K3s vs K8s 2026: Lightweight vs Full Kubernetes

K3s is a certified Kubernetes distribution that runs in 512 MB of RAM. Full K8s (kubeadm) needs 2 GB minimum. Both are 100% conformant — the same workloads run on both. The difference is what is included, what is removed, and where each fits.

Architecture differences

Resource requirements

Installation

K8s (kubeadm)

# Disable swap, load modules, configure sysctl (see full guide)
# Install containerd
sudo apt-get install -y containerd.io

# Install kubeadm
sudo apt-get install -y kubelet kubeadm kubectl

# Initialize
sudo kubeadm init --pod-network-cidr=10.244.0.0/16

# Configure kubectl
mkdir -p ~/.kube && sudo cp /etc/kubernetes/admin.conf ~/.kube/config

# Install CNI
kubectl apply -f https://github.com/flannel-io/flannel/releases/latest/download/kube-flannel.yml

# Join workers (on each worker node)
sudo kubeadm join <master-ip>:6443 --token <token> --discovery-token-ca-cert-hash sha256:<hash>

Full guide: Install Kubernetes on Rocky Linux 9

K3s

# Server (control plane + worker)
curl -sfL https://get.k3s.io | sh -

# That's it. kubectl works immediately:
sudo k3s kubectl get nodes

# Join workers
curl -sfL https://get.k3s.io | K3S_URL=https://<server-ip>:6443 \
  K3S_TOKEN=$(sudo cat /var/lib/rancher/k3s/server/node-token) sh -

One command. No prerequisites beyond a Linux machine.

High availability

K8s HA

# 3 control plane nodes with external etcd or stacked etcd
sudo kubeadm init --control-plane-endpoint "load-balancer:6443" --upload-certs
# Join additional control planes
sudo kubeadm join load-balancer:6443 --control-plane --certificate-key <key>

Requires external load balancer, etcd cluster management, certificate distribution.

K3s HA

# Server 1 (with embedded etcd)
curl -sfL https://get.k3s.io | sh -s - server --cluster-init

# Server 2 and 3
curl -sfL https://get.k3s.io | sh -s - server \
  --server https://server1:6443 \
  --token $(cat /var/lib/rancher/k3s/server/node-token)

K3s handles embedded etcd, certificate management, and load balancing internally. Three commands for a 3-node HA cluster.

What K3s removes

K3s achieves its small footprint by removing and replacing components:

• Cloud controller manager — removed (not needed for edge/bare-metal)
• Storage drivers — in-tree drivers removed (use CSI)
• Legacy APIs — deprecated alpha APIs removed
• Docker — not supported (containerd only)
• etcd — replaced with SQLite by default (etcd available as option)

Everything removed is either deprecated, cloud-specific, or replaceable. K3s is still 100% CNCF conformant — all standard Kubernetes APIs and behaviors work.

Edge and IoT

K3s was built for edge computing:

# ARM64 (Raspberry Pi 4, NVIDIA Jetson)
curl -sfL https://get.k3s.io | sh -

# ARM (Raspberry Pi 3)
curl -sfL https://get.k3s.io | INSTALL_K3S_EXEC="--disable traefik" sh -

# Air-gapped install
# Download binary + images, copy to node
sudo cp k3s /usr/local/bin/
sudo cp k3s-airgap-images-amd64.tar /var/lib/rancher/k3s/agent/images/
sudo k3s server

K3s runs on:

• Raspberry Pi (2 GB+ RAM)
• NVIDIA Jetson (AI at the edge)
• Intel NUC
• Industrial PCs
• VMs with 512 MB RAM

Full K8s does not fit on these devices — the control plane alone exceeds their memory.

When K3s matches K8s

K3s is conformant Kubernetes. If it works on K8s, it works on K3s.

Decision guide

Choose K8s (kubeadm) when:

• You need full control over every component (etcd tuning, custom kubelet flags)
• You are running large clusters (100+ nodes) where etcd performance matters
• Cloud provider integration is needed (cloud controller manager)
• Your organization requires the exact upstream Kubernetes distribution
• You have experienced Kubernetes administrators who manage the cluster

Choose K3s when:

• Edge, IoT, or resource-constrained environments (under 4 GB RAM)
• You want the fastest path to a working cluster (30 seconds)
• Development and testing environments (local Kubernetes)
• Small production clusters (3-20 nodes)
• You want batteries-included (Traefik, Flannel, ServiceLB, Helm controller)
• Air-gapped environments where a single binary is easier to distribute
• Managed by Rancher for multi-cluster

Related

• EKS vs GKE vs AKS 2026
• Kind vs Minikube 2026
• Install Kubernetes on Rocky Linux 9
• Rancher vs OpenShift 2026
• containerd vs CRI-O 2026