How to “kill” or terminate a process/program in Linux Ubuntu?

In this Linux Ubuntu tutorial, we explain how to kill a process or Program in Linux Ubuntu. There are a number of reasons why you would like to terminate a process. Namely, sometimes even if you close an application, the background processes of the same application will still run. On the other hand, sometimes an application might become unresponsive and you would need to terminate it manually. The YouTube video accompanying this tutorial is given below.

There are several ways to kill or terminate a process or an application in Linux Ubuntu.

1. Kill the process on the basis of its PID

In Linux systems, the Process IDentification, or briefly PID is a unique identifier and number assigned to each process or a subprocess of an application running on a Linux System. On the other hand, we also have a PPID number. A PPID stands for Parent Process IDentification. This is the process that created the PID process.

First, let us find the PID identification of the process or program. To do that open a terminal and type:

ps -ef

This will list the currently running processes and programs in Linux Ubuntu. You should see an output similar to this:

The second column represents the PID of the process.

You can also type

ps aux

to get a more detailed response including CPU and memory usage:

Now, you need to identify the process that you want to terminate. That is, you need to find its PID.  You can either search the list or you can filter the results by typing this:

ps -ef | grep <name of the process>

For example, if I want to find a process called snapshot. I will simply type

ps -ef | grep snapshot

The result will look like this

aleksan+   19605    2916  3 22:08 ?        00:00:00 /usr/bin/snapshot

We can also find the PID of a process by using the command

pidof <process name>

For example, to find the PID of firefox, we will simply type

pidof firefox

The output will look like this

We can see that there are several processes associated with firefox apps.

To modify the execution of a specific process, we need to use the kill command. To kill this process, we will need to type

kill <signal> <PID>

This will send a kill signal to that process that will terminate the process with the specific PID. For example, to kill the process/app called snapshot, we need to write this:

kill -9 19605

The command kill has other options also:

SIGHUP -1 Hangup

SIGINT -2 Interrupt from keyboard

SIGKILL -9 Kill signal

SIGTERM -15 Termination signal- allow the program to run the exit code and stop its processing

SIGSTOP -17, -19, -23 Stop the process

2. Kill the process on the basis of its Name

To kill the process/application on the basis of its name, we simply need to write

killall <application or process name>

For example, if we want to kill firefox, we will simply write

kilall firefox

Another approach is to use the command pkill

Again, we will simply write

pkill <name of the process or application>