How To Terminate A Process In Linux – Kill A Process

In Linux, you can terminate a process from the command line. We going to use three different ways to kill a process running on our test server. The only reason these programs exist is to terminate a process, they have no other useful usage.

Kill, Pkill, Killall

The three functions we are going to use are kill, pkill, and killall and the basic commands for all three are mostly the same;

kill
pkill
killall

You should always aim to use the kill command first. It’s worth noting that these functions don’t actually kill the process or terminate the process they simply send the kill command to the program or group. If you do not specify a command the default signal, sigterm is sent.

Terminate A Process or Kill A Process

The fact you are looking at how to terminate a process in Linux suggests you likely already know what you want to terminate. You can use the top screen or ps -a to list all the processes running on the server. top -c is good if you don’t know the process you want to terminate and you can arrange the active processes by resource usage.

Once you have the PID of the process you want to terminate issue the kill command. First, you will want to send the correct signal. A list of signals can

kill -SIGUP <PID>
pkill -SIGKILL <PID>

Most people use SIGKILL (9) and SIGTERM (15) SIGTERM is the safest way to kill a process on your server. If you are using pkill the signal is the same as kill but for killall the signal names are different.

Killall

In cases where you have lots of processes running, it’s very time-consuming typing all the PIDS. You can use killall to terminate all of the processes. It’s much the same as kill or pkill but you use the process name instead of the PID

killall apache

You can also terminate all processes running under a specific username with killall. I want to terminate all of the processes running under the f2h user so the command would be

killall -u f2h

That’s the basics of kill, pkill, and killall and you now know how to kill a process in Linux. For in-depth information, you can check the man page in Linux from your console. Just issue the man kill, man pkill or man killall command for the full manual.