XK0-006 Automation, Orchestration, and Scripting Practice Question
A DevOps engineer is writing a Dockerfile. The application requires environment variables to be set at runtime from a file. Which Dockerfile instruction should be used to achieve this?
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
ENV
The ENV instruction sets environment variables in the Dockerfile, but for runtime from a file, the --env-file option is used with docker run. However, within the Dockerfile, ENV is the instruction to set environment variables.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
CMD export
Why it's wrong here
CMD provides defaults for the command, not for environment variables.
- ✗
ARG
Why it's wrong here
ARG defines build-time variables, not runtime environment variables.
- ✓
ENV
Why this is correct
ENV sets environment variables in the Dockerfile.
- ✗
RUN export
Why it's wrong here
RUN export would set variables only during build, and they are not persisted in the final image.
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Written by Johnson Ajibi, MSc IT Security
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