Use for questions about Red Hat Enterprise Linux (RHEL), a Linux distribution from Red Hat intended for enterprise use. Note there are version-specific RHEL tags for questions unique to a specific version. Use a product-specific tag for questions about other distros in the Red Hat family, like Fedora or CentOS.
Red Hat Enterprise Linux (RHEL) is a Linux distribution from Red Hat intended for enterprise use.
It's business model is based on a paid subscription to underwrite support and upgrades. With an intended usage requiring extreme stability and reliability, major releases can be two to four years apart, with a release life cycle spanning 7-10 years or more. Minor releases, termed updates, are generally more often than once per year.
The Red Hat family of Linux distributions use the RPM Package Manager (a recursive acronym, originally the Red Hat Package Manager).
Fedora is a community-based, open source distribution sponsored by Red Hat. It serves as a test bed for new features, with a major release twice per year. Recent major releases of RHEL have been forked from the Fedora release of a year prior and may incorporate some features from more recent Fedora releases.
CentOS is a community based, open source distribution that is functionally compatible with RHEL. It is based on RHEL source code, with the RHEL branding removed. It is released within a few months of the corresponding RHEL release.
Fedora and CentOS have product-specific tags. Do not use Red Hat tags generically for questions about those products.
A number of third parties produce Linux distributions based on RHEL source code:
Scientific Linux is sponsored by Fermilab. It starts with de-branded RHEL source code similar to CentOS. While CentOS aims to be 100% binary compatible with RHEL, Scientific Linux adds packages and tweaks.
Oracle Linux is also a repackaging of RHEL source code by the Oracle Corporation. It offers the option of an Oracle-enhanced kernel.
Both Scientific Linux and Oracle Linux have dedicated tags. Use those for issues unique to those distributions. For most questions that are common to the Red Hat source, however, you will attract a larger audience of potential answerers by using a corresponding Red Hat or CentOS tag, and then mention the actual distribution in the question.
For issues specific to a particular RHEL version, there are version-specific tags: