company to choose when they change to a new minor version. For the first 6 months of the EUS channel / yum repo, features may be added, but then the channel is locked down so that only bug and security fixes are patched. The organization / company then has 24 months to move to a new EUS branch. EUS allows the organization / company to stay on a minor version if required by a third party application which is only tested with a particular minor version of RHEL, such as Oracle Database, IBM DB2, IBM Cloud Orchestrator, etc. There may also be extra costs associated with using the EUS repos/channels depending on the agreement the organization / company has with Red Hat.[45] For more information on what is Included/Excluded from the EUS see.[46]

    Note

    • The EUS update mechanism for using older minor version branches is not available to CentOS, Oracle Linux and Scientific Linux, as Red Hat do not publish source packages for rebuilding. As such, projects clearly state to ensure users run on the latest available minor version within a supported major release [47]

    RHEL 6

    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[28]
      • 6.7, also termed Update 7, July 22, 2015 (kernel 2.6.32-573)
        • 1st Day of EUS Window July 22, 2015
        • Last Day of EUS Window July 31, 2018
      • 6.8, also termed Update 8, May 10, 2016 (kernel 2.6.32-642)
        • 1st Day of EUS Window May 10, 2016
        • Last Day of EUS Window May 30, 2018[48]

    RHEL 7

    Red Hat Enterprise Linux 7 (Maipo) is based on Fedora 19, upstream Linux kernel 3.10, 10 June 2014, uses Linux kernel 3.10.0-123[28]

    • 7.1, also termed Update 1, March 5, 2015 (kernel 3.10.0-229)[29]
      • 1st Day of EUS Window March 5, 2015
      • Last Day of EUS Window March 31, 2017
    • 7.2, also termed Update 2, November 19, 2015 (kernel 3.10.0-327)[30]
      • 1st Day of EUS Window November 19, 2015
      • Last Day of EUS Window November 30, 2017
    • 7.3, also termed Update 3, November 3, 2016 (kernel 3.10.0-514)[31]
      • 1st Day of EUS Window November 3, 2016
      • Last Day of EUS Window November 30, 2018
      • Features may be updated[48]
    • 7.4, also termed Update 4, August 1, 2017 (kernel 3.10.0-693)[32]
      • 1st Day of EUS Window August 1, 2017
      • Last Day of EUS Window August 31, 2019
    • 7.5, also termed Update 5, April 10, 2018 (kernel 3.10.0-862)[33]
      • 1st Day of EUS Window April 10, 2018
      • Last Day of EUS Window April 30, 2020

    See also

    References

    1. 1 2 "Explaining Why We Don't Endorse Other Systems". the Free Software Foundation. Retrieved March 13, 2011.
    2. ↑ "Red Hat Press Releases". Archived from the original on March 4, 2001. Retrieved 2001-03-04.
    3. ↑ Red Hat Enterprise Linux 7.6 Beta now available
    4. ↑ 7.6 Release Notes
    5. ↑ "Red Hat introduces Arm server support for Red Hat Enterprise Linux". Red Hat. Retrieved 2017-11-17.
    6. ↑ "Supported Architectures". Retrieved 2010-11-21.
    7. ↑ "Tips and tricks: How do I properly refer to Red Hat Enterprise Linux 2.1, Red Hat Enterprise Linux 3, Red Hat Enterprise Linux 4 and Red Hat Enterprise Linux 5 in documentation and when conversing with fellow users and customers?". redhatmagazine.com. 2008-02-04. Retrieved 2008-06-25.
    8. ↑ "ESR: "We Don't Need the GPL Anymore"". onlamp.com. Retrieved 2008-03-04.
    9. ↑ "Downloads : Red Hat Developers". Red Hat. Retrieved 3 June 2016.
    10. ↑ "Enterprise Linux Academic Subscriptions". Red Hat. Retrieved 2014-06-23.
    11. ↑ "Moving to Red Hat Enterprise Linux 5". Red Hat. Archived from the original on October 8, 2009. Retrieved 2009-12-02.
    12. ↑ "Red Hat Enterprise Linux Server Version Comparison Chart". Red Hat. Archived from the original on 2010-01-05. Retrieved 2009-12-02.
    13. ↑ "Red_Hat_Global_Desktop_Linux:_The_Best_Kept_Secret?". linuxtoday.com. Retrieved 2008-03-04.
    14. ↑ "Fedora project wiki, History of Red Hat Linux". fedoraproject.org. Retrieved 2010-05-23.
    15. 1 2 3 "Fedora project wiki, Red Hat Enterprise Linux History". fedoraproject.org. Retrieved 2010-06-08.
    16. 1 2 "Red Hat Announces Availability of Red Hat Enterprise Linux 7 Beta". Red Hat. 2013-12-11. Retrieved 2013-12-11.
    17. ↑ "Fedora project wiki, the difference between Fedora and RHEL". fedoraproject.org. Retrieved 2010-05-23.
    18. ↑ "Linux Distributions - Facts and Figures". distrowatch.com. Retrieved 2008-03-04.
    19. ↑ "SLURM at CEA" (PDF).
    20. ↑ "Controversy surrounds Red Hat's "obfuscated" source code release". The H. Retrieved 12 March 2011.
    21. ↑ "Red Hat defends changes to kernel source distribution". The H. Retrieved 12 March 2011.
    22. ↑ Neil McAllister (12 Nov 2012). "Oracle: Get your Red Hat Linux patches from us, it's easier. New service lets public browse kernel fixes". The Register. Retrieved 1 August 2014.
    23. ↑ "Project: RedPatch". oss.oracle.com. Retrieved 2014-08-04.
    24. ↑ "RHEL 7.5 Release Notes".
    25. ↑ "2013 Red Hat Summit". See for example this presentation
    26. ↑ "Red Hat Enterprise Linux 7 Release Candidate Now Available". redhat.com. 2014-04-15. Archived from the original on 2014-04-27. Retrieved 2014-04-27.
    27. ↑ "Red Hat Unveils Red Hat Enterprise Linux 7". redhat.com. 2014-06-10. Retrieved 2014-06-10.
    28. 1 2 3 4 5 6 7 8 "Red Hat Enterprise Linux Updates and Related Kernel Versions". Red Hat. Retrieved 2012-05-16.
    29. 1 2 "redhat-release enhancement update for Red Hat Enterprise Linux 7.1".
    30. 1 2 "Red Hat Enterprise Linux 7.2 now available". Red Hat, Inc. 2015-11-19. Retrieved 2015-11-19.
    31. 1 2 "Red Hat Enterprise Linux 7.3 now available - Red Hat Customer Portal". access.redhat.com. Retrieved 2016-11-03.
    32. 1 2 "Red Hat Enterprise Linux 7.4 now available". access.redhat.com. Retrieved 2017-08-01.
    33. 1 2 "Red Hat Enterprise Linux 7.5 Released". access.redhat.com. Retrieved 2018-04-10.
    34. ↑ "redhat-release-as-2.1AS-121.src.rpm". Red Hat. Archived from the original on 2012-03-11. Retrieved 2012-05-16.
    35. ↑ "Red Hat Enterprise Linux Life Cycle". Access.redhat.com. Retrieved 2015-01-20.
    36. ↑ "What is the Red Hat Enterprise Linux Extended Life Cycle Support Add-On (ELS), and what is its support life cycle?". Red Hat. Retrieved 2017-01-12.
    37. ↑ "Red Hat Enterprise Linux Errata Support Policy". Red Hat. Archived from the original on 2010-04-05. Retrieved 2012-08-11.
    38. ↑ "Red Hat Enterprise Linux 3 - End Of Life". Red Hat. Retrieved 2010-01-12.
    39. ↑ "Red Hat Enterprise Linux Release Dates". Red Hat. Retrieved 2015-09-30.
    40. ↑ "What is backporting and how does it affect Red Hat Enterprise Linux (RHEL)?". Retrieved 12 May 2016. (Subscription required (help)).
    41. ↑ "Why does Red Hat Linux use such an old kernel?". stackexchange.com.
    42. ↑ "SO_REUSEPORT on linux". StackOverflow.com. Retrieved 12 May 2016.
    43. ↑ "Backport SO_REUSEPORT patch from kernel 3.9+ to help support haproxy graceful restart". Retrieved 12 May 2016. (Subscription required (help)).
    44. ↑ "Which RHEL version supports the SO_REUSEPORT socket option?". Red Hat. (Subscription required (help)).
    45. ↑ "Extended Update Support (EUS) Standard Operating Environment (SOE) Guide".
    46. ↑ "Extended Update Support (EUS) Standard Operating Environment (SOE) Guide:What Is Included/Excluded from EUS".
    47. ↑ CentOS FAQ | https://wiki.centos.org/FAQ/General#head-fe8a0be91ee3e7dea812e8694491e1dde5b75e6d
    48. 1 2 "Red Hat Enterprise Linux Life Cycle:Extended Update Support".

    Further reading

    • Jang, Michael H. (2007). RHCE Red Hat Certified Engineer Linux Study Guide (RHEL 5). New York: McGraw-Hill. ISBN 978-0-07-226454-8.
    • Ghori, Asghar (2009). Red Hat Certified Technician & Engineer (RHEL 5). Reston: Global Village Publishing. ISBN 978-1-61584-430-2.
    • Fox, Tammy (2007). Red Hat Enterprise Linux 5 Administration Unleashed. Indianapolis, Ind.: Sams. ISBN 978-0-672-32892-3. OCLC 137291425.
    • McCarty, Bill (2004). Learning Red Hat Enterprise Linux and Fedora. Sebastopol, CA: O'Reilly. ISBN 978-0-596-00589-4. OCLC 55130915.
    • Negus, Christopher (2008). Fedora 9 and Red Hat Enterprise Linux Bible. Indianapolis, Ind.: Wiley. ISBN 978-0-470-37362-0. OCLC 222155845.
    • Sobell, Mark G. (2008). Practical Guide to Fedora and Red Hat Enterprise Linux. Upper Saddle River, NJ: Prentice Hall. ISBN 978-0-13-714295-8. OCLC 216616647.
    • Collings, Terry (2005). Red Hat Enterprise Linux 4 For Dummies. Hoboken, N.J.: Wiley. ISBN 978-0-7645-7713-0. OCLC 58973830.
    • Petersen, Richard (2005). Red Hat Enterprise Linux & Fedora Core 4: The Complete Reference. London: McGraw-Hill. ISBN 978-0-07-226154-7. OCLC 62293551.
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