Docker Study Portal

Quick recall Q&A

1. Explain Docker image layers

• Each Dockerfile instruction creates a layer
• Layers are cached and reused
• Changes in early layers invalidate subsequent layer cache
• Use multi-stage builds to reduce final image size

2. What's the difference between CMD and ENTRYPOINT?

• ENTRYPOINT: Defines the executable (harder to override)
• CMD: Provides default arguments (easily overridden)
• Combined: ENTRYPOINT ["executable"] + CMD ["arg1", "arg2"]

3. How do you optimize Docker image size?

1. Use minimal base images (alpine, distroless)
2. Multi-stage builds
3. Combine RUN commands
4. Remove unnecessary files in same layer
5. Use .dockerignore
6. Don't install dev dependencies

4. Explain Docker networking modes

• Bridge: Default isolated network, containers communicate via container names
• Host: Container uses host's network, no isolation
• None: No network access
• Overlay: Cross-host networking for orchestration