DCA Practice Questions: Image Creation, Management, and Registry Domain

Published: June 27, 2025 | 5 min read

Test your DCA knowledge with 10 practice questions from the Image Creation, Management, and Registry domain. Includes detailed explanations and answers.

DCA Practice Questions

Master the Image Creation, Management, and Registry Domain

Test your knowledge in the Image Creation, Management, and Registry domain with these 10 practice questions. Each question is designed to help you prepare for the DCA certification exam with detailed explanations to reinforce your learning.

Question 1

You are trying to pull an image from a private Docker registry but are encountering authentication errors. What should you check first?

A) Ensure that your Docker client is up to date.

B) Verify that you have run 'docker login' with the correct credentials.

C) Check if the image is tagged with 'latest'.

D) Ensure that the image is not corrupted.

Show Answer & Explanation

Correct Answer: B

Explanation: If you encounter authentication errors when pulling an image from a private registry, the first step is to verify that you have run 'docker login' with the correct credentials. This ensures that you are authenticated with the registry. Option A, while important, is not directly related to authentication errors. Option C is unrelated to authentication. Option D is not relevant to authentication issues.

Question 2

You have made changes to a Dockerfile and need to rebuild the image without using the cache. Which command should you use?

A) docker build --no-cache -t myimage:latest .

B) docker build --force -t myimage:latest .

C) docker build --rm-cache -t myimage:latest .

D) docker build --rebuild -t myimage:latest .

Show Answer & Explanation

Correct Answer: A

Explanation: The correct command to rebuild a Docker image without using the cache is 'docker build --no-cache'. This option forces Docker to build the image from scratch without using any cached layers. The other options do not exist or do not apply to disabling the cache during a build.

Question 3

Which of the following commands will tag an existing Docker image with a new tag?

A) docker rename

B) docker retag

C) docker tag

D) docker label

Show Answer & Explanation

Correct Answer: C

Explanation: The 'docker tag' command is used to add a new tag to an existing image. This allows you to reference the same image with different tags. 'docker rename' is not a valid command for images, 'docker retag' does not exist, and 'docker label' is used to add metadata to images, not to tag them.

Question 4

You are working with a Docker image that needs environment-specific configurations. What is the recommended way to handle these configurations?

A) Hardcode the configurations directly in the Dockerfile.

B) Use environment variables to pass configurations at runtime.

C) Create separate Dockerfiles for each environment.

D) Store configurations in a text file within the image.

Show Answer & Explanation

Correct Answer: B

Explanation: Using environment variables to pass configurations at runtime is the recommended way to handle environment-specific configurations because it allows flexibility and avoids the need to rebuild images for each environment. Option A is incorrect as it lacks flexibility. Option C is inefficient and can lead to maintenance challenges. Option D is incorrect because configurations should not be hardcoded within the image.

Question 5

You have built a new Docker image and want to ensure that it is free from security vulnerabilities before pushing it to a production registry. Which tool can you use to scan the image for vulnerabilities?

A) Docker Compose

B) Docker Hub

C) Docker Scan

D) Docker CLI

Show Answer & Explanation

Correct Answer: C

Explanation: Docker Scan is a tool integrated with Docker to scan images for vulnerabilities. It uses Snyk to perform security scanning directly from the CLI. Option A, Docker Compose, is used for defining and running multi-container Docker applications. Option B, Docker Hub, is a registry service but does not perform scanning. Option D, Docker CLI, refers to the command-line interface but does not inherently perform security scans without Docker Scan.

Question 6

You have made some changes to a Dockerfile and want to ensure that the new image is built without using the cache. Which flag should you use with the 'docker build' command?

A) --no-cache

B) --force-rebuild

C) --clear-cache

D) --rebuild

Show Answer & Explanation

Correct Answer: A

Explanation: The '--no-cache' flag is used with 'docker build' to ensure that the image is built without using the cache. This forces Docker to rebuild the image from scratch, applying all instructions in the Dockerfile anew. The other options are not valid flags for the 'docker build' command.

Question 7

You need to create a Docker image that includes a specific application and its dependencies. Which of the following should you do to ensure the image is built efficiently and with minimal size?

A) Use multi-stage builds in the Dockerfile.

B) Install all dependencies in a single RUN command.

C) Use a single-layer Dockerfile.

D) Build the image on a different architecture.

Show Answer & Explanation

Correct Answer: A

Explanation: Using multi-stage builds allows you to separate the build environment from the runtime environment, resulting in a smaller final image. This is because only the necessary artifacts are copied to the final image, excluding build dependencies. Installing all dependencies in a single RUN command (option B) can reduce layers but does not necessarily minimize size. A single-layer Dockerfile (option C) is not a recognized concept and does not apply here. Building the image on a different architecture (option D) is unrelated to image size optimization.

Question 8

You need to create a Docker image from a Dockerfile that uses a specific base image version and includes a custom configuration file. Which command should you use to build the image?

A) docker build -t myimage:latest .

B) docker build -f Dockerfile.custom -t myimage:latest .

C) docker create -t myimage:latest .

D) docker run -d myimage:latest

Show Answer & Explanation

Correct Answer: B

Explanation: Option B is correct because it specifies using a custom Dockerfile with the -f flag and tags the image as 'myimage:latest'. Option A assumes a default Dockerfile and does not specify a custom one. Option C is incorrect because 'docker create' is used to create containers, not build images. Option D is incorrect because 'docker run' is used to start containers, not build images.

Question 9

You need to push a Docker image to a private registry. Which command should you use to authenticate to the registry before pushing?

A) docker login

B) docker push

C) docker auth

D) docker connect

Show Answer & Explanation

Correct Answer: A

Explanation: The 'docker login' command is used to authenticate your Docker client to a registry. Once authenticated, you can push images using 'docker push'. The 'docker auth' and 'docker connect' commands do not exist in Docker's CLI.

Question 10

You need to reduce the size of your Docker image. Which of the following strategies is most effective?

A) Use a single RUN instruction to combine all commands in the Dockerfile.

B) Use multiple FROM instructions to split the image into smaller layers.

C) Add more comments to the Dockerfile to explain each step.

D) Include all dependencies in the image to avoid runtime errors.

Show Answer & Explanation

Correct Answer: A

Explanation: Using a single RUN instruction to combine all commands in the Dockerfile is effective for reducing the number of layers in the image, which can help decrease its size. Option B is incorrect because multiple FROM instructions create separate images. Option C does not affect the image size as comments are not included in the final image. Option D is incorrect because including unnecessary dependencies can increase the image size.

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About DCA Certification

The DCA certification validates your expertise in image creation, management, and registry and other critical domains. Our comprehensive practice questions are carefully crafted to mirror the actual exam experience and help you identify knowledge gaps before test day.