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Red Hat Enterprise Linux (often abbreviated to RHEL) is a Linux distribution produced by Red Hat and targeted toward the commercial market, including mainframes. Red Hat commits to supporting each version of RHEL for 7 years after its release. All of Red Hat's official support, and all of Red Hat's training and certification for hardware and software deployment — Red Hat Certified Technician (RHCT), Red Hat Certified Engineer (RHCE), Red Hat Certified Security Specialist (RHCSS) and Red Hat Certified Architect (RHCA) — center on the Red Hat Enterprise Linux platform.
New versions of RHEL are released every 18 to 24 months. When Red Hat releases a new version of RHEL, customers may upgrade to the new version at no additional charge as long as they are in possession of a current subscription (e.g. the subscription term has not yet lapsed).
Red Hat's first Enterprise offering (Red Hat Linux 6.2E) essentially consisted of a version of Red Hat Linux 6.2 with different support levels, and without separate engineering.
The first version of RHEL 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" (RHEL) AS, and added two more variants, RHEL ES and RHEL WS.
Verbatim copying and redistribution of the entire RHEL distribution is not permitted due to trademark restrictions. Eric S. Raymond made note of this in his June 2005 interview with O'Reilly's Federico Biancuzzi. [http://www.onlamp.com/pub/a/onlamp/2005/06/30/esr_interview.html]
Variants
As of 2005 Red Hat distributed four variants of RHEL (AS/ES/WS expansions are unofficial):
* RHEL AS (advanced server) – for mission-critical/enterprise computer systems
* RHEL ES (edge server or entry-level server) – for supported network servers
* RHEL WS (workstation) – for technical power-user desktops or high-performance computing
* Red Hat Desktop – for multiple deployments of single-user desktops
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.
People sometimes mistakenly refer to ES as "Enterprise Server", in contrast to AS (Advanced Server). This may be because Novell has a server distribution called SUSE Linux Enterprise Server (SLES). However, nowhere on its site or in its literature does Red Hat say what AS, ES and WS stand for.
Relationship to free or community versions
Originally, Red Hat based RHEL on Red Hat Linux, but using a much more conservative release cycle. Later versions leveraged technologies from Fedora Core. Roughly every third version of Red Hat Linux (RHL) or Fedora Core (FC) forms the basis for a version of RHEL, thus:
* RHL 6.2 → RHL 6.2E
* RHL 7.2 → RHEL 2.1
* RHL 9 → RHEL 3
* FC 3 → RHEL 4
* FC 6 → RHEL 5 (expected to be released early 2007)
Clones
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 Core as the unsupported version. However, some people found the new products lacking: those who could not afford or did not wish to pay for enterprise-level support but valued the stability and long-term update cycle of the enterprise product.
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 effort include StartCom Enterprise Linux, CentOS, Pie Box Enterprise Linux, Scientific Linux, White Box Enterprise Linux and Lineox. Oracle Corporation has also recently come out with its own repackaging of Red Hat Enterprise Linux called Oracle Enterprise Linux as part of its Unbreakable Linux program.
Commercial products based on Red Hat Enterprise Linux
A number of commercial vendors use Red Hat Enterprise Linux as a base for the operating system in their products. The most well-known is the Console Operating System in VMware ESX Server.
See Commercial products based on Red Hat Enterprise Linux
Version history
* RHL 6.2E (Zoot), 27 March 2000
* RHEL 2.1 AS (Pensacola), 26 March 2002
* RHEL 2.1 ES (Panama), May 2003
* RHEL 3 (Taroon), 22 October 2003
* * RHEL 3 Update 1, 16 January 2004
* * RHEL 3 Update 2, 18 May 2004
* * RHEL 3 Update 3, 3 September 2004
* * RHEL 3 Update 4, 21 December 2004
* * RHEL 3 Update 5, 20 May 2005
* * RHEL 3 Update 6, 28 September 2005
* * RHEL 3 Update 7, 15 March 2006
* * RHEL 3 Update 8, 20 July 2006
* RHEL 4 (Nahant), 15 February 2005
* * RHEL 4 Update 1, 9 June 2005
* * RHEL 4 Update 2, 5 October 2005
* * RHEL 4 Update 3, 7 March 2006
* * RHEL 4 Update 4, 11 August 2006
* * RHEL 4 Update 5, expected early 2007
* RHEL 5 (Tikanga)
* * Beta 1 - 7 September 2006
* * Beta 2 - 20 November 2006
* * Final release is due 28 February 2007 [http://news.zdnet.com/2100-3513_22-6146149.html]
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