MCQs Questions on Working with Docker Images | Docker Multiple Choice Questions

Master the essentials of Docker with this set of Docker MCQ questions and answers designed to test your expertise in creating and managing Docker images, writing Dockerfiles, and optimizing them using best practices. This guide will cover pulling, tagging, and pushing images, multi-stage builds, and techniques for optimizing image sizes.

Multiple Choice Questions (MCQs)

Creating and Managing Docker Images

1. What is a Docker image?
   a) A running instance of a container
   b) A read-only template used to create containers
   c) A script to automate builds
   d) A storage volume for containers
2. Which command is used to build a Docker image?
   a) docker run
   b) docker build
   c) docker create
   d) docker init
3. What is the default name of a Dockerfile?
   a) imagefile
   b) Dockerfile
   c) Containerfile
   d) Buildfile
4. How can you view the list of available Docker images locally?
   a) docker ls
   b) docker list images
   c) docker images
   d) docker show
5. What does the docker rmi command do?
   a) Removes a running container
   b) Deletes a Docker image
   c) Rebuilds an image
   d) Lists all images

Pulling, Tagging, and Pushing Images

6. Which command is used to pull a Docker image from Docker Hub?
   a) docker download
   b) docker pull
   c) docker fetch
   d) docker get
7. What is the purpose of tagging a Docker image?
   a) To group multiple containers
   b) To assign a unique identifier to an image version
   c) To compress the image
   d) To rename the image
8. Which command is used to push a Docker image to a remote repository?
   a) docker deploy
   b) docker upload
   c) docker push
   d) docker send
9. What is the default Docker image repository?
   a) GitHub
   b) Docker Hub
   c) AWS ECR
   d) Google Cloud
10. How can you rename a Docker image?
    a) docker rename
    b) docker retag
    c) docker tag
    d) docker alter

Writing Dockerfiles (Best Practices)

11. What keyword is used in a Dockerfile to specify the base image?
    a) FROM
    b) BASE
    c) IMAGE
    d) START
12. Which command in a Dockerfile copies files from the local machine to the image?
    a) ADD
    b) COPY
    c) MOVE
    d) IMPORT
13. What is the purpose of the CMD instruction in a Dockerfile?
    a) To define the default command to run in the container
    b) To execute a script during build
    c) To expose container ports
    d) To define environment variables
14. How can you reduce the size of a Docker image?
    a) Use fewer RUN instructions
    b) Combine multiple RUN commands
    c) Use smaller base images
    d) All of the above
15. What does the .dockerignore file do?
    a) Ignores build errors
    b) Excludes files from being copied into the image
    c) Disables certain Docker commands
    d) Prevents image compression

Multi-Stage Builds

16. What is the main purpose of multi-stage builds?
    a) To speed up the Docker build process
    b) To reduce the size of the final image
    c) To allow parallel building of images
    d) To create multiple containers at once
17. Which Dockerfile instruction is key to multi-stage builds?
    a) CMD
    b) WORKDIR
    c) FROM
    d) RUN
18. In a multi-stage build, what happens to intermediate stages?
    a) They are saved for debugging purposes
    b) They are discarded after the build completes
    c) They are compressed and added to the final image
    d) They are run as separate containers
19. How do you copy artifacts from one stage to another in a multi-stage build?
    a) Using the COPY --from flag
    b) Using the ADD command
    c) By mounting a shared volume
    d) Using the INCLUDE command
20. Why are multi-stage builds commonly used for production images?
    a) To simplify the deployment process
    b) To separate development and production dependencies
    c) To improve runtime performance
    d) All of the above

Optimizing Image Sizes

21. What is an Alpine image in Docker?
    a) A minimal Linux-based image
    b) A base image for data processing
    c) A specialized image for debugging
    d) An image with pre-installed software
22. Why should you avoid using latest as a tag in production images?
    a) It can lead to unpredictable updates
    b) It makes debugging harder
    c) It increases image size
    d) It consumes more memory
23. How can you remove unused Docker images?
    a) docker clean
    b) docker prune
    c) docker rmi –all
    d) docker rm images
24. What is the primary benefit of using a slim image?
    a) Faster builds
    b) Reduced attack surface
    c) Smaller image size
    d) All of the above
25. Which of the following can increase Docker image size unnecessarily?
    a) Including unnecessary files
    b) Using large base images
    c) Running multiple RUN commands
    d) All of the above
26. How can you clean up dangling images?
    a) docker cleanup
    b) docker rmi dangling
    c) docker image prune
    d) docker remove unused
27. Which command lists the size of Docker images?
    a) docker images –size
    b) docker image ls –size
    c) docker ls images –size
    d) docker inspect size
28. What does the --squash flag do in docker build?
    a) Combines layers into a single layer
    b) Deletes unused layers
    c) Compresses the image
    d) Optimizes build cache
29. Why is layer caching important in Docker builds?
    a) It speeds up subsequent builds
    b) It reduces image size
    c) It allows rollback to previous layers
    d) All of the above
30. Which of these is not a best practice for optimizing Docker images?
    a) Using multi-stage builds
    b) Avoiding large base images
    c) Adding temporary files for debugging
    d) Using .dockerignore

Answer Table