Challenge, Easy,  on  Linux, Programming

Kill a Stubborn Process with SIGKILL

Başar Subaşı
by  Başar Subaşı

When applications trap signals like SIGINT (Ctrl+C) or SIGTERM, they can intercept the signal and refuse to exit.

To handle rogue or unresponsive processes, the Linux kernel provides SIGKILL (Signal 9), the uncatchable signal that bypasses application code entirely and immediately reclaims process resources.

Signal Architecture

In this challenge, you will explore signal handling firsthand by launching a process that traps interrupt signals and terminating it with SIGKILL.

Task Instructions

  1. Start the Process: Execute ~/exercise/stubborn in your terminal (or run it in the background).
  2. Send SIGINT (Ctrl+C): Press Ctrl+C while the process is running (or send kill -2 <PID>). Observe how it catches the signal and refuses to quit.
  3. Terminate with SIGKILL: Use SIGKILL (kill -9 <PID> or pkill -9 stubborn) to force the process to exit (you can open a new terminal from the + icon on the terminal pane).
Hint: Need a Refresher on Signals?

Check out the tutorial Linux Processes: Understanding Signals to learn more about signals, signal handling, and SIGKILL.

How to Author Challenges on iximiuz Labs

Instead of providing a subpar online editing experience, iximiuz Labs offers a helper CLI tool called labctl, allowing you to use your favorite text editor (or a full-featured IDE) to write content from the comfort of your local machine.

Install labctl CLI

curl -sf https://labs.iximiuz.com/cli/install.sh | sh

This will download and install the latest version of the labctl CLI. You only need to do this once per workstation.

Authorize labctl

labctl auth login

This will open a browser window asking you to authorize labctl to access your account. You need to do it after a fresh install of labctl and repeat it whenever the auth session expires.

Pull challenge content

labctl content pull challenge kill-stubborn-process-with-sigkill-33e04027

This will create a local copy of the challenge content in a directory named kill-stubborn-process-with-sigkill-33e04027. You only need to do this once per challenge.

Stream your changes

labctl content push -fw challenge kill-stubborn-process-with-sigkill-33e04027

Run this command in a separate terminal to continuously upload your changes to the server while editing the challenge in your favorite text editor or IDE.

You can also use labctl to create, list, and delete your content. Learn more about the available commands: labctl content --help

Start challenge