Kubernetes in DevOps

Overview :

To work with Kubernetes, you use Kubernetes API object to describe your cluster's desired state.

You set your desired state by creating objects using the Kubernetes API, typically via the command-line interface, kubectl.

You can also use the Kubernetes API directly to interact with the cluster and set or modify your desired state.

Once you've set your desired state, the Kubernetes Control Plane works to make the cluster's state match the desired state.

To do so, Kubernetes performs a variety of tasks automatically-such as starting or restarting containers, scaling the number of replicas of a given application, and more.

The Kubernetes Control Plane consists of a collection of processes running on your cluster.

The Kubernetes Control Plane consists of a collection of process running on your cluster:

The Kubernetes Master: It is a collection of three processes that run on a single node in your cluster, which is designated as the master node.

Those processes are: kube-apiserve, kube-controller-manager and kube-scheduler.

Each individual non-master node in your cluster runs two processes:

kubelet, which communicates with the Kubernetes Master.

kube-proxy, a network proxy which reflects Kubernetes networking services on each node.

Kubernetes Objects :

Kubernetes Objects are persistent entities in the Kubernetes system.

Kubernetes uses these entities to represent the state of your cluster. Specifically, they can describe:

What containerized application are running (and on which nodes)
The resources available to those application
The policies around how those applications behave, such as restart policies, upgrades, and fault-tolerance

The basic Kubernetes objects include:

Pod
Service
Volume
Namespace

In addition, Kubernetes contains a number of higher-level abstractions called Controllers. Controllers build upon the basic objects, and provide additional functionality and convenience features. They include: