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Adding a Node

There are a few steps to adding a new worker node to the Cluster.

  1. Install Base OS (eg: Ubuntu 22.04)
  2. Install Ansible Host SSH Key onto the new node.
  3. Include k8s-node# in the Ansible hosts workers.
  4. Include node in nodes section of gateway-install / defaults / main.yaml.
  5. Run gateway-install and build-k8s-cluster playbooks.

Step 1 - Install Base OS

Method A - Using the PXE Network Installer

The easiest method for adding a new k8s cluster node is to use the pre-configured PXE Installer.

Method B - Manually Install Ubuntu Host OS

You can manually provision the node with Ubuntu 22.04 Server and then attach it to the cluster subnet and run an Ansible Playbook to add it to the k8s cluster. In this scenario, you would start from Step 6 in PXE Installer: Copying over the Ansible Host SSH Keys.

Ensure that you remove /etc/hostname file from the node before connecting it to the cluster subnet. (See dnsmasq: hostname from dhcp for more details)

Step 2 - Install Ansible Host SSH Key

From the Ansible host, install the SSH key to allow Ansible playbook to run. (This is using SSH JumpHost to provision Ansible Playbook on a Worker Node, via the Gateway Device.)

ansible-host#> ssh-copy-id -i ~/.ssh/id_rsa.pub -o \
ProxyCommand="ssh -W %h:%p ubuntu@192.168.1.xxx (Gateway Device)" ubuntu@k8s-node7

If this does not work (eg: permission denied), you can log in from the Gateway Device to the new node and add the Ansible Host’s SSH key in ~/.ssh/authorized_keys file manually.

Step 3 - Update Ansible hosts

Ensure the following section of the hosts file spans k8s-node[1-7] and nodes map in gateway-install / defaults / main.yaml.

[workers]
k8s-node[2:7] ansible_user=ubuntu ansible_ssh_private_key_file=~/.ssh/id_rsa

Step 4 - Use gateway-install Ansible Playbook

Add the new k8s worker nodes defined in gateway-install / defaults / main.yaml

Example shows k8s-node7 being added to the known-nodes list. 

# Known nodes on cluster network
nodes:
...
- name: "k8s-node7"
  mac: "6c:4b:90:57:04:5e"
  static_ip: "192.168.57.37"
  model: "lenovo thinkcentre M910q i7"

Step 5 - Run playbooks

The new node is added to various ansible files, there are two playbooks to run.

  1. Run the gateway-install playbook and this will setup the ecosystem to allow it to connect to the Cluster subnet.

  2. Run the build-k8s-cluster (with {"reset_cluster":False}) Role to include the node as a k8s worker node and leave the rest untouched.

Once these playbooks have run, you should be able to see the new node join the k8s cluster.

gateway-device #> ssh ubuntu@k8s-control-plane-node
k8s-control-plane-node #> sudo su - kube
k8s-control-plane-node #> kubectl get nodes
NAME                     STATUS   ROLES           AGE     VERSION
k8s-control-plane-node   Ready    control-plane   6h32m   v1.25.5
k8s-node2                Ready    <none>          6h32m   v1.25.5
k8s-node3                Ready    <none>          6h32m   v1.25.5
k8s-node4                Ready    <none>          6h32m   v1.25.5
k8s-node5                Ready    <none>          6h32m   v1.25.5
k8s-node6                Ready    <none>          6h32m   v1.25.5
k8s-node7                Ready    <none>          0h32m   v1.25.5