305-300 Container Virtualization Practice Question
Which instruction in a Dockerfile is best suited for installing packages to minimize image size?
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
✓
RUN apt-get update && apt-get install -y package && rm -rf /var/lib/apt/lists/*
Combining the update and install commands with 'rm -rf /var/lib/apt/lists/*' in a single RUN command prevents layer bloat.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
COPY apt-cache /
Why it's wrong here
This is not a standard approach for installing packages.
- ✗
CMD apt-get install package
Why it's wrong here
CMD runs when the container starts, not during build.
- ✗
RUN apt-get update && apt-get install -y package
Why it's wrong here
Without cleaning the cache, the layer remains large.
- ✓
RUN apt-get update && apt-get install -y package && rm -rf /var/lib/apt/lists/*
Why this is correct
This cleans the apt cache, reducing the layer size.
About these practice questions
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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 LPI exam blueprint
This 305-300 practice question is part of Courseiva's free LPI 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 305-300 exam.