This CKAD practice question tests your understanding of application design and build. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
Which instruction in a Dockerfile sets the default command to run when the container starts, but allows overriding?
START
Why wrong: Not a valid Dockerfile instruction.
RUN
Why wrong: RUN executes commands during build.
CMD
CMD provides defaults that can be overridden.
ENTRYPOINT
Why wrong: ENTRYPOINT sets the main command that cannot be overridden by default.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
CMD
Option C is correct. CMD can be overridden by passing arguments to 'docker run'. ENTRYPOINT (option B) is not easily overridden unless combined with CMD. Option A (RUN) is for build-time commands. Option D (START) is invalid.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
START
Why it's wrong here
Not a valid Dockerfile instruction.
RUN
Why it's wrong here
RUN executes commands during build.
CMD
Why this is correct
CMD provides defaults that can be overridden.
Related concept
Read the scenario before looking for a memorised answer.
ENTRYPOINT
Why it's wrong here
ENTRYPOINT sets the main command that cannot be overridden by default.
Common exam traps
Many certification questions include familiar terms but test a specific constraint. Read the exact wording before choosing an answer that is generally true but wrong for this case.
Trap categories for this question
Command / output trap
RUN executes commands during build.
Detailed technical explanation
This question should be treated as a scenario, not a definition check. Identify the problem, the constraint and the best action. Then compare each option against those facts.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
A practitioner preparing for the CKAD exam encounters this exact type of scenario on the job. The correct answer here is not the most general option — it is the best answer for the specific constraint described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Real exam questions reward reading the full scenario before eliminating options, because the constraint defines which answer fits.
What to study next
Identify which CKAD exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
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FAQ
Application Design and Build — This question tests Application Design and Build — Read the scenario before looking for a memorised answer..
The correct answer is: CMD — Option C is correct. CMD can be overridden by passing arguments to 'docker run'. ENTRYPOINT (option B) is not easily overridden unless combined with CMD. Option A (RUN) is for build-time commands. Option D (START) is invalid.
Identify which CKAD exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 21, 2026
This CKAD practice question is part of Courseiva's free CNCF 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 CKAD exam.
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