Our group often has to familiarize research students to also be systems 
software technicians (sysadmin).  (At a minimum, these students have had 
a typical USA undergraduate operating system theory course.)  I 
typically recommend Evi Nemeth's book that readily is available from a 
number of sources (http://www.admin.com/), and then additional reading 
for environment specifics (e.g., EL 6).  I have found the following:

http://www.thegeekstuff.com/linux-sysadmin/

Linux Sysadmin CentOS 6 Course Helps You to Master the Tools, and 
Configure it Right

The course costs $197 .

As CentOS 6, SL6, etc., are essentially the same from the same TUV 
source distribution, this course should cover SL 6.

Is anyone familiar with the above?  Recommendations (good or bad)?

Yasha Karant