Linux

Create a Project Structure

Create a project directory containing a src folder, a tests folder and a README.md. Follow the walkthrough below — every command is explained, and the validator checks what you actually built.

Challenge

Find the Largest Log

Something is writing huge log files to /var/log/app. Inspect the filesystem, find the largest .log file in that directory and record it in ~/report/largest.txt. The walkthrough shows every command.

TOPIC 02

Filesystems & Permissions

Everything is a file: paths, modes, owners and the tools that inspect them.

What you'll practice

Lock Down a Secret File — practice · beginner

A command you'll meet

mkdir ~/secure

Open any task below to get the full step-by-step walkthrough — every command is explained, and the lab validator checks what you actually built.

Hands-On Tasks in This Topic (1)

Lock Down a Secret File

Create a secrets file with restrictive permissions. Only the owner should be able to read and write it — nobody else. This is exactly how SSH private keys work.

TOPIC 03

Text Processing & Pipes

grep, wc, pipes and redirection — how engineers actually read logs.

What you'll practice

Count Errors in a Log — guided · beginner

A command you'll meet

cat /var/log/app/app-2026-09-27.log

Open any task below to get the full step-by-step walkthrough — every command is explained, and the lab validator checks what you actually built.

Hands-On Tasks in This Topic (1)

Guided Task

Count Errors in a Log

The application log at /var/log/app/app-2026-09-27.log is full of noise. Use grep and pipes to count the ERROR lines and save the result.

TOPIC 04

Processes

Everything running on the machine is a process with a PID.

What you'll practice

Identify a Running Process — practice · beginner

A command you'll meet

ps aux

Open any task below to get the full step-by-step walkthrough — every command is explained, and the lab validator checks what you actually built.

Hands-On Tasks in This Topic (1)

Identify a Running Process

An application called 'app' is running on this machine. Find its PID with ps, confirm it from the command line arguments, and record it.

TOPIC 05

Shell Scripting Basics

Turn the one-liners you keep typing into scripts that run the same way every time.

What you'll practice

Write a Backup Script — guided · beginner
Write a Health Check Script — practice · intermediate

A command you'll meet

chmod 700 ~/scripts/backup.sh

A script is a command you stopped retyping. Open the task below for the full walkthrough.

Hands-On Tasks in This Topic (2)

Guided Task

Write a Backup Script

A backup you have to remember to run is a backup you do not have. Write a script that archives the project directory and can only be run by its owner.

intermediate

Write a Health Check Script

Monitoring is a script that reports a number instead of a feeling. Write a health check that reads the application log and prints a verdict a monitoring agent can scrape.