Oracle Linux
Oracle Linux is a free, open-source Linux distribution developed and supported by Oracle Corporation, designed as a secure and high-performance operating environment for deploying, optimizing, and managing applications on-premises, in the cloud, and at the edge.[1] It is binary-compatible with Red Hat Enterprise Linux (RHEL), recompiled from Enterprise Linux (EL) source code provided through initiatives like the Open Enterprise Linux Association (OpenELA), ensuring seamless compatibility for RHEL-based applications and ecosystems.[1] Oracle Linux supports both x86_64 and Arm64 architectures and offers users a choice between the standard RHEL-compatible kernel (Red Hat Compatible Kernel, or RHCK) and Oracle's enhanced Unbreakable Enterprise Kernel (UEK), which includes optimizations for performance, scalability, and Oracle-specific workloads. As of June 2025, the latest major release is Oracle Linux 10, which introduces advanced features like modern cryptography support, improved developer tools, and resilient infrastructure capabilities for cloud-scale deployments.[2] Oracle's involvement with Linux began in the late 1990s, with the company porting its database software to the platform in 1998, but the development of Oracle Linux as a dedicated distribution started in 2006 amid efforts to provide a stable, enterprise-grade OS tailored for Oracle products after tensions with Red Hat.[3] Initially recompiled from RHEL sources, Oracle Linux evolved to address gaps in the Linux ecosystem for mission-critical applications, with early contributions including asynchronous I/O libraries (libaio) in 2001 and the Oracle Cluster File System (OCFS) in 2002, both of which were upstreamed to the mainline kernel.[4] The Unbreakable Enterprise Kernel was first introduced in 2010 as UEK Release 1, building on mainline Linux kernels with Oracle-specific enhancements for stability and performance, and subsequent releases like UEK 8 (based on Linux kernel 6.12) continue to incorporate upstream innovations with minimal backports.[5] In recent years, Oracle has collaborated with partners through OpenELA (announced in 2023) to sustain free access to EL source code following upstream changes in RHEL's distribution model.[1] Key features of Oracle Linux include zero-downtime patching via Ksplice for security updates without reboots, built-in virtualization with KVM, container support through Podman and Docker compatibility, and cloud-native tools like Kubernetes orchestration.[6] It is engineered for high availability, with certifications for FIPS 140-3 and Common Criteria, making it suitable for regulated environments in finance, healthcare, and government.[1] Oracle Linux also provides extensive automation and management capabilities through the OS Management Hub, enabling patch management, compliance reporting, and configuration across hybrid environments. Unlike community-driven distributions, Oracle Linux emphasizes enterprise reliability, with regular updates synchronized closely to RHEL releases—typically within days—and long-term support extending up to 10 years or more with extended options.[7] Oracle offers multiple support tiers for Oracle Linux, including free basic support with access to security errata and updates, as well as paid Premier and Premier Plus options that provide 24/7 expert assistance, indemnification against IP claims, and integration with Oracle's broader ecosystem like Oracle Cloud Infrastructure (OCI).[8] The distribution is widely adopted for running Oracle Database, middleware, and engineered systems, but its RHEL compatibility also makes it a versatile choice for general-purpose servers, edge computing, and DevOps workflows.[1] With over 145 countries covered by Oracle's global support network, Oracle Linux powers millions of deployments, contributing to Oracle's leadership in enterprise Linux solutions.[8]History and Development
Origins and Evolution
Oracle Linux originated as Oracle Enterprise Linux (OEL), with its initial release in late 2006 as a free, downstream distribution derived from the publicly available source code of Red Hat Enterprise Linux (RHEL).[9][10] Oracle developed OEL to deliver enterprise-grade stability and optimizations tailored for its software stack, particularly database and application workloads, while addressing the need for a cost-effective alternative to proprietary Linux support models.[9] The core motivations included providing unrestricted access to RHEL-compatible binaries without mandatory subscription fees, enabling broad adoption for testing, development, and production environments, alongside optional paid support services for enhanced reliability and security updates.[10][11] In October 2010, with the release of version 5.5, Oracle rebranded OEL to Oracle Linux, streamlining its identity as a distinct, fully supported enterprise operating system while preserving its RHEL heritage.[12] This rebranding marked a maturation phase, emphasizing Oracle's commitment to long-term innovation and compatibility without altering the distribution's foundational architecture. The evolution of Oracle Linux accelerated after Red Hat's 2020 announcement to transition CentOS—a popular community-built RHEL clone—to CentOS Stream, a rolling-release model, effectively ending the stable CentOS Linux branch by 2024.[13] In response, Oracle positioned Oracle Linux as a reliable, binary-compatible successor, offering free downloads of stable releases, perpetual access to updates, and enterprise support options to fill the gap left by CentOS's shift.[11] This development reinforced Oracle Linux's role in sustaining an open ecosystem for RHEL users seeking stability and Oracle-specific enhancements without licensing restrictions. Oracle Linux also introduced the Unbreakable Enterprise Kernel (UEK) as an alternative kernel option optimized for performance (detailed in Kernel Options).[9]Key Milestones
Oracle Linux's development has been marked by several pivotal events that shaped its evolution as a enterprise-grade Linux distribution. In 2006, Oracle launched Oracle Linux at Oracle OpenWorld, introducing the initial releases based on Red Hat Enterprise Linux (RHEL), starting with Oracle Enterprise Linux 4 update 4 on October 26, providing binary-compatible support for Oracle applications without additional licensing costs.[9][14] A significant shift occurred in 2010 when Oracle rebranded and enhanced the distribution, officially adopting the name Oracle Linux and announcing the Unbreakable Enterprise Kernel (UEK) in September during Oracle OpenWorld. The UEK, initially based on the mainline Linux kernel, was designed to deliver optimized performance for Oracle workloads while maintaining compatibility with RHEL, marking Oracle's commitment to custom kernel innovations for enterprise stability and scalability.[15][16] In late 2020, following Red Hat's announcement in December to discontinue CentOS Linux as a stable RHEL rebuild in favor of the rolling CentOS Stream, Oracle positioned Oracle Linux as a free, long-term alternative for users seeking RHEL compatibility without subscription fees. This strategic response emphasized Oracle Linux's no-cost access to source code via the Oracle Linux yum server and its decade-long support lifecycle, attracting former CentOS users concerned about the shift to a development-focused model.[17][18] From 2023 to 2025, Oracle Linux advanced its cloud-native focus through major releases and integrations. In August 2023, Oracle co-founded the Open Enterprise Linux Association (OpenELA) with CIQ and SUSE to provide collaborative access to Enterprise Linux source code, addressing changes in Red Hat's distribution practices.[19] Oracle Linux 9 achieved general availability on June 30, 2022, but saw key updates in 2023, including enhanced OCI platform images, establishing it as the default operating system for Oracle Cloud Infrastructure (OCI) workloads starting May 27, 2025. Oracle Linux 10 followed with general availability on June 26, 2025, introducing improvements in automation, management, and security for diverse architectures like x86_64 and aarch64. Deepening ties with OCI, Oracle Linux underpinned all OCI regions globally by 2024, enabling seamless deployment of Oracle Database and other applications with integrated support at no extra cost.[20][21][22] Complementing these releases, the Unbreakable Enterprise Kernel 8 (UEK 8) launched on April 14, 2025, based on Linux kernel 6.12 LTS, featuring enhancements in memory management for large-scale systems and networking optimizations for high-throughput environments, available initially for Oracle Linux 9 Update 6 and later Oracle Linux 10. In May 2025, Oracle extended its collaboration with Red Hat, announced on May 20, to accelerate hybrid cloud adoption by certifying Red Hat OpenShift on OCI Roving Edge Infrastructure, Oracle Compute Cloud@Customer, and Oracle Private Cloud Appliance, fostering interoperability for enterprise hybrid deployments.[23][24][25]Technical Overview
Kernel Options
Oracle Linux provides users with two primary kernel options: the Red Hat Compatible Kernel (RHCK) and the Unbreakable Enterprise Kernel (UEK). These kernels allow flexibility in deployment, with RHCK prioritizing compatibility with Red Hat Enterprise Linux (RHEL) ecosystems and UEK emphasizing performance enhancements tailored to enterprise and Oracle-specific workloads.[26] The RHCK is a direct backport of the corresponding RHEL kernel, ensuring exact binary compatibility for applications and software certified on RHEL. This makes it ideal for environments requiring strict adherence to RHEL standards, such as third-party software stacks that demand unmodified RHEL kernel behavior. By mirroring RHEL's kernel precisely, RHCK facilitates seamless migration and interoperability without recompilation or adjustment.[26] In contrast, the UEK is an Oracle-developed kernel based on recent upstream Linux kernel releases, such as version 6.12 for UEK 8. It incorporates customer-driven enhancements for superior performance, stability, and reliability in large-scale deployments, particularly optimizing for Oracle Database workloads. UEK tracks mainline Linux development closely with minimal backports to maintain enterprise-grade stability while delivering newer features ahead of RHEL schedules. It is extensively tested on x86 (including Intel and AMD), and ARM (aarch64) architectures to support diverse hardware environments like Oracle Cloud Infrastructure.[27][28] UEK includes several specialized features not available in RHCK, such as enhanced memory management with a cgroup slab memory controller (introduced in UEK R7) that enables efficient sharing and accounting of slab memory at the object level across control groups. It also provides improved I/O security through io_uring enhancements, including support for ASMLib v3, which leverages asynchronous I/O for secure and high-performance storage operations in Oracle Database environments. Additionally, UEK offers built-in RDMA support for low-latency, high-throughput networking, integrated with tools like Ksplice for zero-downtime updates and DTrace for observability. These additions focus on reducing latency, improving scalability, and bolstering security for demanding enterprise applications.[29][30][31][32] Users can switch between RHCK and UEK using package management commands and boot configuration tools. To install or switch to UEK, runsudo dnf install kernel-uek; to remove it and revert to RHCK, use sudo dnf remove kernel-uek-core. The default boot kernel is managed via the grubby utility, for example, sudo grubby --set-default /boot/vmlinuz-<version>-uek to select UEK at boot. Both kernels can coexist on the system, allowing runtime selection from the GRUB menu.[26]
Compatibility with RHEL
Oracle Linux provides 100% application binary compatibility with Red Hat Enterprise Linux (RHEL), ensuring that applications certified on RHEL can run seamlessly on Oracle Linux without recompilation or modification.[10] This compatibility extends to the user space, remaining independent of the underlying kernel version, which facilitates straightforward migrations for enterprises using RHEL-certified software stacks.[33] For instance, major Oracle products such as Oracle Database and Oracle Java Development Kit (JDK) are certified on Oracle Linux with the same validation criteria applied to RHEL environments.[34] Oracle Linux is built from the same source code as RHEL, with packages rebuilt and made available through Oracle's public yum repositories, including source RPMs for transparency and equivalent builds.[35] These repositories support standard RHEL package management tools, including the legacy yum utility and its successor dnf, allowing users to install, update, and manage software in a manner identical to RHEL.[36] The Red Hat Compatible Kernel (RHCK), available as an option in Oracle Linux, is compiled directly from RHEL kernel source code to maintain this ecosystem-wide compatibility, as detailed in the kernel options section. A key distinction in the support models is that Oracle Linux offers free downloads of binaries, source code, updates, and errata without requiring a subscription, contrasting with RHEL's model that mandates paid subscriptions for access to these resources.[37] This approach enables broader accessibility while preserving full interoperability, reducing costs for users transitioning from RHEL without sacrificing reliability or certification assurances.[11]Features and Capabilities
Virtualization and Containers
Oracle Linux provides robust support for virtualization through the Kernel-based Virtual Machine (KVM) hypervisor, which is integrated into the Linux kernel and enables the creation and management of virtual machines (VMs) on supported hardware.[38] This allows a single Oracle Linux host to run multiple guest VMs, leveraging hardware virtualization extensions for efficient performance. Oracle Linux Virtualization Manager serves as the primary management platform for KVM-based environments, offering tools to configure, monitor, and automate VM lifecycle operations across clusters.[39] Additionally, Oracle Linux supports guest OS installations, including Oracle Linux itself, under KVM, with certifications for running Oracle workloads in virtualized setups.[40] For container technologies, Oracle Linux has transitioned from legacy Docker support to modern, daemonless tools starting with Oracle Linux 8, emphasizing security and rootless operation. Podman, Buildah, and Skopeo form a cohesive suite for building, running, and inspecting Open Container Initiative (OCI)-compatible containers without requiring elevated privileges, enabling rootless workflows that reduce attack surfaces. As of Oracle Linux 10 (June 2025), Podman is at version 5.4 with enhancements like improved healthcheck event handling and persistent resource changes, while crun is the default container runtime (runc has been removed) and cgroup v2 is the default for containers.[41] CRI-O is also included as a lightweight, Kubernetes-focused container runtime, ensuring compatibility with orchestration platforms by adhering to the Kubernetes Container Runtime Interface (CRI).[42] Orchestration capabilities in Oracle Linux are facilitated through Oracle Linux Cloud Native Environment (OLCNE), which deploys Kubernetes clusters using Podman and CRI-O for container management, supporting scalable application deployment in on-premises environments.[43] This setup integrates with Oracle Cloud Infrastructure (OCI) Container Engine for Kubernetes (OKE), allowing seamless hybrid workflows where Oracle Linux serves as the underlying node OS for managed clusters.[44] While older Oracle Linux Container Services relied on Docker for Kubernetes, current recommendations prioritize OLCNE for its enhanced security and compatibility.[45] The Unbreakable Enterprise Kernel (UEK) includes specific optimizations for virtualization, such as improved NUMA awareness through features like affinity support for unbound workqueues and an enhanced NUMA balancing subsystem, which optimize memory and CPU allocation in multi-socket environments to minimize cross-node access latencies.[46] UEK Release 5 and later further enhance KVM with support for live migration, enabling VMs to move between hosts with minimal downtime using high-bandwidth networks, provided configurations like CPU pinning ensure NUMA alignment.[40] These UEK improvements, as detailed in the kernel options, contribute to reliable performance in virtualized Oracle Linux deployments.[47]Specific Oracle Additions
Oracle Linux introduces several proprietary tools and features that extend beyond the standard Red Hat Enterprise Linux (RHEL) distribution, enhancing observability, security patching, automation, auditing, and performance optimization particularly for enterprise workloads like databases. These additions are integrated into the Unbreakable Enterprise Kernel (UEK) and other components, providing Oracle-specific capabilities for system management and diagnostics. DTrace is a dynamic tracing framework originally developed for Solaris and ported to Oracle Linux to enable comprehensive system observability without requiring code modifications or reboots. It allows administrators to probe kernel functions, user-space applications, and system calls in real-time, facilitating the identification of performance bottlenecks, debugging, and troubleshooting across the software stack. In Oracle Linux, DTrace is available exclusively with the UEK and supports probes for I/O, processes, and function boundaries. A significant enhancement, DTrace v2.0, was introduced in UEK Release 6 (R6), leveraging eBPF for improved stability, efficiency, and broader tracing capabilities on Oracle Linux 8 and later. This version includes advanced features like natural language querying integrations for easier analysis of multithreaded applications and system events.[48][49][50] Ksplice provides zero-downtime patching for the Linux kernel and critical user-space components, allowing security updates and bug fixes to be applied without interrupting running services or requiring system reboots. This tool targets vulnerabilities in the kernel, glibc, and OpenSSL, delivering 100% of important security patches while maintaining application uptime and compliance. In Oracle Linux, Ksplice operates in two modes—online for immediate updates and offline for scheduled maintenance—and is supported on both physical and virtualized environments, reducing operational costs associated with downtime. It integrates seamlessly with Oracle Linux Premier Support, enabling automated patch management for enterprise-scale deployments. Ksplice is supported on Oracle Linux 10.[51][52][53][54] Oracle Linux Automation Manager serves as a centralized web-based interface and task engine for configuration management, compliance enforcement, and orchestration of infrastructure tasks. Built on the Oracle Linux Automation Engine (derived from Ansible), it enables the scheduling and execution of playbooks to deploy software, configure systems, perform upgrades, and ensure regulatory compliance across inventories of servers. The manager provides a visual dashboard for monitoring job status, reporting on automation outcomes, and managing user access, making it suitable for large-scale IT environments. It supports REST APIs for integration with other tools and is available as a free component in Oracle Linux, with enhanced support in cloud deployments on Oracle Cloud Infrastructure.[55][56] Beyond these core tools, Oracle Linux incorporates enhancements to auditing via updates to the auditd daemon, part of the Linux Audit system, which tracks system events like logins, account changes, and privilege escalations for improved security monitoring and forensics. These updates include bug fixes and new facilities for software source tracking to bolster compliance in enterprise settings. In Oracle Linux 10, auditing is further enhanced with the audisp-filter plugin for refined event filtering.[57][58][59][41] Additionally, Oracle-specific tuning parameters optimize kernel settings for database performance, including adjustments to shared memory (SHMMAX), semaphores (SEMMSL), and file handles to accommodate high-throughput Oracle Database workloads without default RHEL limitations. These configurations, detailed in Oracle's installation guides, ensure efficient resource allocation for large-scale data processing.[58][59]Hardware and Software Compatibility
Oracle Linux supports a range of hardware platforms, including x86-64 architectures from Intel and AMD processors, ARM64 with Ampere Altra, Altra Max, and AmpereOne processors, and legacy SPARC systems limited to older releases such as Oracle Linux 6. SPARC support, detailed in the "SPARC Version" subsection, is certified on Oracle's older T-series servers like the T4 and T5 models. It is also certified on third-party hardware like Cisco UCS blade and rack servers, HPE ProLiant DL, ML, RL, and Synergy series (including the Ampere-based RL300 Gen11), and similar offerings from Dell and Lenovo.[60][61][62][63] On the software side, Oracle Linux maintains full binary compatibility with Red Hat Enterprise Linux, enabling seamless operation of RHEL-certified applications. It supports major Oracle products, including Oracle Database (versions 12c through 23c), MySQL, and middleware such as Oracle WebLogic Server (12c, 14c, 15c), Oracle Fusion Middleware components like SOA Suite and Identity Management, and various enterprise applications through Independent Software Vendor (ISV) certifications. Additionally, Oracle Linux integrates natively with Oracle Cloud Infrastructure (OCI), running on OCI's x86-64 and ARM64 hardware shapes for cloud deployments.[64][65][66] The certification process for hardware and software involves Oracle Validated Configurations, which are pre-tested architectures combining Oracle Linux with specific hardware, storage, and network components from partners to ensure reliability and performance in enterprise environments. Hardware vendors and ISVs participate in this program to validate compatibility, often requiring minimal testing due to RHEL interoperability, with results documented in official matrices.[67][64]Versions and Support
Release History
Oracle Linux has followed a structured release cadence aligned with its upstream Red Hat Enterprise Linux (RHEL) base, with major versions typically released every three years and featuring the optional Unbreakable Enterprise Kernel (UEK) for enhanced performance. Each major release incorporates binary compatibility with RHEL while adding Oracle-specific optimizations, particularly through UEK variants that draw from newer upstream Linux kernels. Minor updates, denoted as "." versions (e.g., OL9.4), deliver cumulative errata for security vulnerabilities, bug fixes, and stability improvements without introducing major feature changes.[7][68] The inaugural major release compatible with modern enterprise needs was Oracle Linux 5, generally available in June 2007 and based on RHEL 5. It provided a stable foundation for Oracle workloads, with the initial UEK (R1) introduced later in September 2010, based on upstream Linux kernel 2.6.32, to offer better performance and hardware support without altering application compatibility.[7][15] Oracle Linux 6 followed in February 2011, derived from RHEL 6, and introduced UEK R2 based on Linux kernel 2.6.39, with later UEK R3 on 3.8.13, which included enhancements for virtualization such as improved KVM integration and better scalability for virtualized environments.[7][68][69] In July 2014, Oracle Linux 7 was released, built on RHEL 7, starting with UEK R3 on Linux kernel 3.8.13 and RHCK on 3.10 for initial compatibility and later incorporating UEK R5 on 4.14 for advanced features like container support through Docker integration.[7][70][71][68] Oracle Linux 8 arrived in July 2019, aligned with RHEL 8, featuring UEK R6 based on Linux kernel 5.4 (with the compatible RHCK on 4.18), emphasizing modular packaging and improved security baselines.[7][71] The June 2022 release of Oracle Linux 9, based on RHEL 9, defaulted to UEK R7 on Linux kernel 5.15 (RHCK on 5.14), with additions like enhanced security through AppArmor support and better integration for confidential computing.[7] As the latest major version as of November 2025, Oracle Linux 10 was generally available in June 2025, based on RHEL 10, and ships with UEK 8 on Linux kernel 6.12 by default (RHCK on 6.12), optimized for cloud-native applications and AI/ML workloads via improved memory management and I/O performance.[7][2][68][72] Minor releases occur quarterly or as needed; for instance, Oracle Linux 9.4 was issued in May 2024 to address security issues and bugs, accumulating prior errata into a single update ISO.[73]| Version | General Availability Date | Base (RHEL) | Default UEK (Kernel Version) | Key Additions |
|---|---|---|---|---|
| 5 | June 2007 | 5 | R1 (2.6.32, introduced 2010) | Initial enterprise stability |
| 6 | February 2011 | 6 | R2 (2.6.39), later R3 (3.8.13) | Virtualization improvements |
| 7 | July 2014 | 7 | R3 (3.8.13)/RHCK (3.10), later R5 (4.14) | Container support |
| 8 | July 2019 | 8 | R6 (5.4) | Modular architecture |
| 9 | June 2022 | 9 | R7 (5.15) | Enhanced security features |
| 10 | June 2025 | 10 | 8 (6.12)/RHCK (6.12) | Cloud-native and AI focus |
Support Lifecycle
Oracle Linux follows a structured support lifecycle designed to provide long-term stability for enterprise deployments, with policies aligned to ensure compatibility with Red Hat Enterprise Linux (RHEL) where applicable. The support phases include Basic Support and Premier Support, each spanning 10 years from the general availability (GA) date of a major version, followed by an optional Extended Support phase. These phases offer escalating levels of assistance, from free security updates to comprehensive technical services, while updates are freely available through public yum repositories during the initial support periods.[6][74] Basic Support provides essential maintenance, including security patches for critical vulnerabilities (CVEs) and select bug fixes to maintain system integrity. This level is available at no cost and focuses on production readiness without dedicated technical assistance, allowing users to access errata via the Oracle Linux yum server or Unbreakable Linux Network (ULN). In contrast, Premier Support encompasses all Basic Support benefits plus 24/7 global technical support, unlimited service requests, comprehensive bug fixes, and access to advanced features such as Ksplice for zero-downtime kernel patching, BPR (Backport Request) fixes, and tools like OS Management Hub and DTrace. Premier Support requires a paid subscription, priced per physical CPU pair or for up to two virtual machines per license, and is essential for organizations needing proactive assistance and enhanced reliability.[6][8] Extended Support is an optional, fee-based extension available after the conclusion of Premier Support, offering up to three additional years of critical security patches, select bug fixes for severe issues, and continued access to My Oracle Support and ULN. This phase does not include new hardware certifications, general feature enhancements, or backporting of non-critical fixes, prioritizing stability for legacy environments. A valid Premier Support contract is prerequisite for Extended Support, which helps bridge the gap to newer versions without immediate upgrades. Following Extended Support, indefinite Sustaining Support provides access to existing documentation, online resources, and pre-existing patches but no new fixes or technical assistance.[74][7] The specific support timelines for recent versions reflect this 10-year core period plus optional extension:| Version | GA Date | Premier Support Ends | Extended Support Ends |
|---|---|---|---|
| Oracle Linux 8 | July 2019 | July 2029 | July 2032 |
| Oracle Linux 9 | June 2022 | June 2032 | June 2035 |
| Oracle Linux 10 | June 2025 | June 2035 | June 2038 |