- A
Cosign
Why wrong: Cosign is for image signing and verification, not for enforcing registry allowlists.
- B
Notary
Why wrong: Notary is for content trust and image signing, not for admission control policies.
- C
Trivy
Why wrong: Trivy is a vulnerability scanner, not an admission controller for policy enforcement.
- D
OPA/Gatekeeper
OPA/Gatekeeper can enforce admission policies, such as restricting images to trusted registries.
Question 279 of 997
Restrict Images to a Specific Registry — OPA/Gatekeeper
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.
An administrator wants to ensure that only images from a specific registry (e.g., myregistry.internal) can run in the cluster. Which tool can be used to enforce this via admission control?
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
✓
OPA/Gatekeeper
OPA/Gatekeeper is a Kubernetes admission controller that can enforce policies on pod creation, including restricting which container image registries are allowed. By writing a ConstraintTemplate and Constraint that checks the image field against a whitelist of registries, Gatekeeper can reject any pod that attempts to use an image from an unauthorized source. This directly addresses the requirement to enforce registry restrictions at admission time.
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.
- ✗
Cosign
Why it's wrong here
Cosign is for image signing and verification, not for enforcing registry allowlists.
- ✗
Notary
Why it's wrong here
Notary is for content trust and image signing, not for admission control policies.
- ✗
Trivy
Why it's wrong here
Trivy is a vulnerability scanner, not an admission controller for policy enforcement.
- ✓
OPA/Gatekeeper
Why this is correct
OPA/Gatekeeper can enforce admission policies, such as restricting images to trusted registries.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates confuse tools for image signing or scanning (Cosign, Notary, Trivy) with admission control tools that enforce runtime policies, but only OPA/Gatekeeper provides the Kubernetes-native admission webhook mechanism to block pods based on image registry origin.
Detailed technical explanation
How to think about this question
OPA/Gatekeeper works by intercepting API server requests via a MutatingAdmissionWebhook or ValidatingAdmissionWebhook, evaluating them against Rego policies. A common policy to restrict registries uses a ConstraintTemplate that parses the image field (e.g., `input.request.object.spec.containers[i].image`) and checks if the registry matches a predefined pattern. In real-world scenarios, this prevents supply chain attacks where a compromised CI/CD pipeline might push a malicious image to an untrusted registry, and Gatekeeper ensures only approved registries like `myregistry.internal` are used.
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.
- →
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: OPA/Gatekeeper — OPA/Gatekeeper is a Kubernetes admission controller that can enforce policies on pod creation, including restricting which container image registries are allowed. By writing a ConstraintTemplate and Constraint that checks the image field against a whitelist of registries, Gatekeeper can reject any pod that attempts to use an image from an unauthorized source. This directly addresses the requirement to enforce registry restrictions at admission time.
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.
About these practice questions
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
Same concept, more angles
1 more ways this is tested on CKS
These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. An administrator wants to ensure that only images from a trusted registry 'myregistry.io' can run in the cluster. Which admission controller should be configured?
medium- A.NodeRestriction
- B.MutatingAdmissionWebhook
- ✓ C.ImagePolicyWebhook
- D.PodSecurity
Why C: Option C is correct because the ImagePolicyWebhook admission controller enforces that only images from a trusted registry (e.g., 'myregistry.io') can run. It does this by querying an external webhook to validate the image source against a policy. Options A, B, and D are incorrect: NodeRestriction restricts node API access, MutatingAdmissionWebhook can mutate pods but is not specifically designed for image registry control, and PodSecurity handles pod security contexts, not image source validation.
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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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