uptime
Show how long the system has been running and load average
uptime shows current time, how long the system has been up, logged-in users, and 1/5/15 minute load averages. Load > number of CPUs means the system is overloaded.
Example
$ uptime
14:23:45 up 12 days, 3:47, 2 users, load average: 0.52, 0.41, 0.38
Tip: Type it yourself in the terminal below - reading is not the same as doing.