# What is k8s (Kubernetes)?

**<mark>k8s is a container orchestration system.</mark>** It is used for container deployment and management. Its design is greatly impacted by Google’s internal system Borg.

**<mark>A k8s cluster consists of a set of worker machines, called nodes</mark>**, that run containerized applications. Every cluster has at least one worker node.

The worker node(s) host the **<mark>Pods that are the components of the application workload. </mark>** The control plane manages the worker nodes and the Pods in the cluster. In production environments, the control plane usually runs across multiple computers and a cluster usually runs multiple nodes, providing fault-tolerance and high availability.

* Control Plane Components
    

1. API Server
    
    **<mark>The API server talks to all the components in the k8s cluster. </mark>** All the operations on pods are executed by talking to the API server.
    
2. Scheduler
    
    **<mark>The scheduler watches the workloads on pods and assigns loads on newly created pods.</mark>**
    
3. Controller Manager
    
    **<mark>The controller manager runs the controllers, including Node Controller, Job Controller, EndpointSlice Controller, and ServiceAccount Controller.</mark>**
    
4. etcd
    
    **<mark>etcd is a key-value store used as Kubernetes' backing store for all cluster data.</mark>**
    

* Nodes
    

1. Pods
    
    **<mark>A pod is a group of containers and is the smallest unit that k8s administers.</mark>** Pods have a single IP address applied to every container within the pod.
    
2. Kubelet
    
    **<mark>An agent that runs on each node in the cluster. </mark>** It ensures containers are running in a Pod.
    
3. Kube
    
    **<mark>Proxy kube-proxy is a network proxy that runs on each node in your cluster. </mark>** It routes traffic coming into a node from the service. It forwards requests for work to the correct containers.
    

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