This KCNA practice question tests your understanding of container orchestration. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
A pod is running but its container exits with code 137. The pod logs show 'Killed'. What is the most likely cause?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "most likely"
Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The container was OOMKilled due to memory limit
Exit code 137 (128 + 9) indicates the container was terminated by SIGKILL. Combined with 'Killed' in logs, this is the definitive signature of an OOMKill event, where the Linux kernel's Out-Of-Memory (OOM) killer terminates the container process because it exceeded its memory limit (specified in the pod's resource limits). Kubernetes enforces memory limits via cgroups, and when the container's memory usage surpasses the limit, the OOM killer sends SIGKILL, resulting in exit code 137.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
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's CPU limit was exceeded
Why it's wrong here
CPU limits throttle, they do not kill the container.
✗
The container's liveness probe failed
Why it's wrong here
A failed liveness probe would cause a restart, but exit code would be 1 or similar, not 137.
✓
The container was OOMKilled due to memory limit
Why this is correct
Exit code 137 is SIGKILL, often from OOM. The pod status would show OOMKilled.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
The node ran out of disk space
Why it's wrong here
Disk pressure may evict pods, but exit code would be different.
Common exam traps
Common exam trap: answer the scenario, not the keyword
CNCF often tests the distinction between CPU throttling (which does not kill) and OOMKill (which does), and the trap here is that candidates confuse 'Killed' in logs with a generic failure, not recognizing exit code 137 as the specific OOMKill signal.
Trap categories for this question
Similar concept trap
A failed liveness probe would cause a restart, but exit code would be 1 or similar, not 137.
Detailed technical explanation
How to think about this question
Exit code 137 equals 128 + 9, where 9 is SIGKILL. The OOM killer is a kernel mechanism that selects and terminates processes to free memory when the system is under memory pressure. In Kubernetes, memory limits are enforced via cgroups' memory.max (or memory.limit_in_bytes in older kernels), and the OOM killer is triggered when the container's memory usage exceeds this limit. A real-world scenario: a Java application with a heap size larger than the pod's memory limit will be OOMKilled, even if the node has free memory, because the cgroup limit is hit first.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
TExam Day Tips
→Watch for words such as best, first, most likely and least administrative effort.
→Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A small business has 20 workstations on the 192.168.1.0/24 network and one public IP from its ISP. The router uses PAT (NAT overload) so all 20 devices share one public address using different source ports. NAT questions test whether you understand the four address terms and which direction each translation applies.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this KCNA question in full detail.
Container Orchestration — This question tests Container Orchestration — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The container was OOMKilled due to memory limit — Exit code 137 (128 + 9) indicates the container was terminated by SIGKILL. Combined with 'Killed' in logs, this is the definitive signature of an OOMKill event, where the Linux kernel's Out-Of-Memory (OOM) killer terminates the container process because it exceeded its memory limit (specified in the pod's resource limits). Kubernetes enforces memory limits via cgroups, and when the container's memory usage surpasses the limit, the OOM killer sends SIGKILL, resulting in exit code 137.
What should I do if I get this KCNA question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Question Discussion
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