In order to install Oracle Linux 5.x, please download the Oracle Linux ISO image from Oracle's edelivery website:
http://edelivery.oracle.com. For more information on Oracle Linux's program, visit http://www.oracle.com/linux

NOTE:

Oracle recommends to choose a default list of RPMs during the operating system installation as described in Metalink Note 401167.1,

Defining a “default RPMs” installation of the Oracle Enterprise Linux (OEL) OS.