KCNA Kubernetes Fundamentals Practice Question
A developer deploys a pod with the following resource specification: ```yaml resources: requests: memory: "256Mi" limits: memory: "512Mi" ``` The pod is killed with OOMKilled. What is the most likely cause?
⚠ Common exam trap
CNCF often tests the distinction between requests and limits, trapping candidates who think exceeding a request causes termination, when in fact only exceeding the limit triggers OOMKilled.
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 exceeded the memory limit of 512Mi
The OOMKilled exit code indicates the container was terminated by the Linux kernel's Out-Of-Memory (OOM) killer because it attempted to use more memory than its configured limit of 512Mi. Kubernetes enforces memory limits using cgroups; when the container exceeds the limit, the kernel kills the process, resulting in the OOMKilled status.
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 container exceeded the memory request of 256Mi
Why it's wrong here
The request is a scheduling reservation, not an enforcement ceiling; the kubelet kills the container only when it exceeds the 512Mi limit. It is tempting because requests do influence eviction ordering under node pressure, and that mechanism would be the correct explanation for a pod evicted from a constrained node.
- ✗
The node ran out of memory
Why it's wrong here
A container exceeding its own memory limit is killed by the kubelet on that node, so the limit of 512Mi is the trigger, not node-wide exhaustion. Node memory pressure would evict pods and taint the node, affecting many workloads. Node capacity checks matter when sizing requests against allocatable resources.
- ✗
The CPU limit was too low
Why it's wrong here
OOMKilled is triggered by memory exhaustion, not CPU; an insufficient CPU limit causes throttling, leaving the process slow but alive. It is tempting because CPU and memory limits are configured together, and a low CPU limit would be the correct diagnosis for latency or throttling symptoms rather than termination.
- ✓
The container exceeded the memory limit of 512Mi
Why this is correct
The kernel OOM killer terminates a container when its memory usage breaches the configured limit of 512Mi. Requests of 256Mi only influence scheduling, not termination. Exceeding the limit is therefore the cause of the OOMKilled status described in the stem.
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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.