- A
capabilities: add: ["NET_BIND_SERVICE"]
Why wrong: This only adds, but does not drop all other capabilities.
- B
capabilities: drop: ["ALL"]
Why wrong: This drops all but does not add back NET_BIND_SERVICE.
- C
capabilities: drop: ["ALL"] add: ["NET_BIND_SERVICE"]
Correct. Drops all first, then adds the required capability.
- D
capabilities: drop: ["NET_BIND_SERVICE"] add: ["ALL"]
Why wrong: This would drop NET_BIND_SERVICE and add all, which is not the intended result.
Question 417 of 997
Drop All Capabilities Then Add Specific
This CKS practice question tests your understanding of system hardening. 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.
An administrator wants to drop all capabilities for a container and then add back only NET_BIND_SERVICE. Which securityContext configuration is correct?
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
✓
capabilities: drop: ["ALL"] add: ["NET_BIND_SERVICE"]
Option C is correct because it first drops all capabilities using `drop: ["ALL"]`, which removes every Linux capability from the container, and then explicitly adds back only `NET_BIND_SERVICE`. This follows the principle of least privilege: start with no capabilities and grant only what is needed. The `securityContext` in Kubernetes applies these settings at the container level, ensuring the container can bind to privileged ports (below 1024) without any other elevated permissions.
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.
- ✗
capabilities: add: ["NET_BIND_SERVICE"]
Why it's wrong here
This only adds, but does not drop all other capabilities.
- ✗
capabilities: drop: ["ALL"]
Why it's wrong here
This drops all but does not add back NET_BIND_SERVICE.
- ✓
capabilities: drop: ["ALL"] add: ["NET_BIND_SERVICE"]
Why this is correct
Correct. Drops all first, then adds the required capability.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
capabilities: drop: ["NET_BIND_SERVICE"] add: ["ALL"]
Why it's wrong here
This would drop NET_BIND_SERVICE and add all, which is not the intended result.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Kubernetes often tests the order of operations in capability management — candidates mistakenly think that adding a capability after dropping all is unnecessary or that dropping all alone is sufficient, but the correct sequence must explicitly include both `drop: ["ALL"]` and `add: ["NET_BIND_SERVICE"]` to achieve the intended least-privilege state.
Detailed technical explanation
How to think about this question
Linux capabilities break down the privileges of the root user into distinct units; `NET_BIND_SERVICE` specifically allows a process to bind a socket to Internet domain privileged ports (ports below 1024). The `drop: ["ALL"]` directive in Kubernetes translates to the `cap_drop` field in the container runtime (e.g., Docker or containerd), which removes all capabilities from the bounding set. This is a common pattern for hardening containers, especially in multi-tenant environments where minimizing the kernel attack surface is critical — for example, a web server container that only needs to bind to port 443 should have no other capabilities like `CAP_SYS_ADMIN` or `CAP_NET_RAW`.
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.
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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System Hardening — study guide chapter
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FAQ
Questions learners often ask
What does this CKS question test?
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: capabilities: drop: ["ALL"] add: ["NET_BIND_SERVICE"] — Option C is correct because it first drops all capabilities using `drop: ["ALL"]`, which removes every Linux capability from the container, and then explicitly adds back only `NET_BIND_SERVICE`. This follows the principle of least privilege: start with no capabilities and grant only what is needed. The `securityContext` in Kubernetes applies these settings at the container level, ensuring the container can bind to privileged ports (below 1024) without any other elevated permissions.
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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Last reviewed: Jul 4, 2026
This CKS practice question is part of Courseiva's free CNCF certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the CKS exam.
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