Setting up Kubernetes Clusters using Kubeadm Manual way in RHEL 7 / Centos7

What is Kubeadm?

Kubeadm helps you bootstrap a minimum viable Kubernetes cluster that conforms to best practices. Kubeadm is a tool built to provide kubeadm init and kubeadm join as best-practice “fast paths” for creating Kubernetes clusters.

Goal

• To Install a single master Kubernetes cluster
• To Install a high availability master Kubernetes cluster
• To Install a Pod network on the cluster so that your Pods can talk to each other.

kubeadm’s simplicity means it can serve a wide range of use cases:

• New users can start with kubeadm to try Kubernetes out for the first time.
• Users familiar with Kubernetes can spin up clusters with kubeadm and test their applications.
• Larger projects can include kubeadm as a building block in a more complex system that can also include other installer tools.

Pre-requisite

• One or more machines running a deb/rpm-compatible OS, for example Ubuntu or CentOS
• 2 GB or more of RAM per machine. Any less leaves little room for your apps.
• 2 CPUs or more on the master
• Full network connectivity among all machines in the cluster. A public or private network is fine

Pre-requisite – Installing Docker [ This need to be there in Master and Worker Node. Both]

As part of the installation, every node (master and minions) needs:

• kubeadm: the command to bootstrap the cluster.
• kubelet: the component that runs on all of the machines in your cluster and does things like starting pods and containers.
• kubectl: the command line util to talk to your cluster.
• Docker: Container Enginer
• CNI: Container Network interfacer

Master: Setting Up a Kubernetes Control Plane

Step 1 – Change VMs Mac Address in Virtual box -> Setting -> Network ->Advance

Note – Please POWER off the VM before changing Mac Address.

Step 2 – Change Host Name of Master Server

$ hostnamectl set-hostname rajesh.master.comCode language: JavaScript (javascript)

Step 3 – Stop and Disable Firewall

$ systemctl stop firewalld
$ systemctl disable firewalld

Step 4 – Disable swap

$ sudo swapoff -a
$ sudo sed -i '/ swap / s/^/#/' /etc/fstab

# Reboot a machine after that.	
$ shutdown -r nowCode language: PHP (php)

Step 5 – Install and Start Docker Community Editon in Master Server

Special Step – For Docker Only with Kubernetes 1.22

Step 6 – Setup yum repo for kubelet kubeadm kubectl

Step 7 – Set SELinux in permissive mode (effectively disabling it)

$ setenforce 0
$ sed -i 's/^SELINUX=enforcing$/SELINUX=permissive/' /etc/selinux/configCode language: JavaScript (javascript)

Step 8 – Install kubelet kubeadm kubectl and enable kubelet

$ yum install -y kubelet-1.22.0-0.x86_64 kubeadm-1.22.0-0.x86_64 kubectl-1.22.0-0.x86_64 --disableexcludes=kubernetes
$ systemctl enable --now kubelet

# Latest 
$ yum install -y kubelet kubeadm kubectl --disableexcludes=kubernetes
# Kubernetes 1.23 
$ yum install -y kubelet-1.23.0-0.x86_64 kubeadm-1.23.0-0.x86_64 kubectl-1.23.0-0.x86_64 --disableexcludes=kubernetes
# Kubernetes 1.22
$ yum install -y kubelet-1.22.0-0.x86_64 kubeadm-1.22.0-0.x86_64 kubectl-1.22.0-0.x86_64 --disableexcludes=kubernetes
# Kubernetes 1.21
$ yum install -y kubelet-1.21.0-0.x86_64 kubeadm-1.21.0-0.x86_64 kubectl-1.21.0-0.x86_64 --disableexcludes=kubernetes
# Kubernetes 1.20
$ yum install -y kubelet-1.20.0-0.x86_64 kubeadm-1.20.0-0.x86_64 kubectl-1.20.0-0.x86_64 --disableexcludes=kubernetesCode language: PHP (php)

Step 9 – Finally, initialize a kubernetes clusters

$ kubeadm init --ignore-preflight-errors all

# How to install older version of Kubernetes
# kubeadm init --kubernetes-version=v1.9.2  Code language: PHP (php)

Step 10 – Output

Workstation: Setting Up a Kubernetes Workstation

Step 11 – Setup Workstation in the Master node only. You can be regular user for it.

$ mkdir -p $HOME/.kube
$ sudo cp -i /etc/kubernetes/admin.conf $HOME/.kube/config
$ sudo chown $(id -u):$(id -g) $HOME/.kube/configCode language: PHP (php)

Step 12 – Verify Clustors

$ kubectl get nodes
$ kubectl get pods --all-namespacesCode language: JavaScript (javascript)

Step 13 – Install Kubernetes pod networking

Weave Net provides networking and network policy, will carry on working on both sides of a network partition, and does not require an external database. Kubernetes versions 1.6 and above:

$ 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
$ kubectl get nodesCode language: JavaScript (javascript)

Worker: Setting Up a Kubernetes Worker

Step 14 – Setup nodes [ In the node aka worker

# Follow Step 1 
# Follow Step 2
# Follow Step 3
# Follow Step 4
# Follow Step 5
# Follow Step 6
# Follow Step 7
# Follow Step 8

# Run following commands which we got from kubeadm init
$ kubeadm join 172.31.31.106:6443 --token pdn6in.r0dzhpx1ucrs69au --discovery-token-ca-cert-hash sha256:a9385951e659a3c67f55ccfbdc1169b1f660ba09aaf8cc6d5cc96d71b71900d2Code language: PHP (php)

Rajesh Kumar

I’m Rajesh Kumar, a DevOps, SRE, DevSecOps, Cloud, and Platform Engineering expert passionate about sharing practical knowledge, real-world experiences, and industry best practices. I have worked at Cotocus and regularly write about technology, travel, investing, health, product reviews, and digital marketing through my various platforms.

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