The first rule you should learn is that there is no shortcut to theoretical knowledge and practical experience.
- If with "Operating System" you mean you've never used any Linux at all then you should start with some basic Linux documentation like Rute Tutorial & Exposition
- If you don't have any admin experience then see Linux Newbie Administrator Guide
and The Linux System Administrator's Guide
(both old but useful).
- And if you never used Red Hat Enterprise Linux then install a free version at home (see http://www.centos.org/
) and start working through their documentation: http://www.centos.org/docs/