CKS System Hardening Practice Question
A cluster administrator wants to enforce the Pod Security Standard 'restricted' at the namespace level. Which command applies the PodSecurity admission label to the 'prod' namespace?
⚠ Common exam trap
Watch out — candidates often confuse the three modes (enforce, audit, warn) and often pick `warn` or `audit` thinking they provide enforcement, or they mistakenly use an annotation instead of a label, which is not recognized by the PodSecurity admission controller.
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
✓
kubectl label namespace prod pod-security.kubernetes.io/enforce=restricted
The `enforce` label is the only one that actively blocks pods that violate the specified Pod Security Standard (PSS) level. The command `kubectl label namespace prod pod-security.kubernetes.io/enforce=restricted` applies the 'restricted' policy at the namespace level, causing the PodSecurity admission controller to reject any pod that does not comply with the restricted profile.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
kubectl label namespace prod pod-security.kubernetes.io/warn=restricted
Why it's wrong here
This command applies the `pod-security.kubernetes.io/warn` label, which instructs the Pod Security Admission controller to emit a warning message when a Pod violates the `restricted` policy, but it does not block the Pod's creation. Since admission is still allowed, this does not meet the administrator's requirement to enforce the standard. The `warn` level is typically used for monitoring or gradual rollout, not hard enforcement.
- ✗
kubectl label namespace prod pod-security.kubernetes.io/audit=restricted
Why it's wrong here
Setting `pod-security.kubernetes.io/audit=restricted` makes the admission controller record the violation in the audit event log while still admitting the Pod. This is a non-blocking, observability-oriented mode that does not affect admission decisions, so non-compliant workloads will run normally. The administrator explicitly needs enforcement, which requires the `enforce` label rather than `audit`.
- ✓
kubectl label namespace prod pod-security.kubernetes.io/enforce=restricted
Why this is correct
This command correctly applies the `pod-security.kubernetes.io/enforce` label with the value `restricted`, which makes the Pod Security Admission controller reject any Pod that fails the restricted Pod Security Standard. The enforcement is mandatory: the Pod admission request is denied and the API server returns an error. This is the standard, documented mechanism for enforcing a Pod Security Standard at the namespace level.
- ✗
kubectl annotate namespace prod security.kubernetes.io/pod-security=restricted
Why it's wrong here
This uses an annotation with an incorrect domain. The Pod Security Admission controller recognizes labels under the `pod-security.kubernetes.io/` prefix, not annotations. The key `security.kubernetes.io/pod-security` is not a recognized configuration, so it will be silently ignored and no enforcement will occur. Annotations are metadata only and do not trigger admission behavior in this context.
Go deeper
Related to this question
Learn chapter
Cluster Setup: Secure Configuration and Best Practices
Key term
OPA Gatekeeper
OPA Gatekeeper is a Kubernetes admission controller that enforces custom security and compliance policies on resources before they are created or updated in a cluster.
Key term
Node Restriction
A Kubernetes admission controller that limits what a kubelet can modify on its own node to prevent privilege escalation and unauthorized access.
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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.