Kubernetes and its main components

Kubernetes(K8S) is a Container Orchestration Engine. It automates the process of deploying, scaling and managing containerized applications.

There are many components of Kubernetes. Following are the key components -

• POD : Containers are wrapped into a functional unit known as PODs. Each POD has single IP address.

• Node : PODs(one or multiple) are clubbed into a virtual machine known as Node.

• Cluster : Multiple nodes are clubbed into Cluster. Kubernetes cluster comprises of one Master node and many Worker nodes.

• ReplicaSet : Creates replicas of PODs to ensure no downtime of the application.

• Service : One or more PODs can associate with a single Service. Service provides static IP and DNS name. Service also plays the role of Load Balancer by forwarding the traffic to the appropriate POD. There are three types of Services -
  Cluster IP
  NodePort
  LoadBalancer

• Deployment : Kubernetes objects for managing PODs. Deployments can be created using commands or YML files.

• ConfigMap and Secrets : Configurable properties of the application are stored in ConfigMap. Sensitive Configurable properties of the application are stored in Secrets.

• ETCD : It is a key-vale datastore. Kubernetes cluster configuration is stored in ETCD.

• Volumes : Volumes are used for persistent datastore like database.