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Hello World

First touch of the validator. Demonstrates the 4 check types: file_content, command_output, service_status, lynis_diff.

Duration: 10 minLevel: BeginnerExercises: 4

Validator tour

Welcome — how the validator works

This short intro module shows you how the lab checks your solutions. Every task is automatically validated on your real VM — you get instant feedback whether it passed. There are four kinds of checks, all of which you meet here once:

File content (file_content): checks whether a file contains a certain text.
Command output (command_output): runs a command and checks its output.
Service status (service_status): checks whether a system service is running.
Lynis score (lynis_diff): measures whether your system's security score improved.

This way you know exactly what "Check" means in all later modules. Click Check after each task.

Your goal

You solve one task per check type and see how the automatic validation works.

Exercises

1. File content check
Check type 1: file content. This check verifies whether a file contains a certain text. Write Lab Session into the file /etc/issue (the login banner).
```
echo "Lab Session" | sudo tee /etc/issue
```
Check: /etc/issue contains the text Lab Session.
2. Command output check
Check type 2: command output. This check runs a command and verifies its output. Enable the UFW firewall so that ufw status returns the text Status: active.
```
sudo ufw --force enable
sudo ufw status
```
Check: ufw status outputs Status: active.
3. Service status check
Check type 3: service status. This check verifies whether a system service is running. Start the fail2ban service.
```
sudo systemctl enable --now fail2ban
```
Check: the fail2ban service is active (systemctl is-active fail2ban).
4. Lynis score diff
Check type 4: Lynis score. Lynis is a security audit tool that gives your system a hardening score. This check measures whether the score improved over the start — thanks to the measures in the previous tasks (firewall, fail2ban).

Run the audit:
```
sudo lynis audit system --quiet
```
Since you enabled UFW and fail2ban, the score should have risen.

Check: the Lynis hardening score improved over the baseline.

Now practice it yourself

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Validator tour

Welcome — how the validator works

Your goal

Exercises

1. File content check

2. Command output check

3. Service status check

4. Lynis score diff

Now practice it yourself