= Red Hat Enterprise Linux

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*Red Hat Enterprise Linux* (or RHEL) is a commercially supported
derivative of Fedora tailored to meet the requirements of enterprise
customers. RHEL is a commercial product distributed by Red Hat (Red Hat also sponsors
Fedora as a community project). Fedora is an upstream source for RHEL, but there are many other link:Derived_distributions[Derived
distributions] that are based on Fedora.

[[whats-the-difference-between-fedora-and-red-hat-enterprise-linux]]
What's the difference between Fedora and Red Hat Enterprise Linux?
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Watch a video from
http://www.redhatmagazine.com/2008/09/16/video-the-history-of-fedora/[Red
Hat Magazine].

Both Fedora and Red Hat Enterprise Linux are open source operating systems. 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.

The cost of Red Hat Enterprise Linux comes from the subscription, which
provides assorted certifications and support for additional
architectures, as well as 7 years and more of enterprise support. Red
Hat also enhances its Red Hat Enterprise Linux offerings with additional
software and with certification programs.

More information on the release history and lineage is available at
link:History_of_Red_Hat_Linux[History of Red Hat Linux].

When you purchase Red Hat Enterprise Linux, you are also helping to
support Fedora. Since Red Hat sponsors Fedora, what is good for Red Hat
is usually good for Fedora. The major differences are:

* Support and associated services: Red Hat Enterprise Linux is a
commercially supported product by Red Hat and provides service level
agreements that is important for enterprise customers. This support
involves both product assistance (hand holding) as well as
prioritization of bug fixes and feature requests, certified hardware and
software among other things. Fedora is supported by a wide community of
developers and users but it is not commercially supported by Red Hat.
Red Hat does http://fedoraproject.org/sponsors[sponsor] a large number
of resources and link:Accounting[ funds] to the Fedora project including
engineering, marketing and other services.

* link:LifeCycle[Lifecycle]: A new version of Red Hat Enterprise Linux
comes out every few years and is supported for up to 10 years and can
even be
http://www.redhat.com/rhel/server/extended_lifecycle_support/[extended]
to 13 years or more with additional subscriptions. New Fedora releases
are available about every six months and every release gets updates for
about 13 months.

* Software Packages: Software in Red Hat Enterprise Linux is a limited
subset of Fedora and has about 4000 binary packages (RHEL 6). These are
the ones enterprise customers demand and are supported by Red Hat.
Fedora offers a wide range of software packages and the latest release
has well over 25000 unique (not counting updates in Fedora 15) binary
software packages available in the repository.

* Software Updates: Post release updates of software in Red Hat
Enterprise Linux are usually limited to backported security and bug
fixes, although enhancements are also offered usually via the major
scheduled updates. Red Hat also offers
http://www.press.redhat.com/2008/12/18/red-hat-increases-service-levels-and-reduces-costs-for-customers-with-extended-update-support/[extended
update support] for customers wishing to stick to a single point release
for a longer amount of time. Red Hat also aims to provide ABI
compatibility within a release, whereas this is not guaranteed by the
Fedora Project. Fedora software packages and updates are close to
link:Staying_close_to_upstream_projects[ upstream] and include new
features routinely.

* New Releases: Subscriptions are for a specified time period and not
for a particular release. So you can move to any currently supported
release of Red Hat Enterprise Linux including new versions of RHEL

Red Hat has a page explaining the benefits of the
https://www.redhat.com/rhel/benefits/[subscription] in more detail. It
also provides https://www.redhat.com/software/rhelorfedora/[an older
comparison between the two options].

[[what-about-packages-not-part-of-red-hat-enterprise-linux-what-is-epel]]
What about packages not part of Red Hat Enterprise Linux? What is EPEL?
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

In order to focus Red Hat's efforts and limit support costs, only a
selected subset of packages found in Fedora are included in the
commercially supported product line. The Fedora Project has a community
of people maintaining add-on packages for Red Hat Enterprise Linux and
compatible rebuilds called link:EPEL[Extra Packages for Enterprise
Linux], or EPEL.

[[what-is-the-release-cycle-of-red-hat-enterprise-linux]]
What is the release cycle of Red Hat Enterprise Linux?
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

There is no fixed release schedule for new releases. Red Hat Enterprise
Linux is usually released approximately every 18 to 36 months and each
release is http://www.redhat.com/security/updates/errata/[maintained for
7 years] and can be
http://www.redhat.com/rhel/server/extended_lifecycle_support/[extended]
up to 10 years. Red Hat also offers
http://www.press.redhat.com/2008/12/18/red-hat-increases-service-levels-and-reduces-costs-for-customers-with-extended-update-support/[extended
update support] for customers wishing to stick to a single point release
for a longer amount of time.

[[what-is-the-update-policy-for-red-hat-enterprise-linux]]
What is the update policy for Red Hat Enterprise Linux?
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Red Hat Enterprise Linux updates are more conservative and generally
focus on security and bug fixes . Hardware enablement and targeted
enhancements are delivered via scheduled minor updates and the policy is
described in much more detail
https://access.redhat.com/support/policy/updates/errata/[here]

Fedora's Updates_Policy is more liberal compared to Red Hat Enterprise
Linux.

[[is-red-hat-enterprise-linux-available-for-free-or-low-cost]]
Is Red Hat Enterprise Linux available for free or low cost?
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

It is a commercial product and not available for free. There is a
evaluation version for free download at
https://www.redhat.com/rhel/details/eval/ and a version targeted at
developers for 99$ at

https://www.redhat.com/apps/store/developers/rhel_developer_suite.html

Academic editions are available at a low cost as well

http://www.redhat.com/solutions/education/academic/

http://www.redhat.com/solutions/education/academic/individual/

[[is-red-hat-enterprise-linux-a-open-source-product]]
Is Red Hat Enterprise Linux a open source product?
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Yes. Binaries and updates are part of the
http://www.gnu.org/philosophy/selling.html[commercial] subscription from
Red Hat to its customers. The complete source code in the form of source
RPM's is available publicly at Red Hat's
ftp://ftp.redhat.com/pub/redhat/linux/enterprise/[ftp mirror], which is
above and beyond the requirements of any of the free and open source
licenses. Red Hat participates in the CentOS project and the sources are
available from
http://community.redhat.com/centos-faq/#_git_centos_org[their] site as
well. Red Hat also provides a complementary repository containing small
number of additional packages which are licensed from its partners under
different licensing terms.

[[is-it-possible-to-use-the-publicly-available-source-rpms-to-rebuild-the-distribution]]
Is it possible to use the publicly available source RPMs to rebuild the
distribution?
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Absolutely. All the SRPMS are under free and open source licenses that
permit this. There are several such rebuilds and derivatives of Red Hat
Enterprise Linux available. http://centos.org[CentOS] and
https://www.scientificlinux.org/[Scientific Linux] are popular ones.

[[whats-the-difference-between-rebuilds-and-red-hat-enterprise-linux]]
What's the difference between rebuilds and Red Hat Enterprise Linux ?
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Red Hat Enterprise Linux is commercially supported by Red Hat, and
offers a range of software and hardware certifications including third
party ISV applications. Rebuilds often have a substantial
http://lwn.net/Articles/345028/[delay in releasing updates] and
especially for releasing rebuilds for
https://lwn.net/Articles/435744/[major releases] of RHEL or minor point
updates following that. Red Hat also offers other management features
via a web service called http://rhn.redhat.com[Red Hat Network] that is
not available to such rebuilds. Also, layered products such as Red Hat
Application Stack, Red Hat Directory Server and Red Hat Satellite are
only supported on top of Red Hat Enterprise Linux subscriptions. Many
hardware, software and security certifications are only valid on Red Hat
Enterprise Linux and not the rebuilds. Much of the technical content of
Red Hat http://kbase.redhat.com[knowledge base] and
http://access.redhat.com[customer support portal] is only available to
Red Hat customers as well.

[[whats-the-relationship-between-centos-and-red-hat]]
What's the relationship between CentOS and Red Hat?
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Red Hat has explained this in detail at
http://community.redhat.com/centos-faq/

[[history]]
History
~~~~~~~

Red Hat first offered an enterprise Linux support subscription for Red
Hat Linux 6.1. It was not a separate product but the subscription level
was branded as Red Hat 6.2E. Subsequently, Red Hat started creating a
separate product with commercial service level agreements and longer
lifecyle based on Red Hat Linux and later on Fedora. This was initially
called as Advanced Server and rebranded as Red Hat Enterprise Linux in
2003. The following table gives the lineage:

[cols=",,,",options="header",]
|=======================================================================
|Release |Codename |Release Date |Based on
|Red Hat Linux 6.2E |Zoot |2000-03-27 |Red Hat Linux 6.2

|Red Hat Enterprise Linux 2.1 |Pensacola (AS)/ Panama (ES) |2002-03-26
(AS) |Red Hat Linux 7.2

|Red Hat Enterprise Linux 3 |Taroon |2003-10-22 |Red Hat Linux 9

|Red Hat Enterprise Linux 4 |Nahant |2005-02-15 |Fedora Core 3

|Red Hat Enterprise Linux 5 |Tikanga |2007-03-14 |Fedora Core 6

|Red Hat Enterprise Linux 6 |Santiago |2010-11-10 |Mix of Fedora 12
Fedora 13 and several modifications

|Red Hat Enterprise Linux 7 |Maipo |2014-06-10 |Primarily Fedora 19 with
several changes from 20 and later
|=======================================================================

Note that while during the release, the releases of Red Hat Enterprise
Linux have similarities to the corresponding Fedora releases, the update
cycle is very different between these distributions and hence they
diverge drastically over time. Rebuilds of Red Hat Enterprise Linux
itself such as CentOS and Scientific Linux tend to mirror it quite
closely. If you are looking for packages that are available in Fedora
but not in Red Hat Enterprise Linux, EPEL repository is a good place to
start with.

* http://www.redhat.com/rhel/
* link:Red_Hat_contributions[Red Hat contributions]

[[articles]]
Articles
^^^^^^^^

* http://www.redhat.com/magazine/019may06/features/fedora_rhel_1/
* http://www.redhat.com/magazine/020jun06/features/fedora_rhel_2/
* http://www.redhat.com/magazine/021jul06/features/fedora_rhel_3/
* http://www.redhat.com/magazine/022aug06/features/fedora_rhel_4/
'''

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