How to find out which Linux version you are running?
# cat /proc/version

Output – Linux version 2.6.27-6_1.intel.BHsmp (kernel@bluehost.com) (gcc version 3.4.6 20060404 (Red Hat 3.4.6-10)) #1 SMP Thu Nov 13 15:27:29 MST 2008

how do I show all installed packages in Linux?
# rpm -qa | less
This workes in Red Hat/Fedora Core/CentOS Linux