This CKA practice question tests your understanding of cluster architecture, installation & 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.
A DevOps engineer notices that the kubelet on a node is unable to register with the Kubernetes API server. The kubelet logs show 'Failed to get bootstrap CA certificate' and the node is not yet part of the cluster. 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.
The kubelet configuration file has incorrect node IP.
Why wrong: That would cause connection issues, not bootstrap CA failure.
The node's RBAC permissions are misconfigured.
Why wrong: RBAC is checked after the node is registered.
The API server is not running.
Why wrong: The API server is assumed running if the kubelet can connect.
The bootstrap token used for TLS bootstrapping has expired.
Expired token prevents CA certificate retrieval.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
The bootstrap token used for TLS bootstrapping has expired.
The bootstrap token used for TLS bootstrapping has expired. During the TLS bootstrap process, the kubelet uses a limited-time bootstrap token to authenticate with the API server and request a client certificate. If the token expires before the kubelet completes registration, the kubelet will fail to obtain the bootstrap CA certificate and cannot join the cluster, as indicated by the error 'Failed to get bootstrap CA certificate'.
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.
The kubelet configuration file has incorrect node IP.
Why it's wrong here
That would cause connection issues, not bootstrap CA failure.
The node's RBAC permissions are misconfigured.
Why it's wrong here
RBAC is checked after the node is registered.
The API server is not running.
Why it's wrong here
The API server is assumed running if the kubelet can connect.
The bootstrap token used for TLS bootstrapping has expired.
Why this is correct
Expired token prevents CA certificate retrieval.
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
CNCF often tests the distinction between authentication failures (expired token) and authorization failures (RBAC), leading candidates to incorrectly select RBAC misconfiguration when the actual issue is token expiry.
Detailed technical explanation
TLS bootstrapping uses a bootstrap token (typically a 6-character ID and 16-character secret) stored as a Secret in the kube-system namespace. The token has a limited lifetime defined by the 'expiration' field; after expiry, the kubelet cannot authenticate to the API server's certificate signing endpoint. The kubelet's bootstrap-kubeconfig file references this token, and the error occurs when the API server rejects the expired token during the initial CSR request.
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 & Configuration — This question tests Cluster Architecture, Installation & Configuration — Read the scenario before looking for a memorised answer..
The correct answer is: The bootstrap token used for TLS bootstrapping has expired. — The bootstrap token used for TLS bootstrapping has expired. During the TLS bootstrap process, the kubelet uses a limited-time bootstrap token to authenticate with the API server and request a client certificate. If the token expires before the kubelet completes registration, the kubelet will fail to obtain the bootstrap CA certificate and cannot join the cluster, as indicated by the error 'Failed to get bootstrap CA certificate'.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 30, 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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