Red Hat Enterprise Linux (又は RHEL) は、エンタープライズの顧客の要求を満たす Fedora をベースにした商用サポートリリースです。それはコミュニティプロジェクトとしての Fedora のスポンサーも兼ねる Red Hat 社の商用プロダクトです。Fedora は Red Hat Enterprise Linux のアップストリームですが、他に複数の ディストリビューション も利用できます。
Red Hat Enterprise Linux はオープンソースプロダクトですか？
そうです。バイナリとアップデートパッケージは Red Hat 社からその顧客へ商用サブスクリプションの条項が適用されます。完全なソースコードはソース RPM の形態で Red Hat 社のftp ミラーで公開されています。それはどのようなフリー且つオープンソースライセンスの要求を満たすものです。Red Hat 社は違ったライセンス条項が適用されてそのパートナーから許可を受けた少数の追加パッケージを置く補足的なリポジトリも提供します。
ソースコードはフリーでオープンソースライセンスで公開されているので、誰でもバイナリをリビルドして同じようなプロダクトを作成することができますか？
全くその通りにできます。そのように Red Hat Enterprise Linux をリビルドして提供しているものが複数あります。人気があるものとしてCentOS と Scientific Linux があります。
Red Hat Enterprise Linux とリビルドされたディストリビューションの違いは何でしょうか？
Red Hat Enterprise Linux は Red Hat 社によって商用サポートがあります。そして、サードパーティの ISV アプリケーションを含むソフトウェアやハードウェアの幅広いサーティフィケーションを提供します。また Red Hat 社はリビルドされたディストリビューションでは利用できない Red Hat Network という Web サービスを経由して他の管理機能も提供します。さらに Red Hat Application Stack、Red Hat Directory Server や Red Hat Satellite のような階層プロダクトも Red Hat Enterprise Linux サブスクリプションでしかサポートされません。多くのハードウェア、ソフトウェアやセキュリティサーティフィケーションはリビルドされたディストリビューションでは有効ではありません。その上、リビルドされたディストリビューションは アップデートパッケージのリリースが遅れるといったこともよく起こります。
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.
Red Hat has gone out of its way to make it easier for rebuilds by isolating the Red Hat branding to a couple of specific packages and providing all the source RPM packages in a public location.
What's the difference between Fedora and Red Hat Enterprise Linux?
Watch a video from Red Hat Magazine.
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 releaes 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 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 sponsor a large number of resources and funds to the Fedora project including engineering, marketing and other services.
- Lifecycle: A new version of Red Hat Enterprise Linux comes out every few years and is supported for up to 7 years and can even be extended to 10 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 2500 binary 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 16000 unique (not counting updates) 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 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 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? 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 Extra Packages for Enterprise Linux, or EPEL.
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 maintained for 7 years and can be extended upto 10 years. Red Hat also offers extended update support for customers wishing to stick to a single point release for a longer amount of time.
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:
| 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 |