DCA Technology & Digital Tools 3

Question 1

Which instruction in a Dockerfile is executed at container start time rather than at image build time?

Accepted Answer

ENTRYPOINT

Answer

`ENTRYPOINT` defines the executable that runs when the container starts; `RUN` executes during the build phase.

Question 2

What is the purpose of Docker Content Trust (DCT)?

Accepted Answer

Verifies the integrity and publisher of Docker images using cryptographic signatures

Answer

DCT uses Notary to sign and verify image integrity, ensuring only trusted images are pulled and run.

Question 3

In Docker Swarm, what is a 'task'?

Accepted Answer

An atomic unit of work representing one container instance of a service

Answer

A task is the smallest schedulable unit in Swarm — it represents a single running container assigned to a node.

Question 4

Which `docker volume` sub-command removes all volumes not used by at least one container?

Accepted Answer

docker volume prune

Answer

`docker volume prune` deletes all dangling volumes — those not referenced by any container.

Question 5

When using multi-stage builds in Docker, what is the primary benefit?

Accepted Answer

Smaller final images by discarding build-time dependencies

Answer

Multi-stage builds let you compile or build in an early stage and copy only the artifacts into a lean final image, removing build tools.

DCA - Docker Certified Associate Exam Practice Test