How to create a 3 node Cluster with Kubeadm in Kubernetes
In my example, I am going to create a 3 node cluster in Kubernetes. As a pre-requisite, I have created 3 servers on the Google Cloud with the names:-
1) Ubuntu1 - Master Node/Control Plane Node
2) Ubuntu2 - Worker Node
3) Ubuntu3 - Worker Node
Pre-requisites
1) I am able to access all the servers via the public IP. We have 3 servers here and we have logged into the master control plane server.
2) Install the Kernel modules on all the 3 nodes
Create configuration file for containerd: by running the below command
cat <<EOF | sudo tee /etc/modules-load.d/containerd.conf
overlay
br_netfilter
EOF
This will load the overlay and br_netfilter module
3) Now we will load the modules by running the command:-
sudo modprobe overlay
sudo modprobe br_netfilter
4) Set system configurations for Kubernetes networking:
cat <<EOF | sudo tee /etc/sysctl.d/99-kubernetes-cri.conf
net.bridge.bridge-nf-call-iptables = 1
net.ipv4.ip_forward = 1
net.bridge.bridge-nf-call-ip6tables = 1
EOF
5) Now we will apply the settings by running the command:-
sudo sysctl --system
6) Now we will update the repository and install the containerd
sudo apt-get update && sudo apt-get install -y containerd
7) Now we will create default configuration file for containerd:
sudo mkdir -p /etc/containerd
8) Now we will generate default containerd configuration and save to the newly created default file:
sudo containerd config default | sudo tee /etc/containerd/config.toml
9) Restart containerd to ensure new configuration file usage:
sudo systemctl restart containerd
10) Now we will disable swap by running the command
sudo swapoff -a

11) Now we will disable swap on startup in /etc/fsta by running the command
sudo sed -i '/ swap / s/^\(.*\)$/#\1/g' /etc/fstab
12) Now we will install the dependency packages
sudo apt-get update && sudo apt-get install -y apt-transport-https curl
13) Now we will add the GPG key
curl -s https://packages.cloud.google.com/apt/doc/apt-key.gpg | sudo apt-key add -
14) Now we will add Kubernetes to the repository list
cat <<EOF | sudo tee /etc/apt/sources.list.d/kubernetes.list
deb https://apt.kubernetes.io/ kubernetes-xenial main
EOF
15) Now we will update all the packages
sudo apt-get update
16) Now we will install the kubernetes package
sudo apt-get install -y kubelet=1.20.1-00 kubeadm=1.20.1-00 kubectl=1.20.1-00
17) Now we will hold the automatic updates for the package
sudo apt-mark hold kubelet kubeadm kubectl
18) Now we will login to the 2 worker nodes and perform all the above steps
In my example, the worker nodes are ubuntu-2 and ubuntu-3.
Step -1 - Initialize the cluster
Initialize the Kubernetes cluster on the control plane node using kubeadm (Note: This is only performed on the Control Plane Node). In my example my control plane node is ubuntu-1 server.
sudo kubeadm init --pod-network-cidr 192.168.0.0/16
Step -2 Set kubectl access:
mkdir -p $HOME/.kube
sudo cp -i /etc/kubernetes/admin.conf $HOME/.kube/config
sudo chown $(id -u):$(id -g) $HOME/.kube/config
Step 3 Test Access to the cluster
kubectl version
Step 4 Install the Calico Network Add-On
On the Control plane node (Ubuntu1), we will install the calico network.
kubectl apply -f https://docs.projectcalico.org/manifests/calico.yaml
Step 5 Check the status of the Calico components
kubectl get pods -n kube-system
Step 6 Join the worker nodes to the cluster
In the Control Plane Node, create the token and copy the kubeadm join command (NOTE:The join command can also be found in the output
kubeadm token create --print-join-command
Step 7 - Now run the output of the above command to the 2 worker nodes - Ubuntu2 and Ubuntu-3
kubeadm join 10.0.1.15:6443 --token 4i4md9.oziwagybigu5418f --discovery-token-ca-cert-hash sha256:8c7260dbb1444f043d8f9dc08c7e9a88c824f2daa257297782b6658411f92dc1
Once the nodes are joined to the cluster, we can see the same on them.
Step 8 - In the Control Plane Node, view cluster status. It might take a while for the cluster to come up.
We can check the status by running the command on the control plane node - Ubuntu1
kubectl get nodes
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