- A
The pod is running in a different namespace
Why wrong: Namespace does not affect image pull errors.
- B
The registry requires authentication
Why wrong: Authentication errors produce 'unauthorized' messages, not 'manifest unknown'.
- C
The image tag is misspelled or points to a non-existent tag
'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.
- D
The image is a multi-architecture image and the node does not support the required architecture
Why wrong: Multi-architecture issues typically result in 'exec format error' or 'not found' for the manifest, not 'manifest unknown' for the tag.
Question 74 of 997
ImagePullBackOff — Manifest Not Found: Tag Misspelled
This CKS practice question tests your understanding of supply chain security. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
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?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue:
"most likely"Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
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
Option C is correct because 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.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
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.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
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.
Common exam traps
Common exam trap: answer the scenario, not the keyword
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.
Detailed technical explanation
How to think about this question
The 'manifest unknown' error is returned by the registry API (e.g., Docker Registry HTTP API v2) when the tag does not exist in the repository's manifest list. Even if the image name is correct, a typo in the tag (e.g., 'latests') or a deleted tag causes the registry to respond with a 404 status code for the manifest endpoint. In Kubernetes, the kubelet's image pull logic uses the container runtime (e.g., containerd or CRI-O) to fetch the manifest; if the manifest is missing, the runtime retries with exponential backoff, leading to 'ImagePullBackOff'.
KKey Concepts to Remember
- Read the scenario before looking for a memorised answer.
- Find the constraint that changes the correct option.
- Eliminate answers that are true in general but not in this case.
TExam Day Tips
- Watch for words such as best, first, most likely and least administrative effort.
- Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A practitioner preparing for the CKS exam encounters this exact type of scenario on the job. The correct answer here is not the most general option — it is the best answer for the specific constraint described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Real exam questions reward reading the full scenario before eliminating options, because the constraint defines which answer fits.
Visual reference
What to study next
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
- →
Supply Chain Security — study guide chapter
Learn the concepts, then practise the questions
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FAQ
Questions learners often ask
What does this CKS question test?
Supply Chain Security — This question tests Supply Chain Security — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The image tag is misspelled or points to a non-existent tag — Option C is correct because 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.
What should I do if I get this CKS question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
About these practice questions
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
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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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