Check processes
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
Kill processes
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'?
Reference:
Ask Ubuntu:
http://askubuntu.com/questions/104903/how-do-i-kill-processes-in-ubuntu