Docker Interview Cheat Sheet

1. What problem does Docker solve compared to traditional application deployments?

Entry Full Answer →

2. How is a Docker container different from a virtual machine?

Entry Full Answer →

3. What is a Docker image?

Entry Full Answer →

4. What is the role of a Dockerfile?

Entry Full Answer →

5. What does the FROM instruction do in a Dockerfile?

Entry Full Answer →

6. Why do Docker images contain multiple layers?

Entry Full Answer →

7. What is the purpose of the ENTRYPOINT instruction?

Entry Full Answer →

8. What does docker run -p 8080:80 mean?

Entry Full Answer →

9. What is the difference between CMD and ENTRYPOINT?

Entry Full Answer →

10. What is a container registry?

Entry Full Answer →

11. What is the difference between docker stop and docker kill?

Entry Full Answer →

12. What does docker exec do?

Entry Full Answer →

13. What is a bind mount in Docker?

Entry Full Answer →

14. What is a Docker volume and why is it preferred over bind mounts in production?

Entry Full Answer →

15. What is an image tag?

Entry Full Answer →

16. What is the purpose of .dockerignore?

Entry Full Answer →

17. What happens if you run a container without specifying --name?

Entry Full Answer →

18. What does docker ps -a show?

Entry Full Answer →

19. Why shouldn’t you install unnecessary packages inside a container?

Entry Full Answer →

20. What is Alpine Linux and why is it popular in Docker?

Entry Full Answer →

21. What is the Docker daemon and what role does it play?

Junior Full Answer →

22. Why is the Docker client and Docker daemon separation useful?

Junior Full Answer →

23. What is the difference between a container’s “image layer” and “container layer”?

Junior Full Answer →

24. What happens internally when you run docker build?

Junior Full Answer →

25. What does Docker’s copy-on-write mechanism do?

Junior Full Answer →

26. Why is docker build . slow when your project folder is huge?

Junior Full Answer →

27. What is the purpose of multi-stage builds?

Junior Full Answer →

28. What is the difference between ENTRYPOINT exec form and shell form?

Junior Full Answer →

29. Why do production Dockerfiles avoid using ADD?

Junior Full Answer →

30. What is Docker Hub rate limiting?

Junior Full Answer →

31. What is Docker Compose and why is it useful?

Junior Full Answer →

32. What is the difference between docker-compose up and docker-compose up --build?

Junior Full Answer →

33. How do Compose networks isolate containers?

Junior Full Answer →

34. Why is it a bad practice to store secrets inside images?

Junior Full Answer →

35. What is the concept of image digest?

Junior Full Answer →

36. Why is latest tag dangerous in production?

Junior Full Answer →

37. How does Docker’s overlay filesystem affect performance?

Junior Full Answer →

38. What does stateless container mean?

Junior Full Answer →

39. Why should you avoid running multiple processes in one container?

Junior Full Answer →

40. What is the difference between scaling at container vs node level?

Junior Full Answer →

41. What is the difference between a named volume and an anonymous volume?

Junior Full Answer →

42. What is a healthcheck in Docker?

Junior Full Answer →

43. Why do some Docker images use non-root users?

Junior Full Answer →

44. Explain the difference between docker logs and docker attach.

Junior Full Answer →

45. Why does Docker cache layers but not RUN commands that modify external states?

Junior Full Answer →

46. What is an image base layer?

Junior Full Answer →

47. Why is docker cp not preferred for production?

Junior Full Answer →

48. How does Docker handle environment variables?

Junior Full Answer →

49. What is the difference between restarting and recreating a container?

Junior Full Answer →

50. Why do some images include an .env but avoid copying it?

Junior Full Answer →