1) ps = report process status

ps : typing ps alone would list the current running processes

ps -u username : to search processes run by a certain user

ps ag : to get information about all running process

ps aux : to display the owner of the processes along with the processes

ps ax | grep  processname : to see if a particular process is running or not


2) ptree : to display a tree of processeses

pstree -p | less : also display the pid of the process


3) pgrep : look up or signal processes based on name and other attributes

pgrep sshd : to list the processes called sshd

pgrep -u root sshd : will only list the processes called sshd AND owned by root

pgrep -u root,daemon : will list the processes owned by root OR daemon


4) pidof — find the process ID of a running program

pidof emacs – list the process id for emacs

pgrep and pidof is much the same except that grep is more powerful it has more options (check man pages for both)


5) pkill = kill all processes matching the search text

pkill sshd : kill all sshd processes

pkill -9 –u userlogin : kill a process owned by a particular user


6) kill = Send a signal to terminate one or more process IDs

kill 2345 : terminate process 2345 (to list process id use ps)

kill -9 2345 : if kill 2345 doesnt work, use kill -9 2345 to force it


7) killall = kill all processes by name

killall nautilus

Unlike the kill command, it is not necessary to first try to find the PID(s) for nautilus. And if there are multiple instances of nautilus running, all will be terminated immediately.

killall is similar to pkill