Armar un cluster Kubernetes

Let's begin our journey of learning Kubernetes by setting up a practice cluster. This will allow you to get hands-on with Kubernetes as quickly as possible, so that as you learn about various Kubernetes concepts you will be able to work with them in a real cluster if you choose. In this lesson, I will guide you through the process of setting up a simple Kubernetes cluster using Linux Academy's cloud playground. After completing this lesson, you will have a simple cluster that you can work with, and you will be familiar with the process of standing up a cluster on Ubuntu servers.

Here are the commands used in this lesson. Feel free to use them as a reference, or just use them to follow along!

Add the Docker Repository on all three servers.

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

Add the Kubernetes repository on all three servers.

curl -s https://packages.cloud.google.com/apt/doc/apt-key.gpg | sudo apt-key add -
cat << EOF | sudo tee /etc/apt/sources.list.d/kubernetes.list
deb https://apt.kubernetes.io/ kubernetes-xenial main
EOF

Install Docker, Kubeadm, Kubelet, and Kubectl on all three servers.

NOTE: There are some issues being reported when installing version 1.12.2-00 from the Kubernetes ubuntu repositories. You can work around this by using version 1.12.7-00 for kubelet, kubeadm, and kubectl.

sudo apt-get update
sudo apt-get install -y docker-ce=18.06.1~ce~3-0~ubuntu kubelet=1.12.7-00 kubeadm=1.12.7-00 kubectl=1.12.7-00
sudo apt-mark hold docker-ce kubelet kubeadm kubectl

Enable net.bridge.bridge-nf-call-iptables on all three nodes.

echo "net.bridge.bridge-nf-call-iptables=1" | sudo tee -a /etc/sysctl.conf
sudo sysctl -p

On only the Kube Master server, initialize the cluster and configure kubectl.

sudo kubeadm init --pod-network-cidr=10.244.0.0/16
mkdir -p $HOME/.kube
sudo cp -i /etc/kubernetes/admin.conf $HOME/.kube/config
sudo chown $(id -u):$(id -g) $HOME/.kube/config

Install the flannel networking plugin in the cluster by running this command on the Kube Master server.

kubectl apply -f https://raw.githubusercontent.com/coreos/flannel/bc79dd1505b0c8681ece4de4c0d86c5cd2643275/Documentation/kube-flannel.yml

The kubeadm init command that you ran on the master should output a kubeadm join command containing a token and hash. You will need to copy that command from the master and run it on both worker nodes with sudo.

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

Now you are ready to verify that the cluster is up and running. On the Kube Master server, check the list of nodes.

kubectl get nodes

It should look something like this:

NAME                      STATUS   ROLES    AGE   VERSION
wboyd1c.mylabserver.com   Ready    master   54m   v1.12.2
wboyd2c.mylabserver.com   Ready       49m   v1.12.2
wboyd3c.mylabserver.com   Ready       49m   v1.12.2

Make sure that all three of your nodes are listed and that all have a STATUS of Ready.