Building a Home Lab Kubernetes Cluster with Old Hardware and k3s

If you've read my previous post about building a Raspberry Pi k3s cluster, you know I'm a huge fan of home labs. There's something uniquely satisfying about getting distributed systems running on a bunch of hardware you already own. This time, though, I wanted something a bit more powerful-a cluster that could handle not just learning and tinkering, but also heavier dev, CI/CD, and even ML workloads.

And as it turns out, there's a ton you can do with a handful of old laptops, a simple switch, and Ubuntu Server. If you're thinking about upgrading your home cluster or want to avoid vendor lock-in, this one's for you.

Why Move From Raspberry Pi to x86?

Don't get me wrong-RPi clusters are awesome for learning, hacking, and even some light home automation. But if you've ever tried running real dev pipelines, CI/CD, or any data-heavy ML stuff, you'll hit those limits fast. Plus, WiFi can get a bit flaky when you're trying to keep nodes connected under load.

I had a few spare laptops sitting around, and it made perfect sense to give them a second life and push them to their limits. Bonus: with Ethernet and a decent switch, you get much more reliable connectivity.

Network Setup: Keep It Simple (and Reliable)

For this build, I kept things straightforward: all nodes are wired to a simple network switch. This gives much better performance and reliability compared to WiFi, but honestly, you could still pull this off over wireless if needed.

A quick tip:

• Reserve static IPs for each node using your router's DHCP reservations.
• This makes node management, SSH, and Kubernetes networking so much easier.
• Check your DHCP table and make sure every machine has a unique, predictable IP address.

Getting Ubuntu Server Set Up on Each Node

Here's a high level diagram of what my setup looks like:

Let's talk about prepping each machine. My old laptops had a new lease on life running Ubuntu Server. I recommend Ubuntu Server LTS for its simplicity and compatibility. If you're using VMs, just make sure to set the NIC to bridged mode so each VM acts as a full member of your home LAN.

Here's my go-to checklist for each node:

1. Update the system and install SSH:

   sudo apt update && sudo apt upgrade -y
   sudo apt install openssh-server -y
   sudo systemctl enable ssh
   sudo systemctl start ssh

1. Set a memorable hostname:

   sudo hostnamectl set-hostname master   # or worker-1, etc.

1. (Optional) Update /etc/hosts for local resolution:

   sudo nano /etc/hosts

Change any lines like 127.0.1.1 old-hostname to your new hostname.

1. Find your node's IP address:

   ip a

Use this IP for your DHCP reservation so it always stays the same.

1. Test SSH from another machine:

   ssh <username>@<node-ip>

Installing k3s: Lightweight, Powerful, Familiar

This process feels pretty magical the first time you see it all come together. I stuck with k3s-lightweight and perfect for home or edge clusters.

On the Control Plane Node ("master")

1. Install k3s:

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

1. Check that k3s is running:

   sudo systemctl status k3s

1. Get your cluster join token:

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

Copy this somewhere safe-you'll need it for your worker nodes.

1. Get the node's LAN IP:

   ip a

Let's say your master node IP is 192.168.0.200.

1. Check your cluster status:

   kubectl get nodes

If you ever want to reset/reinstall k3s, just run:

sudo /usr/local/bin/k3s-uninstall.sh

On Each Worker Node ("worker-1", "worker-2", etc.)

1. Join the cluster:

   curl -sfL https://get.k3s.io | K3S_URL=https://192.168.0.200:6443 K3S_TOKEN=<your-token-here> INSTALL_K3S_EXEC="--node-ip=<worker-ip>" sh -

Replace 192.168.0.200 with your control plane's IP.

Replace <your-token-here> with the token from your master node.

Replace <worker-ip> with this worker's IP, e.g., 192.168.0.201.

1. That's it! The node will auto-register with your cluster. No manual kubeconfig needed.

2. Check the cluster again from the master:
   

   kubectl get nodes

You should see both master and your worker(s) as Ready!

Troubleshooting and Gotchas

As with any home lab project, there are always a few snags-here's what I ran into and how to fix it:

• Node not joining?

  • Double-check your token (no spaces, copy the whole thing).
  • Make sure you can ping the control plane from your worker node.
  • Firewalls can get in the way. Ensure port 6443 is open between nodes.
  • If you get hostname conflicts, just change the hostname and restart the k3s agent (sudo systemctl restart k3s-agent).

• Cluster state looks weird after hostname change?

  • You might see both the old and new hostnames in kubectl get nodes. Just delete the old one:

  kubectl delete node <old-node-name>
  

• IP address keeps changing?

  • Make a DHCP reservation for each node's MAC address in your router.

• WiFi unreliable?

  • Ethernet is always the best bet for clusters, especially for heavy workloads.

What's Next?

With the basics in place, you're ready to:

• Run and test real-world apps and dev environments
• Build your own CI/CD pipelines
• Experiment with ML workloads on dedicated nodes

This way, you get all the power of a real Kubernetes lab, but full control and no monthly surprises from a cloud provider.

Lessons Learned

• RPi clusters are great for edge computing and learning, but once you need real muscle, x86 hardware makes a huge difference.
• WiFi is convenient, but Ethernet is still king for stable clusters-especially if you're doing anything performance-sensitive.
• Old laptops/desktops are a goldmine for home lab builds. Don't let them collect dust!

Final Thoughts

If you have old machines and a bit of curiosity, you can build a cluster that's surprisingly capable-no Raspberry Pis required.

And if you've already done it with RPis, this is the perfect upgrade path.

Keep an eye out for my next post where I'll deep-dive into adding observability and tooling!

Happy clustering! 🫡