KCNA Kubernetes Fundamentals Practice Question
You need to ensure that a pod runs on a node with SSD storage. How can you achieve this?
⚠ Common exam trap
Kubernetes often tests the distinction between node affinity (which attracts pods to nodes with specific labels) and taints/tolerations (which repel pods from nodes), leading candidates to incorrectly choose taints/tolerations when the goal is to ensure a pod runs on a node with a specific feature.
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
✓
Use node affinity with requiredDuringSchedulingIgnoredDuringExecution
Node affinity with `requiredDuringSchedulingIgnoredDuringExecution` is the correct approach because it allows you to specify a hard constraint that the pod must be scheduled on a node with a specific label (e.g., `disk=ssd`). This ensures the pod runs only on nodes that have SSD storage, as the scheduler enforces this rule during pod placement.
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 with a label that matches nodes having SSDs
Why it's wrong here
While `nodeSelector` is a valid Kubernetes mechanism for influencing pod placement, it fails here because it relies on pre-existing node labels. The question implies a need to *ensure* a pod runs on a node with SSD storage, which `nodeSelector` cannot actively guarantee if no node is labelled as such. It is tempting because `nodeSelector` is the standard way to direct pods to nodes with specific characteristics, and would be correct if the nodes were already appropriately labelled with an `ssd: "true"` or similar annotation.
- ✗
Use a taint on nodes without SSDs and a toleration on the pod
Why it's wrong here
Taints and tolerations are used to repel pods from nodes, not to attract them to specific nodes.
- ✗
Use pod anti-affinity to avoid nodes without SSDs
Why it's wrong here
Pod anti-affinity is used to spread pods across nodes, not to select nodes based on hardware.
- ✓
Use node affinity with requiredDuringSchedulingIgnoredDuringExecution
Why this is correct
Node affinity allows you to specify hard or soft constraints. Using requiredDuringSchedulingIgnoredDuringExecution ensures the pod is only scheduled on nodes with the specified label.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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