CKA Troubleshooting Practice Question
You have a Deployment with 3 replicas. After updating the container image, the new pods are in 'ImagePullBackOff' state. You run 'kubectl describe pod <pod-name>' and see the event: 'Failed to pull image "myregistry/myapp:latest": rpc error: code = Unknown desc = Error response from daemon: manifest for myregistry/myapp:latest not found: manifest unknown: manifest unknown'. What is the MOST likely cause?
⚠ Common exam trap
Kubernetes often tests the distinction between registry reachability errors and image existence errors, where candidates mistakenly assume network or authentication issues when the actual problem is a missing tag in the registry.
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 'latest' does not exist in the registry
The error message 'manifest unknown' indicates that the registry successfully reached but the specific image tag 'latest' does not exist in the repository. This is a registry-side error, not a network or authentication issue. The container runtime can communicate with the registry but cannot find the manifest for the requested 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 registry is unreachable from the nodes
Why it's wrong here
If the container runtime on the worker nodes could not establish a network connection to the container registry, the kubelet would report a connection timeout, DNS resolution failure, or connection refused error. Instead, receiving a "manifest not found" error confirms that a successful connection was established and the registry actively responded to the API request, but could not locate the requested image metadata.
- ✓
The image tag 'latest' does not exist in the registry
Why this is correct
The error "manifest not found" specifically indicates that the container registry was successfully contacted, but it does not contain a schema or manifest matching the requested repository and tag combination. This occurs when the deployment specifies an image tag, such as "latest", that was never pushed to the registry or has been deleted.
- ✗
The registry requires authentication and the pod does not have an imagePullSecret
Why it's wrong here
When a private registry requires authentication and the pod lacks a valid imagePullSecret, the registry rejects the request with an HTTP 401 Unauthorized or 403 Forbidden status. The resulting Kubernetes event would explicitly state "unauthorized: authentication required" or "pull access denied", rather than indicating that the manifest itself was missing.
- ✗
The container runtime is out of disk space
Why it's wrong here
Insufficient disk space on the worker node's container storage partition prevents the runtime from extracting or saving the image layers. This condition triggers a "no space left on device" error or disk pressure taints on the node, rather than an upstream registry error indicating that a specific image manifest does not exist.
Go deeper
Related to this question
Learn chapter
Network Policies and Secure Connectivity
Key term
Pod Failure Troubleshooting
Pod failure troubleshooting is the process of identifying and resolving issues that cause Kubernetes pods to crash, restart, or become unavailable.
Key term
kubectl Command Reference
kubectl is the command-line tool used to interact with and manage Kubernetes clusters by sending commands to the Kubernetes API.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This CKA 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 CKA exam.