Linux+ Linux+ Container Operations with Docker 2

Question 1

Which Docker command displays real-time resource usage statistics for all running containers?

Accepted Answer

docker stats

Answer

docker stats streams live CPU, memory, network I/O, and block I/O metrics for running containers.

Question 2

What does the Docker instruction ENTRYPOINT do differently than CMD in a Dockerfile?

Accepted Answer

ENTRYPOINT defines the executable that cannot be overridden by docker run arguments; CMD provides defaults that can be overridden

Answer

ENTRYPOINT sets the fixed executable for the container, while CMD arguments can be replaced by passing arguments to docker run.

Question 3

A developer needs to pass a build-time variable to a Dockerfile during docker build. Which instruction should be used?

Accepted Answer

ARG

Answer

ARG declares a variable that users can pass at build-time with --build-arg, unlike ENV which sets runtime environment variables.

Question 4

Which command removes all stopped containers, unused networks, dangling images, and build cache?

Accepted Answer

docker system prune

Answer

docker system prune is a bulk cleanup command that reclaims disk space by removing all unused Docker objects.

Question 5

When using docker cp, what is the correct syntax to copy a file from a running container to the host?

Accepted Answer

docker cp container_name:container_path host_path

Answer

docker cp uses container_name:path as the source and host path as destination when copying from a container to the host.

Linux Practice Test