Linux+ Container Operations with Docker Flashcards

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

Answer: docker stats

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

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

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

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

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

Answer: ARG

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

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

Answer: docker system prune

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

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

Answer: docker cp container_name:container_path host_path

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

Which Docker networking mode allows a container to share the host machine's network stack directly?

Answer: host

Host network mode removes network isolation between container and host, making the container use the host's IP and ports directly.

What is the purpose of a Docker multi-stage build?

Answer: To reduce final image size by copying only needed artifacts from earlier build stages

Multi-stage builds use multiple FROM instructions so only compiled artifacts are copied into the final lightweight image, discarding build tools.