Docker MCQ Questions with answers and solutions Page 32

Q. Which instruction in Dockerfile is used to specify the base image?

(A) BASE
(B) FROM
(C) IMAGE
(D) START

💬 Discuss

✅ Correct Answer: (B) FROM

Explanation: The `FROM` instruction sets the base image for the Docker image.

Published by Mr. Dubey ⭐ 111.54K Points at 24-Jul-2025 07:06 am in Docker

Q. What does the `RUN` instruction do in a Dockerfile?

(A) Defines a default command
(B) Executes a command at container runtime
(C) Executes a command at image build time
(D) Deletes a file

💬 Discuss

✅ Correct Answer: (C) Executes a command at image build time

Explanation: `RUN` is used to execute commands while building the image.

Published by Mr. Dubey ⭐ 111.54K Points at 24-Jul-2025 07:06 am in Docker

Q. Which instruction is used to specify the default command when a container starts?

(A) RUN
(B) CMD
(C) ENTRYPOINT
(D) START

💬 Discuss

✅ Correct Answer: (B) CMD

Explanation: `CMD` provides defaults for the executing container.

Published by Mr. Dubey ⭐ 111.54K Points at 24-Jul-2025 07:06 am in Docker

Q. How can you add metadata to an image using Dockerfile?

(A) META
(B) LABEL
(C) ANNOTATE
(D) INFO

💬 Discuss

✅ Correct Answer: (B) LABEL

Explanation: `LABEL` is used to add metadata as key-value pairs to Docker images.

Published by Mr. Dubey ⭐ 111.54K Points at 24-Jul-2025 07:06 am in Docker

Q. What is the difference between `CMD` and `ENTRYPOINT`?

(A) CMD is required; ENTRYPOINT is optional
(B) ENTRYPOINT allows arguments; CMD does not
(C) CMD provides defaults; ENTRYPOINT defines fixed commands
(D) They are interchangeable

💬 Discuss

✅ Correct Answer: (C) CMD provides defaults; ENTRYPOINT defines fixed commands

Explanation: `CMD` can be overridden, while `ENTRYPOINT` defines the main command that always runs.

Published by Mr. Dubey ⭐ 111.54K Points at 24-Jul-2025 07:06 am in Docker

Q. What is the purpose of the `COPY` instruction?

(A) To copy from image to host
(B) To copy from container to host
(C) To copy files from host to image
(D) To copy files from one image to another

💬 Discuss

✅ Correct Answer: (C) To copy files from host to image

Explanation: `COPY` transfers files from the local file system into the image.

Published by Mr. Dubey ⭐ 111.54K Points at 24-Jul-2025 07:06 am in Docker

Q. What does `EXPOSE 80` do in a Dockerfile?

(A) Starts a service on port 80
(B) Makes port 80 available for linking containers
(C) Opens a host port
(D) Assigns 80 as container ID

💬 Discuss

✅ Correct Answer: (B) Makes port 80 available for linking containers

Explanation: `EXPOSE` is a documentation instruction to inform Docker about ports the container listens on.

Published by Mr. Dubey ⭐ 111.54K Points at 24-Jul-2025 07:06 am in Docker

Q. What does `ENV APP_ENV=production` do?

(A) Creates a label
(B) Runs a command
(C) Sets an environment variable
(D) Creates a user

💬 Discuss

✅ Correct Answer: (C) Sets an environment variable

Explanation: `ENV` sets environment variables inside the container.

Published by Mr. Dubey ⭐ 111.54K Points at 24-Jul-2025 07:06 am in Docker

Q. Which instruction allows combining multiple commands into one layer?

(A) MULTI
(B) SHELL
(C) RUN with &&
(D) STACK

💬 Discuss

✅ Correct Answer: (C) RUN with &&

Explanation: Using `&&` in `RUN` chains multiple commands into one image layer.

Published by Mr. Dubey ⭐ 111.54K Points at 24-Jul-2025 07:06 am in Docker

Q. What is the result of using multiple `FROM` instructions?

(A) Error in build
(B) Multiple base images
(C) Multi-stage build
(D) Multiple containers

💬 Discuss

✅ Correct Answer: (C) Multi-stage build

Explanation: Multiple `FROM` instructions enable multi-stage builds for smaller, optimized images.

Published by Mr. Dubey ⭐ 111.54K Points at 24-Jul-2025 07:06 am in Docker

Docker MCQs with answers Page - 32

Q. Which instruction in Dockerfile is used to specify the base image?

Q. What does the `RUN` instruction do in a Dockerfile?

Q. Which instruction is used to specify the default command when a container starts?

Q. How can you add metadata to an image using Dockerfile?

Q. What is the difference between `CMD` and `ENTRYPOINT`?

Q. What is the purpose of the `COPY` instruction?

Q. What does `EXPOSE 80` do in a Dockerfile?

Q. What does `ENV APP_ENV=production` do?

Q. Which instruction allows combining multiple commands into one layer?

Q. What is the result of using multiple `FROM` instructions?

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