K3s add node

This guide walks you through adding a new agent node to an existing K3s cluster. You'll need access to both the master node and the new agent node.

Prerequisites

• An existing K3s cluster with at least one master/server node
• Root or sudo access on both the master and agent nodes
• Network connectivity between the nodes on port 6443

Step 1: Get the Node Token

On your K3s master/server node, retrieve the cluster token that will authenticate the new agent:

1sudo cat /var/lib/rancher/k3s/server/node-token

This command displays the secure token required for agent nodes to join the cluster. Copy this token - you'll need it in the next step.

Step 2: Add the Agent Node

On your new agent node, run the following command to install K3s and join the cluster:

1curl -sfL https://get.k3s.io | \
2  INSTALL_K3S_VERSION=v1.26.7+k3s1 \
3  INSTALL_K3S_EXEC="agent --server https://192.168.3.2:6443 --node-ip 192.168.3.3 --node-external-ip 192.168.3.3" \
4  K3S_TOKEN=<your-k3s-token> \
5  K3S_NODE_NAME=agent \
6  sh -

Important: Customize These Values

Before running the command, replace the following values with your own:

• INSTALL_K3S_VERSION: Specify the K3s version (use v1.26.7+k3s1 or match your master node version)
• --server https://192.168.3.2:6443: Replace 192.168.3.2 with your master node's IP address
• --node-ip 192.168.3.3: Replace 192.168.3.3 with this agent node's IP address
• --node-external-ip 192.168.3.3: Replace with this agent node's external-facing IP (usually the same as node-ip)
• K3S_TOKEN: Replace with the token from Step 1
• K3S_NODE_NAME: Choose a descriptive name for this agent node

What This Command Does

1. Downloads the K3s installation script
2. Installs K3s in agent mode (not as a server)
3. Configures the agent to connect to your master node
4. Registers the node with your specified name and IP addresses
5. Automatically starts the K3s agent service

Verify the Node Joined

Back on your master node, verify the new agent appears in the cluster:

1kubectl get nodes

You should see your new agent node listed with a "Ready" status after a few moments.