K3sUp Setup Guide

Overview

This guide will help you set up a lightweight Kubernetes cluster using k3sup. The script automates the installation of K3s on multiple nodes, setting up a primary server and joining additional nodes.

Prerequisites

Before running the script, ensure you have the following:

• A set of Linux servers (e.g., cloud VMs or Raspberry Pis) with SSH access
• SSH key-based authentication set up for the user running the script
• k3sup installed on your local machine (Installation Guide)

Script Breakdown

1. Install the Primary Server

The script installs K3s on the primary server with TLS settings and saves the kubeconfig locally:

echo "Setting up primary server 1"
k3sup install --host <PRIMARY_SERVER_IP> \
--user <SSH_USER> \
--sudo \
--ssh-key ~/.ssh/id_rsa \
--cluster \
--local-path kubeconfig \
--context default \
--k3s-extra-args "--tls-san <ADDITIONAL_IPS>"

2. Retrieve the Node Token

The script fetches the node-token, which is required for adding worker nodes:

export NODE_TOKEN=$(k3sup node-token --host <PRIMARY_SERVER_IP> --user <SSH_USER>)

3. Join Additional Nodes

To add more nodes to the cluster, the script runs:

echo "Setting up additional server: 2"
k3sup join \
--host <NODE_IP> \
--server-host <PRIMARY_SERVER_IP> \
--server \
--user <SSH_USER> \
--ssh-key ~/.ssh/id_rsa \
--sudo \
--k3s-extra-args "--node-label node.kubernetes.io/worker=true"

Repeat this step for each additional node you want to add.

Running the Script

1. Update the script with the correct server IPs and SSH user.

2. Ensure your SSH key is in place (~/.ssh/id_rsa by default).

3. Run the script:

   chmod +x k3sup.sh
   ./k3sup.sh

Verifying the Cluster

Once the script completes, you can check the cluster status:

kubectl --kubeconfig kubeconfig get nodes

You should see all your nodes listed as Ready.

Troubleshooting

• Ensure firewall rules allow traffic on required ports (e.g., 6443 for API server).
• Verify SSH access between the nodes.
• Check K3s logs for errors: journalctl -u k3s -f on each node.

Next Steps

Now that your cluster is up and running, you can deploy applications using Kubernetes manifests or Helm charts. Happy clustering!