EX188 Container Image Building Practice Question
A developer needs to optimize image size by removing build caches and temporary package manager cache files within the same RUN instruction. Why must this be done in a single RUN instruction?
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
✓
Because file deletions in separate layers do not reduce the final image size due to the layered filesystem.
Docker/Podman image layers are read-only snapshots. Deleting a file in a later layer only hides it; it does not remove it from previous layers.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Because file deletions in separate layers do not reduce the final image size due to the layered filesystem.
Why this is correct
Layers are additive; removing files in a subsequent layer just adds a whiteout file, leaving previous layers intact.
- ✗
Because package managers lock the database across different layers.
Why it's wrong here
Package managers do not maintain locks across independent layer creation.
- ✗
Because the container build engine will fail if cache cleanup happens in a separate layer.
Why it's wrong here
The build will not fail, but the image size will not decrease.
- ✗
To ensure environment variables persist between installation and cleanup.
Why it's wrong here
Environment variables persist via ENV, not layer consolidation.
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JA
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.