CKA Practice Question: Cluster Architecture, Installation and Configuration
A Pod is stuck in Pending state. Running 'kubectl describe pod' shows '0/3 nodes are available: 1 node(s) had taint {node-role.kubernetes.io/control-plane: }, 2 node(s) had taint {node-role.kubernetes.io/master: }'. The Pod does not have tolerations. What is the most likely cause?
⚠ Common exam trap
Test-takers frequently confuse taints/tolerations with node selectors or resource constraints, but the error message explicitly lists taints as the reason, making it a direct match to the toleration requirement.
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 control-plane or master taints.
The Pod is stuck in Pending state because it does not have tolerations for the taints present on the nodes. The error message explicitly states that 1 node has the control-plane taint and 2 nodes have the master taint. By default, Pods without matching tolerations cannot be scheduled onto tainted nodes. Since all available nodes are tainted, the scheduler has no eligible node to place the Pod, leaving it in Pending.
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 scheduler is not running.
Why it's wrong here
If the kube-scheduler control plane component were completely inactive, the Pod would remain in a Pending state indefinitely without any scheduling decision events. The kubectl describe output would show no scheduling attempts or events at all, rather than specific scheduling failure events pointing to taints or toleration mismatches.
- ✗
The Pod requests more CPU than any node can provide.
Why it's wrong here
When a Pod cannot be scheduled due to insufficient CPU, the scheduler emits a specific FailedScheduling event indicating 'Insufficient cpu' on the candidate nodes. In this scenario, the scheduling failure event explicitly references taints and tolerations rather than resource exhaustion or capacity limits.
- ✗
The Pod has a node selector that doesn't match any node.
Why it's wrong here
If a Pod specifies a nodeSelector or nodeAffinity that cannot be satisfied by any active node, the scheduler reports a FailedScheduling event with a 'node(s) didn't match Pod affinity/selector' message. This is distinct from taint-related rejections, which are triggered by the node's taints repelling the Pod.
- ✓
The Pod does not have tolerations for the control-plane or master taints.
Why this is correct
Control-plane and master nodes are typically configured with taints like node-role.kubernetes.io/control-plane:NoSchedule to prevent user workloads from running on them. Because the Pod lacks the corresponding tolerations in its specification, the scheduler filters out these nodes, leaving the Pod in a Pending state with a taint-related scheduling failure event.
Go deeper
Related to this question
Learn chapter
Kubernetes Architecture Overview
Key term
kubectl Command Reference
kubectl is the command-line tool used to interact with and manage Kubernetes clusters by sending commands to the Kubernetes API.
Key term
Ingress Resources
Ingress Resources are Kubernetes API objects that manage external access to services inside a cluster, typically HTTP and HTTPS traffic, by defining rules for routing requests based on hostnames and paths.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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.