CKA Practice Question: Cluster Architecture, Installation and Configuration
You run 'kubectl get nodes' and see that one node is marked as 'NotReady'. Which component is likely failing on that node?
⚠ Common exam trap
Candidates often confuse the container runtime (e.g., containerd) as the direct cause of node unreadiness, but the kubelet is the component that reports the node condition, and a runtime failure would manifest as a kubelet-level error (e.g., 'runtime network not ready') rather than a missing heartbeat.
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
✓
kubelet
The kubelet is the primary node agent that runs on every node and is responsible for registering the node with the cluster and reporting its status via periodic heartbeats (NodeStatus updates). When a node is marked as 'NotReady', it means the kubelet has failed to send these heartbeats to the control plane (specifically, the node controller) within the --node-monitor-grace-period (default 40s), indicating the kubelet process is likely down, unresponsive, or misconfigured.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
kube-proxy
Why it's wrong here
The kube-proxy component is responsible for implementing Kubernetes Service abstraction on each node by maintaining network rules (e.g., iptables or IPVS). Its primary function is to enable network communication to pods via Services. If kube-proxy fails, network connectivity to Services might be disrupted, or load balancing may not function correctly for pods on that node, but the node itself would still be considered Ready by the control plane, as the kubelet would continue to report its health and resources.
- ✗
kube-scheduler
Why it's wrong here
The kube-scheduler is a crucial control plane component that watches for newly created Pods with no assigned node and selects a node for them to run on. It considers various factors like resource requirements, policies, and node affinity/anti-affinity during this process. A failure of the kube-scheduler would prevent new pods from being scheduled onto any node in the cluster, but it has no direct impact on the operational status or readiness of an existing node, as the kubelet on each node operates independently to report its status.
- ✓
kubelet
Why this is correct
The kubelet is the primary agent that runs on each worker node and is responsible for registering the node with the API server, ensuring that containers are running in a Pod, and continuously monitoring the node's health and resources. It reports this critical information back to the Kubernetes control plane. If the kubelet itself fails, stops communicating with the API server, or cannot perform its duties (e.g., due to resource exhaustion or internal errors), the control plane will mark that specific node as NotReady because it can no longer receive reliable status updates or manage pods on it.
- ✗
container runtime (e.g., containerd)
Why it's wrong here
While a container runtime failure can cause kubelet to report NotReady, the kubelet is the component that directly reports status; however, the question asks for the component likely failing, and kubelet is the direct cause. Container runtime failure would be a symptom reported by kubelet. But in practice, if kubelet cannot communicate with runtime, it may also mark node NotReady. However, the typical answer is kubelet. Given options, kubelet is the best choice.
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JA
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.