This KCNA practice question tests your understanding of container orchestration. 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 developer wants to ensure that a pod runs only on nodes with SSDs. Which mechanism should be used?
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 disktype: ssd
Option C is correct because `nodeSelector` is a simple and direct mechanism in Kubernetes to constrain a pod to run only on nodes that have a specific label, such as `disktype=ssd`. By labeling nodes with SSDs and adding the corresponding `nodeSelector` in the pod spec, the scheduler ensures the pod is placed exclusively on those nodes. This approach is straightforward and does not require complex scheduling constraints or resource management.
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.
✗
Apply a taint to nodes without SSDs and add tolerations to the pod
Why it's wrong here
Taints are used to repel pods; adding tolerations to all pods would not restrict to SSD nodes.
✗
Use pod anti-affinity
Why it's wrong here
Anti-affinity spreads pods across nodes, not based on node labels.
✓
Add a nodeSelector with disktype: ssd
Why this is correct
nodeSelector ensures pods are scheduled on nodes with the specified label.
Related concept
Read the scenario before looking for a memorised answer.
✗
Define a ResourceQuota
Why it's wrong here
ResourceQuota limits resource consumption, not node placement.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse taints/tolerations with node selection, thinking they can be used to force pods onto specific hardware, when in fact taints repel pods and tolerations allow exceptions, whereas `nodeSelector` or `nodeAffinity` are the correct tools for positive selection.
Detailed technical explanation
How to think about this question
Under the hood, `nodeSelector` matches against node labels set via `kubectl label node <node-name> disktype=ssd`; the kube-scheduler evaluates this constraint during pod scheduling by filtering nodes that lack the required label. A real-world scenario is when you have a mixed cluster with some nodes having local SSDs for high I/O workloads and others with HDDs for archival; using `nodeSelector` ensures pods for databases land on SSD nodes without needing custom schedulers or admission controllers.
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.
Container Orchestration — This question tests Container Orchestration — 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 disktype: ssd — Option C is correct because `nodeSelector` is a simple and direct mechanism in Kubernetes to constrain a pod to run only on nodes that have a specific label, such as `disktype=ssd`. By labeling nodes with SSDs and adding the corresponding `nodeSelector` in the pod spec, the scheduler ensures the pod is placed exclusively on those nodes. This approach is straightforward and does not require complex scheduling constraints or resource management.
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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