How to find out linux release information?

For Oracle Enterprise Linux:
$ rpm -qf /etc/redhat-release
enterprise-release-5-0.0.9
$ cat /etc/enterprise-release
Enterprise Linux Enterprise Linux Server release 5.2 (Carthage)

For RedHat Enterprise Linux:
$ rpm -qf /etc/redhat-release
redhat-release-4AS-5.5
$ cat /etc/redhat-release
Red Hat Enterprise Linux AS release 4 (Nahant Update 4)

For SuSE, use “/etc/SuSE-release”:
$ cat /etc/SuSE-release
SUSE LINUX Enterprise Server 9 (i586)
VERSION = 9