To get running version type this in command line:
uname -a
Output:
Linux asterisk1.local 2.6.9-34.0.2.EL #1 Fri Jul 7 19:24:57 CDT
2006 i686 i686 i386 GNU/Linux
To get release version which was used during installation type this:
cat /etc/*-release
Output:
CentOS release 4.3 (Final)
179b4521-3386-495c-b0e0-8dccc5989e90|0|.0