Cluster Architecture
A Kubernetes cluster has a control plane that makes decisions and worker nodes that run your containers.
A Kubernetes cluster is a set of machines, called nodes, split into two roles.
The control plane
The control plane is the brain of the cluster. It decides what runs where and keeps the desired state. Its main pieces are:
- kube-apiserver — the front door; everything talks to it.
- etcd — a key-value database storing all cluster data.
- kube-scheduler — picks which node a new Pod runs on.
- kube-controller-manager — runs the reconciliation loops.
Worker nodes
Each worker node actually runs your containers. Every node runs:
- kubelet — the agent that starts and watches containers.
- kube-proxy — handles cluster networking rules.
- A container runtime (such as containerd) that runs the containers.
Example
# List the nodes (machines) in your cluster
kubectl get nodes
# Example output:
# NAME STATUS ROLES AGE VERSION
# control Ready control-plane 5d v1.30.0
# worker-1 Ready <none> 5d v1.30.0
# worker-2 Ready <none> 5d v1.30.0When to use it
- An ops team monitors the kube-apiserver audit logs to track who changed a Deployment configuration in production.
- A platform engineer adds a new worker node to the cluster so the scheduler can place additional pods on it.
- A developer inspects etcd backups to restore the last known good cluster state after a configuration incident.
More examples
List control-plane components
Lists every system pod in kube-system, revealing the running control-plane components that manage the cluster.
kubectl get pods -n kube-system
# kube-apiserver, etcd, kube-scheduler, kube-controller-managerInspect node roles and status
Shows each node's role (control-plane vs worker) and readiness status so you know which nodes can schedule pods.
kubectl get nodes -o wide
# NAME STATUS ROLES AGE
# control-plane Ready control-plane 10d
# worker-1 Ready <none> 10dDescribe a worker node
Dumps full details for a worker node including CPU/memory capacity, allocatable resources, and scheduled pod list.
kubectl describe node worker-1
# Sections: Conditions, Capacity, Allocatable, Non-terminated Pods
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