k0s GA: Zero-Friction Kubernetes for Edge and CI/CD

Introduction

In mid-2020, k0s reached general availability, delivering on its promise of zero-friction Kubernetes. Unlike k3s (single binary with SQLite) or microk8s (snap-based), k0s offered a truly minimal Kubernetes distribution with no host OS dependencies, making it ideal for edge computing, air-gapped deployments, and CI/CD pipelines.

This mattered because it represented the evolution of lightweight Kubernetes beyond convenience to absolute minimalism. k0s’s single-binary model, container runtime agnosticism, and air-gapped capabilities addressed use cases where even k3s or microk8s were too heavy or had too many dependencies.

Historical note: k0s had been in preview since late 2019, with GA in 2020 marking its production readiness. Developed by Mirantis, k0s would become a key player in the lightweight Kubernetes ecosystem alongside k3s and microk8s.

k0s GA Features

Zero-Friction Architecture

• Single Binary: All Kubernetes components in one ~50MB binary with no external dependencies.
• No Docker Required: Works with containerd, CRI-O, or Docker—your choice.
• No Host OS Dependencies: Doesn’t require specific OS packages or configurations.
• Static Binary: Fully static binary works on any Linux distribution.

Edge Computing Optimized

• Minimal Footprint: ~400MB memory for single-node cluster.
• Fast Startup: Clusters start in seconds, ideal for edge device reboots.
• Offline Capable: Can be deployed in completely air-gapped environments.
• ARM Support: Excellent ARM64 support for edge devices.

Production Ready

• High Availability: Full HA support with multiple control plane nodes.
• Upgrade Workflows: In-place upgrades with minimal downtime.
• Security Hardening: Production-grade security defaults and configurations.
• Enterprise Support: Mirantis provides enterprise support and SLAs.

k0s vs k3s vs microk8s: Updated Comparison (2020)

Single Binary Deployment Model

k0s’s single-binary approach eliminates installation complexity:

# Download binary
wget https://github.com/k0sproject/k0s/releases/download/v1.0.0/k0s-v1.0.0-linux-amd64
chmod +x k0s-v1.0.0-linux-amd64
sudo mv k0s-v1.0.0-linux-amd64 /usr/local/bin/k0s

# Create and start controller
sudo k0s install controller
sudo k0s start

# Get kubeconfig
sudo k0s kubeconfig admin > ~/.kube/config

No package managers, no dependencies, no configuration files—just a binary.

Edge Computing Patterns

Raspberry Pi Deployment

# On Raspberry Pi (ARM64)
wget https://github.com/k0sproject/k0s/releases/download/v1.0.0/k0s-v1.0.0-linux-arm64
chmod +x k0s-v1.0.0-linux-arm64
sudo mv k0s-v1.0.0-linux-arm64 /usr/local/bin/k0s

# Start controller
sudo k0s install controller --single
sudo k0s start

Multi-Node Edge Cluster

# On controller node
sudo k0s install controller
sudo k0s start
sudo k0s token create --role=worker > worker-token.txt

# On worker nodes
sudo k0s install worker --token-file worker-token.txt
sudo k0s start

Air-Gapped Deployment

k0s excels in air-gapped environments:

# On internet-connected machine
# Download k0s binary and container images
k0s airgap bundle

# Transfer bundle to air-gapped environment
scp k0s-airgap-bundle.tar air-gapped-host:/tmp/

# On air-gapped host
sudo k0s install controller --airgap-file /tmp/k0s-airgap-bundle.tar
sudo k0s start

CI/CD Integration

k0s’s fast startup and single-binary model make it ideal for CI/CD:

# GitHub Actions example
name: Kubernetes Tests
on: [push]
jobs:
  test:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v2
      - name: Install k0s
        run: |
          wget https://github.com/k0sproject/k0s/releases/download/v1.0.0/k0s-v1.0.0-linux-amd64
          chmod +x k0s-v1.0.0-linux-amd64
          sudo mv k0s-v1.0.0-linux-amd64 /usr/local/bin/k0s
      - name: Start k0s
        run: |
          sudo k0s install controller --single
          sudo k0s start
          sudo k0s kubeconfig admin > $HOME/.kube/config
      - name: Run tests
        run: |
          kubectl get nodes
          # Run your tests
      - name: Cleanup
        if: always()
        run: sudo k0s stop

Comparison: k0s vs k3s for Edge

Choose k0s When:

• Zero Dependencies: Need absolute minimal host OS dependencies.
• Container Runtime Choice: Want to choose between containerd, CRI-O, or Docker.
• Air-Gapped: Deploying in completely offline environments.
• Static Binary: Need a fully static binary that works anywhere.

Choose k3s When:

• Rancher Integration: Using Rancher for cluster management.
• SQLite Simplicity: Single-node deployments benefit from SQLite backend.
• ARM32 Support: Need ARM32 support (k0s focuses on ARM64).
• Ecosystem: Want access to Rancher’s ecosystem and tools.

Practical Considerations

Resource Requirements

Even with minimal footprint, k0s needs:

• Memory: ~400MB for single-node, ~200MB per additional node.
• CPU: 0.5 cores minimum, 1 core recommended.
• Disk: ~500MB for binary and cluster state.

Container Runtime Selection

k0s supports multiple container runtimes:

• containerd: Default, recommended for production.
• CRI-O: Alternative OCI-compliant runtime.
• Docker: Legacy support, not recommended for new deployments.

Upgrade Workflows

k0s supports in-place upgrades:

# Upgrade to new version
sudo k0s stop
sudo k0s install controller --force
sudo k0s start

Upgrades are designed to be zero-downtime for HA clusters.

Caveats & Lessons Learned

• Container Runtime: Must install and configure container runtime separately (containerd, CRI-O, or Docker).
• Networking: Requires CNI plugin installation; no default networking included.
• Add-Ons: All add-ons (DNS, storage, ingress) require manual installation.
• Learning Curve: Single-binary model is simple, but understanding k0s-specific commands takes time.

Common Failure Modes

• “Container runtime not found”: k0s requires a container runtime; install containerd, CRI-O, or Docker first.
• “No CNI installed”: Pods won’t start without a CNI plugin; install Calico, Flannel, or Cilium.
• “Air-gap bundle missing”: Air-gapped deployments require pre-downloaded bundles; plan ahead.

Conclusion

k0s’s general availability in 2020 marked the maturation of zero-friction Kubernetes. Its single-binary model, container runtime agnosticism, and air-gapped capabilities made it the most minimal production-ready Kubernetes distribution available. While k3s and microk8s remained popular for their specific strengths (Rancher integration, easy add-ons), k0s carved out a niche for absolute minimalism and flexibility.

For edge computing, air-gapped deployments, and CI/CD pipelines, k0s provided a compelling alternative to heavier distributions. Its zero-dependency model and single-binary deployment made Kubernetes accessible in environments where traditional distributions were impractical or impossible.

The lightweight Kubernetes ecosystem had matured: k3s for Rancher-managed edge, microk8s for Ubuntu-based development, and k0s for zero-friction deployments. Teams could now choose the right lightweight distribution based on their specific needs, dependencies, and operational preferences.