As everybody knows, Linux regroups several operating system families. The most popular Linux OS are Debian, Red Hat, or Suse. But each family has many derived Linux distributions. In November 2006, Oracle released the first version of its operating system, totally based on Red Hat Enterprise Linux: Enterprise Linux.

Up to release 5, the system came with two kernels:

  • A customized kernel with bug fixes, based on Red Hat kernel, installed and started by default
  • An unmodified Red Hat kernel for manual installation, identical to the one released on Red Hat Enterprise Linux systems

From Enterprise Linux 5 to Enterprise Linux 5 Update 4, the unmodified Red Hat kernel was installed by default and the kernel with bug fixes had to be installed manually.

In Oracle Linux 5 Update 5, Oracle introduced a new Kernel: the UEK (for Unbreakable Enterprise Kernel). This kernel consists in an upgraded kernel, with specific features or enhancements for Oracle software. In Oracle Linux 5.5, the Red Hat kernel was still installed and started by default, the UEK and the kernel with bug fixes had both to be installed manually.

Since Oracle Linux 5 Update 6, the Oracle UEK has replaced the Red Hat kernel. It is installed and started by default, and the Red Hat kernel is just installed, but not enabled. The kernel with bug fixes remains uninstalled but still available for a manual install.

The following table lists all Oracle Linux releases, associated to the corresponding kernel(s) and release date (dates are approximations from information displayed on oss.oracle.com and wikipedia.org):

Release name Release date Default kernel Optionnal kernel
Enterprise Linux 4.4 10/2006 Kernel with bug fixes 2.6.9-42.0.0.0.1.EL n/c
Enterprise Linux 4.5 05/2007 Kernel with buf fixes 2.6.9-55.0.0.0.2.EL n/c
Enterprise Linux 4.6 04/2008 Kernel with bug fixes 2.6.9-67.0.0.0.1.EL n/c
Enterprise Linux 4.7 07/2008 Kernel with bug fixes 2.6.18-78.0.0.0.1.EL 2.6.18-78 (manually)
Enterprise Linux 4.8 05/2009 Kernel with bug fixes 2.6.9-89.0.0.0.1.EL 2.6.9-89 (manually)
Enterprise Linux 4.9 02/2011 Kernel with bug fixes 2.6.9-100.0.0.0.1.EL 2.6.9-100.EL
Enterprise Linux 5 06/2007 2.6.18-8.el5 Kernel with bug fixes 2.6.18-8.0.0.4.1.el5 (manually)
Enterprise Linux 5.1 04/2008 2.6.18-53.el5 Kernel with bug fixes 2.6.18-53.0.0.0.1.el5 (manually)
Enterprise Linux 5.2 06/2008 2.6.18-92.el5 Kernel with big fixes 2.6.18-92.0.0.0.1.el5 (manually)
Oracle Enterprise Linux 5.3 (OEL) 01/2009 2.6.18-128.el5 Kernel with bug fixes 2.6.18-128.0.0.0.1.el5 (manually)
Oracle Enterprise Linux 5.4 (OEL) 09/2009 2.6.18-164.el5 Kernel with bug fixes 2.6.18-164.0.0.0.1.el5 (manually)
Oracle Linux 5.5 09/2010 2.6.18-194.el5

Kernel with bug fixes 2.6.18-194.0.0.0.3.el5 (manually)

UEK 2.6.32-100.0.19.el5 (via uln)

Oracle Linux 5.6 06/2011 UEK 2.6.32-100.26.2.el5

2.6.18-238.el5 (disabled)

Kernel with bug fixes 2.6.18-238.0.0.0.1.el5 (manually)

Oracle Linux 5.7 07/2011 UEK 2.6.32-200.13.1.el5uek

2.6.18-274.el5 (disabled)

Kernel with bug fixes 2.6.18-274.0.0.0.1.el5 (manually)

Oracle Linux 5.8 02/2012 UEK 2.6.32-300.10.1.el5uek

2.6.18-308.el5 (disabled)

Kernel with bug fixes 2.6.18-308.0.0.0.1.el5 (manually)

Oracle Linux 5.9 01/2013 UEK R2 QU2 2.6.39-300.26.1.el5uek

2.6.18-348.el5 (disabled)

Kernel with bug fixes 2.6.18-348.0.0.0.1.el5 (manually)

Oracle Linux 5.10 10/2013 UEK R2 QU5
2.6.39-400.209.1.el5uek
2.6.18-371.el5 (disabled)Kernel with bug fixes 2.6.18-371.0.0.0.1.el5 (manually)
Oracle Linux 5.11 09/2014 UEK R2 QU5
2.6.39-400.215.10.el5uek
 2.6.18-398.el5 (disabled)Kernel with bug fixes 2.6.18-398.0.0.0.1.el5 (manually)
Oracle Linux 6 02/2011 UEK 2.6.32-100.28.5.el6 2.6.32-71.el6 (disabled)
Oracle Linux 6.1 06/2011 UEK 2.6.32-100.34.1.el6 2.6.32-131.0.15.el6 (disabled)
Oracle Linux 6.2 12/2011 UEK 2.6.32-300.3.1.el6uek 2.6.32-220.el6 (disabled)
Oracle Linux 6.3 06/2012 UEK R2 2.6.39-200.24.1.el6uek 2.6.32-279.el6 (disabled)
Oracle Linux 6.4 02/2013 UEK R2 QU3
2.6.39-400.17.1.el6uek
2.6.32-358.el6 (disabled)
Oracle Linux 6.5 11/2013 UEK R2 QU5 2.6.39-400.211.1.el6uek (i386 media)UEK R3 3.8.13-16.2.1.el6uek (x86_64 media)
2.6.32-431.el6 (disabled)
Oracle Linux 6.6 10/2014 UEK R2 QU5
2.6.39-400.215.10.el6uek
(i386 media)UEK R3 QU3
3.8.13-44.1.1.el6uek
(x86_64 media)
 2.6.32-504.el6 (disabled)

I will regulary update this table with new releases of Oracle Linux.

UPDATE

In february 28th 2013, Oracle released Oracle Linux 6 Update 4, shipped with the UEK R2 Quarterly Update 3 (2.6.39-400.17.1).

In July 2013, Oracle released the UEK R2 Quarterly Update 4 (2.6.39-400.109.1).

In September 2013, Oracle released the UEK R2 Quarterly Update 5 (2.6.39-400.209.1).

In October 2013, Oracle released the UEK R3 (3.8.13-16.el6uek.x86_64), and Oracle Linux 5 Update 10, shipped with the UEK R2 Quarterly Update 5 (2.6.39-400.209.1).

In November 2013, Oracle released Oracle Linux 6 Update 5, shipped with the UEK R2 Quarterly Update 5 (2.6.39-400.211.1) for the i386 media, or UEK R3 (3.8.13-16.2.1) for the x86_64 media, since UEK R3 is not compatible with i386.

In Septembre 2014, Oracle released Oracle Linux 5 Update 11, shipped with the UEK R2 Quarterly Update 5 (2.6.39-400.215.10).

In October 2014, Oracle released Oracle Linux 6 Update 6, shipped with the UEK R2 Quarterly Update 5 (2.6.39-400.215.10) for the i386 media, or UEK R3 Quarterly Update 3 (3.8.13-44.1.1) for the x86_64 media, since UEK R3 is not compatible with i386.

You can find the release notes on the Oracle website:

For Oracle Linux 5

For Oracle Linux 6

Note that in July 2014, Oracle released the new Oracle Linux 7. See the release not.