CKS Minimize Microservice Vulnerabilities Practice Question
This CKS practice question tests your understanding of minimize microservice vulnerabilities. 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.
A DevOps engineer wants to ensure that all microservice containers run with a read-only root filesystem to prevent unauthorized writes. What is the simplest way to enforce this at the Pod level?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Set `securityContext.readOnlyRootFilesystem: true` in the Pod spec
Option C is correct because setting `securityContext.readOnlyRootFilesystem: true` in the Pod spec directly enforces that the container's root filesystem is read-only, preventing any unauthorized writes to the root filesystem. This is the simplest and most direct way to achieve the requirement at the Pod level, as it applies to all containers in the Pod unless overridden at the container level.
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.
✗
Set `securityContext.runAsNonRoot: true` in the Pod spec
Why it's wrong here
This only ensures the container runs as a non-root user, not that the filesystem is read-only.
✗
Mount an emptyDir volume to the container's writable directories
Why it's wrong here
This does not make the root filesystem read-only; emptyDir is writable.
✓
Set `securityContext.readOnlyRootFilesystem: true` in the Pod spec
Why this is correct
This directly enforces a read-only root filesystem for all containers in the Pod.
Related concept
Read the scenario before looking for a memorised answer.
✗
Set `securityContext.privileged: false` in the Pod spec
Why it's wrong here
This disables privileged mode but does not prevent writes to the root filesystem.
Common exam traps
Common exam trap: answer the scenario, not the keyword
CNCF often tests the distinction between security contexts that control user identity (runAsNonRoot) versus those that control filesystem permissions (readOnlyRootFilesystem), and the trap here is that candidates may confuse 'non-root' with 'read-only' or assume that disabling privileged mode is sufficient to prevent writes.
Detailed technical explanation
How to think about this question
Under the hood, `readOnlyRootFilesystem: true` leverages the Linux kernel's mount namespace and the `MS_RDONLY` flag to remount the container's root filesystem as read-only. This is enforced by the container runtime (e.g., containerd or CRI-O) during container creation. A subtle behavior is that even with this setting, containers can still write to volumes mounted at specific paths (e.g., emptyDir, hostPath), which is why combining it with volume mounts for temporary data is a common pattern in production.
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.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this CKS question in full detail.
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: Set `securityContext.readOnlyRootFilesystem: true` in the Pod spec — Option C is correct because setting `securityContext.readOnlyRootFilesystem: true` in the Pod spec directly enforces that the container's root filesystem is read-only, preventing any unauthorized writes to the root filesystem. This is the simplest and most direct way to achieve the requirement at the Pod level, as it applies to all containers in the Pod unless overridden at the container level.
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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Question Discussion
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