- A
spec.containers[].securityContext.readOnlyRootFilesystem
Why wrong: This makes the root filesystem read-only but does not prevent running as root.
- B
spec.containers[].securityContext.runAsUser: 0
Why wrong: Setting runAsUser to 0 runs as root, the opposite of the requirement.
- C
spec.containers[].securityContext.runAsNonRoot
Setting runAsNonRoot: true ensures the container runs with a non-root user.
- D
spec.containers[].securityContext.allowPrivilegeEscalation
Why wrong: This controls privilege escalation, not the root user.
Question 171 of 997
Enforcing Non-Root Containers with runAsNonRoot in SecurityContext
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.
Which YAML field in a Deployment specifies the container user should not run as root?
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
✓
spec.containers[].securityContext.runAsNonRoot
Option C is correct because `spec.containers[].securityContext.runAsNonRoot: true` explicitly enforces that the container's user ID is non-zero, preventing the container from running as root. This is a key Pod Security Standard (PSS) control for the 'Restricted' profile, ensuring compliance with the principle of least privilege. The field rejects the container if the user is set to root (UID 0) or if no user is specified and the image defaults to root.
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.
- ✗
spec.containers[].securityContext.readOnlyRootFilesystem
Why it's wrong here
This makes the root filesystem read-only but does not prevent running as root.
- ✗
spec.containers[].securityContext.runAsUser: 0
Why it's wrong here
Setting runAsUser to 0 runs as root, the opposite of the requirement.
- ✓
spec.containers[].securityContext.runAsNonRoot
Why this is correct
Setting runAsNonRoot: true ensures the container runs with a non-root user.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
spec.containers[].securityContext.allowPrivilegeEscalation
Why it's wrong here
This controls privilege escalation, not the root user.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The CKS exam often tests the distinction between `runAsNonRoot` (which enforces a non-root user) and `runAsUser: 0` (which explicitly sets root), and candidates mistakenly think setting `runAsUser` to a non-zero value is equivalent to `runAsNonRoot`, but `runAsNonRoot` is a boolean enforcement that rejects root regardless of the image's default user.
Detailed technical explanation
How to think about this question
Under the hood, `runAsNonRoot` leverages the Linux kernel's user namespace and UID checks at container startup; if the container attempts to run with UID 0, the container runtime (e.g., containerd) rejects the pod creation with an error. A subtle behavior is that this field does not validate the user at runtime—only at pod creation—so an image that switches to root via a `USER root` directive in the Dockerfile after startup would bypass the check, though this is uncommon in practice. In a real-world scenario, this is critical for supply chain security, as it prevents compromised images that default to root from gaining full host access.
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.
- →
Supply Chain Security — study guide chapter
Learn the concepts, then practise the questions
- →
Supply Chain Security practice questions
Targeted practice on this topic area only
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Certified Kubernetes Security Specialist CKS study guide
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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: spec.containers[].securityContext.runAsNonRoot — Option C is correct because `spec.containers[].securityContext.runAsNonRoot: true` explicitly enforces that the container's user ID is non-zero, preventing the container from running as root. This is a key Pod Security Standard (PSS) control for the 'Restricted' profile, ensuring compliance with the principle of least privilege. The field rejects the container if the user is set to root (UID 0) or if no user is specified and the image defaults to root.
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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