KCNA Kubernetes Fundamentals Practice Question
You have a Pod with a container that runs a web server. The Pod has a memory request of 256Mi and a memory limit of 512Mi. The container attempts to allocate 600Mi of memory. What happens?
⚠ Common exam trap
A common misconception is that memory limits are 'soft' or 'advisory' (like CPU limits), but in Kubernetes, memory limits are hard and enforced by the kernel's OOM killer, causing container termination when exceeded.
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 is killed by the OOM killer, and the Pod enters CrashLoopBackOff
When a container's memory usage exceeds its memory limit (512Mi), the Linux Out-Of-Memory (OOM) killer terminates the container process. Kubernetes then restarts the container based on the Pod's restart policy, but because the container immediately tries to allocate 600Mi again, it is repeatedly killed, resulting in a CrashLoopBackOff state. Memory limits are hard constraints enforced by the kernel via cgroups, not soft limits.
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 memory limit is automatically increased to 600Mi
Why it's wrong here
Limits are not auto-adjusted; they must be changed in the YAML.
- ✓
The container is killed by the OOM killer, and the Pod enters CrashLoopBackOff
Why this is correct
Exceeding the memory limit triggers OOM kill; the container restarts and may crash again.
- ✗
The Pod is evicted from the node
Why it's wrong here
Eviction happens when the node is under resource pressure, not directly due to a single container exceeding its limit.
- ✗
The container is allowed to use up to 600Mi because the limit is a soft constraint
Why it's wrong here
Limits are hard constraints; exceeding them causes termination.
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Same concept, more angles
1 more way this is tested on KCNA
These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. A developer deploys a pod that continuously restarts. 'kubectl describe pod' shows the container exits with code 137. What is the most likely cause?
medium- ✓ A.The container is exceeding its memory limit and being OOM-killed.
- B.The liveness probe is failing and restarting the container.
- C.The init container is failing and blocking the main container.
- D.The pod is hitting a resource quota limit at the namespace level.
Why A: Exit code 137 (128 + 9) indicates the container was killed by SIGKILL. In Kubernetes, this most commonly occurs when the container exceeds its memory limit, triggering the OOM (Out-Of-Memory) killer. The kubelet enforces the resource limits specified in the pod spec, and when memory usage surpasses the limit, the kernel terminates the process with SIGKILL, resulting in exit code 137.
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.