This CKS practice question tests your understanding of system hardening. Match the stated requirement to the specific cloud service, access model, or configuration option — many options are valid in isolation but not for this scenario. 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.
Which of the following fields in a PodSecurityPolicy (or Pod Security Standards) prevents a container from running as root?
runAsUser: RunAsAny
Why wrong: RunAsAny allows any user, including root.
runAsGroup: MustRunAsNonRoot
Why wrong: This controls the group, not the user.
runAsUser: MustRunAsNonRoot
This rule requires containers to run as non-root user.
seLinuxContext: MustRunAsNonRoot
Why wrong: SELinux context is different from user ID.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
runAsUser: MustRunAsNonRoot
Option C is correct because `runAsUser: MustRunAsNonRoot` in a PodSecurityPolicy (or the equivalent Pod Security Standard `restricted` profile) enforces that the container's user ID (UID) must not be 0 (root). This directly prevents the container from running as root, as the security context will reject any pod that specifies `runAsUser: 0` or omits the field when the policy requires a non-root user.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
runAsUser: RunAsAny
Why it's wrong here
RunAsAny allows any user, including root.
runAsGroup: MustRunAsNonRoot
Why it's wrong here
This controls the group, not the user.
runAsUser: MustRunAsNonRoot
Why this is correct
This rule requires containers to run as non-root user.
Related concept
Read the scenario before looking for a memorised answer.
seLinuxContext: MustRunAsNonRoot
Why it's wrong here
SELinux context is different from user ID.
Common exam traps
CNCF often tests the distinction between `runAsUser` and `runAsGroup`, where candidates mistakenly think setting `runAsGroup: MustRunAsNonRoot` prevents root execution, but it only restricts the group ID, not the user ID.
Detailed technical explanation
Under the hood, the `MustRunAsNonRoot` strategy in the `runAsUser` field validates that the container's `securityContext.runAsUser` is set to a non-zero value or that the container image specifies a non-root user via the `USER` directive. In Pod Security Standards (PSS), the `restricted` profile enforces this by default, and the admission controller (e.g., PodSecurity admission plugin) rejects pods that violate the rule. A subtle behavior is that if `runAsUser` is not set but the image's `USER` is root, the policy will still reject the pod unless `MustRunAsNonRoot` is explicitly satisfied.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
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
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FAQ
System Hardening — This question tests System Hardening — Read the scenario before looking for a memorised answer..
The correct answer is: runAsUser: MustRunAsNonRoot — Option C is correct because `runAsUser: MustRunAsNonRoot` in a PodSecurityPolicy (or the equivalent Pod Security Standard `restricted` profile) enforces that the container's user ID (UID) must not be 0 (root). This directly prevents the container from running as root, as the security context will reject any pod that specifies `runAsUser: 0` or omits the field when the policy requires a non-root user.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 30, 2026
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