This CKS practice question tests your understanding of system hardening. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. 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.
An administrator wants to ensure that containers in a pod cannot run with any Linux capabilities except the minimal required for the container runtime. The pod is subject to the 'restricted' Pod Security Standard. Which capability configuration should be set in the pod's security context?
capabilities: drop: ["ALL"]
Under the restricted profile, you must drop all capabilities. Adding capabilities is not allowed.
capabilities: drop: ["NET_RAW", "CHOWN"]
Why wrong: You must drop all capabilities, not just a few.
capabilities: add: ["NET_BIND_SERVICE"]
Why wrong: Adding capabilities is not allowed under the restricted profile.
capabilities: add: ["ALL"]
Why wrong: Adding all capabilities is not allowed under restricted.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
capabilities: drop: ["ALL"]
The 'restricted' Pod Security Standard (PSS) requires that all Linux capabilities be dropped except those essential for the container runtime (e.g., CAP_NET_BIND_SERVICE is allowed by default in some runtimes, but the standard explicitly mandates dropping all capabilities). Option A correctly uses `drop: ["ALL"]` to remove every capability, ensuring the container runs with the minimal set required by the runtime, which aligns with the PSS 'restricted' profile. This approach enforces the principle of least privilege by preventing the container from gaining any unnecessary kernel privileges.
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.
capabilities: drop: ["ALL"]
Why this is correct
Under the restricted profile, you must drop all capabilities. Adding capabilities is not allowed.
Related concept
Read the scenario before looking for a memorised answer.
capabilities: drop: ["NET_RAW", "CHOWN"]
Why it's wrong here
You must drop all capabilities, not just a few.
capabilities: add: ["NET_BIND_SERVICE"]
Why it's wrong here
Adding capabilities is not allowed under the restricted profile.
capabilities: add: ["ALL"]
Why it's wrong here
Adding all capabilities is not allowed under restricted.
Common exam traps
CNCF often tests the misconception that dropping only specific dangerous capabilities (like `NET_RAW` and `CHOWN`) is sufficient for the 'restricted' PSS, when in fact the standard requires dropping all capabilities to achieve the minimal privilege level.
Detailed technical explanation
Under the hood, Linux capabilities are implemented as bitmasks in the kernel's task struct, and `drop: ["ALL"]` effectively clears all capability bits from the container's bounding set, leaving only the runtime's default permitted set (e.g., `CAP_NET_BIND_SERVICE` for some runtimes). The 'restricted' PSS enforces this by checking that no capabilities are added and that `drop: ["ALL"]` is present; if a container explicitly adds a capability, the pod fails validation. In real-world scenarios, misconfiguring capabilities can lead to container escapes, such as using `CAP_SYS_ADMIN` to mount host filesystems or `CAP_NET_RAW` to craft raw packets for network attacks.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
A junior network technician can log in to a core router but cannot reach the enable prompt or configuration mode. The AAA server is authenticating the login — but the authorisation policy only grants privilege level 1, not 15. Authentication (who you are) is working; authorisation (what you can do) is not.
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: capabilities: drop: ["ALL"] — The 'restricted' Pod Security Standard (PSS) requires that all Linux capabilities be dropped except those essential for the container runtime (e.g., CAP_NET_BIND_SERVICE is allowed by default in some runtimes, but the standard explicitly mandates dropping all capabilities). Option A correctly uses `drop: ["ALL"]` to remove every capability, ensuring the container runs with the minimal set required by the runtime, which aligns with the PSS 'restricted' profile. This approach enforces the principle of least privilege by preventing the container from gaining any unnecessary kernel privileges.
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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