Fundamentals

1. What is Docker?

   • Docker is an open-source platform for building, shipping, and running applications in containers.

2. What are containers?

   • Lightweight, portable, and self-sufficient packages that contain everything an application needs to run: code, libraries, runtime, system tools, and settings.

3. What are the key benefits of using Docker?

   • Portability: Run applications consistently across different environments.
   • Isolation: Isolate applications from each other and the host system.
   • Efficiency: Lightweight and resource-efficient compared to virtual machines.
   • Scalability: Easily scale applications horizontally.
   • Rapid deployment: Quickly deploy and update applications.

4. What is a Docker image?

   • A read-only template that contains the application code, libraries, dependencies, and configurations.

5. What is a Docker container?

   • A running instance of a Docker image.

Docker Commands

6. What is the command to build a Docker image?

   • docker build -t <image_name>:<tag> .

7. What is the command to run a Docker container?

   • docker run <image_name>:<tag>

8. What is the command to list running containers?

   • docker ps

9. What is the command to list all containers (running and stopped)?

   • docker ps -a

10. What is the command to stop a running container?

    • docker stop <container_id>

11. What is the command to remove a stopped container?

    • docker rm <container_id>

12. What is the command to remove a Docker image?

    • docker rmi <image_name>:<tag>

13. What is the command to search for Docker images on Docker Hub?

    • docker search <image_name>

14. What is the command to pull an image from Docker Hub?

    • docker pull <image_name>:<tag>

15. What is the command to inspect a container or image?

    • docker inspect <container_id> or docker inspect <image_name>:<tag>

Dockerfile

16. What is a Dockerfile?

    • A text file that contains instructions for building a Docker image.

17. What is the FROM instruction in a Dockerfile?

    • Specifies the base image for the new image.

18. What is the WORKDIR instruction in a Dockerfile?

    • Sets the working directory within the container.

19. What is the COPY instruction in a Dockerfile?

    • Copies files or directories from the host machine to the container.

20. What is the RUN instruction in a Dockerfile?

    • Executes a command within the container.

21. What is the CMD instruction in a Dockerfile?

    • Specifies the default command to run when the container starts.

22. What is the EXPOSE instruction in a Dockerfile?

    • Declares the ports that the container will listen on.

Docker Compose

23. What is Docker Compose?

    • A tool for defining and running multi-container Docker applications.

24. What is a Docker Compose file (docker-compose.yml)?

    • A YAML file that defines the services, networks, and volumes for a multi-container application.

25. How do you start all services defined in a Docker Compose file?

    • docker-compose up -d

26. How do you stop all services defined in a Docker Compose file?

    • docker-compose down

Docker Networking

27. What are Docker networks?

    • Define how containers can communicate with each other.

28. What is the default Docker network?

    • bridge network.

29. How do you create a custom Docker network?

    • docker network create <network_name>

30. How do you connect a container to a specific network?

    • Specify the network in the docker run command.

Docker Volumes

31. What are Docker volumes?

    • Persistent storage for containers.

32. How do you create a named volume?

    • docker volume create <volume_name>

33. How do you mount a volume to a container?

    • Specify the volume name or path in the docker run command.

Docker Swarm

34. What is Docker Swarm?

    • A native clustering and orchestration system for Docker.

35. What is a Docker Swarm cluster?

    • A group of Docker nodes that work together as a single virtual machine.

36. What is a Docker Swarm manager node?

    • Controls the cluster and schedules tasks.

37. What is a Docker Swarm worker node?

    • Runs containers.

Docker Security

38. What are some security best practices for Docker?
    • Use multi-stage builds to minimize image size.
    • Regularly update images and base images.
    • Limit resource usage for containers.
    • Use least privilege principles (run containers with minimal necessary permissions).
    • Scan images for vulnerabilities.

Docker and Kubernetes

39. What is Kubernetes?

    • A powerful and widely-used container orchestration platform.

40. How do Docker and Kubernetes relate?

    • Docker provides the technology for building and running containers, while Kubernetes provides the orchestration and management layer for containerized applications.

Advanced Topics

41. What are Docker labels?

    • Metadata that can be added to images and containers.

42. What are Docker secrets?

    • A secure way to store and manage sensitive information (passwords, API keys) within a Docker environment.

43. What is Docker Registry?

    • A centralized repository for storing and managing Docker images.

44. What is Docker Hub?

    • A public Docker Registry hosted by Docker.

45. What is the difference between a base image and a derived image?

    • Base image: A foundational image that other images are built upon (e.g., alpine, ubuntu).
    • Derived image: An image created by modifying a base image.

46. What is the purpose of the .dockerignore file?

    • Specifies files and directories that should be excluded from the Docker build context.

47. What are some common Docker use cases?

    • Microservices architecture, continuous integration/continuous delivery (CI/CD), application development and testing, and more.

48. How can you improve the performance of Docker images?

    • Minimize image size, use multi-stage builds, and optimize the build process.

49. What are some challenges of using Docker?

    • Debugging and troubleshooting container issues can be complex.
    • Managing large numbers of containers can be challenging.

50. How can you stay updated on the latest Docker features and best practices?

    • Follow Docker documentation, attend Docker meetups and conferences, and explore the Docker community.

I hope these questions are helpful for your Docker interview preparation!