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Red Hat Enterprise Linux (RHEL) is a widely used Linux distribution developed by Red Hat for enterprise-level computing environments. It offers a stable, secure, and well-supported platform for running mission-critical applications. Each version of RHEL introduces new features, improvements in security, and extended support for modern hardware architectures, making it a popular choice for organizations looking for a long-term, enterprise-ready operating system. Below is a comprehensive version history of RHEL, highlighting key features and changes introduced in each major release.

RHEL 9 was designed with a focus on security, performance, and cloud-native development. It introduced support for modern hardware and streamlined development tools, catering to enterprise workloads and hybrid cloud environments.

• Linux kernel 5.14. Included Linux kernel 5.14, offering improved support for modern hardware, performance enhancements, and better memory management.
• Enhanced security features. Introduced new security features, such as integrity measurement architecture (IMA), which verifies the integrity of the operating system at runtime.
• Performance improvements. Optimized the system for running containers, virtual machines, and cloud-native applications with better resource management and performance tracking.
• Streamlined updates. Made it easier to manage system updates using tools like dnf and Leapp for upgrading from RHEL 8.
• Hybrid cloud support. Extended support for hybrid cloud deployments with better integration with Red Hat OpenShift and Ansible Automation Platform.

Official documentation: https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/9

RHEL 8 was a major release that modernized the operating system for cloud computing, containers, and DevOps workflows. It provided a more flexible and automated system administration experience.

• Linux kernel 4.18. Used Linux kernel 4.18, which included many improvements in security, networking, and file systems.
• AppStream. Introduced the Application Streams concept, separating the operating system's core from application modules, allowing for faster updates and more flexible application versions.
• Cockpit improvements. Enhanced Cockpit, the web-based management tool, making it easier for administrators to manage systems through a graphical interface.
• Performance tuning. Added tools like Tuned profiles for better performance tuning of workloads, especially on modern hardware.
• Integrated container tools. Enhanced container support with tools like Podman, Buildah, and Skopeo, providing an alternative to Docker for containerized environments.

Official documentation: https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/8

RHEL 7 introduced a new system architecture with a focus on performance, scalability, and support for modern workloads. It was a significant update that set the foundation for cloud-native and containerized environments.

• Systemd. Replaced the traditional init system with systemd, improving system startup times and managing system services more efficiently.
• XFS as default file system. Set XFS as the default file system, allowing support for larger file systems and better performance with large files.
• Docker integration. Integrated Docker as a core part of the system, making containerized applications more accessible.
• Firewalld. Replaced the old iptables-based firewall with Firewalld, providing a more dynamic and flexible firewall management solution.
• Improved performance. Added support for large memory and storage capacities, as well as better handling of multi-threaded applications.

Official documentation: https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/7

RHEL 6 brought improvements in system performance, security, and virtualization capabilities, making it ideal for enterprise data centers and cloud environments.

• Linux kernel 2.6.32. Included Linux kernel 2.6.32, providing improved performance, memory management, and support for newer hardware architectures.
• KVM virtualization. Enhanced KVM (Kernel-based Virtual Machine) support, improving virtualization performance and enabling better management of virtual machines.
• Cgroups. Introduced Control Groups (cgroups), enabling more fine-grained control over resource allocation for system processes and containers.
• GRUB 2. Replaced the older GRUB bootloader with GRUB 2, improving boot performance and adding more features for boot management.
• IPv6 improvements. Enhanced IPv6 support, making it easier to deploy RHEL in modern networking environments.

Official documentation: https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/6

RHEL 5 was built around improved security and virtualization support, making it a stable platform for server environments.

• Xen virtualization. Introduced support for Xen virtualization, allowing users to run virtual machines directly on the RHEL platform.
• SELinux enhancements. Enhanced SELinux (Security-Enhanced Linux), providing better access controls and security policies for enterprise environments.
• Improved file system support. Enhanced file system support, including ext3, which provided better journaling and faster recovery after crashes.
• Better hardware support. Added support for a broader range of hardware, improving compatibility and performance on newer systems.
• Cluster and storage improvements. Improved cluster and storage management tools, making RHEL more suitable for enterprise data centers.

Official documentation: https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/5

RHEL 4 was focused on improving system scalability and security, particularly for enterprise workloads in mission-critical environments.

• Linux kernel 2.6. Used Linux kernel 2.6, which introduced new features like improved multi-threading, better memory management, and new file system capabilities.
• SELinux integration. Integrated SELinux as a core part of the system, offering mandatory access controls for increased system security.
• Improved scalability. Enhanced support for larger systems, including multi-processor servers and high-memory configurations.
• Cluster Suite. Introduced Red Hat Cluster Suite, providing better tools for managing clustered environments and high-availability systems.
• New hardware support. Improved hardware support, making it easier to deploy RHEL on a wide range of server hardware.

Official documentation: https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/4

RHEL 3 was designed with improved stability and performance for enterprise workloads, making it a reliable platform for mission-critical applications.

• Linux kernel 2.4. Used Linux kernel 2.4, providing better networking and file system performance.
• Improved scalability. Enhanced scalability features, allowing better performance on systems with multiple CPUs and larger memory configurations.
• Security enhancements. Introduced new security features, including support for iptables for better firewall management and access controls.
• Enhanced file system support. Improved support for file systems, including ext3 and NFS, making it easier to manage large data sets.
• Better hardware compatibility. Provided broader support for enterprise-grade hardware, ensuring RHEL could run on a wide range of systems.

Official documentation: https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/3

RHEL 2.1 was the first release under the Red Hat Enterprise Linux branding, marking a shift toward providing a stable, long-term supported Linux distribution for enterprise customers.

• Linux kernel 2.4. Introduced Linux kernel 2.4, which provided better performance, especially for networking and storage operations.
• Enterprise focus. Laid the foundation for enterprise-level support and service contracts, ensuring businesses had access to regular updates and security patches.
• Improved security. Included security features like iptables for firewall management and enhanced access control lists (ACLs) for better data security.
• File system improvements. Added support for newer file systems, improving data integrity and performance in large-scale environments.

Official documentation: https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/2.1

RHEL 1 was the predecessor to the modern RHEL series, although it wasn’t branded under the RHEL name. It marked the transition from Red Hat Linux to a more stable, enterprise-focused Linux distribution.

• Linux kernel 2.2. Used Linux kernel 2.2, which offered improved networking capabilities and better hardware support compared to earlier releases.
• Focus on stability. Prioritized stability and long-term support for enterprise customers, marking the beginning of Red Hat’s enterprise focus.
• Foundation for enterprise Linux. Set the stage for future RHEL releases by establishing the core principles of long-term stability, security updates, and enterprise-grade support.

Official documentation: https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/1

Since its initial release in 2000, Red Hat Enterprise Linux (RHEL) has evolved into one of the most reliable and secure operating systems for enterprise environments. Each major release has introduced new features and enhancements to support modern workloads, cloud-native development, and containerized applications. From the introduction of SELinux in RHEL 4 to full hybrid cloud support in RHEL 9, RHEL has continually adapted to meet the needs of organizations looking for a stable, secure, and scalable Linux platform. With its long-term support and robust security features, RHEL remains a cornerstone

in the enterprise Linux landscape.