This part of the course will be very UNIX specific. It isn't really possible to teach tools and scripts without actual examples. However, many programs listed in this section are available on many different platforms and operating systems. Most of those that are not, have equivalents. I'm afraid it is left up to the reader to discover these if they wish.
Most tools start with simple unix utilities such as du, telnet and ps.
These are used all the time by sysadmins to check the status of running machines, see what users are doing, and test that certain services are working. If a machine is running slowly, a good bet is that there are too many processes or one process is taking up too much CPU time. However, once you get a handle on it, you can write very powerful one-line scripts to do such things as recursively remove all files that have not been accessed in the past 10 days, and print out the names as you do it. Something like this could be put in a cron job to clean up disk space. It's most often used to see what files a process is accessing.