EX188 Container Image Building Practice Question
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?
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 APP_PORT=8080
The ENV instruction sets environment variables that persist when the container runs.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
EXPORT APP_PORT=8080
Why it's wrong here
EXPORT is a bash shell command.
- ✓
ENV APP_PORT=8080
Why this is correct
ENV defines persistent environment variables in the image.
- ✗
VAR APP_PORT=8080
Why it's wrong here
VAR is not a valid Containerfile instruction.
- ✗
SET APP_PORT=8080
Why it's wrong here
SET is a Windows shell command, not a Containerfile instruction.
About these practice questions
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Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed August 2026 · checked against the official Red Hat exam blueprint
This EX188 practice question is part of Courseiva's free Red Hat certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the EX188 exam.