CKA Troubleshooting Practice Question

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 nodes do not have enough resources to run the metrics collection

  Why it's wrong here

  The metrics-server is designed to be very lightweight and typically consumes only a few tens of millicores of CPU and a few MiB of memory per node. If nodes were critically under-resourced, you'd see pod scheduling failures, OOMKilled events, or the metrics-server failing to start with a resource-specific message, not a generic "error metric" when running kubectl top nodes. The absence or failure of metrics-server is the direct cause of that error, independent of node resource capacity.

• ✗

  You do not have permission to view node metrics

  Why it's wrong here

  RBAC would produce a distinct error: kubectl top nodes queries the metrics.k8s.io API. If the current user lacked permissions, the API server would return a 403 Forbidden response with a message like "nodes.metrics.k8s.io is forbidden: User ... cannot list resource". That is a very different error from "error metric", which indicates the API endpoint itself is unavailable or has no data. Permission errors are immediately identifiable and are not phrased as a metric collection failure.

• ✗

  The kubelet is not running on the nodes

  Why it's wrong here

  If kubelet were down, the node would be reported NotReady and would not appear in kubectl get nodes as Ready; metrics-server also ingests data from the kubelet's summary API, so a down kubelet would cause missing metrics for that node and likely a "unknown" status. The error "error: metrics not available yet" or "error metric" is typically returned when the metrics API has no registered data source — i.e., no metrics-server is serving the API — not because the source agent (kubelet) is down. Also, with kubelet down, kubectl top would fail to get node list or show all nodes not ready.

• ✓

  The metrics-server is not installed or not running

  Why this is correct

  kubectl top nodes relies on the metrics-server to collect resource usage from each kubelet and expose them through the metrics.k8s.io API. If metrics-server is not installed, the API endpoint returns 404 or no data, and kubectl top prints an error such as "error: metrics not available yet". If metrics-server is installed but not running (CrashLoopBackOff, pending), the same failure occurs because the API aggregator has no healthy backing service. Therefore, verifying the metrics-server deployment and its API service is the first step.

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