This CKS practice question tests your understanding of system hardening. 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.
A DevOps team wants to ensure that all container images are pulled from a trusted registry only. Which cluster-level configuration should be applied?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Enable ImagePolicyWebhook admission controller
Option D is correct because the ImagePolicyWebhook admission controller allows you to configure a cluster-level admission plugin that intercepts all Pod creation requests and validates the container images against an external webhook backend. This backend can enforce policies such as allowing only images from a trusted registry (e.g., `mytrustedregistry.io/*`), rejecting any image that does not match the whitelist. It operates at the API server level, ensuring that no Pod with an untrusted image can be created in the cluster.
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.
✗
Configure kubelet with --pod-manifest-path pointing to a whitelist
Why it's wrong here
This is for static pods, not for restricting image sources for all pods.
✗
Enable PodSecurity with restricted profile
Why it's wrong here
PodSecurity does not validate image registries.
✗
Use NetworkPolicy to block traffic to untrusted registries
Why it's wrong here
NetworkPolicy cannot block image pulls; images are pulled before pod creation.
✓
Enable ImagePolicyWebhook admission controller
Why this is correct
ImagePolicyWebhook can reject images from untrusted registries based on external policy.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Common exam trap: answer the scenario, not the keyword
CNCF often tests the distinction between admission controllers that validate image sources (ImagePolicyWebhook) versus those that enforce Pod security contexts (PodSecurity), leading candidates to mistakenly choose PodSecurity when the question is about registry trust.
Detailed technical explanation
How to think about this question
The ImagePolicyWebhook admission controller works by sending an `ImageReview` request to an external webhook service over HTTPS, which must return an `allowed` or `denied` response based on the image name and registry. A common real-world scenario is using a tool like OPA Gatekeeper or a custom webhook to enforce that only images signed by a trusted authority or hosted on a private registry (e.g., `gcr.io/my-org/*`) are permitted, blocking supply-chain attacks from public or unknown registries.
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 small business has 20 workstations on the 192.168.1.0/24 network and one public IP from its ISP. The router uses PAT (NAT overload) so all 20 devices share one public address using different source ports. NAT questions test whether you understand the four address terms and which direction each translation applies.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this CKS question in full detail.
System Hardening — This question tests System Hardening — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Enable ImagePolicyWebhook admission controller — Option D is correct because the ImagePolicyWebhook admission controller allows you to configure a cluster-level admission plugin that intercepts all Pod creation requests and validates the container images against an external webhook backend. This backend can enforce policies such as allowing only images from a trusted registry (e.g., `mytrustedregistry.io/*`), rejecting any image that does not match the whitelist. It operates at the API server level, ensuring that no Pod with an untrusted image can be created in the cluster.
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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