Question 791 of 997

Monitoring, Logging and Runtime Security →hardMultiple ChoiceObjective-mapped

DaemonSet Stuck in Pending State Due to Node Taints

This CKS practice question tests your understanding of monitoring, logging and runtime security. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. 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.

You have deployed a DaemonSet to run a logging agent on every node. After an update, the new pods are stuck in 'Pending' state. You run 'kubectl describe pod ds-pod-xxxxx' and see '0/3 nodes are available: 3 node(s) had taint {node-role.kubernetes.io/master: }, that the pod didn't tolerate'. 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.

A
The DaemonSet has a nodeSelector that doesn't match any nodes
Why wrong: The message mentions taints, not nodeSelector.
B
The DaemonSet uses hostNetwork which conflicts with existing pods
Why wrong: The error message clearly states taint issue.
C
The DaemonSet does not have tolerations for the node taints
The taint prevents scheduling unless the pod has a matching toleration.
D
The nodes are cordoned
Why wrong: Cordoning would show a different message, e.g., 'node(s) cordoned'.

Full breakdown with real-world context →

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 DaemonSet does not have tolerations for the node taints

The error message indicates that the pod cannot be scheduled because all three nodes have a taint (specifically `node-role.kubernetes.io/master`), and the DaemonSet's pod template does not include a corresponding toleration. By default, control-plane nodes are tainted to prevent general workloads from running on them, so a DaemonSet intended to run on all nodes must include tolerations for these taints. Without tolerations, the scheduler will not place the pod on tainted nodes, leaving it in Pending state.

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 DaemonSet has a nodeSelector that doesn't match any nodes
Why it's wrong here
The message mentions taints, not nodeSelector.
✗
The DaemonSet uses hostNetwork which conflicts with existing pods
Why it's wrong here
The error message clearly states taint issue.
✓
The DaemonSet does not have tolerations for the node taints
Why this is correct
The taint prevents scheduling unless the pod has a matching toleration.
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 nodes are cordoned
Why it's wrong here
Cordoning would show a different message, e.g., 'node(s) cordoned'.

Common exam traps

Common exam trap: answer the scenario, not the keyword

The trap here is that candidates often assume DaemonSets automatically run on all nodes regardless of taints, but in reality, DaemonSets respect taints and tolerations just like any other workload, and failing to add tolerations for control-plane taints is a common misconfiguration.

Trap categories for this question

Command / output trap
Cordoning would show a different message, e.g., 'node(s) cordoned'.

Detailed technical explanation

How to think about this question

Taints and tolerations work as a scheduling constraint: a taint on a node repels pods that do not explicitly tolerate it. The `node-role.kubernetes.io/master` taint is commonly applied to control-plane nodes to isolate system workloads. DaemonSets, by default, do not include tolerations, so they must be added manually in the pod spec (e.g., `tolerations: - key: node-role.kubernetes.io/master effect: NoSchedule`). In Kubernetes 1.24+, the taint may also include `node-role.kubernetes.io/control-plane`, requiring tolerations for both.

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 CKS 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 CKS question test?

Monitoring, Logging and Runtime Security — This question tests Monitoring, Logging and Runtime Security — Read the scenario before looking for a memorised answer..

What is the correct answer to this question?

The correct answer is: The DaemonSet does not have tolerations for the node taints — The error message indicates that the pod cannot be scheduled because all three nodes have a taint (specifically `node-role.kubernetes.io/master`), and the DaemonSet's pod template does not include a corresponding toleration. By default, control-plane nodes are tainted to prevent general workloads from running on them, so a DaemonSet intended to run on all nodes must include tolerations for these taints. Without tolerations, the scheduler will not place the pod on tainted nodes, leaving it in Pending state.

What should I do if I get this CKS 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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