KCNA Kubernetes Fundamentals Practice Question
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?
⚠ Common exam trap
Many exam-takers 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.
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
✓
Add a nodeSelector with 'disk-type: ssd' to the pod spec
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.
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.
- ✗
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.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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