Gnome: System Monitor Application To Kill a Process

To start System Monitor GUI, click on System menu > Select Administration > System Monitor. Alternatively, open a command-line terminal (select Applications > Accessories > Terminal), and then type:
$ gnome-system-monitor



































now select the process you want to kill and End Process.


To kill from command line option 


 $ ps aux | grep program_name

 ps - report a snapshot of the current processes.

To end a process, enter:


$ kill -s 15 PID