How do I kill processes in Ubuntu?

To kill all the processes that you have the permission to kill, simply run the command

kill -15 -1 or kill -9 -1 depending on the desired behavior (use man kill for details)

To kill a specific process, say, firefox, simply run

pkill firefox or killall firefox depending on the behavior you want: What's the difference between 'killall' and 'pkill'?

If you want to see what processes are running use the command

ps -ef

If you want to look up all processes by user bob, this might help

pgrep -l -u bob

or

ps -ef | grep bob

Use sudo kill <pid> or sudo killall <process-name>

You can use

ps -ax | grep application name 

If your searching for firefox type in terminal like ps -ax | grep firefox, it shows the process id of corresponding application. You can stop that application by kill command if process id=1317,

kill -9 1317