Learn Linux http://www.tldp.org/LDP/intro-linux/html/ | http://manuals.bioinformatics.ucr.edu/home/linux-basics | UNIX http://www.ee.surrey.ac.uk/Teaching/Unix/ | En/Decryption, Hacking, Security and anything related. Off topic is allowed so long as you are being polite to others.. Google is your friend!