This CKS practice question tests your understanding of cluster setup. 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.
During a cluster upgrade, the kubelet on a worker node fails to start after updating the kubelet binary. The kubelet logs show: 'failed to load bootstrap client certificate: open /var/lib/kubelet/pki/kubelet-client-current.pem: no such file or directory'. 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.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The bootstrap kubeconfig file is missing or misconfigured
The error 'failed to load bootstrap client certificate: open /var/lib/kubelet/pki/kubelet-client-current.pem: no such file or directory' indicates that the kubelet cannot find the bootstrap client certificate file. This file is generated from the bootstrap kubeconfig file during the initial TLS bootstrapping process. If the bootstrap kubeconfig file is missing or misconfigured, the kubelet cannot request or renew its client certificate, leading to this failure.
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 kubelet's node IP has changed
Why it's wrong here
This would cause certificate mismatch, not missing file.
✗
The kubelet's certificate has expired
Why it's wrong here
Expired cert would show 'certificate has expired' error, not missing file.
✗
The kubelet is using an outdated kubeconfig
Why it's wrong here
An outdated kubeconfig would cause authentication failure, not missing file.
✓
The bootstrap kubeconfig file is missing or misconfigured
Why this is correct
The bootstrap kubeconfig is used to initially request a client certificate; missing file leads to this error.
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
CNCF often tests the distinction between bootstrap kubeconfig errors and certificate expiry errors; the trap here is that candidates confuse a missing file (bootstrap configuration issue) with a certificate expiry or authentication problem, leading them to choose options B or C.
Trap categories for this question
Command / output trap
Expired cert would show 'certificate has expired' error, not missing file.
Detailed technical explanation
How to think about this question
Kubernetes TLS bootstrapping uses a bootstrap kubeconfig (typically at /etc/kubernetes/bootstrap-kubelet.conf) containing a token or certificate to authenticate to the API server and request a signed client certificate. The kubelet then saves the issued certificate to /var/lib/kubelet/pki/kubelet-client-current.pem. If the bootstrap kubeconfig is missing or misconfigured (e.g., wrong server URL, invalid token), the kubelet cannot initiate the CSR process, and the certificate file is never created. This is a common issue during upgrades when the bootstrap configuration is not properly preserved or updated.
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.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this CKS question in full detail.
Cluster Setup — This question tests Cluster Setup — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The bootstrap kubeconfig file is missing or misconfigured — The error 'failed to load bootstrap client certificate: open /var/lib/kubelet/pki/kubelet-client-current.pem: no such file or directory' indicates that the kubelet cannot find the bootstrap client certificate file. This file is generated from the bootstrap kubeconfig file during the initial TLS bootstrapping process. If the bootstrap kubeconfig file is missing or misconfigured, the kubelet cannot request or renew its client certificate, leading to this failure.
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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Question Discussion
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