Following up on the tutorial about installing Kubernetes and Flannel on Ubuntu, might be useful for some people to automatically install K8s via a bash script. The code below will take care of that. It includes removal of existing Docker and Kubernetes installation (if any), and install fresh copies while updating the hostname, configures Docker to use Systemd as native cgroupdriver. It disables swap, adjusts user privileges, and lastly installs Kubernetes and Flannel while performs a sanity check in the end.

#!/bin/bash
echo "Disabling swap...."
sudo swapoff -a
sudo sed -i.bak '/ swap / s/^\(.*\)$/#\1/g' /etc/fstab
echo "Installing necessary dependencies...."
sudo apt-get install apt-transport-https ca-certificates curl gnupg-agent software-properties-common -y
echo "Setting up hostname...."
sudo hostnamectl set-hostname "k8s-master"
PUBLIC_IP_ADDRESS=`hostname -I|cut -d" " -f 1`
sudo echo "${PUBLIC_IP_ADDRESS}  k8s-master" >> /etc/hosts
echo "Removing existing Docker Installation...."
sudo apt-get purge aufs-tools docker-ce docker-ce-cli containerd.io pigz cgroupfs-mount -y
sudo apt-get purge kubeadm kubernetes-cni -y
sudo rm -rf /etc/kubernetes
sudo rm -rf $HOME/.kube/config
sudo rm -rf /var/lib/etcd
sudo rm -rf /var/lib/docker
sudo rm -rf /opt/containerd
sudo apt autoremove -y
  
echo "Installing Docker...."
curl -fsSL https://download.docker.com/linux/ubuntu/gpg | sudo apt-key add -
sudo apt-key fingerprint 0EBFCD88
### Add Docker apt repository.
sudo add-apt-repository "deb [arch=amd64] https://download.docker.com/linux/ubuntu $(lsb_release -cs) stable"

## Install Docker CE.
sudo apt-get update
sudo apt-get install docker-ce docker-ce-cli containerd.io -y

# Setup daemon.

sudo mkdir -p /etc/systemd/system/docker.service.d

cat > /etc/docker/daemon.json <<EOF
{
  "exec-opts": ["native.cgroupdriver=systemd"],
  "log-driver": "json-file",
  "log-opts": {
    "max-size": "100m"
  },
  "storage-driver": "overlay2"
}
EOF
# Restart docker.
sudo usermod -aG docker $USER
sudo systemctl daemon-reload
sudo systemctl restart docker
echo "Disabling Swap..."
echo "Setting up Kubernetes Package Repository..."
sudo apt-get install apt-transport-https curl -y 
sudo curl -s https://packages.cloud.google.com/apt/doc/apt-key.gpg | sudo apt-key add 
sudo apt-add-repository "deb http://apt.kubernetes.io/ kubernetes-xenial main"
echo "Installing Kubernetes..."
sudo apt install kubeadm
sudo kubeadm init --pod-network-cidr=10.244.0.0/16
sudo sleep 10
mkdir -p $HOME/.kube
sudo cp -i /etc/kubernetes/admin.conf $HOME/.kube/config
sudo chown $(id -u):$(id -g) $HOME/.kube/config
echo "Installing Flannel..."
sudo kubectl apply -f https://raw.githubusercontent.com/coreos/flannel/master/Documentation/kube-flannel.yml
echo "Kubernetes Installation finished..."
echo "Waiting 30 seconds for the cluster to go online..."
sudo sleep 30
sudo export KUBECONFIG=$HOME/.kube/config
echo "Testing Kubernetes namespaces... "
kubectl get pods --all-namespaces
echo "Testing Kubernetes nodes... "
kubectl get nodes
echo "All ok ;)"

The Kubernetes cluster will automatically start in case of a server reboot. The above script can be found also on Gihub.

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