Question 74 of 866
CKS Supply Chain Security Practice Question
An administrator runs 'kubectl run test-pod --image=nginx:latest' and the pod fails to start. The event log shows 'ImagePullBackOff' with error 'manifest for nginx:latest not found: manifest unknown'. The image 'nginx:latest' exists in the registry. What is the most likely cause?
⚠ Common exam trap
CNCF CKS often tests the distinction between registry authentication errors and manifest resolution errors, where candidates mistakenly assume that any 'ImagePullBackOff' with a registry-related error is due to missing credentials, but the specific 'manifest unknown' message points to a tag issue, not authentication.
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 image tag is misspelled or points to a non-existent tag
The error message 'manifest for nginx:latest not found: manifest unknown' indicates that the image tag 'latest' does not exist in the registry's manifest list, even though the image 'nginx:latest' exists. This typically occurs when the tag is misspelled or points to a non-existent tag, such as 'lates' instead of 'latest', or when the tag has been deleted from the registry. The 'ImagePullBackOff' error specifically arises from the container runtime failing to resolve the manifest for the given tag.
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 pod is running in a different namespace
Why it's wrong here
Namespace does not affect image pull errors.
- ✗
The registry requires authentication
Why it's wrong here
Authentication errors produce 'unauthorized' messages, not 'manifest unknown'.
- ✓
The image tag is misspelled or points to a non-existent tag
Why this is correct
'Manifest unknown' means the specific tag is not found. The user might have made a typo or the tag doesn't exist in the registry.
- ✗
The image is a multi-architecture image and the node does not support the required architecture
Why it's wrong here
Multi-architecture issues typically result in 'exec format error' or 'not found' for the manifest, not 'manifest unknown' for the tag.
Visual reference
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Last reviewed: Jul 4, 2026
This CKS 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 CKS exam.
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