Which linux distribution, build, version am I running

Simply run the following command

$ cat /proc/version

Sample output:

Linux version 2.6.30.10-105.2.4.fc11.i686.PAE (mockbuild@x86-05.phx2.fedoraproject.org) (gcc version 4.4.1 20090725 (Red Hat 4.4.1-2) (GCC) ) #1 SMP Tue Jan 19 22:46:27 UTC 2010
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