Docker Scenario Labs

Debug Dockerfiles, fix multi-stage builds, and repair container configs

10 Scenarios ~15 min each

How It Works

Each lab drops you into a broken config. Your job: find the bug and fix it.

Read the Scenario

Understand what went wrong — a teammate pushed broken config and CI is failing.

Debug in the Terminal

Run the tool, read the errors, and trace them back to the source.

Fix & Verify

Edit the config, re-run the check, and confirm a clean result.

Terminal

Beginner(4)

Intermediate(3)

Advanced(3)

Beginner

4 labs

Start here — core concepts and simple fixes

Fix Base Image Reference

Fix a broken FROM instruction and WORKDIR typo in a Node.js Dockerfile.

Beginner

Fix Docker Compose File

Fix broken service references, environment variables, and networking in a docker-compose.yml.

Beginner

Fix COPY Instructions

Fix incorrect COPY source and destination paths in a Python Flask Dockerfile.

Beginner

Fix .dockerignore

Optimize a bloated Docker image by fixing .dockerignore to exclude unnecessary files.

Beginner

Level Up to Intermediate

Intermediate

3 labs

Level up — multi-resource configs and debugging

Fix Environment Variables

Fix incorrect ARG vs ENV usage — build-time variables used at runtime cause the app to crash.

Intermediate

Fix EXPOSE and CMD

Fix a port mismatch between EXPOSE and the app, and correct CMD exec form syntax.

Intermediate

Fix Health Check Configuration

Add a HEALTHCHECK instruction and fix a broken health endpoint for production readiness.

Intermediate

Level Up to Advanced

Advanced

3 labs

Expert mode — complex configurations and edge cases

Fix Layer Caching Order

Reorder Dockerfile instructions to leverage Docker layer caching and speed up builds.

Advanced

Fix Multi-Stage Build

Fix broken COPY --from references and wrong base image in a multi-stage Go Dockerfile.

Advanced

Fix User and Permissions

Add a non-root user to a Dockerfile that currently runs as root — a critical security fix.

Advanced