Linux+ Container Operations with Docker Questions and Answers

Question 1

A Linux administrator is performing maintenance on a Docker host and needs to reclaim disk space.
Which command should they use to remove all unused images, including tagged images that are not associated with any container?

Accepted Answer

docker image prune -a

Answer

docker system prune

Answer

docker rmi $(docker images -q)

Answer

docker image prune

Question 2

Which of the following commands will start a new container from the `ubuntu:latest` image, name it `my-test-container`, and ensure it runs in the background as a daemon?

Accepted Answer

docker run -d --name my-test-container ubuntu:latest

Answer

docker run -it --name my-test-container ubuntu:latest

Answer

docker start my-test-container

Answer

docker create --name my-test-container ubuntu:latest

Question 3

A developer needs to deploy a database in a Docker container. It is critical that the database's data persists even if the container is removed. Which command correctly maps a Docker-managed named volume called `db_data` to the `/var/lib/mysql` directory inside the container?

Accepted Answer

docker run -d --mount type=volume,source=db_data,target=/var/lib/mysql mysql

Answer

docker run -d --mount type=bind,source=/data,target=/var/lib/mysql mysql

Answer

docker run -d --volume /data:/var/lib/mysql mysql

Answer

docker run -d --tmpfs /var/lib/mysql mysql

Question 4

An administrator is troubleshooting a network connectivity issue with a running container named `api-gateway`. Which command would they use to view detailed configuration information about the container, including its assigned IP address, mounts, and port mappings?

Accepted Answer

docker inspect api-gateway

Answer

docker logs api-gateway

Answer

docker ps --filter name=api-gateway

Answer

docker stats api-gateway

Question 5

A developer has created a web application that listens on port 3000 inside its container. To make this application accessible on port 80 on the host machine, which `docker run` flag and argument should be used?

Accepted Answer

-p 80:3000

Answer

-p 3000:80

Answer

--expose 80

Answer

--net=host

Question 6

When building a Docker image with a Dockerfile, which instruction specifies the default command to be executed when a container is started, and is designed to be easily overridden by providing arguments to the `docker run` command?

Accepted Answer

CMD

Answer

RUN

Answer

ENTRYPOINT

Answer

EXEC