By Konstantinos Patronas — 29 Mar 2021

Create a kubernetes cluster

This tutorial has been tested with an ubuntu 18.04 distribution and its purpose is to create a controller host and any number of worker…

This tutorial has been tested with an ubuntu 18.04 distribution and its purpose is to create a controller host and any number of worker hosts.

The bellow steps must executed to all hosts of the cluster

Containerd

We will use containerd as CRI runtime, this means that we need to enable and load some kernel modules and do some network configuration changes as well.

Execute the following as root or with sudo

cat <<EOF | sudo tee /etc/modules-load.d/containerd.conf 
overlay 
br_netfilter 
EOF 
 
sudo modprobe overlay 
sudo modprobe br_netfilter 
 
# Setup required sysctl params, these persist across reboots. 
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 sysctl params without reboot 
sudo sysctl --system

Now we need to install containerd

apt-get update && sudo apt-get install -y containerd 
mkdir -p /etc/containerd 
containerd config default | sudo tee /etc/containerd/config.toml 
systemctl restart containerd

Disabling swap

Kubernetes requires swap being disabled to work

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

Install kubeadm, kubelet, kubectl

apt-get update && sudo apt-get install -y apt-transport-https curl 
curl -s https://packages.cloud.google.com/apt/doc/apt-key.gpg | apt-key add - 
 
cat <<EOF | sudo tee /etc/apt/sources.list.d/kubernetes.list 
deb https://apt.kubernetes.io/ kubernetes-xenial main 
EOF 
 
sudo apt-get update 
 
sudo apt-get install -y kubelet=1.20.1-00 kubeadm=1.20.1-00 kubectl=1.20.1-00 
 
sudo apt-mark hold kubelet kubeadm kubectl

The following steps needs to performed on control host only

Initiate the cluster

sudo kubeadm init --pod-network-cidr 192.168.0.0/16 
mkdir -p $HOME/.kube 
sudo cp -i /etc/kubernetes/admin.conf $HOME/.kube/config 
sudo chown $(id -u):$(id -g) $HOME/.kube/config

Install Calico network add-on.

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

Wait until the Calico related pods have been start using the following command

kubectl get pods -n kube-system

Create a join token

To add workers to the cluster we need first to generate a join command, to do this on the control host enter

kubeadm token create --print-join-command

Adding a worker to the cluster

Copy the join command fron the previous step and run it as sudo or root on the worker host

How to verify cluster

To verify that all cluster members are up and running enter the following on the control hostkubectl get nodes

You should see something like this