DCA Technology & Digital Tools 2

Question 1

Which Docker command displays real-time resource usage statistics for 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 is the default network driver created when Docker is installed on a Linux host?

Accepted Answer

bridge

Answer

Docker creates a default `bridge` network (docker0) on installation, used by containers unless another network is specified.

Question 3

In a Dockerfile, which instruction sets environment variables that persist into the running container?

Accepted Answer

ENV

Answer

`ENV` sets environment variables that are available both during the build and at container runtime.

Question 4

Which Docker Swarm command promotes a worker node to a manager?

Accepted Answer

docker node promote <NODE>

Answer

`docker node promote <NODE>` changes a worker's role to manager within the swarm cluster.

Question 5

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

Accepted Answer

Makes the container's root filesystem read-only

Answer

`--read-only` mounts the container's root filesystem in read-only mode, preventing writes to it at runtime.

DCA - Docker Certified Associate Exam Practice Test