What is Kubernetes? Know About Architecture, Components and Setup

Kubernetes Architecture

Kubernetes Components:

Web UI (Dashboard)

The dashboard is a web-based Kubernetes user interface. You can use Dashboard to deploy containerized applications to a Kubernetes cluster, troubleshoot your containerized application, and manage the cluster itself along with its available resources.

Kubectl

Kubectl is a command-line configuration tool (CLI) for Kubernetes used to interact with a master node of Kubernetes. Kubectl has a config file called kubeconfig. This file has the information about the server and authentication information to access the API Server.

Master Node

●The master node is responsible for the management of the Kubernetes cluster

API Server:- Kube API Server interacts with API, its frontend of the Kubernetes cluster plane. 

Scheduler:- Scheduler watches the pods and assigns the pods to run on specific hosts.

Controller Manager:- Controller manager runs the controllers in the background which runs different tasks in the Kubernetes cluster, performs cluster-level functions (replication, keeping track of worker nodes, handling nodes failures…).

Etcd:- Kubernetes uses etcd as its database to store all cluster data. 

Worker Nodes 

Worker nodes are the nodes where the application is actually running in the Kubernetes cluster, Each worker node are controlled by the master node using a kubelet process.

Kubelet:- Kubelet is the primary node agent that runs on each node and reads the container manifests which ensures that containers are running and healthy. 

Kube-proxy:-  It helps us to have a network proxy and load balancer for the services in a single worker node. Worker nodes can be exposed to the internet via Kube proxy. 

Installation 

Different ways to install Kubernetes

●GCP - Google Kubernetes Engine (GKE)

●AWS - Amazon EKS

●Azure - Azure Kubernetes Services (AKS)

●Minikube → Using Minikube we can setup single node K8s cluster, 

kubeadm → we can setup multi-node k8s cluster

KOPS → Kubernetes operations, it is a software using which we can set up  highly available Kubernetes clusters in AWS

Kubernetes Setup Using Kubeadm In AWS EC2 Ubuntu Servers

Prerequisite:

=============

2 - Ubuntu Serves (Minimum Required)

1 - Manager  (4GB RAM , 2 Core) t2.medium 

1 - Workers  (1 GB RAM, 1 Core) t2.micro

Open Required Ports In AWS Security Groups.

# After launching the Two instances try to connect through Mobaxterm or Putty or Powershell etc,,,

1.Master Node                                                      

2.Worker Node

Then we will try to setup some required packages

# First, login as ‘root’ user because the following set of commands need to be executed with ‘sudo’ permissions.

sudo su -

# Install Required packages and apt keys.

apt-get update -y

apt-get install -y apt-transport-https

# Above command helps you to download through Internet Secure Protocol

# Adding GPG Key

curl -s https://packages.cloud.google.com/apt/doc/apt-key.gpg | apt-key add -

cat <<EOF >/etc/apt/sources.list.d/kubernetes.list

deb https://apt.kubernetes.io/ kubernetes-xenial main

EOF

apt-get update -y

#Turn Off Swap Space

swapoff -a

sed -i '/ swap / s/^\(.*\)$/#\1/g' /etc/fstab

# Installing Docker

apt install docker.io -y

usermod -aG docker ubuntu

# Restart docker with the following command

systemctl restart docker

# Enable docker service, it is done with the following command

systemctl enable docker.service

# update the existing packages

apt-get update

# Install the Kubelet, Kubeadm, and Kubectl

apt-get install -y kubelet kubeadm kubectl

# Now reload daemon

systemctl daemon-reload

# Start kubelet, this can be done with the help of the following command

systemctl start kubelet

# Enable kubelet service, this can be done with the help of the following command

systemctl enable kubelet.service

==========COMMON FOR MASTER & SLAVES END=====

===========In Master Node Start====================

# Steps Only For Kubernetes Master

# Switch to the root user.

sudo su -

# Initialize Kubernetes master by executing below command.

kubeadm init

# It is clear that the Kubernetes master has successfully initialized. Now to use this cluster please run the above three commands mentioned

mkdir -p $HOME/.kube

sudo cp -i /etc/kubernetes/admin.conf $HOME/.kube/config

sudo chown $(id -u):$(id -g) $HOME/.kube/config

# To verify, if kubectl is working or not, run the following command.

kubectl get pods -o wide –all-namespaces

# You will notice from the previous command, that all the pods are running except one: ‘core-dns’. For resolving this we will install a # pod network. To install the weave pod network, run the following command:

kubectl apply -f "https://cloud.weave.works/k8s/net?k8s-version=$(kubectl version | base64 | tr -d '\n')"

kubectl get nodes

kubectl get pods --all-namespaces

# Get token

kubeadmtoken create --print-join-command

=========In Master NodeEnd====================

AddWorker Machines to Kubernetes Master

=========================================

Copy kubeadm join token from and execute in WorkerNodes to join to cluster

Blue/ Green (or Red / Black) deployments 

Service

●      A service is responsible formaking our Pods discoverable inside the network or exposing them to theinternet. A Service identifies Pods by its LabelSelector.

Types of services available:

ClusterIP – Exposes the service on acluster-internal IP. Service is only reachable from within the cluster.

NodePort – Exposes the service on each Node’s IP at a static port. Service is reachable from outside the cluster (internet).

LoadBalancer – Exposes the service externally using a cloud provider’s load balancer. NodePort and ClusterIP services, to which the external load balancer will route, are automatically created.