k3s: A Lightweight Kubernetes Distribution

What is k3s?

k3s is a lightweight Kubernetes distribution developed by Rancher Labs. It is designed for resource-constrained environments like IoT devices, home labs, or small-scale deployments. This document covers its key features and installation steps on both Raspberry Pi and multi-node clusters.

Key Features of k3s

• Lightweight: Smaller footprint and fewer system resources than standard Kubernetes.
• Simplified Deployment: Runs as a single binary, reducing complexity.
• Built-in SQLite or etcd: Simplifies setup by eliminating external dependencies.
• IoT & Edge Compatibility: Works well on Raspberry Pi and ARM architectures.
• Helm Support: Allows easy application deployment.

Installing k3s on Raspberry Pi

Step 1: Prepare the Raspberry Pi

Ensure your system is up to date:

sudo apt-get update && sudo apt-get upgrade -y

Step 2: Install k3s

curl -sfL https://get.k3s.io | sh -

This installs k3s as a service and sets up a single-node cluster.

Step 3: Verify Installation

sudo kubectl get nodes

Your Raspberry Pi should be listed as Ready .

Step 4: Deploy a Test Application

kubectl create deployment nginx-test --image=nginx
kubectl expose deployment nginx-test --type=NodePort --port=80

Access nginx via your Raspberry Pi’s IP address.

Setting Up a Multi-Node k3s Cluster

Step 1: Install the k3s Server (Control Plane)

curl -sfL https://get.k3s.io | sh -

Retrieve the token for joining worker nodes:

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

Step 2: Join Worker Nodes

curl -sfL https://get.k3s.io | K3S_URL="https://YOUR_K3S_SERVER_IP:6443" K3S_TOKEN="YOUR_NODE_TOKEN" sh -

Replace the placeholders with the actual server IP and token.

Step 3: Verify Cluster Status

kubectl get nodes

All nodes should appear with the status Ready .

Step 4: Deploy Applications

Use kubectl or Helm to deploy applications.

Example Deployment Manifest

apiVersion: apps/v1
kind: Deployment
metadata:
  name: hello-k3s
spec:
  replicas: 1
  selector:
    matchLabels:
      app: hello-k3s
  template:
    metadata:
      labels:
        app: hello-k3s
    spec:
      containers:
      - name: hello-k3s
        image: nginx
        ports:
        - containerPort: 80

Apply Deployment

kubectl apply -f deployment.yaml

Expose Service

kubectl expose deployment hello-k3s --type=NodePort --port=80

Conclusion

k3s makes it easier to deploy Kubernetes in constrained environments while retaining compatibility with standard Kubernetes features. By following these steps, you can set up a k3s cluster for learning, development, or small-scale production use.