User and system tasks each take place within a well-defined container called a process on Unix-like system.

Any time something isn’t behaving as expected or a process appears to be frozen inspect the process and kill it to clear things up.1

Show all processes on system,

ps aux

ps, reports a snapshot of the current processes.

aux, shows all users’ process listed in a user oriented fashion, include processes like services2,

a = show processes for all users
u = display the process's user/owner
x = also show processes not attached to a terminal

To find the target process using pipe,

ps aux | grep process-name

Command above shows detailed info. for the processes match the process-name keyword.

To terminate the process,

kill -15 12241 # 12241 is the process ID

15 is the linux signals, a list of all Linux signals can be found at here3.

To kill all the processes that matching a particular process name,

pkill -15 -f process-name