KCNA Kubernetes Fundamentals Practice Question
Which control plane component is responsible for persisting the entire cluster state?
⚠ Common exam trap
A common trap is to think the kube-apiserver persists state because it is the central API gateway, but in reality, the API server is stateless and relies entirely on etcd for durable storage.
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
✓
etcd
etcd is the distributed key-value store that serves as the single source of truth for the entire cluster state, including all objects (Pods, Services, ConfigMaps, etc.) and their desired and current status. The kube-apiserver is the only component that directly communicates with etcd, ensuring that all state changes are persisted durably and consistently. Without etcd, the cluster would have no record of its configuration or running workloads.
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-controller-manager
Why it's wrong here
kube-controller-manager runs reconciliation loops that watch cluster state and drive it toward the declared spec, but it reads and writes through the API server rather than persisting anything itself. It is tempting because it continuously observes state; a question about which component runs controllers for nodes, replicas or endpoints would select it.
- ✓
etcd
Why this is correct
etcd is the distributed key-value store that holds all cluster state, including object definitions, configuration and metadata. The API server reads and writes exclusively through it, making etcd the sole control plane component responsible for persisting the entire cluster state.
- ✗
kube-apiserver
Why it's wrong here
kube-apiserver exposes the REST interface and validates requests, but etcd is the component that persists the entire cluster state; the API server only reads from and writes to it. It is tempting because every state change passes through it, and a question about the cluster's single entry point for API operations would select it.
- ✗
kube-scheduler
Why it's wrong here
kube-scheduler only assigns newly created pods to nodes by evaluating resource requests and constraints; it holds no cluster state itself and writes nothing to etcd. It is tempting because it is a control plane component that reads cluster data, but a scenario about pod placement decisions would correctly select it.
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