KCNA Kubernetes Fundamentals Practice Question
A Deployment named 'nginx' is failing to update. You run 'kubectl rollout status deployment nginx' and see 'Waiting for deployment "nginx" rollout to finish: 0 out of 3 new replicas have been updated...'. The pod template has an image that does not exist. What is the most likely cause?
⚠ Common exam trap
Watch out — candidates often confuse a stuck rollout with resource constraints (memory/CPU) or assume the deployment is paused, but the specific status message '0 out of 3 new replicas have been updated' directly points to an image pull failure, not a scheduling or pause issue.
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 image tag is incorrect or does not exist in the registry
The rollout status shows that no new replicas have been created, which is a classic symptom of a container image pull failure. When the image tag specified in the pod template does not exist in the registry, the kubelet cannot pull the image, so the ReplicaSet controller cannot start new pods. This prevents the rollout from progressing past 0 out of 3 new replicas.
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 cluster is out of memory
Why it's wrong here
Out of memory would cause OOMKilled, not ImagePullBackOff.
- ✗
The deployment has exceeded the revision history limit
Why it's wrong here
Revision history limit does not affect rollout progress.
- ✗
The deployment is paused
Why it's wrong here
A paused deployment would show 'rollout paused' in status, not waiting for replicas.
- ✓
The new image tag is incorrect or does not exist in the registry
Why this is correct
Non-existent image leads to ImagePullBackOff, preventing new replicas from becoming ready.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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