What Is the Kubernetes Control Plane?
The control plane is the set of components that manage the entire cluster:
API Server
etcd
Scheduler
Controller Manager
Cloud Controller Manager
It decides what should run, where it should run, and how the system should stay stable.
This article breaks down how everything works — in exactly
🧠 1. API Server — The Front Door of Kubernetes
1.Acts as the entry point for every Kubernetes request.
2.All kubectl, controllers, and operators talk only to the API Server.
3.Exposes a REST API with strict validation.
4.Uses OpenAPI schemas to validate resource structure.
5.Stores cluster state in etcd.
6.Applies RBAC to control access.
7.Runs admission controllers (mutating + validating).
8.Acts as the gateway between user…
What Is the Kubernetes Control Plane?
The control plane is the set of components that manage the entire cluster:
API Server
etcd
Scheduler
Controller Manager
Cloud Controller Manager
It decides what should run, where it should run, and how the system should stay stable.
This article breaks down how everything works — in exactly
🧠 1. API Server — The Front Door of Kubernetes
1.Acts as the entry point for every Kubernetes request.
2.All kubectl, controllers, and operators talk only to the API Server.
3.Exposes a REST API with strict validation.
4.Uses OpenAPI schemas to validate resource structure.
5.Stores cluster state in etcd.
6.Applies RBAC to control access.
7.Runs admission controllers (mutating + validating).
8.Acts as the gateway between users & controllers.
9.Watches etcd for state changes.
10.Exposes the watch API for real-time updates.
11.Scales horizontally — stateless by design.
12.The single most critical component of Kubernetes.
🗄️ 2.etcd — The Cluster’s Source of Truth
13.etcd is a distributed key-value store.
14.Stores every Kubernetes object — pods, services, secrets, etc.
15.Uses Raft for consistency and leader election.
16.Only the API Server communicates with it.
17.Stores the desired state of the cluster.
18.Supports watch events for live updates.
19.Replicates data across the etcd cluster.
20.Any corruption here = the cluster becomes unusable.
🎯 3.Scheduler — Deciding Where Pods Run
21.Watches the API Server for unscheduled pods.
22.Filters nodes based on resource availability.
23.Considers CPU, RAM, affinity, taints, policies.
24.Scores nodes to pick the best one.
25.Uses plugins for custom scheduling.
26.Makes a binding decision.
27.Sends binding to the API Server.
28.Updates pod’s .spec.nodeName.
29.Kubelet on that node takes over.
30.Scheduler ensures pods are placed efficiently.
🔁 4.Controller Manager — Keeping the Cluster Stable
31.Runs the core control loops of Kubernetes.
32.Watches the API Server for desired vs actual drift.
33.Node Controller handles node health.
34.ReplicaSet Controller maintains replica counts.
35.Deployment Controller manages rollout/rollback.
36.StatefulSet Controller handles ordered pods.
37.Service Account Controller manages tokens.
38.Job Controller manages job lifecycle.
39.Uses informers/watchers for reactive behavior.
40.Updates the API Server to fix state drift.
☁️ 5.Cloud Controller Manager — Cloud Integration
41.Connects Kubernetes with AWS, Azure, and GCP.
42.Creates cloud load balancers when Services need them.
43.Manages persistent volume provisioning.
44.Maintains node information via cloud APIs.
45.Separates cloud logic from core Kubernetes controllers.
🔄 6. How Everything Works Together
46.User applies YAML → API Server validates & stores it in etcd.
47.Controllers detect state drift via watches.
48.Scheduler assigns nodes to pending pods.
49.Kubelet starts containers & reports status.
50.API Server commits updates to etcd → controllers maintain stability.