Question 323 of 997
Pod Pending Due to Taints — Diagnosing Node Taints and Tolerations
This KCNA practice question tests your understanding of kubernetes fundamentals. 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 stuck in Pending state. You run 'kubectl describe pod' and see the event '0/3 nodes are available: 1 node(s) had taint(s) that the pod didn't tolerate, 2 node(s) had insufficient memory.'. 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 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 pod does not have tolerations for the node's taints and memory is insufficient on other nodes
The event '0/3 nodes are available: 1 node(s) had taint(s) that the pod didn't tolerate, 2 node(s) had insufficient memory' directly indicates that the pod failed scheduling because it lacks required tolerations for a tainted node, and the remaining nodes do not have enough memory to satisfy the pod's resource requests. This matches option A, as the pod's tolerations are missing for the tainted node, and memory is insufficient on the other two nodes.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The CNCF exam often tests the distinction between scheduling failures (like taints and resource insufficiency) and runtime failures (like missing container runtime or scheduler), tricking candidates into picking a generic cause like 'kube-scheduler not running' when the detailed event clearly shows the scheduler is working.
Detailed technical explanation
How to think about this question
The Kubernetes scheduler uses predicates like 'PodToleratesNodeTaints' and 'CheckNodeMemoryPressure' to filter nodes; if a node has a taint (e.g., 'node.kubernetes.io/unschedulable') and the pod lacks a matching toleration, that node is immediately excluded. The remaining nodes are then checked for sufficient allocatable memory based on the pod's resource requests, and if all fail, the pod stays Pending. In real-world scenarios, this often happens when a cluster has a dedicated node for critical workloads (tainted) and other nodes are under-provisioned.
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 practitioner preparing for the KCNA exam encounters this exact type of scenario on the job. The correct answer here is not the most general option — it is the best answer for the specific constraint described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Real exam questions reward reading the full scenario before eliminating options, because the constraint defines which answer fits.
What to study next
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
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FAQ
Questions learners often ask
What does this KCNA question test?
Kubernetes Fundamentals — This question tests Kubernetes Fundamentals — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The pod does not have tolerations for the node's taints and memory is insufficient on other nodes — The event '0/3 nodes are available: 1 node(s) had taint(s) that the pod didn't tolerate, 2 node(s) had insufficient memory' directly indicates that the pod failed scheduling because it lacks required tolerations for a tainted node, and the remaining nodes do not have enough memory to satisfy the pod's resource requests. This matches option A, as the pod's tolerations are missing for the tainted node, and memory is insufficient on the other two nodes.
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.
About these practice questions
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
Same concept, more angles
1 more ways 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 pod is stuck in 'Pending' state. 'kubectl describe pod' shows '0/4 nodes are available: 4 node(s) had taint {node.kubernetes.io/unreachable: }, that the pod didn't tolerate.' What is the most likely cause?
easy- A.All nodes have disk pressure.
- ✓ B.All nodes are unreachable or have been cordoned.
- C.The pod has a toleration that matches the taint.
- D.The nodes do not have enough CPU or memory.
Why B: The taint `node.kubernetes.io/unreachable` is automatically added by the node controller when a node becomes unreachable (e.g., network failure, kubelet stops heartbeating). The error shows all 4 nodes have this taint and the pod has no matching toleration, meaning the scheduler cannot place the pod. This directly indicates all nodes are unreachable or have been cordoned (which also adds the `node.kubernetes.io/unschedulable` taint, but here the specific taint is `unreachable`).
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Last reviewed: Jul 4, 2026
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.
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