K3s: The Lightweight Kubernetes for the Edge and IoT

Kubernetes has become the go-to orchestration tool for deploying containerized applications at scale. However, for small environments, IoT devices, and edge computing, the full Kubernetes distribution can be overkill due to its complexity and resource consumption. This is where K3s comes in — a lightweight, simplified version of Kubernetes that is designed for smaller environments but still offers the core benefits of Kubernetes.

In this blog, we'll explore what K3s is, why it’s gaining popularity, and how it makes deploying and managing Kubernetes easier for smaller-scale environments.

What is K3s?

K3s is a lightweight Kubernetes distribution designed to run in resource-constrained environments, like edge devices, IoT devices, and CI/CD pipelines. Developed by Rancher Labs, K3s aims to provide a simplified, faster, and resource-efficient version of Kubernetes without sacrificing compatibility.

K3s retains the core features of Kubernetes, so it’s fully compatible with Kubernetes API, kubectl, and Helm charts, but it has been optimized to use less memory, CPU, and storage.

Why Use K3s?

While full Kubernetes offers powerful orchestration for large clusters, it often requires more system resources and can be challenging to manage. Here’s why K3s stands out:

1. Lightweight and Fast

K3s is designed to be small and efficient. The entire K3s installation is a single binary, typically around 100MB. This is significantly smaller than the traditional Kubernetes, which can require hundreds of megabytes due to multiple components running in parallel (API server, controller manager, etc.).

With K3s, you can deploy Kubernetes on devices with limited resources such as Raspberry Pi, IoT devices, or even virtual machines with lower memory or storage capabilities.

2. Simplified Architecture

K3s reduces the complexity of the traditional Kubernetes setup by combining several components into a single binary. It replaces some Kubernetes components with simpler alternatives. For example:

etcd (the default key-value store in Kubernetes) is replaced by SQLite, reducing the memory footprint.
Containerd is used instead of Docker for managing container lifecycles, as Docker's resource usage is higher.

The simplified architecture of K3s results in faster startups, lower resource consumption, and more manageable clusters.

3. Built-in Features for Edge and IoT

K3s includes several built-in components that make it a great choice for edge and IoT applications:

Flannel (networking)
CoreDNS (DNS service)
Traefik (Ingress controller) All these are bundled by default, reducing the setup time and configuration complexity. This makes K3s ideal for environments like smart homes, factories, and remote locations.

4. Fully Compatible with Kubernetes

Despite its smaller size, K3s is still 100% Kubernetes-compatible. This means you can use the same kubectl commands, Helm charts, and Kubernetes APIs that you’re already familiar with. You won’t lose the power and flexibility of Kubernetes, and you can scale up to a full Kubernetes setup when needed.

How Does K3s Work?

K3s works by simplifying Kubernetes components to improve performance and reduce the need for hardware resources. Key differences include:

Single Binary: K3s bundles all of the Kubernetes components (API server, scheduler, controller manager, etc.) into a single binary file, which reduces both memory and CPU overhead.
Database: K3s uses SQLite (by default) as the storage backend, replacing the traditional etcd database used in full Kubernetes. For highly available configurations, K3s supports using etcd as well.
Containerd: K3s uses containerd as the container runtime instead of Docker, which reduces overhead and complexity.
K3s Agent: The K3s agent is a lighter-weight node agent that replaces the standard Kubernetes kubelet.

When Should You Use K3s?

K3s is perfect for specific use cases where lightweight and resource-efficient Kubernetes clusters are needed:

1. Edge Computing & IoT

K3s is designed for environments where the hardware is limited. If you’re deploying applications on devices like Raspberry Pi, ARM-based systems, or remote edge nodes, K3s ensures you have Kubernetes without the heavy resource overhead.

2. Development & Testing

K3s is an excellent choice for development and testing environments. It allows you to run Kubernetes on your local machine or on a virtual machine without consuming a lot of system resources, so you can quickly spin up Kubernetes clusters without the need for complex configuration.

3. CI/CD Pipelines

If you need a Kubernetes cluster for running tests in CI/CD pipelines, K3s can quickly spin up and tear down clusters with minimal overhead. It’s ideal for use cases where fast deployments are essential.

4. Small-Scale Deployments

For small production workloads where you need Kubernetes orchestration but don’t require the complexity and overhead of a large Kubernetes deployment, K3s provides a great solution.

Installing K3s

Installing K3s is incredibly easy, and it takes just a few commands to get started:

Single-Node Setup:

Run the following installation script:
```
 curl -sfL https://get.k3s.io | sh -
```
This script installs K3s and automatically starts the Kubernetes server and agent on your node.
Verify the installation:
```
 sudo k3s kubectl get node
```
You should see your node listed as ready!

Multi-Node Setup:

To create a multi-node K3s cluster, you need to install K3s on additional nodes by passing the master node’s token.

sudo k3s server &
# Kubeconfig is written to /etc/rancher/k3s/k3s.yaml
sudo k3s kubectl get node

# On a different node run the below command. 
# NODE_TOKEN comes from /var/lib/rancher/k3s/server/node-token on your server
sudo k3s agent --server https://myserver:6443 --token ${NODE_TOKEN}

K3s vs. Full Kubernetes

Feature	K3s 🚀 (Lightweight)	Kubernetes 🏗️ (Full)
Size	~100MB (single binary)	Larger, multi-component setup
Database	SQLite (default)	etcd
Container Runtime	containerd	Docker (by default)
Resource Usage	Low memory and CPU usage	High memory and CPU usage
Use Case	Edge, IoT, Development, CI/CD	Large scale production

Conclusion

K3s is an excellent solution for smaller environments that need the power of Kubernetes but with minimal resource consumption. Whether you’re working with edge devices, running a CI/CD pipeline, or building a lightweight development environment, K3s provides the perfect balance of simplicity, performance, and Kubernetes compatibility.

Its lightweight nature doesn’t mean it lacks features. It includes everything you need for container orchestration, and because it's fully compatible with Kubernetes, you won’t have to worry about compatibility issues when scaling up.

If you're looking to deploy Kubernetes on resource-constrained devices or want a more efficient setup for small-scale deployments, K3s should be at the top of your list.