Kubernetes Architecture

Think of Kubernetes in two layers: the control plane (decisions) and the nodes (execution).

Control plane

• API Server: the single entry point
• etcd: stores cluster state
• Scheduler: picks the target node
• Controller Manager: keeps desired state true

Node components

• kubelet: runs Pod lifecycle
• Container runtime: containerd or CRI-O
• kube-proxy: service forwarding rules
• CNI/CSI: networking and storage plugins

Simple mental map

kubectl -> apiserver -> etcd
              |-> scheduler
              |-> controllers
nodes: kubelet + runtime + kube-proxy

Once you know these parts, you can tell whether a failure lives in the control plane or on a node.

Practical notes

• Start with a quick inventory: kubectl get nodes, kubectl get pods -A, and kubectl get events -A.
• Compare desired vs. observed state; kubectl describe usually explains drift or failed controllers.
• Keep names, labels, and selectors consistent so Services and controllers can find Pods.

Quick checklist

• The resource matches the intent you described in YAML.
• Namespaces, RBAC, and images are correct for the target environment.
• Health checks and logs are in place before promotion.

References

• Kubernetes Components
• Cluster Architecture