Linux+ Linux+ Container Operations with Docker 3

Question 1

A container is running but needs to be stopped gracefully. Which signal does docker stop send by default before force-killing the process?

Accepted Answer

SIGTERM

Answer

docker stop sends SIGTERM first, giving the process time to shut down cleanly, then sends SIGKILL after a timeout (default 10 seconds).

Question 2

Which Dockerfile instruction is used to define the default working directory for subsequent RUN, CMD, ENTRYPOINT, COPY, and ADD instructions?

Accepted Answer

WORKDIR

Answer

WORKDIR sets the working directory inside the container image and creates it if it does not exist.

Question 3

What does the --read-only flag do when passed to docker run?

Accepted Answer

Makes the container's root filesystem read-only, preventing writes

Answer

The --read-only flag mounts the container's root filesystem as read-only, improving security by preventing unauthorized file modifications.

Question 4

A Linux administrator wants containers on two different Docker hosts to communicate. Which network driver should be used?

Accepted Answer

overlay

Answer

Overlay networks span multiple Docker hosts using VXLAN encapsulation and require a key-value store like etcd or Consul for coordination.

Question 5

What happens to container data stored in a named volume when the container is deleted with docker rm?

Accepted Answer

The volume persists and must be removed separately with docker volume rm

Answer

Named volumes have an independent lifecycle from containers; deleting a container does not remove its associated named volumes.

Linux Practice Test