This CKA practice question tests your understanding of cluster architecture, installation and configuration. 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.
Which kubectl command is used to mark a node as unschedulable for new pods without affecting existing running pods?
kubectl cordon <node-name>
Cordon marks the node as unschedulable.
kubectl uncordon <node-name>
Why wrong: Uncordon makes a node schedulable again.
kubectl drain <node-name>
Why wrong: Drain evicts pods and marks the node unschedulable, affecting existing pods.
kubectl taint nodes <node-name> key=value:NoSchedule
Why wrong: Taints affect scheduling but do not prevent new pods that tolerate the taint; cordon is more direct.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
kubectl cordon <node-name>
The `kubectl cordon` command marks a node as unschedulable by setting the `node.Spec.Unschedulable` field to `true`. This prevents the Kubernetes scheduler from placing new pods onto the node, while existing pods continue to run unaffected. It is the correct tool for this specific maintenance task.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
kubectl cordon <node-name>
Why this is correct
Cordon marks the node as unschedulable.
Related concept
Read the scenario before looking for a memorised answer.
kubectl uncordon <node-name>
Why it's wrong here
Uncordon makes a node schedulable again.
kubectl drain <node-name>
Why it's wrong here
Drain evicts pods and marks the node unschedulable, affecting existing pods.
kubectl taint nodes <node-name> key=value:NoSchedule
Why it's wrong here
Taints affect scheduling but do not prevent new pods that tolerate the taint; cordon is more direct.
Common exam traps
The trap here is that candidates confuse `kubectl drain` (which evicts pods and then cordons) with `kubectl cordon` (which only prevents new scheduling), leading them to select drain when the question explicitly states 'without affecting existing running pods'.
Detailed technical explanation
Under the hood, `kubectl cordon` patches the node object to set `spec.unschedulable: true`, which the scheduler checks via the node's `Node.Spec.Unschedulable` field during pod scheduling. A real-world scenario is performing node OS updates: you cordon the node first to stop new workloads, then drain it to evict existing pods, update the node, uncordon it to resume scheduling. The `kubectl taint` approach with `NoSchedule` is more granular, as it allows selective scheduling based on tolerations, but does not achieve a blanket unschedulable state.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
A practitioner preparing for the CKA 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
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FAQ
Cluster Architecture, Installation and Configuration — This question tests Cluster Architecture, Installation and Configuration — Read the scenario before looking for a memorised answer..
The correct answer is: kubectl cordon <node-name> — The `kubectl cordon` command marks a node as unschedulable by setting the `node.Spec.Unschedulable` field to `true`. This prevents the Kubernetes scheduler from placing new pods onto the node, while existing pods continue to run unaffected. It is the correct tool for this specific maintenance task.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 24, 2026
This CKA 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 CKA exam.
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