Explore Kubernetes Control Plane and Worker Node Components

Table of Contents

1. Introduction

2. Listing All Control Plane Components

3. Explore Individual Control Plane Components

4. Explore Worker Node Components

5. References

Introduction

So far we have gone through the basics of docker. Let's dive into Kubernetes by exploring the control plane and worker node components.

Listing All Control Plane Components

The control plane components run in the 'kube-system' namespace. To list all pods in the 'kube-system' namespace, use the following command:

kubectl get pods -n kube-system

This lists all the control plane components.

Exploring Individual Control Plane Components

We can obtain a detailed description of each pod. Let's see how to do it for each control plane component:

API Server

kubectl -n kube-system describe pod -l component=kube-apiserver

etcd

kubectl -n kube-system describe pod -l component=etcd

Scheduler

kubectl -n kube-system describe pod -l component=kube-scheduler

Controller Manager

kubectl -n kube-system describe pod -l component=kube-controller-manager

DNS (CoreDNS or kube-dns)

kubectl -n kube-system describe pod -l k8s-app=kube-dns

Exploring Worker Node Components

Worker nodes run the workloads and communicate with the control plane through the Kubernetes API. The main components of a worker node are:

• Kubelet: This is the primary node agent that communicates with the API server to ensure that containers are running in a pod.

This need to be execute from the worker nodes as the root user.

Get the status of kubelet

systemctl status kubelet

• Kube-proxy: This is a network proxy that maintains network rules on the node. These network rules allow network communication to your Pods from network sessions inside or outside of your cluster.

Get information about kube-proxy

kubectl -n kube-system get pod -o wide | grep kube-proxy

• Container Runtime: This is the software that is responsible for running containers. Kubernetes supports several runtimes: Docker, containerd, CRI-O, and any implementation of the Kubernetes CRI (Container Runtime Interface).

This need to be execute from the worker nodes as the root user.

Get the status of containerd

systemctl status containerd

References

1. Kubernetes Components

2. Kubernetes Namespaces

3. Rajith's Kubernetes Guide