In this tutorial, we’ll spin up a Kubernetes cluster on Ubuntu 18.04.

This guide uses Ubuntu 18.04 droplets on DigitalOcean. Feel free to swap out DigitalOcean for a different cloud hosting provider or your own on-premise environment.

Dependencies:

  1. Docker v18.06.0-ce
  2. Kubernetes v1.11.2

Contents

Provision the Machines

Following along with the DigitalOcean example?

  1. Sign up for an account (if you don’t already have one).
  2. Generate an access token so you can access the DigitalOcean API.
  3. Spin up three new droplets (one master and two workers) that have 4 GB of memory and 2 vCPUs either from the DigitalOcean console or doctl, the DigitalOcean.

doctl example:

# authenticate
$ doctl auth init

# spin up the droplets
$ for i in 1 2 3; do
    doctl compute droplet create \
      node-$i \
      --region nyc1 \
      --image ubuntu-18-04-x64 \
      --size 4gb
done

Wait a few seconds for the droplets to spin up, and then run:

$ doctl compute droplet list

You should see something like:

ID         Name    Public IPv4     Memory  VCPUs  Disk  Region  Image             Status
106096338  node-1  142.93.198.67   4096    2      60    nyc1    Ubuntu 18.04 x64  active
106096340  node-2  142.93.198.167  4096    2      60    nyc1    Ubuntu 18.04 x64  active
106096345  node-3  142.93.206.39   4096    2      60    nyc1    Ubuntu 18.04 x64  active

Take note of the public IP addresses.

Refer to the How To Use Doctl guide for more info on using the doctl CLI tool.

Configure the Master Node

SSH into the machine that will serve as the Kubernetes master, and then run the following commands…

Install Dependencies

Install Docker along with-

  1. kubeadm - bootstraps a Kubernetes cluster
  2. kubelet - configures containers to run on a host
  3. kubectl - deploys and manages apps on Kubernetes
$ apt-get update && apt-get install -y apt-transport-https
$ curl -s https://download.docker.com/linux/ubuntu/gpg | sudo apt-key add -
$ add-apt-repository \
    "deb [arch=amd64] https://download.docker.com/linux/ubuntu bionic stable"
$ apt update && apt install -qy docker-ce
$ curl -s https://packages.cloud.google.com/apt/doc/apt-key.gpg | apt-key add -
$ echo "deb http://apt.kubernetes.io/ kubernetes-xenial main" \
    > /etc/apt/sources.list.d/kubernetes.list
$ apt-get update && apt-get install -y kubeadm kubelet kubectl

As of writing, Kubernetes for Ubuntu 18.04 (Bionic) is not yet available, but Ubuntu 16.04 (Xenial) works just fine. Also, Kubernetes 1.11 does not officially support Docker 18.06. It should work fine, but it could bring up some unexpected issues.

Configure Kubernetes

Init Kubernetes:

$ kubeadm init --apiserver-advertise-address=<MASTER_IP> --pod-network-cidr=192.168.1.0/16

Be sure to replace <MASTER_IP> with the machine’s IP address.

Take note of the join token command. For example:

kubeadm join 142.93.198.67:6443 \
  --token 58f5m6.rms4ycepgmtvjl9z --discovery-token-ca-cert-hash sha256:<hash>

Then, create a new user:

$ adduser michael
$ usermod -aG sudo michael
$ su - michael

Set up the Kubernetes config as the user you created:

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

Again, as the new user, deploy a flannel network to the cluster:

$ kubectl apply -f https://raw.githubusercontent.com/coreos/flannel/master/Documentation/kube-flannel.yml

Configure the Worker Nodes

The following commands should be run on each of the worker machines.

Install Dependencies

Again, install Docker, kubeadm, kubelet, and kubectl:

$ apt-get update && apt-get install -y apt-transport-https
$ curl -s https://download.docker.com/linux/ubuntu/gpg | sudo apt-key add -
$ add-apt-repository \
    "deb [arch=amd64] https://download.docker.com/linux/ubuntu bionic stable"
$ apt update && apt install -qy docker-ce
$ curl -s https://packages.cloud.google.com/apt/doc/apt-key.gpg | apt-key add -
$ echo "deb http://apt.kubernetes.io/ kubernetes-xenial main" \
    > /etc/apt/sources.list.d/kubernetes.list
$ apt-get update && apt-get install -y kubeadm kubelet kubectl

Configure Kubernetes

Using the join command from above, join the worker to the cluster.

Sanity Check

Back on the master node, run the following command as the user you created:

$ kubectl get nodes

You should see something similar to:

NAME      STATUS    ROLES     AGE       VERSION
node-1    Ready     master    28m       v1.11.2
node-2    Ready     <none>    3m        v1.11.2
node-3    Ready     <none>    35s       v1.11.2

That’s it!


Remove the droplets once done:

$ for i in 1 2 3; do
    doctl compute droplet delete node-$i
done