Day3 -Kubernetes Assignment

What is Kubernetes?
Kubernetes is a open source platform for managing containerized workloads and services, that facilitates both declarative configuration and automation
Why Kubernetes
What is Kubernetes and why it is used?
Kubernetes helps you to build cloud-native microservices-based apps. It also supports containerization of existing apps, thereby becoming the foundation of application modernization and letting you develop apps faster
Explained Kubernetes Architecture

A Kubernetes cluster has two main components—the control plane and data plane
The control plane hosts the components used to manage the Kubernetes cluster.

1. kube-apiserver Provides an API that serves as the front end of a Kubernetes control plane. It is responsible for handling external and internal requests—determining whether a request is valid and then processing it. The API can be accessed via the kubectl command-line interface or other tools like kubeadm, and via REST calls.
2. kube-scheduler This component is responsible for scheduling pods on specific nodes according to automated workflows and user defined conditions, which can include resource requests, concerns like affinity and taints or tolerations, priority, persistent volumes (PV), and more.
3. kube-controller-manager The Kubernetes controller manager is a control loop that monitors and regulates the state of a Kubernetes cluster. It receives information about the current state of the cluster and objects within it, and sends instructions to move the cluster towards the cluster operator’s desired state.

The controller manager is responsible for several controllers that handle various automated activities at the cluster or pod level, including replication controller, namespace controller, service accounts controller, deployment, statefulset, and daemonset.

1. etcd A key-value database that contains data about your cluster state and configuration. Etcd is fault tolerant and distributed. Worker nodes can be virtual machines (VMs) or physical machines. A node hosts pods, which run one or more containers.

Master Components

1. kube-apiserver Provides an API that serves as the front end of a Kubernetes control plane. It is responsible for handling external and internal requests—determining whether a request is valid and then processing it. The API can be accessed via the kubectl command-line interface or other tools like kubeadm, and via REST calls.
2. kube-scheduler This component is responsible for scheduling pods on specific nodes according to automated workflows and user defined conditions, which can include resource requests, concerns like affinity and taints or tolerations, priority, persistent volumes (PV), and more.
3. kube-controller-manager The Kubernetes controller manager is a control loop that monitors and regulates the state of a Kubernetes cluster. It receives information about the current state of the cluster and objects within it, and sends instructions to move the cluster towards the cluster operator’s desired state. The controller manager is responsible for several controllers that handle various automated activities at the cluster or pod level, including replication controller, namespace controller, service accounts controller, deployment, statefulset, and daemonset.
4. etcd A key-value database that contains data about your cluster state and configuration. Etcd is fault tolerant and distributed. Worker Components
5. Nodes Nodes are physical or virtual machines that can run pods as part of a Kubernetes cluster. A cluster can scale up to 5000 nodes. To scale a cluster’s capacity, you can add more nodes.
6. Pods A pod serves as a single application instance, and is considered the smallest unit in the object model of Kubernetes. Each pod consists of one or more tightly coupled containers, and configurations that govern how containers should run. To run stateful applications, you can connect pods to persistent storage, using Kubernetes Persistent Volumes—learn more in the following section.
7. Container Runtime Engine Each node comes with a container runtime engine, which is responsible for running containers. Docker is a popular container runtime engine, but Kubernetes supports other runtimes that are compliant with Open Container Initiative, including CRI-O and rkt.
8. kubelet Each node contains a kubelet, which is a small application that can communicate with the Kubernetes control plane. The kubelet is responsible for ensuring that containers specified in pod configuration are running on a specific node, and manages their lifecycle.. It executes the actions commanded by your control plane.
9. kube-proxy All compute nodes contain kube-proxy, a network proxy that facilitates Kubernetes networking services. It handles all network communications outside and inside the cluster, forwarding traffic or replying on the packet filtering layer of the operating system.

Workstation Components
Kubectl CLI utility
What is POD?
A pod is the smallest execution unit in Kubernetes. A pod encapsulates one or more applications. Pods are ephemeral by nature, if a pod (or the node it executes on) fails, Kubernetes can automatically create a new replica of that pod to continue operations.