What is Kubernetes?

• Kubernetes also known as K8s, is an open-source Container Management tool

• It provides a container runtime, container orchestration, container-centric

  infrastructure orchestration, self-healing mechanisms, service discovery, load balancing and container (de)scaling.

• Initially developed by Google, for managing containerized applications in a cluster

  environment but later donated to CNCF

• Written in Golang

Kubernetes Architecture

Kubernetes Master

• Master is responsible for managing the complete cluster.

• You can access master node via the CLI, GUI, or API

• The master watches over the nodes in the cluster and is responsible for the actual orchestration of containers on the worker nodes

• It is the access point from which administrators and other users interact with the cluster to manage the scheduling and deployment of containers.

• It has four components: ETCD, Scheduler, Controller and API Server

  1 - ETCD

  • ETCD is a distributed reliable key-value store used by Kubernetes to store all data used to manage the cluster.

  • When you have multiple nodes and multiple masters in your cluster, etcd stores all that information on all the nodes in the cluster in a distributed manner.

  • ETCD is responsible for implementing locks within the cluster to ensure there are no conflicts between the Masters

2 - Scheduler

• The scheduler is responsible for distributing work or containers across multiple nodes.

• It looks for newly created containers and assigns them to Nodes.

3 - API server manager

• Masters communicate with the rest of the cluster through the kube-apiserver, the main access point to the control plane.

• It validates and executes user’s REST commands

• kube-apiserver also makes sure that configurations in etcd

  match with configurations of containers deployed in the cluster.

4 - Controller manager

• The controllers are the brain behind orchestration.

• They are responsible for noticing and responding when nodes, containers or endpoints go down. The controllers make decisions to bring up new containers in such cases.

• The kube-controller-manager runs control loops that manage the state of the cluster by checking if the required deployments, replicas, and nodes are running in the cluster

5 - Kubectl

• kubectl is the command line utility using which we can interact with k8s cluster

• Uses APIs provided by API server to interact.

• Also known as the kube command line tool or kubectl or kube control.

• Used to deploy and manage applications on a Kubernetes

Kubernetes Worker

• runs your containerized applications

1 - Kubelet

• Worker nodes have the kubelet agent that is responsible for interacting with the master to provide health information of the worker node

• To carry out actions requested by the master on the worker nodes.

2 - Kube proxy

• The kube-proxy is responsible for ensuring network traffic is routed properly to internal and external services as required and is based on the rules defined by network policies in kube-controller-manager and other custom controllers.

Installing Kubeadm: How to Set Up a Kubernetes Cluster

Requirements:

1. Two machines running Ubuntu 22.04 LTS, one for the master and one worker node.

2. The master node requires a minimum 2 vCPU and 4 GB memory. Select t2.medium instance type.

3. Sudo privileges are required on both machines.

Step - 1 : Install docker version on Both Master & Worker Node

•   sudo apt update -y
  
    sudo apt install docker.io -y
  
    sudo systemctl start docker
  
    sudo systemctl enable docker
  

Step - 2 : Install Kubernetes Components on Both Nodes

•   sudo curl -fsSLo /usr/share/keyrings/kubernetes-archive-keyring.gpg https://packages.cloud.google.com/apt/doc/apt-key.gpg
  
    echo "deb [signed-by=/usr/share/keyrings/kubernetes-archive-keyring.gpg] https://apt.kubernetes.io/ kubernetes-xenial main" | sudo tee /etc/apt/sources.list.d/kubernetes.list
  
    sudo apt update -y 
  
    sudo apt install kubeadm=1.20.0-00 kubectl=1.20.0-00 kubelet=1.20.0-00 -y
  

Step - 3: Configure Master Node

•   sudo su
  
    kubeadm init
  
    mkdir -p $HOME/.kube
    sudo cp -i /etc/kubernetes/admin.conf $HOME/.kube/config
    sudo chown $(id -u):$(id -g) $HOME/.kube/config
  
    kubectl apply -f https://github.com/weaveworks/weave/releases/download/v2.8.1/weave-daemonset-k8s.yaml
  
    kubeadm token create --print-join-command
  

• The kubeadm init command initializes the master node.

• The mkdir command creates a directory for the Kubernetes configuration file.

• The cp and chown commands copy the configuration file and set the correct permissions.

• The kubectl apply command installs Weave Net, which is a popular networking plugin for Kubernetes.

• The kubeadm token create command creates a token for joining worker nodes to the cluster.

Step - 4: Configure the Worker Node & Join to Master Node

•   sudo su
  
    kubeadm reset pre-flight checks
  
    # Paste the Join command on worker node with `--v=5`
  

• The kubeadm reset pre-flight checks command checks if the system meets the requirements for joining the Kubernetes cluster.

• Then, paste the kubeadm token create command output from the master node on the worker node with the --v=5 flag. This joins the worker node to the Kubernetes cluster.

Step - 5 : Verify Nodes from Master

• This command will list down the nodes, if everything is setup correctly.

Thanks For Reading 😊

Happy Learing

Vishal Ranmale

https://www.linkedin.com/in/vishal-ranmale-907307114/