Guide to Setting Up a Kubernetes Cluster on CentOS

Are you looking to set up a Kubernetes cluster for your applications but unsure where to start? Kubernetes, an open-source container orchestration platform, can help manage and scale your containerized applications with ease. In this guide, we'll walk you through the step-by-step process of setting up a Kubernetes cluster on CentOS, using Kubernetes version 1.27.

Prerequisites

Before we dive into the installation process, ensure that you have the following prerequisites:

• 2 CPUs on the machine that you use as a control-plane node.
• 2 GiB or more of RAM per machine.
• One or more machines running a deb/rpm-compatible Linux OS (e.g., CentOS).
• Full network connectivity among all machines in the cluster.

Step 1: Installing a Runtime

Remove the Older Version of the Docker

sudo yum remove docker \

docker-client \

docker-client-latest \

docker-common \

docker-latest \

docker-latest-logrotate \

docker-logrotate \

docker-engine

Set Up the Docker Repository

sudo yum install -y yum-utils

sudo yum-config-manager --add-repo https://download.docker.com/linux/centos/docker-ce.repo

Install Containerd

sudo yum install docker-ce docker-ce-cli containerd.io

Step 2: Install and Configure Prerequisites

sudo tee /etc/modules-load.d/k8s.conf <<EOF

overlay

br_netfilter

EOF

sudo modprobe overlay

sudo modprobe br_netfilter

sudo tee /etc/sysctl.d/k8s.conf <<EOF

net.bridge.bridge-nf-call-iptables = 1

net.bridge.bridge-nf-call-ip6tables = 1

net.ipv4.ip_forward = 1

EOF

sudo sysctl --system

Verify sysctl Configuration

sysctl net.bridge.bridge-nf-call-iptables

sysctl net.bridge.bridge-nf-call-ip6tables

sysctl net.ipv4.ip_forward

Step 3: Configuring the systemd cgroup driver

Edit the Containerd Configuration

sudo tee -a /etc/containerd/config.toml <<EOF

[plugins."io.containerd.grpc.v1.cri".containerd.runtimes.runc]

[plugins."io.containerd.grpc.v1.cri".containerd.runtimes.runc.options]

SystemdCgroup = true

EOF

sudo systemctl restart containerd

Step 4: Install Kubeadm, Kubelet, and Kubectl

Set SELinux to Permissive Mode

sudo setenforce 0

sudo sed -i 's/^SELINUX=enforcing$/SELINUX=permissive/' /etc/selinux/config

Add the Kubernetes yum Repository

sudo tee /etc/yum.repos.d/kubernetes.repo <<EOF

[kubernetes]

name=Kubernetes

baseurl=https://pkgs.k8s.io/core:/stable:/v1.28/rpm/

enabled=1

gpgcheck=1

gpgkey=https://pkgs.k8s.io/core:/stable:/v1.28/rpm/repodata/repomd.xml.key

exclude=kubelet kubeadm kubectl cri-tools kubernetes-cni

EOF

sudo yum install -y kubelet kubeadm kubectl --disableexcludes=kubernetes

sudo systemctl enable --now kubelet

Step 5: Initialize the Control Plane

Make sure Containerd is running

sudo systemctl status containerd

Initialize the control plane

kubeadm init

Step 6: Post-Initialization Setup

After the control plane has been initialized successfully, run these commands

mkdir -p $HOME/.kube

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

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

Step 7: Join the nodes

Use the join token to join the worker nodes to the cluster.

kubeadm join <control-plane-host>

Step 8: Install the Pod Network

kubectl apply -f https://github.com/weaveworks/weave/releases/download/v2.8.1/weave-daemonset-k8s.yaml

Change the Configuration Options

kubectl get ds -A

kubectl edit ds weavenet

Under the environment variable section, add:

- name: IPALLOC_RANGE

value: 10.244.0.0/16