Overview of the Red Hat Linux Ecosystem
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Red Hat is, and has long been, the leading contributor to the Linux world making the most popular business Linux distribution, the most popular free (unsupported) enterprise Linux distro and one of the most popular desktop and cutting edge Linux distro. They are also key contributors to many Linux projects from the kernel to KVM virtualization to Gluster and more.
Red Hat makes three key operating system products: Red Hat Enterprise Linux (or RHEL), CentOS and Fedora. Working in the Red Hat world, we need to understand the relationship between these three products.
At the top of the chain is Fedora. Fedora Linux releases a new version roughly twice a year. Fedora is a free distribution and very cutting edge. It has a strong bias towards a large base of software included with it, a lot of focus on desktop usage and leans towards new, cutting edge features over stability. It is meant to be used primarily by enterprises looking to see features before they hit the main stream, desktop users both at home and at the office, hobbyists and anyone needing a reliable Linux server but with very recent updates. Fedora has been making large strides towards being a key contender for server deployments, in addition to its traditional role in lab and desktop deployments.
Fedora, every several years, is "frozen" to a specific version, often with tweaks made between features in a few different releases, and put into a long term, enterprise support model, the packages supplied with it reduced to those that are stable, supportable and sensible for business use and supplied as the extremely mature and robust Red Hat Enterprise Linux, known as RHEL for short. RHEL is heavily supported and designed completely around the intent that stability and security trump all things. All support is extremely long term and RH has some of the best support in the business. This is an extreme enterprise server OS. It is also rather costly.
CentOS, formerly an independent distribution but later acquired by and managed by Red Hat themselves, is a rebuild of RHEL from the original sources, the same as RHEL itself, but without RHEL branding and without the support and support hooks of RHEL. In this way CentOS and RHEL are the same product, from the same company, CentOS simply is the completely free version and comes without any RH official support. CentOS normally releases a day or two after RHEL simply because it takes time to prepare and it is secondary in priority.
For educational uses, CentOS is used because it is simply the free version of RHEL. All experience and documentation is shared between them. Many businesses that do not wish to pay for enterprise OS support choose CentOS for this reason as well.
Review: Fedora is the main, base system. RHEL is the commercial, long term support "frozen" release based on Fedora. CentOS is RHEL's official free close. All three systems are made by Red Hat.
