- A
A constraint that uses a pattern to match the image field against allowed registries
By matching the 'image' field in containers, you can ensure only images from trusted registries are used.
- B
A constraint that validates the cluster's registry mirror configuration
Why wrong: Registry mirror configuration is a cluster-level setting, not a per-pod enforcement mechanism.
- C
A constraint that inspects the image field in the Pod's metadata annotations
Why wrong: The image is not specified in annotations; it is in the container spec.
- D
A constraint that checks the imagePullSecrets field in the Pod spec
Why wrong: imagePullSecrets is used for authentication, not to restrict the registry.
Question 980 of 997
OPA/Gatekeeper Constraint Template for Allowed Image Registries
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.
A security team wants to ensure that only container images from a trusted registry (mytrustedregistry.io) are deployed in the cluster. They plan to use OPA/Gatekeeper. Which kind of Gatekeeper constraint template and constraint should they create?
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
✓
A constraint that uses a pattern to match the image field against allowed registries
Option A is correct because OPA/Gatekeeper enforces policies via constraint templates that define Rego rules. To restrict container images to a trusted registry, you create a constraint template that inspects the `spec.containers[*].image` field in the Pod spec and uses a pattern (e.g., regex or prefix match) to ensure the image string starts with `mytrustedregistry.io/`. The constraint then applies this template to the cluster, rejecting any Pod that references an image from an untrusted registry.
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.
- ✓
A constraint that uses a pattern to match the image field against allowed registries
Why this is correct
By matching the 'image' field in containers, you can ensure only images from trusted registries are used.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
A constraint that validates the cluster's registry mirror configuration
Why it's wrong here
Registry mirror configuration is a cluster-level setting, not a per-pod enforcement mechanism.
- ✗
A constraint that inspects the image field in the Pod's metadata annotations
Why it's wrong here
The image is not specified in annotations; it is in the container spec.
- ✗
A constraint that checks the imagePullSecrets field in the Pod spec
Why it's wrong here
imagePullSecrets is used for authentication, not to restrict the registry.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The CKS exam often tests the misconception that image validation is done via annotations or `imagePullSecrets`, but the actual image source is always in the `spec.containers[*].image` field, and Gatekeeper policies must target that field directly.
Detailed technical explanation
How to think about this question
Under the hood, OPA/Gatekeeper uses an admission webhook that intercepts Pod creation requests. The constraint template defines a Rego rule that iterates over `input.review.object.spec.containers` and checks each `image` field against a whitelist of allowed registries (e.g., using `startswith` or regex). A subtle behavior is that the image field may include a tag or digest (e.g., `mytrustedregistry.io/app:v1`), so the pattern must match the registry prefix before the first slash. In real-world scenarios, you must also handle init containers and ephemeral containers, which are separate fields in the Pod spec.
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
- →
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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: A constraint that uses a pattern to match the image field against allowed registries — Option A is correct because OPA/Gatekeeper enforces policies via constraint templates that define Rego rules. To restrict container images to a trusted registry, you create a constraint template that inspects the `spec.containers[*].image` field in the Pod spec and uses a pattern (e.g., regex or prefix match) to ensure the image string starts with `mytrustedregistry.io/`. The constraint then applies this template to the cluster, rejecting any Pod that references an image from an untrusted registry.
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 →
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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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