KCNA Container Orchestration Practice Question
A Kubernetes cluster has a Deployment running three replicas of an application. You need to update the container image to a new version with zero downtime. Which approach is most appropriate?
⚠ Common exam trap
CNCF often tests the misconception that manually deleting pods or scaling to zero is a valid zero-downtime strategy, but these actions cause service disruption because they do not maintain the desired number of available replicas during the update.
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 'kubectl set image deployment/<name> <container>=<new-image>' to trigger a rolling update
`kubectl set image deployment/<name> <container>=<new-image>` triggers a rolling update, which is the default update strategy for Deployments. This gradually replaces old pods with new ones, ensuring that the desired number of replicas is always available, thus achieving zero downtime.
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 'kubectl set image deployment/<name> <container>=<new-image>' to trigger a rolling update
Why this is correct
Setting the image on the Deployment triggers a rolling update, which incrementally replaces pods while respecting readiness probes and maxUnavailable, so traffic continues throughout. This satisfies the zero-downtime constraint, unlike recreating pods or editing a ReplicaSet directly.
- ✗
Manually delete each pod and rely on the ReplicaSet to recreate them with the new image
Why it's wrong here
Deleting pods manually leaves the ReplicaSet recreating them from the existing pod template, which still references the old image, so no update occurs. It is tempting because ReplicaSets do self-heal pod counts, and would be correct for recovering failed pods, not for rolling out a new image version.
- ✗
Delete the Deployment and recreate it with the new image
Why it's wrong here
Deleting the Deployment terminates all three replicas simultaneously, causing an outage until the new Deployment schedules pods, so zero downtime fails. It is tempting because it guarantees a clean state with the new image, and would be correct for a non-production environment where brief unavailability is acceptable.
- ✗
Scale the Deployment to zero and then scale back up with the new image
Why it's wrong here
Scaling to zero stops every replica before the new image starts, producing a full outage rather than the required zero downtime. It is tempting because it avoids mixed-version traffic and guarantees all pods run the new image, and would be correct for a maintenance window where the service may be taken offline.
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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.