Create a Kubernetes Docker Cluster on Ubuntu Server 🌱

Cluster VM Network Diagram

Preparing the VMs

1. Log into a freshly installed Ubuntu VM
2. Run the following commands
   # set the hostname
   sudo hostnamectl set-hostname kubernetes
   # update hosts file
   sudo nano /etc/hosts
3. Update the 127.0.01 to the new hostname, kubernetes
4. Press CTRL+O, Enter, CTRL+X to write the changes to hosts
5. Continue with the following commands
   # disable the firewall
   sudo ufw disable
   # disable the swap file
   sudo swapoff -a
   # disable swap partition
   sudo sed -i '/ swap / s/^\(.*\)$/#\1/g' /etc/fstab
   sudo echo "vm.swappiness=0" | sudo tee --append /etc/sysctl.conf
   # update sysctl networking
   cat < net.bridge.bridge-nf-call-ip6tables = 1
   net.bridge.bridge-nf-call-iptables = 1
   EOF
   sudo sysctl --system
   # apply the changes
   sudo sysctl -p

Installing Docker

1. Continue with the following commands in terminal
   # install prerequisites
   sudo apt install apt-transport-https ca-certificates curl software-properties-common gnupg-agent -y
   # add docker gpg key
   curl -fsSL https://download.docker.com/linux/ubuntu/gpg | sudo apt-key add -
   # add docker software repository
   sudo add-apt-repository "deb [arch=amd64] https://download.docker.com/linux/ubuntu $(lsb_release -cs) stable"
   # install docker
   sudo apt install docker-ce docker-compose containerd.io -y
   # enable and start docker service
   sudo systemctl enable docker && sudo systemctl start docker
   # add the current user to the docker group
   sudo usermod -aG docker $USER
   # reauthenticate for the new group membership to take effect
   su - $USER

Installing Kubernetes

1. Continue with the following commands in terminal
   # add kubernetes gpg key
   curl -s https://packages.cloud.google.com/apt/doc/apt-key.gpg | sudo apt-key add -
   # add the kubernetes software repo
   echo 'deb http://apt.kubernetes.io/ kubernetes-xenial main' | sudo tee /etc/apt/sources.list.d/kubernetes.list
   # update software repositories
   sudo apt update
   # install kubernetes
   sudo apt install kubelet kubeadm kubectl -y
   # shutdown the VM
   sudo shutdown now

Cloning the VirtualBox VM

1. In VirtualBox Manager, right click on the Kubernetes VM > Clone...
2. Name the cloned VM Docker1 > Click Next
3. Make sure Full Clone is selected > Click Clone
4. In VirtualBox Manager, right click on the Ubuntu VM again > Clone...
5. Name the cloned VM Docker2 > Click Next
6. Make sure Full Clone is selected > Click Clone
7. Right click the Kubernetes VM > Start > Normal Start
8. Right click the Docker1 VM > Start > Normal Start
9. Once the VM boots, log in and run the following commands
   # set the hostname
   sudo hostnamectl set-hostname docker1
   # update hosts file
   sudo nano /etc/hosts
10. Update the 127.0.01 to the new hostname, docker1
11. Press CTRL+O, Enter, CTRL+X to write the changes to hosts
12. Reboot the VM with the following command
    sudo reboot now
13. Back in VirtualBox Manager, right click the Docker2 VM > Start > Normal Start
14. Once the VM boots, log in and run the following commands
    # set the hostname
    sudo hostnamectl set-hostname docker2
    # update hosts file
    sudo nano /etc/hosts
15. Update the 127.0.01 to the new hostname, docker2
16. Press CTRL+O, Enter, CTRL+X to write the changes to hosts
17. Reboot the VM with the following command
    sudo reboot now
18. At this point we have 3 Ubuntu VMs (kubernetes, docker1, docker2) running with swap disabled and docker and kubernetes installed
19. All 3 VMs will need static IP addresses, I prefer to create static DHCP leases on my router for a single point of configuration, but the VM IP addresses can be set with the following command if needed
    sudo nano /etc/netplan/01-installer-config.yaml
20. Set DHCP4 = no and update the IP address, gateway and nameservers

    dhcp4: no
    addresses: [192.168.100.100/24]
    gateway4: 192.168.100.1
    nameservers:
    addresses: [192.168.100.1,8.8.8.8]

Configuring the Kubernetes Cluster

Follow the steps below only on the kubernetes VM

1. Log into the kubernetes VM and run the following commands in terminal
   # initialize the cluster, copy the kubeadm join command for use later when joining the docker hosts to the cluster
   sudo kubeadm init --pod-network-cidr=10.244.0.0/16 --apiserver-advertise-address=10.10.27.100 --kubernetes-version "1.20.4"
   # create .kube config directory and copy configuration
   mkdir -p $HOME/.kube
   sudo cp -i /etc/kubernetes/admin.conf $HOME/.kube/config
   sudo chown $(id -u):$(id -g) $HOME/.kube/config
   # deploy the flannel network
   kubectl apply -f https://raw.githubusercontent.com/coreos/flannel/master/Documentation/kube-flannel.yml

Joining Docker Nodes to the Cluster

Follow the steps below only on the docker1 and docker2 VMs

1. Log into each of the Docker VMs and run the following commands in terminal
   # paste the kubeadm join command copied earlier, the command will look similar to the one below
   sudo kubeadm join 10.10.27.100:6443 --token ua6bhl.wuzsqhnf0h40hgxr \
   --discovery-token-ca-cert-hash sha256:69a89f8d81dbfc08e4098f3d43e42c78429369ca41cb2954bcbcbb15405d69ef

Verifying the Cluster and Testing

Follow the steps below on the kubernetes VM

1. Log into kubernetes VM and run the following commands in terminal
   
   # list kubernetes nodes, all 3 VMs should be listed
   kubectl get nodes
   # deploy an example guestbook application
   # deploy mongoDB
   kubectl apply -f https://k8s.io/examples/application/guestbook/mongo-deployment.yaml
   # deploy mongoDB service
   kubectl apply -f https://k8s.io/examples/application/guestbook/mongo-service.yaml
   # deploy guestbook frontend
   kubectl apply -f https://k8s.io/examples/application/guestbook/frontend-deployment.yaml
   # deploy frontend service
   kubectl apply -f https://k8s.io/examples/application/guestbook/frontend-service.yaml
   # watch as the pods are created and start running, press ctrl+c once all pods are in running status
   watch -n 3 kubectl get pods
   # forward host port 8080 to container port 80
   kubectl port-forward --address 0.0.0.0 svc/frontend 8080:80

Removing the Test Deployments

Follow the steps below on the kubernetes VM

1. Log into kubernetes VM and run the following commands in terminal
   # list the running pods
   kubectl get pods
   # delete the test pods created earlier
   kubectl delete deployment -l app.kubernetes.io/name=mongo
   kubectl delete service -l app.kubernetes.io/name=mongo
   kubectl delete deployment -l app.kubernetes.io/name=guestbook
   kubectl delete service -l app.kubernetes.io/name=guestbook
   # watch as the pods are terminated and deleted, press ctrl+c to return to the terminal
   watch -n 3 kubectl get pods