- A
To reduce the attack surface and limit potential damage if the container is compromised
Non-root users have fewer privileges, limiting the impact of a breach.
- B
To improve performance
Why wrong: Non-root does not impact performance.
- C
To comply with Kubernetes requirements
Why wrong: Kubernetes does not require non-root users; it is a best practice.
- D
To allow the container to bind to privileged ports
Why wrong: Non-root users cannot bind to ports below 1024 without additional capabilities.
Question 95 of 997
Why Use a Non-Root User in Container Images
This CKS practice question tests your understanding of supply chain security. 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.
What is the purpose of using a non-root user in a container image?
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
✓
To reduce the attack surface and limit potential damage if the container is compromised
Running containers as a non-root user reduces the attack surface by ensuring that even if an attacker exploits a vulnerability in the application, they do not gain root privileges inside the container. This limits the potential damage, such as modifying system binaries, escaping the container via kernel exploits, or accessing host resources. In Kubernetes, this is enforced by setting `securityContext.runAsNonRoot: true` or specifying a non-root user in the Dockerfile with `USER` directive.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
To reduce the attack surface and limit potential damage if the container is compromised
Why this is correct
Non-root users have fewer privileges, limiting the impact of a breach.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
To improve performance
Why it's wrong here
Non-root does not impact performance.
- ✗
To comply with Kubernetes requirements
Why it's wrong here
Kubernetes does not require non-root users; it is a best practice.
- ✗
To allow the container to bind to privileged ports
Why it's wrong here
Non-root users cannot bind to ports below 1024 without additional capabilities.
Common exam traps
Common exam trap: answer the scenario, not the keyword
CKS often tests the misconception that Kubernetes mandates non-root containers, but the trap is that it is a security best practice, not a hard requirement, and the default behavior is to run as root unless explicitly configured.
Detailed technical explanation
How to think about this question
Under the hood, Linux user namespaces can map a non-root user inside the container to a non-root user on the host, but by default Docker does not use user namespaces. The `USER` directive in a Dockerfile sets the UID for the container process, and Kubernetes `securityContext` can enforce `runAsUser: 1000` and `runAsNonRoot: true`. A real-world scenario is the 'container escape' via CVE-2019-5736, where a root container could overwrite the host runc binary; running as non-root would have prevented the overwrite because the attacker lacks write permissions to host binaries.
KKey Concepts to Remember
- Read the scenario before looking for a memorised answer.
- Find the constraint that changes the correct option.
- Eliminate answers that are true in general but not in this case.
TExam Day Tips
- Watch for words such as best, first, most likely and least administrative effort.
- Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A junior network technician can log in to a core router but cannot reach the enable prompt or configuration mode. The AAA server is authenticating the login — but the authorisation policy only grants privilege level 1, not 15. Authentication (who you are) is working; authorisation (what you can do) is not.
What to study next
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
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Supply Chain Security — study guide chapter
Learn the concepts, then practise the questions
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FAQ
Questions learners often ask
What does this CKS question test?
Supply Chain Security — This question tests Supply Chain Security — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: To reduce the attack surface and limit potential damage if the container is compromised — Running containers as a non-root user reduces the attack surface by ensuring that even if an attacker exploits a vulnerability in the application, they do not gain root privileges inside the container. This limits the potential damage, such as modifying system binaries, escaping the container via kernel exploits, or accessing host resources. In Kubernetes, this is enforced by setting `securityContext.runAsNonRoot: true` or specifying a non-root user in the Dockerfile with `USER` directive.
What should I do if I get this CKS question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Last reviewed: Jul 4, 2026
This CKS 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 CKS exam.
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