CKA Troubleshooting Practice Question
After deploying a new Deployment, you notice that the pods are stuck in ImagePullBackOff. What is the most common cause?
⚠ Common exam trap
A common mix-up: candidates confuse ImagePullBackOff with CrashLoopBackOff, but ImagePullBackOff specifically relates to image retrieval failures, not container runtime errors.
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 container image name or tag is incorrect
The ImagePullBackOff status indicates that the kubelet is unable to pull the container image from the registry. The most common cause is an incorrect image name or tag, which results in a manifest not found error. This triggers an exponential backoff retry loop, leading to the ImagePullBackOff state.
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 liveness probe is misconfigured
Why it's wrong here
A misconfigured liveness probe will cause Kubernetes to repeatedly restart a container after it has successfully started, eventually leading to a `CrashLoopBackOff` status. It does not prevent the container runtime from pulling the image, which is a prerequisite phase before any probes are executed.
- ✗
The node has insufficient resources
Why it's wrong here
When a node lacks sufficient CPU or memory to host a pod, the scheduler cannot assign the pod to that node, leaving the pod in a `Pending` state with a `FailedScheduling` event. This resource constraint occurs during the scheduling phase, long before the kubelet attempts to pull any container images.
- ✓
The container image name or tag is incorrect
Why this is correct
Providing an invalid image name or an unavailable tag causes the container registry to return a 404 error to the kubelet. Consequently, the pod transitions into `ErrImagePull` and then `ImagePullBackOff` because the container runtime cannot locate or download the specified image layers.
- ✗
The container command fails on startup
Why it's wrong here
If the container's entrypoint command or arguments fail during startup, the container process exits with a non-zero exit code. The kubelet detects this failure and transitions the pod into a `CrashLoopBackOff` state, which indicates the image was successfully pulled and executed but failed during runtime.
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JA
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.