KCNA Container Orchestration Practice Question
An administrator runs 'kubectl get pods' and sees that a pod named 'app-pod' is in 'CrashLoopBackOff'. They run 'kubectl logs app-pod' and see a segmentation fault error. What is the most likely cause?
⚠ Common exam trap
CNCF often tests the distinction between application-level errors (like segfaults) and infrastructure or configuration issues, tempting candidates to blame resource constraints or probe misconfiguration when the logs clearly point to a runtime crash.
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 code has a bug
A segmentation fault (segfault) is a specific error caused by a program attempting to access memory it does not have permission to access, typically due to a bug in the application code (e.g., null pointer dereference, buffer overflow). Since the container starts but then crashes repeatedly (CrashLoopBackOff), the segfault indicates the application itself is failing, not the infrastructure or configuration. This is the most direct cause of the pod entering CrashLoopBackOff.
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 node is out of memory
Why it's wrong here
Node memory exhaustion triggers eviction and a pod status of Evicted or OOMKilled, not CrashLoopBackOff with a segmentation fault logged by the container itself. Node capacity is the correct diagnosis when kubectl describe node shows MemoryPressure and pods are evicted rather than restarting.
- ✗
The container has a configuration error
Why it's wrong here
A configuration error typically yields a clear startup exception or exit code, not a segmentation fault, which is a memory-safety crash inside the process. Configuration fixes are the right answer when logs show missing environment variables or unreadable config files rather than a native crash.
- ✓
The application code has a bug
Why this is correct
A segmentation fault indicates the application process accessed invalid memory, which is a defect within the application code itself. CrashLoopBackOff results because Kubernetes repeatedly restarts the container after each crash, confirming the code bug as the cause.
- ✗
The readiness probe is misconfigured
Why it's wrong here
A misconfigured readiness probe removes the pod from Service endpoints but does not terminate the container, so it cannot produce CrashLoopBackOff or a segmentation fault in logs. Readiness probes are the correct mechanism when you need traffic withheld until an application is genuinely ready.
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JA
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.