KCNA Kubernetes Fundamentals Practice Question
You deploy a new version of your application by updating the container image in the Deployment manifest. The rollout seems to be progressing, but after a few minutes you notice that the new Pods are failing and the old Pods are still running. What is the most likely reason?
⚠ Common exam trap
The CNCF Kubernetes exam often tests the distinction between liveness and readiness probes; candidates mistakenly think a failing liveness probe causes the same behavior, but only readiness probe failures pause a rollout while liveness failures restart the Pod without affecting the rollout progress.
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
✓
The new Pods are failing readiness probes, so the Deployment pauses the rollout and keeps the old replicas
When a new Pod fails its readiness probe, the Deployment controller considers the new ReplicaSet unhealthy and pauses the rollout. The controller keeps the old ReplicaSet running to maintain the desired number of available replicas, preventing traffic disruption until the new Pods pass their probes or the rollout is manually resumed.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
The Deployment was created with 'kubectl create deployment' instead of 'kubectl apply'
Why it's wrong here
Both commands can create deployments; the issue is not about the command used.
- ✓
The new Pods are failing readiness probes, so the Deployment pauses the rollout and keeps the old replicas
Why this is correct
If readiness probes fail, the new Pods are not considered ready, and the Deployment controller will not continue the rollout, preserving the old replicas.
- ✗
The new Pods are not receiving traffic because the Service selector doesn't match
Why it's wrong here
A Service selector mismatch would affect traffic routing, but the rollout itself would not fail; the new Pods would still be created.
- ✗
The Deployment's update strategy is set to 'Recreate'
Why it's wrong here
A Recreate strategy would delete all old Pods before creating new ones, so old Pods would not remain running.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This KCNA practice question is part of Courseiva's free CNCF certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the KCNA exam.