EX188 Container Image Building — 10 Questions

Question 1

When writing a Containerfile, which instruction specifies the base image to be used for the subsequent build steps?

Accepted Answer

FROM. Every Containerfile must start with a FROM instruction to define the base image.

Answer

BASE

Answer

INIT

Answer

PARENT

Question 2

Which instruction documents the network ports on which a container listens at runtime?

Accepted Answer

EXPOSE. EXPOSE functions as a type of documentation between the person who builds the image and the person who runs the container.

Answer

LISTEN

Answer

PORT

Answer

OPEN

Question 3

A developer wants to build a container image using podman build, but the Containerfile is named 'Customfile' and located in a subdirectory named 'dockerfiles'. Which command accomplishes this?

Accepted Answer

podman build -f dockerfiles/Customfile .. The -f flag specifies the path to the Containerfile relative to the build context.

Answer

podman build --file-path dockerfiles/Customfile .

Answer

podman build -p dockerfiles/Customfile .

Answer

podman build --config dockerfiles/Customfile .

Question 4

You need to set a persistent environment variable named 'APP_PORT' with the value '8080' inside a container image via the Containerfile. Which instruction should you use?

Accepted Answer

ENV APP_PORT=8080. The ENV instruction sets environment variables that persist when the container runs.

Answer

EXPORT APP_PORT=8080

Answer

VAR APP_PORT=8080

Answer

SET APP_PORT=8080

Question 5

Which instruction should be used in a Containerfile to copy local files from the host machine into the container filesystem?

Accepted Answer

COPY. The COPY instruction takes files from the local context and adds them to the container's filesystem.

Answer

TRANSFER

Answer

ADD

Answer

MOVE

Question 6

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

Accepted Answer

WORKDIR. The WORKDIR instruction sets the working directory for any instructions that follow it in the Containerfile.

Answer

PATH

Answer

ENV

Answer

RUN

Question 7

Which user instruction changes the user name or UID and group name or GID to use when running subsequent instructions in the Containerfile?

Accepted Answer

USER. The USER instruction sets the user name or UID to use for running the image and for any RUN, CMD and ENTRYPOINT instructions that follow it.

Answer

LOGIN

Answer

IDENTITY

Answer

ACCOUNT

Question 8

A container image needs to automatically extract a local tar archive file named 'app.tar.gz' into the destination directory '/opt/app' during the build process. Which instruction should be used?

Accepted Answer

ADD app.tar.gz /opt/app/. The ADD instruction automatically extracts local tar archives, whereas COPY does not.

Answer

COPY app.tar.gz /opt/app/

Answer

EXTRACT app.tar.gz /opt/app/

Answer

RUN tar -xzf app.tar.gz -C /opt/app/

Question 9

You are troubleshooting a build where a RUN instruction fails because it cannot reach a remote URL to download a file. The local network uses an HTTP proxy. How should you pass the proxy settings to the build command without hardcoding them into the image?

Accepted Answer

podman build --build-arg HTTP_PROXY=http://proxy.example.com:8080 .. Build arguments can be passed via --build-arg to provide proxy settings dynamically.

Answer

podman build --proxy http://proxy.example.com:8080 .

Answer

podman build --env HTTP_PROXY=http://proxy.example.com:8080 .

Answer

podman build --set-proxy http://proxy.example.com:8080 .

Question 10

You want to build an image that has a build-time argument named 'VERSION'. How do you declare this variable inside the Containerfile so it can be used during the build steps?

Accepted Answer

ARG VERSION. The ARG instruction defines a variable that users can pass at build-time with podman build --build-arg =.

Answer

DEFINE VERSION

Answer

ENV VERSION=1.0

Answer

VAR VERSION