- A
Set spec.runtimeClassName: gvisor
The runtimeClassName field in Pod spec selects the RuntimeClass resource, which points to the gVisor runtime handler.
- B
Set spec.nodeSelector with 'gvisor: true'
Why wrong: NodeSelector selects nodes, not runtime classes.
- C
Define an environment variable RUNTIME=gvisor in the container
Why wrong: Environment variables do not affect runtime selection.
- D
Add an annotation 'container.runtime: gvisor' to the Pod
Why wrong: Kubernetes does not use annotations to select runtime classes; it uses the runtimeClassName field.
Question 384 of 997
How to Use gVisor RuntimeClass for Container Sandboxing
This CKS practice question tests your understanding of minimize microservice vulnerabilities. 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.
You want to run a container with gVisor for sandboxing. After installing gVisor and creating a RuntimeClass named 'gvisor', which Pod configuration enables it?
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
✓
Set spec.runtimeClassName: gvisor
Option A is correct because the `spec.runtimeClassName` field in a Pod spec is the standard Kubernetes mechanism to select a specific container runtime for that Pod. When a RuntimeClass named 'gvisor' is created, setting `spec.runtimeClassName: gvisor` instructs the kubelet to use the gVisor runtime (runsc) to run the Pod's containers, providing an additional sandboxing layer for security.
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 spec.runtimeClassName: gvisor
Why this is correct
The runtimeClassName field in Pod spec selects the RuntimeClass resource, which points to the gVisor runtime handler.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Set spec.nodeSelector with 'gvisor: true'
Why it's wrong here
NodeSelector selects nodes, not runtime classes.
- ✗
Define an environment variable RUNTIME=gvisor in the container
Why it's wrong here
Environment variables do not affect runtime selection.
- ✗
Add an annotation 'container.runtime: gvisor' to the Pod
Why it's wrong here
Kubernetes does not use annotations to select runtime classes; it uses the runtimeClassName field.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap is that candidates may mistakenly think that nodeSelector, environment variables, or annotations can select a runtime, but only spec.runtimeClassName directly references a RuntimeClass object. For gVisor, a CNCF sandbox project, the RuntimeClass must be created separately, and the Pod simply references it by name.
Detailed technical explanation
How to think about this question
Under the hood, when a RuntimeClass is defined, it references a handler (e.g., 'runsc') that the CRI (Container Runtime Interface) implementation, such as containerd or CRI-O, maps to a specific OCI-compatible runtime binary. The kubelet reads the Pod's `runtimeClassName`, looks up the corresponding RuntimeClass object, and passes the handler name to the CRI, which then launches the container using the specified runtime (e.g., gVisor's runsc) instead of the default runc. This mechanism allows per-Pod runtime selection without modifying the node's default runtime.
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.
- →
Minimize Microservice Vulnerabilities — study guide chapter
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FAQ
Questions learners often ask
What does this CKS question test?
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 spec.runtimeClassName: gvisor — Option A is correct because the `spec.runtimeClassName` field in a Pod spec is the standard Kubernetes mechanism to select a specific container runtime for that Pod. When a RuntimeClass named 'gvisor' is created, setting `spec.runtimeClassName: gvisor` instructs the kubelet to use the gVisor runtime (runsc) to run the Pod's containers, providing an additional sandboxing layer for security.
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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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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