Add an IP to an existing k3s cluster

add-ip-to-k3s.md

Problem: Let's say you have created a k3s cluster and now you want to access it from outside the network. To do that you need to assign a public IP to your machine the cluster is running on. Recently I installed tailscale on the VM (on which a k3s cluster was running) so that I can access the cluster from my home. Here's how I did that.

1. First we need to add the Tailscale IP to tls-san of the cluster.

By default, configuration files are read from /etc/rancher/k3s/config.yaml and /etc/rancher/k3s/config.yaml.d/*.yaml in alphabetical order. 1

So, we create a config file if it doesn't exist:

cd /etc/rancher/k3s
touch config.yaml

And, add this content to the file:

tls-san:
  - <tailscale-ip>
  - <other ips>

2. Restart k3s cluster service

systemctl restart k3s

3. Collect the update kubeconfig file and update the following field:

    server: <tailscale-ip>:6443