System information

uname -r          -> shows system information
uname -a          -> shows kernel release information
uptime            -> shows how long the system has been running, including load average
hostname          -> shows system hostname
hostname -i       -> shows the IP address of the system
last reboot       -> shows system reboot history
date              -> shows current time and date
timedatectl       -> queries and change the system clock
cal               -> shows current calender month and day
w                 -> shows logged in users in the system
whoami            -> shows user you are using
finger [username] -> shows information about a user