How To Kill A Process.
In this article, we will show you how to use kill, killall, and pkill commands to terminate a process.
The main difference between these tools is that kill terminates processes based on Process ID number (PID), while the killall and pkill commands terminate running processes based on their names and other attributes.
System Kill Signals.
kill, killall, and pkill send a given signal to specified processes or process groups. When no signal is specified, each tool sends 15 (TERM).
The most commonly used signals are:
1 (-HUP): to reload a process.
9 (-KILL): to kill a process.
15 (-TERM): to gracefully stop a process.
Signals can be specified in three different ways:
using a number (e.g., -1)
with the “SIG” prefix (e.g., -SIGHUP)
without the “SIG” prefix (e.g., -HUP).
Use the -l option to list all available signals:
kill -l # or killall -l
Terminating Processes Using the kill Command
To terminate a process with the kill command first, you need to find the process PID. You can do this using different commands such as top, ps , pidof, and pgrep .
Let’s say the chrome browser has become unresponsive, and you need to kill the browser process. To find the process ID, use the pidof command:
pidof chrome
The command will print all chrome processes:
2551 2514 1963 1856 1771
Once you know the chrome processes PIDs to terminate all of them send the TERM signal:
kill -9 2551 2514 1963 1856 1771
Terminating Processes Using the killall Command
The killall command terminates all programs that match a specified name.
Using the same scenario as before, you can kill the chrome process by typing:
killall -9 chrome
killall accepts several options such as sending signals to processes owned by a given user, matching processes names against regular expressions, and the creation time. You can get a list of all options by typing killall (without any arguments) on your terminal.
For example, to terminate all processes running as a user “sara”, you would run the following command:
sudo killall -u sara
Terminating Processes Using the pkill Command
pkill terminates processes that match the pattern given on the command line:
pkill -9 chrome
The name of the process doesn’t have to be an exact match.
With pkill you can also send a signal to processes that are owned by a given user. To kill only the chrome processes owned by the user “sara”, you would type:
pkill -9 -u sara chrome
Conclusion
Terminating unresponsive programs using the kill, killall and pkill commands is an easy task. You only need to know the process name or PID.
