Kubernetes architecture (control plane and nodes) - Commands & Configuration

Introduction

Kubernetes helps run many applications on many computers easily. It does this by splitting work between a control center and worker computers called nodes. This setup keeps apps running smoothly and lets you add or fix computers without stopping everything.

When you want to manage many app copies across several computers automatically

When you need to fix or add computers without stopping your app

When you want a central place to control how apps run on many machines

When you want to keep apps running even if some computers fail

When you want to organize computers into groups for different tasks

Commands

This command shows all the worker computers (nodes) connected to the Kubernetes control plane. It helps you see which computers are ready to run apps.

Terminal

kubectl get nodes

Expected Output

NAME           STATUS   ROLES    AGE   VERSION

worker-node1   Ready    <none>   10d   v1.27.3

worker-node2   Ready    <none>   10d   v1.27.3

This command lists all running app parts (pods) in all groups (namespaces). It shows what the control plane is managing on the nodes.

Terminal

kubectl get pods -A

Expected Output

NAMESPACE     NAME                                   READY   STATUS    RESTARTS   AGE

kube-system   coredns-66bff467f8-7x9q2              1/1     Running   0          10d

kube-system   kube-proxy-worker-node1                1/1     Running   0          10d

→

-A - Show pods in all namespaces

This command shows the main addresses of the Kubernetes control plane components. It helps confirm the control center is running and reachable.

Terminal

kubectl cluster-info

Expected Output

Kubernetes control plane is running at https://192.168.1.100:6443

CoreDNS is running at https://192.168.1.100:6443/api/v1/namespaces/kube-system/services/kube-dns:dns/proxy

Key Concept

If you remember nothing else from this pattern, remember: Kubernetes splits control tasks to the control plane and runs apps on worker nodes to keep everything organized and reliable.

Common Mistakes

Trying to run app containers directly on nodes without using Kubernetes pods

This bypasses Kubernetes management, causing loss of benefits like automatic restarts and scaling

Always deploy apps as pods managed by Kubernetes through manifests or commands

Ignoring node status and assuming all nodes are ready

If nodes are NotReady, apps won't run properly and may fail silently

Use 'kubectl get nodes' regularly to check node health before deploying apps

Summary

Use 'kubectl get nodes' to see all worker computers ready to run apps.

Use 'kubectl get pods -A' to view all app parts running across the cluster.

Use 'kubectl cluster-info' to check the control plane's main addresses and status.