This KCNA practice question tests your understanding of kubernetes fundamentals. 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.
A cluster administrator wants to ensure that a specific pod only runs on nodes that have an SSD for local storage. The nodes with SSDs have the label 'disk-type: ssd'. How should the administrator configure the pod to enforce this constraint?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Add a nodeSelector with 'disk-type: ssd' to the pod spec
Option B is correct because the `nodeSelector` field in a Pod spec is the standard Kubernetes mechanism for constraining a Pod to run only on nodes that match specific labels. By setting `nodeSelector: { disk-type: ssd }`, the scheduler will ensure the Pod is placed exclusively on nodes with that label, enforcing the administrator's requirement.
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.
✗
Add a toleration for node.kubernetes.io/disk-type: ssd
Why it's wrong here
Tolerations are used to allow pods to schedule on tainted nodes, not to select nodes by label.
✓
Add a nodeSelector with 'disk-type: ssd' to the pod spec
Why this is correct
nodeSelector is the simplest way to constrain a pod to nodes with specific labels.
Related concept
Read the scenario before looking for a memorised answer.
✗
Use a readiness probe to check for SSD
Why it's wrong here
Readiness probes check container health, not node hardware.
✗
Add an annotation 'disk-type: ssd' to the pod
Why it's wrong here
Annotations are metadata; they do not influence scheduling.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates confuse tolerations (for taints) with node selectors (for labels), or think annotations or probes can influence scheduling, when only `nodeSelector` or node affinity directly control node placement based on labels.
Detailed technical explanation
How to think about this question
Under the hood, the Kubernetes scheduler evaluates `nodeSelector` as a hard constraint during the filtering phase, matching the Pod's label selector against node labels. This is distinct from node affinity, which offers more expressive operators (e.g., `In`, `NotIn`) and can be required or preferred. In real-world scenarios, `nodeSelector` is ideal for simple, static placement rules, while node affinity is better for complex scheduling policies like preferring SSDs but falling back to HDDs.
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 practitioner preparing for the KCNA exam encounters this exact type of scenario on the job. The correct answer here is not the most general option — it is the best answer for the specific constraint described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Real exam questions reward reading the full scenario before eliminating options, because the constraint defines which answer fits.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this KCNA question in full detail.
Kubernetes Fundamentals — This question tests Kubernetes Fundamentals — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Add a nodeSelector with 'disk-type: ssd' to the pod spec — Option B is correct because the `nodeSelector` field in a Pod spec is the standard Kubernetes mechanism for constraining a Pod to run only on nodes that match specific labels. By setting `nodeSelector: { disk-type: ssd }`, the scheduler will ensure the Pod is placed exclusively on nodes with that label, enforcing the administrator's requirement.
What should I do if I get this KCNA 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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