Red Hat Enterprise Linux (RHEL)

Red Hat Enterprise Linux (RHEL) is the cornerstone of the Enterprise Linux ecosystem. Nearly every EL-compatible distribution — CentOS Stream, AlmaLinux, Rocky Linux, and others — is built around RHEL. Understanding RHEL is the first step to mastering the entire Enterprise Linux world.

What is RHEL

RHEL is a commercial Linux distribution developed and maintained by Red Hat (now an IBM subsidiary). It uses Fedora as its upstream, and after extensive testing, hardening, and certification, is released for enterprise users who need long-term stability and commercial support.

RHEL is not a “free” distribution — it provides software updates and technical support through a subscription model. However, its source code is fully open, which is the foundation for the many RHEL-compatible distributions that exist.

History

Year	Event
1994	Red Hat Linux 1.0 released
2002	Red Hat Linux split into RHEL (enterprise) and Fedora (community)
2004	RHEL 4 released, establishing the enterprise Linux benchmark
2010	RHEL 6 released, introducing Upstart (precursor to systemd)
2014	RHEL 7 released, fully adopting systemd
2019	IBM acquires Red Hat for $34 billion
2019	RHEL 8 released, introducing Application Streams and modularity
2022	RHEL 9 released, based on Fedora 34
2023	Red Hat restricts RHEL source code access (only available through CentOS Stream git)
2025	RHEL 10 released, based on Fedora 40

Subscription Model

Paid Subscriptions

RHEL commercial subscriptions come in multiple tiers:

Self-Support: Software updates only, no technical support
Standard: Business-hours technical support
Premium: 24/7 technical support with 1-hour critical issue response

Subscriptions are priced per physical host or virtual machine socket pair. Cloud instances are typically billed hourly or through cloud marketplace subscriptions.

Free Developer Subscription

Red Hat offers a Red Hat Developer Subscription for Individuals:

Free registration, no credit card required
Usable on up to 16 physical or virtual machines
Full access to RHEL software repositories
Can be used for development, testing, and small-scale production
Does not include Red Hat technical support

Registration: developers.redhat.com

This is an excellent option for personal learning and development — you can legally use the official RHEL distribution without paying anything.

Free Team Subscription

Red Hat also offers a Red Hat Developer Subscription for Teams, aimed at development teams, also free, suitable for CI/CD and development environments.

Release Cycle and Lifecycle

RHEL follows a predictable release and support cycle:

Major versions: Released approximately every 3 years (RHEL 8: 2019, RHEL 9: 2022, RHEL 10: 2025)
Minor versions: Released approximately every 6 months (e.g., 9.0, 9.1, 9.2…)

Each major version lifecycle:

Phase	Duration	Content
Full Support	5 years	New features, bug fixes, security updates
Maintenance Support	5 years	Critical bug fixes and security updates only
Extended Life Cycle Support (ELS)	Paid add-on	Critical security fixes

This means a RHEL major version typically has 10 years of official support.

Key Features

Stability

RHEL is renowned for stability. Package versions remain fixed within a major release cycle (only backporting security patches), ensuring that the runtime environment for applications does not change unexpectedly due to system updates.

Security

SELinux: Mandatory Access Control enabled by default
FIPS 140-2/140-3 certification: Meets compliance requirements for government and financial industries
Common Criteria certification
CIS Benchmark: Official security hardening guides
OVAL data: Supports automated security compliance scanning

Certification and Compatibility

RHEL has the broadest hardware and software certification ecosystem:

All major server hardware vendors (Dell, HPE, Lenovo, etc.) certify RHEL
Enterprise software (Oracle, SAP, IBM DB2, etc.) is officially certified on RHEL
All major cloud platforms (AWS, Azure, GCP) provide official RHEL images

Application Streams

Application Streams (AppStream), introduced in RHEL 8, allow multiple versions of user-space components on the same system:

# List available Python module streams
dnf module list python3*

# Enable Python 3.11 stream
dnf module enable python311

Container Tools

RHEL includes daemonless container tools by default:

Podman: Container runtime replacing Docker
Buildah: Build OCI container images
Skopeo: Container image management tool

RHEL and Fedora Relationship

Fedora (upstream) → CentOS Stream (midstream) → RHEL (downstream release)

Fedora is RHEL’s upstream innovation lab, released every 6 months with the latest packages
Each RHEL major version is based on a specific Fedora release (e.g., RHEL 9 is based on Fedora 34)
Red Hat selects and stabilizes components from Fedora, passes them through the CentOS Stream intermediate stage, and finally releases them as RHEL

Repository Structure

RHEL’s main software repositories:

Repository	Content
BaseOS	Core OS components providing foundational functionality
AppStream	User-space applications, language runtimes, databases
CodeReady Builder	Developer tools and libraries (not enabled by default)
Supplementary	Non-open-source packages distributed by Red Hat

Enable the CodeReady Builder repository (usually needed before installing EPEL):

subscription-manager repos --enable codeready-builder-for-rhel-9-x86_64-rpms

Who Should Use RHEL

RHEL is suitable for:

Production environments: Enterprise servers needing long-term stability and commercial support
Compliance requirements: Finance, government, healthcare, and other industries with strict security certification requirements
Software certification: Running commercial software certified for RHEL (e.g., SAP, Oracle DB)
Hybrid cloud: Using a unified OS platform across on-premises and cloud
Personal learning: Experiencing enterprise-grade Linux through the free developer subscription

If you do not need commercial support and official certifications, RHEL-compatible distributions like AlmaLinux or Rocky Linux may be more economical — they provide nearly identical software experiences to RHEL.

Getting Started

Register for a Red Hat developer account: developers.redhat.com
Download the RHEL ISO image
Register your system after installation:

subscription-manager register --username <your-username>
subscription-manager attach --auto

Update the system:

dnf update -y

Check system information:

cat /etc/redhat-release
subscription-manager status