What is Kubernetes?
Kubernetes, also known as K8s, is an open-source platform that is used to manage Containers over private, public, and hybrid cloud environments. Business organizations can use Kubernetes to manage microservice architecture.
Kubernetes is used by IT system administrators and DevOps engineers to deploy, scale, maintain, and schedule multiple application containers across the clusters of nodes. Kubernetes cluster is nothing but a set of nodes that runs containerized applications inside the pod. A node is a worker server or machine in Kubernetes which is managed by the control plane or master node. The containers run on top of the common shared operating system (OS) on the host machines. These are isolated from each other unless a user chooses to connect them.
As the name suggests, a Kubernetes cluster is a group of nodes. IT engineers run the containerized application inside the Kubernetes cluster. It allows the application to be more easily developed, moved, and managed, We can run the containers inside the Kubernetes cluster in multiple machines and environments. These environments can be virtual, physical, cloud-based, or on-premises. The Kubernetes containers are not restricted to the specific operating system.
The Kubernetes Cluster has at least one master node and several worker nodes. These nodes can be computers or virtual machines. The master node is the component that controls the state of the cluster. It controls the application running and its container image inside the cluster. The master node, also known as the control plane is the origin of all the task assignments. It controls various processes such as:
- Updating the cluster
- Scaling and scheduling the applications
- Maintaining the state of the cluster
The worker node is the component that runs the applications. The worker node performs the tasks that are assigned by the master node. These nodes can be either virtual machines or physical computers.
The Kubernetes cluster must contain at least 1 master node and one worker node to be operational. For the various environments such as production, and staging, the cluster is distributed across the multiple worker nodes. For the testing, the components can be run on the same node.
A node can contain several pods. Pod is the smallest unit that Kubernetes controls. A pod can run more than containers inside it. Kubernetes contains various features to handle the failure of pods. We can set a replica in the config file of Kubernetes that can automatically create a new pod when the old pod is failed. Pods provide the environmental dependencies such as persistent volumes and configuration data that are needed to run the container within the pod.
Pod represents the processes that run inside the cluster. We can schedule multiple pods inside a node. And a pod can run multiple containers. But the container running the pod is tightly coupled i.e. they have lots of dependencies. So if one of the containers fails, all the containers inside the pod fail.
Containers are the lightweight packages of the application that container dependencies such as the specific version of programming runtimes and libraries that are required to run the software services. This container can be of docker or any other containerization platform. Docker container is widely used around the world. It is a lightweight, executable package of software.
Namespace is the way to organize the clusters. It can be helpful to the different teams of the organization that shares the Kubernetes cluster. The Namespaces cannot be nested with each other. The namespaces are supported within the cluster and logically separated from the others but can communicate with each other within the cluster.
To get a replica of the pod, we can use ReplicaSet in the config file. It is an object that ensures that there is always a stable set of running pods for the specific workload. The ReplicaSet config file defines the number of identical pods that are required. If the pod is failed, it creates more pods as defined in the config file.