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 security admin wants to drop all Linux capabilities for a container and then add only CAP_NET_BIND_SERVICE. Which YAML snippet correctly achieves this?
Option D is correct because it uses the standard Kubernetes `securityContext.capabilities` field with `drop: ['ALL']` to remove all Linux capabilities from the container, then `add: ['NET_BIND_SERVICE']` to grant only the `CAP_NET_BIND_SERVICE` capability. This is the proper YAML syntax for the desired capability set.
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.
This correctly drops all capabilities and adds the required one.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Common exam trap: answer the scenario, not the keyword
CNCF often tests the distinction between the correct `capabilities` object syntax and the incorrect flat field names like `capDrop`/`capAdd`, and the trap is that candidates confuse `privileged: true` with a fine-grained capability control, when in fact it bypasses all capability restrictions.
Detailed technical explanation
How to think about this question
Linux capabilities break down the privileges of the root user into distinct units (e.g., CAP_NET_BIND_SERVICE allows binding to ports below 1024). The `drop: ['ALL']` directive removes all 40+ capabilities, then `add: ['NET_BIND_SERVICE']` selectively re-adds only the needed one. Under the hood, Kubernetes translates this into `cap_drop` and `cap_add` in the container runtime spec (e.g., containerd or CRI-O), which invokes the `capset` system call to set the effective, permitted, and inheritable capability sets. A real-world scenario is running a web server in a container that must bind to port 80 without granting full root privileges.
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: ['NET_BIND_SERVICE'] — Option D is correct because it uses the standard Kubernetes `securityContext.capabilities` field with `drop: ['ALL']` to remove all Linux capabilities from the container, then `add: ['NET_BIND_SERVICE']` to grant only the `CAP_NET_BIND_SERVICE` capability. This is the proper YAML syntax for the desired capability set.
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.
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Question Discussion
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