What Sets K3s Apart from Kubernetes? A Hands‑On Guide to Lightweight Clusters

1. K3s: A Lightweight Kubernetes

K3s is a CNCF‑certified Kubernetes distribution and part of the Sandbox project, designed for low‑resource environments and maintained by Rancher Labs. It provides a small‑overhead Kubernetes cluster while retaining most of the core architecture and features of K8s.

Reasons K3s is lightweight:

Packaged as a single binary with minimal external dependencies.

Low hardware and memory requirements.

Can run as a single‑server or high‑availability server.

K3s bundles the standard Kubernetes components into a binary under 100 MB by removing extra drivers, optional volume plugins, and third‑party cloud integrations.

It runs on Linux with at least 512 MiB RAM (1 GiB recommended) and a single CPU. Its architecture mirrors K8s with master and agent nodes, includes CoreDNS, an Ingress controller, and a built‑in SQLite database, though external databases like etcd, MySQL, or PostgreSQL can be used for HA.

YAML manifests used with kubectl work the same as on K8s, allowing you to manage workloads, pods, services, and load balancing.

2. Using K3s

2.1 Installation

Basic installation command: curl -sfL https://get.k3s.io | sh - This runs the official K3s install script and starts K3s as a service.

Alternatively, download a specific version and install it, mixing server configuration options with environment variables, e.g., disabling Flannel:

$ curl -sfL https://get.k3s.io | sh - --flannel-backend none

Or set the environment variable before starting the server:

$ INSTALL_K3S_EXEC="--flannel-backend none" k3s server

2.2 Accessing the Cluster

K3s creates a kubeconfig file at /etc/rancher/k3s/k3s.yaml. Export it to use kubectl: $ export KUBECONFIG=/etc/rancher/k3s/k3s.yaml Or copy it to the default location:

$ mkdir -p ~/.kube
$ sudo k3s kubectl config view --raw | tee ~/.kube/config
$ chmod 600 ~/.kube/config

Check the cluster status: $ kubectl get nodes List all pods:

$ kubectl get pods --all-namespaces

2.3 Deploying a Service

Create a deployment:

$ kubectl create deployment nginx --image=nginx --port=80 --replicas=3

Expose it with a ClusterIP service:

$ kubectl create service clusterip nginx --tcp=80:80

Describe the service to see endpoints: $ kubectl describe service nginx Define an Ingress resource to route traffic to the service:

apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  name: nginx
  annotations:
    ingress.kubernetes.io/ssl-redirect: "false"
spec:
  rules:
  - http:
      paths:
      - path: /
        pathType: Prefix
        backend:
          service:
            name: nginx
            port:
              number: 80

Apply the Ingress:

$ kubectl apply -f <nginx-ingress-file>.yaml
$ kubectl describe ingress nginx

3. Differences Between K3s and K8s

The most noticeable difference is packaging: K3s is a single binary under 100 MB, whereas K8s consists of multiple components running as separate processes.

K3s starts a cluster in seconds and runs on AMD64, ARM64, and ARMv7, making it suitable for edge devices like Raspberry Pi Zero and low‑bandwidth environments.

For simple use cases and quick onboarding, K3s requires fewer commands and less operational overhead than full‑featured K8s.

However, for complex clusters or heavy workloads, K8s remains the preferred choice, especially when advanced HA configurations, external databases, or cloud provider integrations are needed.