Getting Started

Your First Lab

A complete walkthrough of starting, solving, and validating your first TLD lab.

This walkthrough uses the dkr-fix-stopped-container lab — a beginner Docker lab where a container has stopped unexpectedly and you need to diagnose and restart it correctly.

Pick a lab

bash

# See all available labs by track

$ tld lab list

# Filter by track

$ tld lab list --track docker

# Output:

# TRACK LAB ID DIFFICULTY STATUS

# docker dkr-fix-stopped-container beginner available

# docker dkr-fix-broken-dockerfile beginner available

# docker dkr-container-networking intermediate available

# ...

Start the lab

bash

$ tld lab start dkr-fix-stopped-container

# Pulling lab environment... done

# Starting containers...

# Lab: Fix the Stopped Container

# Difficulty: Beginner

# Track: Docker

# Something is wrong. A containerized web service has stopped.

# Your job: get it running again and serving traffic on port 8080.

# Read the full scenario: cat ~/.tld/labs/current/README.md

# When ready: tld check

Read the scenario

bash

$ cat ~/.tld/labs/current/README.md

Read the whole README

The README contains the scenario, your objective, and any constraints. Skipping it means missing context that makes the fix obvious.

Investigate

bash

# Check what containers exist

$ docker ps -a

# CONTAINER ID IMAGE STATUS NAMES

# a3f9b2c1d4e5 nginx:alpine Exited (1) 2 minutes ago web-service

# Check the logs to see why it exited

$ docker logs web-service

# nginx: [emerg] bind() to 0.0.0.0:80 failed (98: Address already in use)

# Check what's using port 80

$ lsof -i :80

Fix it

bash

# Kill the process occupying port 80

$ sudo kill $(lsof -t -i:80)

# Restart the container

$ docker start web-service

# Verify it's running

$ docker ps

# CONTAINER ID IMAGE STATUS NAMES

# a3f9b2c1d4e5 nginx:alpine Up 3 seconds web-service

# Confirm it's serving

$ curl http://localhost:8080

Validate

bash

$ tld check

# Running validator...

# ✓ Container web-service is running

# ✓ Container has been running for > 30 seconds

# ✓ Port 8080 is accessible

# ✓ HTTP 200 response from http://localhost:8080

# All 4 checks passed.

# Lab complete! +150 XP earned.

Cleanup

bash

# Stop and remove the lab environment

$ tld lab stop

# Or force-remove everything including volumes

$ tld lab stop --clean

Next steps

Now try a lab without hints. Browse the Beginner Labs page for your next challenge.

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