how can we track user activity?
Solution 1:
There are a couple software tools to do this in a GUI:
-
RescueTime [Paid]
Allows tracking of user activity, what apps they're using, etc. -
arbtt [Free]
Allows tracking of what applications are open and for how long. Most similar to RescueTime, but free.
For the commandline, you can track .bash_history and record all the commands executed.
However, you must trust your users. Anything you install can (pretty easily) be disabled by the end-users to hide their true activity and time.