Docker Containerization Dockerfile and Image Building 3

Question 1

What is the difference between the ARG and ENV instructions in a Dockerfile?

Accepted Answer

ARG is only available during the build process; ENV persists in the final image and running containers

Answer

ARG persists in the final image; ENV is only available at build time

Answer

ARG and ENV are interchangeable at both build time and runtime

Answer

ARG sets system-level variables; ENV sets application-level variables

Question 2

What is the key behavioral difference between ENTRYPOINT and CMD in a Dockerfile?

Accepted Answer

ENTRYPOINT defines a fixed executable that is not overridden by 'docker run' arguments; CMD provides defaults that are replaced by those arguments

Answer

ENTRYPOINT runs once; CMD runs on every request

Answer

CMD defines the executable; ENTRYPOINT provides optional arguments

Answer

They are identical but ENTRYPOINT has higher priority in all cases

Question 3

Which Dockerfile instruction is used to switch the user context for subsequent RUN, CMD, and ENTRYPOINT instructions?

Accepted Answer

USER

Answer

OWNER

Answer

AS

Answer

SUDO

Question 4

What is the Docker build context?

Accepted Answer

The set of files and directories sent to the Docker daemon when you run 'docker build'

Answer

The metadata stored inside the final Docker image

Answer

The configuration namespace used to isolate builds on the same machine

Answer

The network configuration applied during the build process

Question 5

What does the HEALTHCHECK instruction in a Dockerfile do?

Accepted Answer

It defines a command Docker runs periodically to test whether the container is functioning correctly

Answer

It validates Dockerfile syntax before building

Answer

It monitors host system resources during the build

Answer

It checks network connectivity when the container starts

Question 6

Which Dockerfile instruction adds key-value metadata to an image?

Accepted Answer

LABEL

Answer

META

Answer

TAG

Answer

ANNOTATE

Question 7

What is the exec form of a Dockerfile instruction, and why is it preferred for ENTRYPOINT and CMD?

Accepted Answer

ENTRYPOINT ["executable", "param1"] — preferred because it runs the executable directly without a shell, so signals are received correctly

Answer

ENTRYPOINT command param1 — preferred because it uses the shell's PATH

Answer

ENTRYPOINT {executable: param1} — preferred because it is JSON-compatible

Answer

ENTRYPOINT (executable param1) — preferred because it enables parameter substitution