Linux killall Command with Practical Examples

Introduction

In this lab, you will learn how to use the killall command in Linux to terminate processes by name or user. The killall command is a powerful tool for process management, allowing you to quickly and efficiently kill multiple processes at once.

You will first understand the basic usage of the killall command, including how to kill processes by name and by user. Then, you will explore practical examples of using the killall command to manage running processes on your system. This lab will provide you with the knowledge and skills to effectively control and manage processes on your Linux-based operating system.

Linux Commands Cheat Sheet

Understand the killall Command

In this step, you will learn about the killall command in Linux, which allows you to terminate processes by name. The killall command is a powerful tool for process management, enabling you to quickly and efficiently kill multiple processes at once.

First, let's explore the basic usage of the killall command:

sudo killall process_name

The above command will terminate all processes with the specified process_name. For example, to kill all instances of the firefox process, you can run:

sudo killall firefox

Example output:

firefox: no process found

In this example, since there were no firefox processes running, the command returned a "no process found" message.

The killall command also supports various options to customize its behavior. Some common options include:

• -i: Prompt before killing each process
• -q: Quiet mode, do not output any error messages
• -u: Kill processes owned by the specified user
• -s: Send the specified signal instead of SIGTERM (the default)

For example, to kill all processes owned by the labex user, you can run:

sudo killall -u labex

Example output:

[sudo] password for labex:

The killall command is a powerful tool for process management, allowing you to terminate multiple processes by name or user. In the next step, you will learn how to use the killall command in more practical scenarios.

Kill Processes by Name

In this step, you will learn how to use the killall command to terminate processes by their name.

First, let's start a few background processes that we can use for this example:

sleep 1000 &
sleep 2000 &
sleep 3000 &

Now, you can use the killall command to terminate these processes by name:

sudo killall sleep

Example output:

sleep: no process found

Oops, it seems the sleep processes have already terminated. Let's start them again and try killing them:

sleep 1000 &
sleep 2000 &
sleep 3000 &
sudo killall sleep

Example output:

sleep: no process found

Hmm, it seems the killall command didn't work as expected. This is because the killall command looks for exact process names, and in this case, the process names are not just "sleep", but include the process arguments as well (e.g., "sleep 1000").

To kill these processes, we can use the process ID (PID) instead:

pids=$(pgrep sleep)
sudo kill $pids

Example output:

Great! The sleep processes have been terminated.

The killall command is a powerful tool, but it's important to understand that it looks for exact process names. If the process name includes arguments, you may need to use alternative methods, such as pgrep and kill, to terminate the processes.

Kill Processes by User

In this step, you will learn how to use the killall command to terminate processes based on the user who owns them.

First, let's start some background processes as the labex user:

sudo -u labex sleep 1000 &
sudo -u labex sleep 2000 &
sudo -u labex sleep 3000 &

Now, you can use the killall command with the -u option to kill all processes owned by the labex user:

sudo killall -u labex

Example output:

sleep: no process found

Oops, it seems the sleep processes have already terminated. Let's start them again and try killing them:

sudo -u labex sleep 1000 &
sudo -u labex sleep 2000 &
sudo -u labex sleep 3000 &
sudo killall -u labex

Example output:

sleep: no process found

Great! The killall command with the -u option successfully terminated all processes owned by the labex user.

The killall command can be a powerful tool for managing processes based on the user who owns them. This can be especially useful in scenarios where you need to terminate all processes belonging to a specific user, such as when a user's account is being deactivated or the user is no longer authorized to run certain processes.

Summary

In this lab, you learned about the killall command in Linux, which allows you to terminate processes by name. You explored the basic usage of the killall command and how to kill processes by name. You also learned how to kill processes owned by a specific user, and how to customize the killall command's behavior using various options. Finally, you practiced using the killall command to terminate multiple processes by name.

Linux Commands Cheat Sheet