KCNA Kubernetes Fundamentals Practice Question
Network Topology
Refer to the exhibit. A pod 'my-pod' shows repeated 'BackOff' events after the container starts. Which is the most likely cause?
⚠ Common exam trap
The KCNA exam often tests the distinction between 'ImagePullBackOff' (image not found) and 'CrashLoopBackOff' (container crashes after start), so candidates must recognize that 'BackOff' events after the container starts point to a runtime crash, not a pull failure.
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 application crashes shortly after starting.
The 'BackOff' event in Kubernetes indicates that the container has started but repeatedly crashes, causing the kubelet to increase the restart delay. Option D is correct because an application that crashes shortly after starting will trigger this restart loop, as the container exits with a non-zero exit code, leading to exponential backoff.
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 image 'myapp:v2' does not exist.
Why it's wrong here
A missing image tag yields ErrImagePull/ImagePullBackOff before any container starts, which matches the exhibit's pull-stage backoff rather than a running container. It is tempting because image errors are the classic BackOff cause, but the stem states the container starts, so the failure occurs after startup.
- ✗
The container exceeds its memory limit.
Why it's wrong here
Exceeding the memory limit triggers OOMKilled and exit code 137, restarting a container that had started, not the pull-stage backoff shown. It is tempting because memory exhaustion is a common restart cause, but the exhibit's events point to image retrieval failing before the container ever runs.
- ✗
The liveness probe is failing.
Why it's wrong here
A failing liveness probe restarts a running container, producing 'Unhealthy' and restart counts, not 'BackOff' on image pulls. It is tempting because probe failures do cause CrashLoopBackOff, but that requires the container to have started successfully first; the exhibit shows pull-stage backoff.
- ✓
The application crashes shortly after starting.
Why this is correct
BackOff means the kubelet is delaying a restart after a container exit, with the delay growing exponentially. Repeated events after startup indicate the process terminates on its own, typically from a crash or failed health check, rather than an image pull or scheduling failure.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This KCNA 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 KCNA exam.