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.
Which TWO of the following are valid approaches to restrict which nodes a pod can run on?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Use nodeSelector in pod spec
Option A is correct because `nodeSelector` is a simple field in the Pod spec that constrains which nodes a Pod can be scheduled on by matching against node labels. This is a native Kubernetes scheduling mechanism that directly restricts node placement based on key-value pairs defined on nodes.
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.
✓
Use nodeSelector in pod spec
Why this is correct
nodeSelector matches nodes with specific labels.
Related concept
Read the scenario before looking for a memorised answer.
✗
Define NetworkPolicy to allow only certain nodes
Why it's wrong here
NetworkPolicy controls network traffic, not pod scheduling.
✗
Enable PodSecurity with baseline profile
Why it's wrong here
PodSecurity does not affect scheduling.
✗
Use tolerations in pod spec
Why it's wrong here
Tolerations allow scheduling on tainted nodes, but do not restrict to specific nodes.
✓
Use nodeAffinity in pod spec
Why this is correct
nodeAffinity can require or prefer nodes based on labels.
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 scheduling constraints (`nodeSelector`, `nodeAffinity`) and scheduling permissions (`tolerations`), where candidates mistakenly think tolerations restrict placement when they actually only allow scheduling on tainted nodes.
Detailed technical explanation
How to think about this question
Under the hood, `nodeSelector` is implemented as a `NodeSelectorTerm` in the `nodeAffinity` field of the Pod spec, using a `matchExpressions` with `In` operator. In real-world scenarios, you might combine `nodeSelector` with `nodeAffinity` for more complex scheduling rules, such as requiring a pod to run on nodes with specific hardware (e.g., GPU labels) while also preferring certain zones for high availability.
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 small business has 20 workstations on the 192.168.1.0/24 network and one public IP from its ISP. The router uses PAT (NAT overload) so all 20 devices share one public address using different source ports. NAT questions test whether you understand the four address terms and which direction each translation applies.
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: Use nodeSelector in pod spec — Option A is correct because `nodeSelector` is a simple field in the Pod spec that constrains which nodes a Pod can be scheduled on by matching against node labels. This is a native Kubernetes scheduling mechanism that directly restricts node placement based on key-value pairs defined on nodes.
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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