- A
apiVersion: v1 kind: Pod metadata: name: sandbox-pod annotations: runtimeClass: gvisor spec: containers: - name: app image: nginx
Why wrong: runtimeClassName is a spec field, not an annotation.
- B
apiVersion: v1 kind: Pod metadata: name: sandbox-pod spec: runtimeClassName: gvisor containers: - name: app image: nginx
Correct usage: runtimeClassName set to the name of the RuntimeClass resource.
- C
apiVersion: v1 kind: Pod metadata: name: sandbox-pod spec: nodeSelector: runtime: gvisor containers: - name: app image: nginx
Why wrong: nodeSelector is used for node affinity, not for specifying a runtime class.
- D
apiVersion: v1 kind: Pod metadata: name: sandbox-pod spec: runtimeClass: name: gvisor containers: - name: app image: nginx
Why wrong: runtimeClass is a string field, not an object.
How to Use RuntimeClass for Sandboxed Containers (gVisor, Kata) in Kubernetes
This CKS practice question tests your understanding of minimize microservice vulnerabilities. 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.
You want to run a workload in a sandboxed container using gVisor. You have created a RuntimeClass named 'gvisor' that references the 'runsc' handler. Which of the following Pod specs correctly uses this RuntimeClass?
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
apiVersion: v1 kind: Pod metadata: name: sandbox-pod spec: runtimeClassName: gvisor containers: - name: app image: nginx
Option B is correct because the `runtimeClassName` field in the Pod spec is the standard Kubernetes API field used to specify a RuntimeClass for a Pod. The RuntimeClass named 'gvisor' must be defined in the cluster with a handler 'runsc', and setting `runtimeClassName: gvisor` in the Pod spec instructs the kubelet to use the gVisor runtime (runsc) to run the containers in a sandboxed environment, minimizing microservice vulnerabilities.
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.
- ✗
apiVersion: v1 kind: Pod metadata: name: sandbox-pod annotations: runtimeClass: gvisor spec: containers: - name: app image: nginx
Why it's wrong here
runtimeClassName is a spec field, not an annotation.
- ✓
apiVersion: v1 kind: Pod metadata: name: sandbox-pod spec: runtimeClassName: gvisor containers: - name: app image: nginx
Why this is correct
Correct usage: runtimeClassName set to the name of the RuntimeClass resource.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
apiVersion: v1 kind: Pod metadata: name: sandbox-pod spec: nodeSelector: runtime: gvisor containers: - name: app image: nginx
Why it's wrong here
nodeSelector is used for node affinity, not for specifying a runtime class.
- ✗
apiVersion: v1 kind: Pod metadata: name: sandbox-pod spec: runtimeClass: name: gvisor containers: - name: app image: nginx
Why it's wrong here
runtimeClass is a string field, not an object.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The CNCF-CKS exam often tests the distinction between `runtimeClassName` (a flat string field) and incorrect nested or annotation-based approaches, as candidates may confuse it with other Pod spec fields like `nodeSelector` or `annotations`.
Detailed technical explanation
How to think about this question
The RuntimeClass resource defines a handler (e.g., 'runsc') that maps to a container runtime configured on the node, such as gVisor's runsc binary. When a Pod specifies `runtimeClassName`, the kubelet reads the RuntimeClass object, validates it, and passes the handler to the container runtime (e.g., containerd or CRI-O) via the CRI, which then launches the container using the specified sandbox runtime. This mechanism is critical for enforcing isolation in multi-tenant clusters without modifying node configurations per Pod.
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
Learn the concepts, then practise the questions
- →
Minimize Microservice Vulnerabilities practice questions
Targeted practice on this topic area only
- →
All CKS questions
997 questions across all exam domains
- →
Certified Kubernetes Security Specialist CKS study guide
Full concept coverage aligned to exam objectives
- →
CKS practice test guide
How to use practice tests most effectively before exam day
Related practice questions
Related CKS practice-question pages
Use these pages to review the topic behind this question. This is how one missed question becomes focused revision.
Monitoring Logging and Runtime Security practice questions
Practise CKS questions linked to Monitoring Logging and Runtime Security.
Cluster Setup and Hardening practice questions
Practise CKS questions linked to Cluster Setup and Hardening.
System Hardening practice questions
Practise CKS questions linked to System Hardening.
Minimize Microservice Vulnerabilities practice questions
Practise CKS questions linked to Minimize Microservice Vulnerabilities.
Supply Chain Security practice questions
Practise CKS questions linked to Supply Chain Security.
Monitoring, Logging and Runtime Security practice questions
Practise CKS questions linked to Monitoring, Logging and Runtime Security.
Cluster Setup practice questions
Practise CKS questions linked to Cluster Setup.
Cluster Hardening practice questions
Practise CKS questions linked to Cluster Hardening.
CKS fundamentals practice questions
Practise CKS questions linked to CKS fundamentals.
CKS scenario practice questions
Practise CKS questions linked to CKS scenario.
CKS troubleshooting practice questions
Practise CKS questions linked to CKS troubleshooting.
Practice this exam
Start a free CKS practice session
Short sessions build daily habit. Longer sessions build exam-day stamina. Try a timed session to simulate real conditions.
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: apiVersion: v1 kind: Pod metadata: name: sandbox-pod spec: runtimeClassName: gvisor containers: - name: app image: nginx — Option B is correct because the `runtimeClassName` field in the Pod spec is the standard Kubernetes API field used to specify a RuntimeClass for a Pod. The RuntimeClass named 'gvisor' must be defined in the cluster with a handler 'runsc', and setting `runtimeClassName: gvisor` in the Pod spec instructs the kubelet to use the gVisor runtime (runsc) to run the containers in a sandboxed environment, minimizing microservice vulnerabilities.
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
2 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. Which container runtime is specifically designed for sandboxing containers with a lightweight kernel?
easy- A.Docker
- B.containerd
- ✓ C.gVisor (runsc)
- D.runc
Why C: gVisor (runsc) is a container runtime that provides a lightweight kernel written in Go, which intercepts system calls from the container and handles them in user space. This creates a strong sandbox between the container and the host kernel, making it specifically designed for sandboxing containers with a lightweight kernel, unlike standard runtimes that share the host kernel directly.
Variation 2. Which THREE of the following are features of container sandboxing solutions like gVisor or Kata Containers?
medium- ✓ A.They are compatible with the OCI runtime specification
- B.They improve container performance over native runc
- ✓ C.They can be used with RuntimeClass to select the sandbox runtime per pod
- ✓ D.They provide an additional layer of isolation between containers and the host kernel
- E.They use the host kernel directly for all system calls
Why A: Option A is correct because both gVisor and Kata Containers implement the OCI (Open Container Initiative) runtime specification, which allows them to be used as drop-in replacements for runc. This compatibility ensures that container images and tools like containerd can interface with these sandboxed runtimes without modification, as they expose the same runtime lifecycle commands (create, start, delete).
Keep practising
More CKS practice questions
- Which flag is used to restrict the kubelet's ability to modify node status and pods?
- A Falco rule has priority `WARNING` and output: `Sensitive file opened (user=%user.name command=%proc.cmdline file=%fd.n…
- Falco detects a shell being opened inside a container. Which Falco rule field is used to specify the syscall condition f…
- A security audit reveals that a ServiceAccount named 'monitor' has a ClusterRoleBinding to the cluster-admin role. What…
- Match each Kubernetes security component to its description.
- Match each Kubernetes certificate type to its usage.
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.
Question Discussion
Share a tip, memory trick, or ask about the reasoning behind this question. Do not post real exam questions, leaked content, braindumps, or copyrighted exam material. Comments are moderated and may be removed without notice.
Sign in to join the discussion.