Building a Kubernetes 1.20v Cluster with kubeadm

Kubeadm is a tool that can be used to build a minimal viable Kubernetes Cluster of production grade.

Step 1: Install Packages

ssh into each node and create containerd configuration file by executing the below command. This command will instruct the node to load overlay and br_netfilter kernal modules.

cat <<EOF | sudo tee /etc/modules-load.d/containerd.conf 
overlay 
br_netfilter 
EOF

We have to restart nodes to load them. Instead of restarting, run the below commands to load modules immediately

sudo modprobe overlay 
sudo modprobe br_netfilter

Then set these 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

Apply those settings by executing the below command

sudo sysctl --system

Now install containerd

sudo apt-get update && sudo apt-get install -y containerd

Inside the /etc folder, create a configuration file for containerd and generate the default configuration file

sudo mkdir -p /etc/containerd
sudo containerd config default | sudo tee /etc/containerd/config.toml

Now restart containerd to ensure new configuration file usage

sudo systemctl restart containerd

Kubernetes does require to disable swap memory, because the Kubernetes scheduler determines the best available node on which to deploy newly created pods. If memory swapping is allowed to occur on a host system, this can lead to performance and stability issues within Kubernetes. For this reason, Kubernetes requires that you disable swap in the host system.

sudo swapoff -a

To disable swap after server restart, in other terms, to persist the swap disable in the node, execute bellow command as well

sudo sed -i '/ swap / s/^\(.*\)$/#\1/g' /etc/fstab

Now, let’s install dependency packages

sudo apt-get update && sudo apt-get install -y apt-transport-https curl

Then download and add the GPG key

curl -s https://packages.cloud.google.com/apt/doc/apt-key.gpg | sudo apt-key add -

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

Update package listings

sudo apt-get update

Install Kubernetes packages (Note: If you get a dpkg lock message, just wait few minutes before trying the command again)

sudo apt-get install -y kubelet=1.20.1-00 kubeadm=1.20.1-00 kubectl=1.20.1-00

Turn off automatic updates

sudo apt-mark hold kubelet kubeadm kubectl

Initialize the Cluster

This only needs to perform on the control plane node only. (If you have multiple control plane nodes, do the same)

sudo kubeadm init --pod-network-cidr 192.168.0.0/16

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

Test access to cluster

kubectl version

Install Calico Network Add-On

Calico provides a simple, high-performance, secure networking. Calico is trusted by the major cloud providers, with EKS, AKS, GKE, and IKS all having integrated Calico as part of their offerings.

On the control plane node, install Calico networking

kubectl apply -f https://docs.projectcalico.org/manifests/calico.yaml

Check the status of calico components

kubectl get pods -n kube-system

Join the worker nodes to the Cluster

In the control plane node, create the token and copy the kubeadm join command (The join command can also be found in the output from kubeadm init command)

kubeadm token create --print-join-command

In worker nodes, paste the kubeadm join command to join the cluster

sudo kubeadm join <join command from previous command>

Now you can view the cluster status in the control plane node

kubectl get nodes

Hope you learned something. Read upgrading Kubernetes cluster using Kubeadm form here.