Control plane components (API server, scheduler, controller manager, etcd) in Kubernetes - Commands & Configuration

Introduction

Kubernetes control plane components manage the cluster's state and operations. They ensure your applications run smoothly by controlling scheduling, state storage, and responding to changes.

When you want to understand how Kubernetes manages your app deployments behind the scenes

When you need to troubleshoot why a pod is not starting or scheduling

When you want to monitor or secure the cluster's core services

When you plan to set up a highly available Kubernetes cluster

When you want to backup or restore the cluster state stored in etcd

Commands

This command checks the health of the main control plane components like the API server, scheduler, and controller manager.

Terminal

kubectl get componentstatuses

Expected Output

NAME                 STATUS    MESSAGE             ERROR

scheduler            Healthy   ok                  

controller-manager   Healthy   ok                  

apiserver            Healthy   ok                  

This command lists the API server pods running in the kube-system namespace to verify they are running.

Terminal

kubectl get pods -n kube-system -l component=kube-apiserver

Expected Output

NAME                        READY   STATUS    RESTARTS   AGE

kube-apiserver-master-1     1/1     Running   0          10m

→

-n - Specifies the namespace to look in

→

-l - Filters pods by label

This command lists the scheduler pods to confirm the scheduler is active.

Terminal

kubectl get pods -n kube-system -l component=kube-scheduler

Expected Output

NAME                        READY   STATUS    RESTARTS   AGE

kube-scheduler-master-1     1/1     Running   0          10m

→

-n - Specifies the namespace to look in

→

-l - Filters pods by label

This command lists the controller manager pods to verify they are running.

Terminal

kubectl get pods -n kube-system -l component=kube-controller-manager

Expected Output

NAME                                READY   STATUS    RESTARTS   AGE

kube-controller-manager-master-1   1/1     Running   0          10m

→

-n - Specifies the namespace to look in

→

-l - Filters pods by label

This command lists the etcd pods which store the cluster's state data.

Terminal

kubectl get pods -n kube-system -l component=etcd

Expected Output

NAME                READY   STATUS    RESTARTS   AGE

etcd-master-1       1/1     Running   0          10m

→

-n - Specifies the namespace to look in

→

-l - Filters pods by label

Key Concept

If you remember nothing else from this pattern, remember: the control plane components work together to keep your Kubernetes cluster healthy and running by managing state, scheduling, and responding to changes.

Common Mistakes

Trying to check control plane health without specifying the kube-system namespace

Control plane components run in the kube-system namespace, so commands without this context may show no results or errors.

Always include '-n kube-system' when querying control plane pods.

Assuming control plane components are normal pods you can delete or restart like app pods

Control plane components are critical; deleting them without proper procedure can cause cluster downtime.

Use proper cluster management tools or procedures to manage control plane components.

Ignoring the output of 'kubectl get componentstatuses' because it looks technical

This command quickly shows if core components are healthy, ignoring it can delay troubleshooting.

Regularly check component statuses to catch issues early.

Summary

Use 'kubectl get componentstatuses' to check the health of control plane components.

List control plane pods in the kube-system namespace with label selectors to verify they are running.

Control plane components include the API server, scheduler, controller manager, and etcd, which together manage cluster state and scheduling.