Install Kubernetes Cluster using kubeadm on a simple Master and Worker node

Follow this documentation to set up a Kubernetes cluster on CentOS 7.

This documentation guides you in setting up a cluster with one master node and one worker node.

Assumptions

Role	FQDN	IP	OS	RAM	CPU
Master	kmaster.example.com	172.16.16.100	CentOS 7	2G	2
Worker	kworker.example.com	172.16.16.101	CentOS 7	1G	1

On both Kmaster and Kworker

Perform all the commands as root user unless otherwise specified

Disable Firewall

systemctl disable firewalld; systemctl stop firewalld

Disable swap

swapoff -a; sed -i '/swap/d' /etc/fstab

Disable SELinux

setenforce 0
sed -i --follow-symlinks 's/^SELINUX=enforcing/SELINUX=disabled/' /etc/sysconfig/selinux

Update sysctl settings for Kubernetes networking

cat >>/etc/sysctl.d/kubernetes.conf<<EOF
net.bridge.bridge-nf-call-ip6tables = 1
net.bridge.bridge-nf-call-iptables = 1
EOF
sysctl --system

Install docker engine

yum install -y yum-utils device-mapper-persistent-data lvm2
yum-config-manager --add-repo https://download.docker.com/linux/centos/docker-ce.repo
yum install -y docker
systemctl enable --now docker

Kubernetes Setup

Add yum repository

cat >>/etc/yum.repos.d/kubernetes.repo<<EOF
[kubernetes]
name=Kubernetes
baseurl=https://packages.cloud.google.com/yum/repos/kubernetes-el7-x86_64
enabled=1
gpgcheck=1
repo_gpgcheck=1
gpgkey=https://packages.cloud.google.com/yum/doc/yum-key.gpg
        https://packages.cloud.google.com/yum/doc/rpm-package-key.gpg
EOF

Install Kubernetes components

yum install -y kubeadm kubelet kubectl

Enable and Start kubelet service

systemctl enable --now kubelet

On kmaster

Initialize Kubernetes Cluster

kubeadm init --apiserver-advertise-address=<node ip> --pod-network-cidr=192.168.0.0/16

Deploy Calico network

kubectl --kubeconfig=/etc/kubernetes/admin.conf create -f https://docs.projectcalico.org/v3.20/manifests/calico.yaml

Cluster join command

kubeadm token create --print-join-command

To be able to run kubectl commands as non-root user

If you want to be able to run kubectl commands as non-root user, then as a non-root user perform these

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

On Kworker

Join the cluster

Use the output from kubeadm token create command in previous step from the master server and run here.

Verifying the cluster

Get Nodes status

kubectl get nodes

Get component status

kubectl get cs

Install Calicoctl on a Single host

1. Log into the host, open a terminal prompt, and navigate to the location where you want to install the binary. Tip: Consider navigating to a location that’s in your PATH. For example, /usr/local/bin/.

2. Use the following command to download the calicoctl binary.

curl -o calicoctl -O -L  "https://github.com/projectcalico/calicoctl/releases/download/v3.19.0/calicoctl" 

3. Set the file to be executable.

chmod +x calicoctl

check if calicoctl is installed correctly

calicoctl version

Note: If the location of calicoctl is not already in your PATH, move the file to one that is or add its location to your PATH. This will allow you to invoke it without having to prepend its location.