Kubernetes Installation on Ubuntu 20.04

Get the detailed information about the installation from the below-mentioned websites of Docker and Kubernetes.

Docker

Kubernetes

Set up the Docker and Kubernetes repositories:

Update the IP address as required or note the current IP address of the machine/VM. We'll use the IP address 10.0.1.19/24 for the Kube master and 10.0.1.20/24, 10.0.1.21/24, ... for the Kube nodes.

Update hostname

nano /etc/hostname

Download the GPG key for docker

curl -fsSL https://download.docker.com/linux/ubuntu/gpg | sudo apt-key add -

Add the docker repository

# Docker has release the repository for Ubuntu 20.04 Focal LTS.
# we can get the latest release versions from https://docs.docker.com

sudo add-apt-repository "deb [arch=amd64] https://download.docker.com/linux/ubuntu $(lsb_release -cs) stable"

Add the GPG key for kubernetes

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

Add the kubernetes repository

Check for the latest release in https://packages.cloud.google.com/apt/dists

cat << EOF | sudo tee /etc/apt/sources.list.d/kubernetes.list
deb https://apt.kubernetes.io/ kubernetes-xenial main
EOF

Update the repository

# Update the repositiries
sudo apt-get update

Install Docker and Kubernetes packages.

Note that if you want to use a newer version of Kubernetes, change the version installed for kubelet, kubeadm, and kubectl and be sure that all three use the same version. These version should support the Docker CE version.

# Use the same versions to avoid issues with the installation.
sudo apt-get install -y docker-ce=5:20.10.7~3-0~ubuntu-$(lsb_release -cs) kubelet=1.21.1-00 kubeadm=1.21.1-00 kubectl=1.21.1-00

If you encounter an error (E: dpkg was interrupted, ...) at this stage, run the following command to correct the problem and then run the above command again.

sudo dpkg --configure -a

To hold the versions so that the versions will not get accidently upgraded.

sudo apt-mark hold docker-ce kubelet kubeadm kubectl

Enable the iptables bridge

#Set a value in the sysctl file , to allow proper network settings for Kubernetes on all the servers.
echo "net.bridge.bridge-nf-call-iptables=1" | sudo tee -a /etc/sysctl.conf

#To make the changes to take immediate effect for the iptables
sudo sysctl -p

If you encounter an error (sysctl: cannot stat /proc/sys/ ...) at this stage, reboot to correct the problem, run the above command again and then continue with the next steps.

Disable swap

#Disable swap.
sudo swapoff -a

#Disable swap permanently from /etc/fstab
sudo sed -i '/\/swap.img/ s/^/#/' /etc/fstab

On the Kube master server

Initialize the cluster by passing the cidr value and the IP address of the master. These values will depend on the type of network CLI you choose and your IP address configuration.

Use either Flannel or Calico and replace 10.0.1.19 below with the IP address of the Kube master (if necessary)

# For flannel network
# Initialize.
sudo kubeadm init --pod-network-cidr=10.244.0.0/16 --apiserver-advertise-address=10.0.1.19

# Copy your join command and keep it safe.
# Below is a sample
kubeadm join 10.128.0.2:6443 --token swi0ci.jq9l75eg8lvpxz6g --discovery-token-ca-cert-hash sha256:2c3cdfa898334b0dfc0f73bbccb998d03f61252ee50f0405c85ba735ff90b4d1

# For Calico network
# Initialize.
sudo kubeadm init --pod-network-cidr=192.168.0.0/16 --apiserver-advertise-address=10.0.1.19

# Copy your join command and keep it safe.
# Below is a sample
kubeadm join 10.128.0.2:6443 --token swi0ci.jq9l75eg8lvpxz6g --discovery-token-ca-cert-hash sha256:2c3cdfa898334b0dfc0f73bbccb998d03f61252ee50f0405c85ba735ff90b4d1

To start using the cluster with current user.

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

Set the flannel networking

# Use this if you have initialised the cluster with Flannel network add on.
kubectl apply -f https://raw.githubusercontent.com/coreos/flannel/master/Documentation/kube-flannel.yml

To set up the Calico network

# Use this if you have initialised the cluster with Calico network add on.
kubectl apply -f https://docs.projectcalico.org/manifests/calico.yaml

Check the nodes

# Check the status on the master node.
kubectl get nodes

On each of Kube node server

Joining the node to the cluster:

sudo kubeadm join $controller_private_ip:6443 --token $token --discovery-token-ca-cert-hash $hash

TIP

If the joining code is lost, it can retrieve using below command

kubeadm token create --print-join-command