Source : http://www.everymanit.com/
Users, Groups and Permissions : http://www.youtube.com/watch?v=zRw0SKaXSfI&feature=related
Network Configuration: http://www.youtube.com/watch?v=PEa1xopeufQ&feature=fvwrel
FileSystem: http://www.youtube.com/watch?v=-UeuoG5sAA4&feature=related
Hacking : http://www.youtube.com/watch?v=yGIHjTmTFfA&feature=relmfu
Load Balance : http://www.everymanit.com/2011/11/13/bandwidth-throttling-with-netbalancer/