The answer is the kubelet. After running kubeadm init, if the control-plane node shows a NotReady status, the kubelet is almost certainly the component that is not functioning correctly, as it is the primary node agent responsible for registering the node with the cluster and managing pod lifecycle. Without a healthy kubelet, the control plane cannot report its readiness or run essential static pods. On the CKA exam, this scenario tests your understanding of node bootstrapping and the dependency chain: kubeadm initializes the control plane, but the kubelet must be running and properly configured to connect to the container runtime—often containerd or CRI-O—and to apply a CNI network plugin. A common trap is assuming the issue is with the API server or etcd, but the kubelet’s logs (via journalctl -u kubelet) will reveal the real problem, such as a missing container runtime socket or a paused cgroup driver. Memory tip: “Kubelet is the node’s heartbeat—if it’s silent, the node stays NotReady.”
CKA Practice Question: Cluster Architecture, Installation and Configuration
This CKA practice question tests your understanding of cluster architecture, installation and configuration. 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 are using kubeadm to initialize a Kubernetes cluster. After running 'kubeadm init', the control-plane node is not ready. You run 'kubectl get nodes' and see the node status as 'NotReady'. Which component is most likely not functioning correctly?
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 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 maintaining pod lifecycle. After 'kubeadm init', if the control-plane node shows 'NotReady', it almost always indicates that the kubelet is not running or is failing to communicate with the control plane, often due to missing or misconfigured container runtime (e.g., containerd, CRI-O) or network plugin (CNI).
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.
✗
kube-scheduler
Why it's wrong here
The scheduler assigns pods to nodes; it does not affect node readiness.
✗
etcd
Why it's wrong here
etcd is the key-value store; its failure would cause cluster instability but not directly cause a node to be NotReady.
✗
kube-apiserver
Why it's wrong here
The API server is the front-end of the control plane; its failure would cause kubectl to fail, but node status is reported by the kubelet.
✓
kubelet
Why this is correct
The kubelet is responsible for node status. If it is not running or cannot communicate with the API server, the node will be NotReady.
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.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse control-plane component failures (like scheduler or API server) with node-level agent failures, but the 'NotReady' status is specifically a kubelet-driven condition, not a control-plane component status.
Detailed technical explanation
How to think about this question
The kubelet uses the NodeStatus update mechanism, posting a heartbeat via the API server every --node-status-update-frequency (default 10s). If the kubelet cannot reach the container runtime (e.g., due to a misconfigured cri.socket path in /var/lib/kubelet/kubeadm-flags.env), it will report the node as NotReady. A common real-world scenario is forgetting to install a CNI plugin like Calico or Flannel, which causes the kubelet to fail the NodeReady condition because the container runtime cannot start essential pods like CoreDNS.
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 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.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this CKA question in full detail.
Cluster Architecture, Installation and Configuration — This question tests Cluster Architecture, Installation and Configuration — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: kubelet — The kubelet is the primary node agent that runs on every node and is responsible for registering the node with the cluster and maintaining pod lifecycle. After 'kubeadm init', if the control-plane node shows 'NotReady', it almost always indicates that the kubelet is not running or is failing to communicate with the control plane, often due to missing or misconfigured container runtime (e.g., containerd, CRI-O) or network plugin (CNI).
What should I do if I get this CKA 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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