This CKS practice question tests your understanding of system hardening. 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.
A container runs as non-root and needs to perform operations that require CAP_SYS_PTRACE. Which YAML snippet correctly adds only this capability while following the principle of least privilege?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "least"
Why it matters: You want the option with minimum overhead, fewest steps, or lowest impact — not the most feature-rich or comprehensive answer.
Option B is correct because it first drops all capabilities with `drop: ['ALL']` and then explicitly adds only `SYS_PTRACE`, ensuring the container runs with the minimum privileges required. This follows the principle of least privilege by removing any inherited or default capabilities before granting only the needed one. In Kubernetes, capabilities are Linux kernel capabilities; dropping all and adding only what is necessary is the recommended security practice.
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.
The clue word "least" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
securityContext:
capabilities:
drop: ['ALL']
Why it's wrong here
This drops all but does not add SYS_PTRACE, so the operation fails.
✗
securityContext:
privileged: true
Why it's wrong here
Privileged gives all capabilities, which is excessive.
Common exam traps
Common exam trap: answer the scenario, not the keyword
CNCF often tests the misconception that simply adding a capability is sufficient, but the trap is that candidates forget to drop all other capabilities first, leaving the container with more privileges than intended.
Detailed technical explanation
How to think about this question
Linux capabilities break down root privileges into distinct units; `CAP_SYS_PTRACE` specifically allows tracing arbitrary processes using `ptrace()`, which is needed for tools like strace or debuggers. Dropping all capabilities first (`drop: ['ALL']`) ensures no inherited capabilities from the container runtime or image remain, which is critical in multi-tenant clusters where base images may have unexpected capabilities. A real-world scenario is a monitoring sidecar that needs to attach to other containers for debugging; using `drop: ['ALL']` and `add: ['SYS_PTRACE']` prevents it from performing other privileged operations like mounting filesystems or changing system time.
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 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.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this CKS question in full detail.
System Hardening — This question tests System Hardening — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: securityContext:
capabilities:
drop: ['ALL']
add: ['SYS_PTRACE'] — Option B is correct because it first drops all capabilities with `drop: ['ALL']` and then explicitly adds only `SYS_PTRACE`, ensuring the container runs with the minimum privileges required. This follows the principle of least privilege by removing any inherited or default capabilities before granting only the needed one. In Kubernetes, capabilities are Linux kernel capabilities; dropping all and adding only what is necessary is the recommended security practice.
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: "least". You want the option with minimum overhead, fewest steps, or lowest impact — not the most feature-rich or comprehensive answer.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Question Discussion
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