Joining Linux Nodes to a Cluster

Once you have setup a Kubernetes master node and selected your desired network solution, you are ready to join Linux nodes to your cluster. This requires some preparation on the Linux node before joining.

Tip

The Linux instructions are tailored towards Ubuntu 16.04. Other Linux distributions certified to run Kubernetes should also offer equivalent commands that you can substitute. They will also interoperate successfully with Windows.

Preparing a Linux node

Note

Unless explicitly specified otherwise, run any commands in an elevated, root-user shell.

First, get into a root shell:

sudo –s

Make sure your machine is up to date:

apt-get update && apt-get upgrade

Install Docker

To be able to use containers, you need a container engine, such as Docker. To get the most recent version, you can use these instructions for Docker installation. You can verify that docker is installed correctly by running hello-world image:

docker run hello-world

Install kubeadm

Download kubeadm binaries for your Linux distribution and initialize your cluster.

Important

Depending on your Linux distribution, you may need to replace kubernetes-xenial below with the correct codename.

curl -s https://packages.cloud.google.com/apt/doc/apt-key.gpg | apt-key add -
cat <<EOF >/etc/apt/sources.list.d/kubernetes.list
deb http://apt.kubernetes.io/ kubernetes-xenial main
EOF
apt-get update && apt-get install -y kubelet kubeadm kubectl 

Disable swap

Kubernetes on Linux requires swap space to be turned off:

nano /etc/fstab  # (remove a line referencing 'swap.img' , if it exists)
swapoff -a

(Flannel Only) Enable bridged IPv4 traffic to iptables

If you chose Flannel as your networking solution it is recommended to enable bridged IPv4 traffic to iptables chains. You should have already done this for the master and now need to repeat it for the Linux node intending to join. It can be done using the following command:

sudo sysctl net.bridge.bridge-nf-call-iptables=1

Copy Kubernetes certificate

As regular, (non-root) user, perform the following 3 steps.

  1. Create Kubernetes for Linux directory:
mkdir -p $HOME/.kube
  1. Copy the Kubernetes certificate file ($HOME/.kube/config) from master and save as $HOME/.kube/config on the worker.

Tip

You can use scp-based tools such as WinSCP to transfer the config file between nodes.

  1. Set file ownership of the copied config file as follows:
sudo chown $(id -u):$(id -g) $HOME/.kube/config

Joining node

Finally, to join the cluster, run the kubeadm join command we noted down earlier as root:

kubeadm join <Master_IP>:6443 --token <some_token> --discovery-token-ca-cert-hash <some_hash>

If successful, you should see similar output to this:

text

Next steps

In this section, we covered how to join Linux workers to our Kubernetes cluster. Now you are ready for step 6: