What is a Kubernetes Node?

What is a Kubernetes Node?

Kubernetes nodes are the worker machines in a Kubernetes cluster. They are responsible for running the containerized applications and communicating with the Kubernetes master.

A node can be either a virtual or a physical machine, and each node runs a container runtime, such as Docker, and the kubelet, which is an agent for communicating with the Kubernetes master. The kubelet is responsible for starting, stopping, and managing the containers on the node.

Each node also runs the kube-proxy, which is responsible for maintaining the network rules on the node and forwarding network traffic to the appropriate pods.

Nodes can be grouped into two types:

1. Master Nodes: These are the nodes that run the control plane components, such as the API server, etcd, and the controller manager. The master nodes are responsible for managing the state of the cluster and making decisions about how to respond to changes in the cluster.
2. Worker Nodes: These are the nodes that run the containerized applications. The worker nodes are responsible for running the pods and communicating with the master nodes.

An example of a Kubernetes cluster with three nodes:

• Node 1: Master Node – running the control plane components and the kubelet
• Node 2: Worker Node – running the kubelet and several pods
• Node 3: Worker Node – running the kubelet and several pods

In this example, the master node is responsible for managing the state of the cluster and making decisions about how to respond to changes. The worker nodes are responsible for running the pods and communicating with the master node.

Another example is of a cloud provider, such as AWS, GCP, or Azure, provide Kubernetes as a service, these nodes are managed by the cloud provider, and you only have to manage the pods and services running on top of it.

In general, nodes are the fundamental building blocks of a Kubernetes cluster and are responsible for running the containerized applications and communicating with the master. Understanding how nodes work is essential for effectively managing and scaling a Kubernetes cluster.