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Building a Kubernetes Cluster with Kubeadm

Hands-On Lab

 

Photo of Will Boyd

Will Boyd

DevOps Team Lead in Content

Length

01:00:00

Difficulty

Beginner

A Kubernetes cluster is a powerful tool for managing containers in a highly-available manner. Kubeadm greatly simplifies the process of setting up a simple cluster. In this hands-on lab, you will build your own working Kubernetes cluster using Kubeadm.

What are Hands-On Labs?

Hands-On Labs are scenario-based learning environments where learners can practice without consequences. Don't compromise a system or waste money on expensive downloads. Practice real-world skills without the real-world risk, no assembly required.

Building a Kubernetes Cluster with Kubeadm

Introduction

A Kubernetes cluster is a powerful tool for managing containers in a highly-available manner. Kubeadm greatly simplifies the process of setting up a simple cluster. In this hands-on lab, you will build your own working Kubernetes cluster using Kubeadm.

Solution

Begin by logging in to the lab servers using the credentials provided on the hands-on lab page:

ssh cloud_user@PUBLIC_IP_ADDRESS

Install Docker on all three nodes

Do the following on all three nodes:

  1. Add the Docker GPG key:

    curl -fsSL https://download.docker.com/linux/ubuntu/gpg | sudo apt-key add -
  2. Add the Docker repository:

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

    sudo apt-get update
  4. Install Docker:

    sudo apt-get install -y docker-ce=18.06.1~ce~3-0~ubuntu
  5. Hold Docker at this specific version:

    sudo apt-mark hold docker-ce
  6. Verify that Docker is up and running with:

    sudo systemctl status docker

    Make sure the Docker service status is active (running)!

Install Kubeadm, Kubelet, and Kubectl on all three nodes

Install the Kubernetes components by running this on all three nodes:

  1. Add the Kubernetes GPG key:

    curl -s https://packages.cloud.google.com/apt/doc/apt-key.gpg | sudo apt-key add -
  2. Add the Kubernetes repository:

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

    sudo apt-get update
  4. Install kubelet, kubeadm, and kubectl:

    sudo apt-get install -y kubelet=1.12.7-00 kubeadm=1.12.7-00 kubectl=1.12.7-00
  5. Hold the Kubernetes components at this specific version:

    sudo apt-mark hold kubelet kubeadm kubectl

Bootstrap the cluster on the Kube master node

  1. On the Kube master node, do this:

    sudo kubeadm init --pod-network-cidr=10.244.0.0/16

    That command may take a few minutes to complete.

  2. When it is done, set up the local kubeconfig:

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

    Take note that the kubeadm init command printed a long kubeadm join command to the screen. You will need that kubeadm join command in the next step!

  3. Run the following command on the Kube master node to verify it is up and running:

    kubectl version

    This command should return both a Client Version and a Server Version.

Join the two Kube worker nodes to the cluster

  1. Copy the kubeadm join command that was printed by the kubeadm init command earlier, with the token and hash. Run this command on both worker nodes, but make sure you add sudo in front of it:

    sudo kubeadm join $some_ip:6443 --token $some_token --discovery-token-ca-cert-hash $some_hash
  2. Now, on the Kube master node, make sure your nodes joined the cluster successfully:

    kubectl get nodes

    Verify that all three of your nodes are listed. It will look something like this:

    NAME            STATUS     ROLES    AGE   VERSION
    ip-10-0-1-101   NotReady   master   30s   v1.12.2
    ip-10-0-1-102   NotReady   <none>   8s    v1.12.2
    ip-10-0-1-103   NotReady   <none>   5s    v1.12.2

    Note that the nodes are expected to be in the NotReady state for now.

Set up cluster networking with flannel

  1. Turn on iptables bridge calls on all three nodes:

    echo "net.bridge.bridge-nf-call-iptables=1" | sudo tee -a /etc/sysctl.conf
    sudo sysctl -p
  2. Next, run this only on the Kube master node:

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

    Now flannel is installed! Make sure it is working by checking the node status again:

    kubectl get nodes

    After a short time, all three nodes should be in the Ready state. If they are not all Ready the first time you run kubectl get nodes, wait a few moments and try again. It should look something like this:

    NAME            STATUS   ROLES    AGE   VERSION
    ip-10-0-1-101   Ready    master   85s   v1.12.2
    ip-10-0-1-102   Ready    <none>   63s   v1.12.2
    ip-10-0-1-103   Ready    <none>   60s   v1.12.2

Conclusion

Congratulations — you've completed this hands-on lab!