Simple but useful command to know who logged on to your systems
Tool 1: w - Show who is logged on and what they are doing
# w
Tool 2: who - Show who is logged on
# who
# who -q (All login name and count number of user logged on)
Tool 3: last - show listing of last logged in users
# last
Tool 4: uptime - Tell how long the system has been running
# uptime
