Red Hat Enterprise Linux (or RHEL) is a commercial derivative of Fedora tailored to meet the requirements of enterprise customers. It is a commercial product from Red Hat which also sponsors Fedora as a community project. Fedora is upstream for Red Hat Enterprise Linux but there are several other derivative distributions available too.
Is Red Hat Enterprise Linux an open source product?
Yes. Binaries and updates are part of the 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 mirror, which is above and beyond the requirements of any of the free and open source licenses. Red Hat also provides a complementary repository containing small number of additional packages which are licensed from its partners under different licensing terms.
If the source is publicly available, can anyone rebuild the binaries and produce a similar product?
Absolutely. There are several such rebuilds and derivatives of Red Hat Enterprise Linux available. CentOS and Scientific Linux are popular ones.
What's the difference between rebuilds and Red Hat Enterprise Linux ?
Red Hat Enterprise Linux is commercially supported by Red Hat, and is a commercial product with a range of software and hardware certifications including third party ISV applications. Red Hat also offers other management features via a web service called Red Hat Network that is not available to such rebuilds. Also, layered products such as Red Hat Application Stack and Red Hat Directory Server are only supported on top of Red Hat Enterprise Linux subscriptions. Many hardware, software and security certifications are not valid on the rebuilds.
What's the relationship between rebuilds and Red Hat?
There is no official relationship, but it is a complementary one for which Red Hat has publicly expressed its support, since many of the users using such rebuilds become Red Hat customers when they move into production deployments requiring commercial backing and support.
What's the difference between Fedora and Red Hat Enterprise Linux?
Watch a video at http://www.redhatmagazine.com/2008/09/16/video-the-history-of-fedora/
Both Fedora and Red Hat Enterprise Linux are open source. Fedora is a community project and serves as the base platform on which RHEL is built. Fedora is a general purpose system that gives Red Hat and the rest of its contributor community the chance to premier and provide feedback on technologies that may surface later in RHEL releases. RHEL has its own set of test phases which are separate and distinct from Fedora.
The cost of RHEL comes from the subscription, which provides assorted certifications and support for additional architectures, as well as 7 years of enterprise support. Red Hat also enhances its RHEL offerings with additional software and with certification programs.
More information on the release history and lineage is available at History.
When you purchase RHEL, 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 sponsor a large number of resources and funds to the Fedora project including engineering, marketing and other services.
- Lifecyle: A new version of Red Hat Enterprise Linux is released about every 18-24 months and supported for up to 7 years. New Fedora releases are available every six months and every release gets updates for about 13 months.
- Software Packages: Software in Red Hat Enterprise Linux is limited to about 2000 packages. 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 10,000 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 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 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 subscription in more detail. It also provides an older comparison between the two options.
What about packages not part of Red Hat Enterprise Linux?
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 Extra Packages for Enterprise Linux, or EPEL.
What is the release cycle of Red Hat Enterprise Linux?
Red Hat Enterprise Linux is released approximately every 18 to 24 months.
History
Red Hat first offered a 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
| 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 | N/A | N/A | N/A |