Docker Containerization Dockerfile and Image Building

Question 1

Which Dockerfile instruction specifies the base image for a new build?

Accepted Answer

FROM

Answer

BASE

Answer

IMAGE

Answer

SOURCE

Question 2

What is the key difference between the ADD and COPY instructions in a Dockerfile?

Accepted Answer

ADD supports remote URLs and auto-extracts tar archives; COPY only copies local files as-is

Answer

COPY supports remote URLs; ADD only handles local files

Answer

ADD and COPY are functionally identical

Answer

COPY auto-extracts archives; ADD requires manual extraction

Question 3

Which Dockerfile instruction sets the working directory for all subsequent RUN, CMD, ENTRYPOINT, COPY, and ADD instructions?

Accepted Answer

WORKDIR

Answer

DIR

Answer

PATH

Answer

CD

Question 4

What is the purpose of a .dockerignore file?

Accepted Answer

To specify files and directories to exclude from the build context sent to the Docker daemon

Answer

To prevent Docker from pulling certain base images

Answer

To ignore syntax errors in the Dockerfile

Answer

To disable specific Docker daemon features during build

Question 5

Which Dockerfile instruction sets a persistent environment variable that is available both during the build and when the container runs?

Accepted Answer

ENV

Answer

SET

Answer

VAR

Answer

ARG

Question 6

What does the EXPOSE instruction in a Dockerfile actually do?

Accepted Answer

It documents which network ports the container intends to listen on at runtime

Answer

It automatically publishes the port to the host machine

Answer

It blocks all ports except the ones specified

Answer

It configures the container's firewall rules

Question 7

Which Dockerfile instruction defines the default command to run when a container starts, and can be overridden by arguments passed to 'docker run'?

Accepted Answer

CMD

Answer

RUN

Answer

EXECUTE

Answer

START