Red Hat Enterprise Linux

Red Hat Enterprise Linux

Red Hat Enterprise Linux 6's default GNOME desktop
Company / developer	Red Hat, Inc.
OS family	Unix-like (based on Red Hat Linux/Fedora)
Working state	Current
Source model	Free and open source software (with exceptions)[1]
Initial release	March 31, 2003 (2003-03-31) (RHL discontinued) & started as RHEL on March 26, 2002[clarification needed]
Latest stable release	6.4, 5.9 / February 21, 2013; 36 days ago (2013-02-21), January 7, 2013; 2 months ago (2013-01-07)
Marketing target	Commercial market (including for mainframes, servers, supercomputers)
Available language(s)	Multilingual
Update method	Yum / PackageKit
Package manager	RPM Package Manager
Supported platforms	x86, x86-64; POWER; S/390; z/Architecture[2]
Kernel type	Monolithic (Linux)
Default user interface	GNOME
License	Various free software licenses, plus proprietary binary blobs.[1]
Official website	www.redhat.com/rhel

Red Hat Enterprise Linux (RHEL) is a Linux-based operating system 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 Red Hat's official support and training and the Red Hat Certification Program center around the Red Hat Enterprise Linux platform. Red Hat Enterprise Linux is often abbreviated to RHEL, although this is not an official designation.^[3]

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.

While Red Hat uses strict trademark rules to restrict free re-distribution of their officially supported versions of Red Hat Enterprise Linux,^[4] Red Hat freely provides the source code for the distribution's software even for software where this is not mandatory. As a result, several distributors have created re-branded and/or community-supported re-builds of Red Hat Enterprise Linux that can legally be made available, without official support from Red Hat. CentOS and Oracle Linux aim to provide 100% binary compatibility with Red Hat Enterprise Linux.

Variants

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.

In Red Hat Enterprise Linux 5 there are new editions that substitute former Red Hat Enterprise Linux AS/ES/WS/Desktop:^[5][6]

• Red Hat Enterprise Linux Advanced Platform (former AS)
• Red Hat Enterprise Linux (former ES) (limited to 2 CPU-s)
• 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".^[7]

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.

“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.”[10]

Relationship to free and community distributions

Originally, Red Hat sold support for versions of Red Hat Linux (Red Hat Linux 6.2E was essentially a version of Red Hat Linux 6.2 with different support levels.)^[8] 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.^[9] 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^[9]:

• Red Hat Linux 6.2 → Red Hat Linux 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^[9]

(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.

“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.”^[10]

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),^[11] 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. ^[12] 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.^[13] 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.^[14]

Commercial products using it

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

RHEL 2.1

• Red Hat Enterprise Linux 2.1 AS (Pensacola), 2002-03-26. Uses Linux 2.4.9-e.3^[15]
  • Update 1, 2003-02-14 (kernel 2.4.9-e.12)^[15]
  • Update 2, 2003-05-29 (kernel 2.4.9-e.24)^[15]
  • Update 3, 2003-12-19 (kernel 2.4.9-e.34)^[15]
  • Update 4, 2004-04-21 (kernel 2.4.9-e.40)^[15]
  • Update 5, 2004-08-18 (kernel 2.4.9-e.49)^[15]
  • Update 6, 2004-12-13 (kernel 2.4.9-e.57)^[15]
  • Update 7, 2005-04-28^[16]
• Red Hat Enterprise Linux 2.1 ES (Panama), May 2003^{[citation needed]}

RHEL 3

• Red Hat Enterprise Linux 3 (Taroon), 2003-10-22. Uses Linux 2.4.21-4^[15]
  • Update 1, 2004-01-16 (kernel 2.4.21-9)^[15]
  • Update 2, 2004-05-12 (kernel 2.4.21-15)^[15]
  • Update 3, 2004-09-03 (kernel 2.4.21-20)^[15]
  • Update 4, 2004-12-12 (kernel 2.4.21-27)^[15]
  • Update 5, 2005-05-18 (kernel 2.4.21-32)^[15]
  • Update 6, 2005-09-28 (kernel 2.4.21-37)^[15]
  • Update 7, 2006-03-17 (kernel 2.4.21-40)^[15]
  • Update 8, 2006-07-20 (kernel 2.4.21-47)^[15]
  • Update 9, 2007-06-15 (kernel 2.4.21-50)^[15]

RHEL 4

• Red Hat Enterprise Linux 4 (Nahant), 2005-02-15. Uses Linux kernel 2.6.9-5^[15]
  • 4.1, also termed Update 1, 2005-06-08 (kernel 2.6.9-11)^[15]
  • 4.2, also termed Update 2, 2005-10-05 (kernel 2.6.9-22)^[15]
  • 4.3, also termed Update 3, 2006-03-12 (kernel 2.6.9-34)^[15]
  • 4.4, also termed Update 4, 2006-08-10 (kernel 2.6.9-42)^[15]
  • 4.5, also termed Update 5, 2007-05-01 (kernel 2.6.9-55)^[15]
  • 4.6, also termed Update 6, 2007-11-15 (kernel 2.6.9-67)^[15]
  • 4.7, also termed Update 7, 2008-07-29 (kernel 2.6.9-78)^[15]
  • 4.8, also termed Update 8, 2009-05-19 (kernel 2.6.9-89)^[15]
  • 4.9, also termed Update 9, 2011-02-16 (kernel 2.6.9-100)^[15]

RHEL 5

• Red Hat Enterprise Linux 5 (Tikanga), 2007-03-14. Uses Linux kernel 2.6.18-8^[15]
  • 5.1, also termed Update 1, 2007-11-07 (kernel 2.6.18-53)^[15]
  • 5.2, also termed Update 2, 2008-05-21 (kernel 2.6.18-92)^[15]
  • 5.3, also termed Update 3, 2009-01-20 (kernel 2.6.18-128)^[15]
  • 5.4, also termed Update 4, 2009-09-02 (kernel 2.6.18-164)^[15]
  • 5.5, also termed Update 5, 2010-03-30 (kernel 2.6.18-194)^[15]
  • 5.6, also termed Update 6, 2011-01-13 (kernel 2.6.18-238)^[15]
  • 5.7, also termed Update 7, 2011-07-21 (kernel 2.6.18-274)^[15]
  • 5.8, also termed Update 8, 2012-02-20 (kernel 2.6.18-308)^[15]
  • 5.9, also termed Update 9, 2013-01-07 (kernel 2.6.18-348)^[15]

RHEL 6

• Red Hat Enterprise Linux 6 (Santiago), 2010-11-10 Uses Linux kernel 2.6.32-71^[15]
  • 6.1, also termed Update 1, 2011-05-19 (kernel 2.6.32-131)^[15]
  • 6.2, also termed Update 2, 2011-12-06 (kernel 2.6.32-220)^[15]
  • 6.3, also termed Update 3, 2012-06-20 (kernel 2.6.32-279)^[15]
  • 6.4, also termed Update 4, 2013-02-21 (kernel 2.6.32-358)^[15]

RHEL 7

• Red Hat Enterprise Linux 7 (?), 2013-6+ Will be based on Fedora 18^[17], which as of March 2013 uses Linux kernel 3.8.^[18]

Life-cycle dates

Red Hat Enterprise Linux versions 5 and 6 share a multiphase life-cycle that can span 13 years, while versions 3 and 4 share a life cycle of 10 years. During the first five and a half years of the life cycle ("production 1"), Red Hat provides full support and updates software and hardware drivers. In later phases, support and updates are gradually reduced, with only critical and security-related bug fixes being provided to customers who pay for support in the last three years ("extended life cycle").^[19]

Note: A version outside of its Regular Life Cycle is normally unsupported, but for RHEL3 and RHEL4, support can still be obtained through Red Hat for a subset of packages while the release is in its Extended Life Cycle through an add-on subscription, Extended Life Cycle Support.

References

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. 

External links

• Official website
• Brian Stevens, CTO and vice president of engineering, Red Hat on why Red Hat Enterprise Linux is "The Business OS for Flexibility and Value"
• Red Hat Enterprise Linux at DistroWatch