- A
Deploy a ValidatingWebhookConfiguration that checks for readOnlyRootFilesystem: true
Validating webhooks can reject non-compliant pods.
- B
Use a Gatekeeper policy to drop all capabilities
Why wrong: Dropping capabilities does not enforce read-only root filesystem.
- C
Enable Pod Security Admission (PSA) with the 'restricted' profile
The restricted profile requires readOnlyRootFilesystem: true.
- D
Deploy a MutatingWebhookConfiguration that adds readOnlyRootFilesystem: true to all pods
Mutating webhooks can automatically add the setting.
- E
Apply a NetworkPolicy that denies egress
Why wrong: Network policies do not affect filesystem permissions.
Question 368 of 997
How to Enforce readOnlyRootFilesystem: true for All Pods
This CKS practice question tests your understanding of minimize microservice vulnerabilities. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. 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 THREE of the following are valid approaches to enforce that all pods in a cluster run with a read-only root filesystem? (Select THREE)
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
✓
Deploy a ValidatingWebhookConfiguration that checks for readOnlyRootFilesystem: true
Option A is correct because a ValidatingWebhookConfiguration can intercept pod creation requests and reject any pod that does not have `readOnlyRootFilesystem: true` set in its security context. This enforces the requirement without modifying the pod spec, ensuring only compliant pods are admitted.
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.
- ✓
Deploy a ValidatingWebhookConfiguration that checks for readOnlyRootFilesystem: true
Why this is correct
Validating webhooks can reject non-compliant pods.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Use a Gatekeeper policy to drop all capabilities
Why it's wrong here
Dropping capabilities does not enforce read-only root filesystem.
- ✓
Enable Pod Security Admission (PSA) with the 'restricted' profile
Why this is correct
The restricted profile requires readOnlyRootFilesystem: true.
Related concept
Read the scenario before looking for a memorised answer.
- ✓
Deploy a MutatingWebhookConfiguration that adds readOnlyRootFilesystem: true to all pods
Why this is correct
Mutating webhooks can automatically add the setting.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Apply a NetworkPolicy that denies egress
Why it's wrong here
Network policies do not affect filesystem permissions.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Candidates often confuse dropping capabilities with making the root filesystem read-only. Dropping capabilities limits kernel privileges but does not prevent writes to the filesystem; they are separate security contexts.
Detailed technical explanation
How to think about this question
Under the hood, `readOnlyRootFilesystem: true` in a PodSecurityContext sets the container's root filesystem to be mounted read-only by the container runtime (e.g., containerd). This is enforced at the kernel level via the `MS_RDONLY` mount flag, preventing any writes to the root filesystem even if the container runs as root. In a real-world scenario, applications that need to write temporary files must use an emptyDir volume or a writable volume mount, as the root filesystem itself is immutable.
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 practitioner preparing for the CKS 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
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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Minimize Microservice Vulnerabilities — study guide chapter
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FAQ
Questions learners often ask
What does this CKS question test?
Minimize Microservice Vulnerabilities — This question tests Minimize Microservice Vulnerabilities — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Deploy a ValidatingWebhookConfiguration that checks for readOnlyRootFilesystem: true — Option A is correct because a ValidatingWebhookConfiguration can intercept pod creation requests and reject any pod that does not have `readOnlyRootFilesystem: true` set in its security context. This enforces the requirement without modifying the pod spec, ensuring only compliant pods are admitted.
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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