Question 941 of 997

Minimize Microservice Vulnerabilities →mediumMultiple ChoiceObjective-mapped

Creating a RuntimeClass for gVisor (runsc) — Sandboxed Runtime Setup | Certified Kubernetes Security Specialist Explained

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 need to run a container with a sandboxed runtime using gVisor (runsc). Which Kubernetes resource must be created first to enable this?

Clue words in this question

Noticing these words before you look at the options changes how you read each choice.

Clue: "first"
Why it matters: Order matters here. You are being tested on which action comes before the others — not which action is generally useful.

A
A RuntimeClass resource with handler: runsc
RuntimeClass defines the container runtime to use for pods.
B
A PodSecurityPolicy that allows the runsc runtime
Why wrong: PodSecurityPolicy is deprecated and does not control runtime selection.
C
A ValidatingWebhookConfiguration to validate the runtime
Why wrong: Not required for using a runtime class.
D
A priorityClass with a high priority
Why wrong: PriorityClass does not affect runtime selection.

Full breakdown with real-world context →

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 RuntimeClass resource with handler: runsc

A RuntimeClass resource is required to define a container runtime configuration that uses gVisor (runsc). When you create a RuntimeClass with handler: runsc, you can then reference it in a Pod spec via the runtimeClassName field, which instructs the kubelet to use the runsc runtime instead of the default runc. This is the foundational step to enable sandboxed runtime isolation for containers.

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 RuntimeClass resource with handler: runsc
Why this is correct
RuntimeClass defines the container runtime to use for pods.
Clue confirmation
The clue word "first" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
A PodSecurityPolicy that allows the runsc runtime
Why it's wrong here
PodSecurityPolicy is deprecated and does not control runtime selection.
✗
A ValidatingWebhookConfiguration to validate the runtime
Why it's wrong here
Not required for using a runtime class.
✗
A priorityClass with a high priority
Why it's wrong here
PriorityClass does not affect runtime selection.

Common exam traps

Common exam trap: answer the scenario, not the keyword

A common misconception is that runtime selection is done via PodSecurityPolicy or admission webhooks, when in fact it requires a dedicated RuntimeClass resource that maps to a runtime handler configured in the container runtime (e.g., containerd).

Detailed technical explanation

How to think about this question

Under the hood, when a Pod specifies runtimeClassName: my-gvisor, the kubelet reads the corresponding RuntimeClass object to get the handler (runsc). It then passes this handler to the CRI (Container Runtime Interface) implementation, which in turn launches the container using the gVisor runsc binary instead of runc. A real-world scenario is running untrusted workloads (e.g., multi-tenant SaaS) where gVisor provides an additional kernel-level sandbox, but you must first create the RuntimeClass to make the runtime available cluster-wide.

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.

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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: A RuntimeClass resource with handler: runsc — A RuntimeClass resource is required to define a container runtime configuration that uses gVisor (runsc). When you create a RuntimeClass with handler: runsc, you can then reference it in a Pod spec via the runtimeClassName field, which instructs the kubelet to use the runsc runtime instead of the default runc. This is the foundational step to enable sandboxed runtime isolation for containers.

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.

Are there clue words in this question I should notice?

Yes — watch for: "first". Order matters here. You are being tested on which action comes before the others — not which action is generally useful.

What is the key concept behind this question?

Read the scenario before looking for a memorised answer.

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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. You want to run a container with gVisor (runsc) runtime for sandboxing. Which resource is required to use a non-default runtime?

medium

A.PodSecurityPolicy
B.ContainerRuntime resource
✓ C.RuntimeClass resource
D.Node runtime configuration only

Why C: In Kubernetes, to use a non-default runtime like gVisor (runsc), you must define a RuntimeClass resource that references the runtime handler (e.g., 'runsc') configured on the node. The RuntimeClass acts as a bridge between the Pod spec and the node's container runtime configuration, allowing the scheduler to select the appropriate runtime for sandboxing. Without a RuntimeClass, the default runtime (typically runc) is used, which does not provide the same isolation level.

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