Oracle Unbreakable Enterprise Kernel Release 2 Release Notes

Updated March 2012


  1. Oracle Unbreakable Enterprise Kernel Release 2 Release Notes
    1. Introduction
    2. New features
      1. Updates/Improvements added by Oracle
        1. Btrfs
        2. Xen domU improvements
        3. Other improvements
      2. Driver Updates
        1. Storage drivers
        2. Network drivers
        3. Other drivers
      3. Notable improvements in mainline Linux since Linux 2.6.32
    3. Updated or added utilities
      1. Oracle Linux 6
      2. Oracle Linux 5
    4. Technology Preview Features
    5. Compatibility
    6. Availability
    7. Installation
    8. Known Issues


The Unbreakable Enterprise Kernel Release 2 is Oracle's second major release of its heavily tested and optimized operating system kernel for Oracle Linux 5 and Oracle Linux 6. It is based on the mainline Linux 3.0 version 3.0.16. It contains a large number of improvements and new features that have been incorporated into mainline Linux since the first version of the Unbreakable Enterprise Kernel, which was based on Linux 2.6.32.

Note: the actual version number displayed by the kernel and on the RPM packages is 2.6.39. This was done to avoid potential breakage of certain low-level utilities of the Oracle Linux distribution (also known as the "plumbing") that potentially can't cope with the new 3.x version scheme. Regular Linux applications are usually not aware or affected by Linux kernel version numbers.

New features

Updates/Improvements added by Oracle

This release of the Unbreakable Enterprise Kernel has been improved/enhanced by Oracle in several areas, including bug fixes and extended functionality. All of these modifications have been contributed back upstream and are available in mainline Linux.


Btrfs provides a flexible way to manage storage, without needing a separate volume manager. It provides built-in RAID support and ensures data integrity by using redundancy and checksums. Btrfs also supports lightweight copies/clones of files or directories with snapshots as well as online data compression. The Btrfs code in the Unbreakable Enterprise Kernel Release 2 includes many new features as well as numerous performance improvements, that were merged from a number of long running projects and cleanup queues.

New Btrfs features/functionality

Btrfs bug fixes and performance improvements

Xen domU improvements

Several bug fixes and improvements have been incorporated to make the Unbreakable Enterprise Kernel scale and cooperate better as a guest (domU) in Oracle VM and Xen.

Other improvements

Driver Updates

The Unbreakable Enterprise Kernel supports a vast range of hardware and devices. In close cooperation with hardware and storage vendors, several device drivers have been updated by Oracle. The list below only indicates the updated drivers that deviate from the versions included in mainline Linux 3.0.16.

Storage drivers

Network drivers

Other drivers

Notable improvements in mainline Linux since Linux 2.6.32

This section lists a some of the most visible/noteworthy improvements that have taken place in mainline Linux since the Unbreakable Enterprise Kernel Release 1 (which was based on mainline Linux 2.6.32). It is by no means exhaustive or complete, as a full list would exceed the scope of these release notes.

Updated or added utilities

In order to support the newly added functionality provided by the Unbreakable Enterprise Kernel Release 2, the following RPM packages were added or updated from the ones included in the base distribution and are included in the respective channels/repositories:

Oracle Linux 6



Oracle Linux 5



Technology Preview Features

In addition to the features listed above, the Unbreakable Enterprise Kernel Release 2 includes the following features which are still under development, but are already made available for testing/evaluation purposes.


Oracle Linux maintains user-space compatibility with Red Hat Enterprise Linux, which is independent of the kernel version running underneath the operating system. The existing applications will continue to run unmodified on Unbreakable Enterprise Kernel Release 2 and no re-certifications are needed for RHEL certified applications.

As Unbreakable Enterprise Kernel Release 2 is based on mainline Linux 3.0.16, we expect it to have a different kernel ABI from Unbreakable Enterprise Kernel Release 1 which is based on 2.6.32. The Oracle Linux engineering team works closely with ISVs that develop kernel modules, to ensure that kernel interoperability is obtained with Unbreakable Enterprise Kernel Release 2.

It is possible that kernel modules will have to be recompiled to interoperate with Unbreakable Enterprise Kernel Release 2. Oracle Linux team will work closely with the affected kernel module developers to mitigate the impact.


The Unbreakable Enterprise Kernel is available as binary RPM packages that can be installed from Oracle's public yum repository as well as the Unbreakable Linux Network. The kernel's source code is available via a public git source code repository from


The Unbreakable Enterprise Kernel Release 2 can be installed on Oracle Linux 5 Update 8 or newer, as well as Oracle Linux 6 Update 2 or newer. If you're still running an older version of Oracle Linux, make sure to first update your system to the latest available update release. The Unbreakable Enterprise Kernel Release 2 will be provided via dedicated channels on the Oracle Unbreakable Linux Network and the public yum repositories.

See the "Getting Started with the Unbreakable Enterprise Kernel for Oracle Linux" document on the Oracle Technology Network for detailed instructions on how to download and install the Unbreakable Enterprise Kernel on Oracle Linux.

Known Issues