How to build your own Raspberry Pi Kubernetes Cluster

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Overview

Kubernetes is a very powerful platform to scale your applications, and the Raspberry Pi is a low-cost computer with excellent power efficiencty you can use to run tasks without breaking the bank. If you put the two together, you can have a low-cost and scalable platform for Kubernetes on the Raspberry Pi. In this video, we take a look at how to create a Pi-powered Kubernetes cluster.

Relevant Links
Original Video
Raspbian Downloads

Errata

Pods created do not have access to the Internet. The instructions on this page have been fixed, but as a result, one command will be changed from the video and one new command was added that was not present in the video.

What You'll Need

  • At least two Raspberry Pi boards (Pi 4 is best)
  • A Raspberry-certified power supply for each
  • An SD card with decent speed
  • SD card flashed with Raspbian (Lite edition preferred)


Set-up Process (do the following on each Raspberry Pi)

Edit the host name

Edit /etc/hosts and /etc/hostname on the SD card to the actual name of the instance

For example: 

 k8s-master
 k8s-worker-01

(Or whatever naming scheme you wish)

Configure boot options

Edit /boot/cmndline.txt and add: 

cgroup_enable=cpuset cgroup_memory=1 cgroup_enable=memory

Note: Add that to the end of the first line, do not create a new line.

Install all updates
 sudo apt update && sudo apt dist-upgrade
Disable swap
 sudo dphys-swapfile swapoff
 sudo dphys-swapfile uninstall
 sudo apt purge dphys-swapfile
Reboot

Reboot each Pi: 

 sudo reboot
Install Docker
 curl -sSL get.docker.com | sh
 sudo usermod -aG docker jay
Set Docker daemon options

Edit the daemon.json file (this file most likely won't exist yet) 

 sudo vim /etc/docker/daemon.json

 {
   "exec-opts": ["native.cgroupdriver=systemd"],
   "log-driver": "json-file",
   "log-opts": {
     "max-size": "100m"
   },
   "storage-driver": "overlay2"
 }

== Enable routing

Find the following line in the file: 

 /etc/sysctl.conf

   #net.ipv4.ip_forward=1

Uncomment that line.

Reboot again
 sudo reboot
Add Kubernetes repository
 sudo vim /etc/apt/sources.list.d/kubernetes.list

Add: 

 deb http://apt.kubernetes.io/ kubernetes-xenial main

Add the GPG key to the Pi: 

 curl -s https://packages.cloud.google.com/apt/doc/apt-key.gpg | sudo apt-key add -
Install required Kubernetes packages
 sudo apt update
 sudo apt install kubeadm kubectl kubelet

Note: If you get errors with the first command, wait a few minutes and try again.

Master-only

Initialize Kubernetes

Run: 

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

Note: The video, and the previous version of this article recommended the following command: 

 kubeadm init --pod-network-cidr=10.17.0.0/16 --service-cidr=10.18.0.0/24 --service-dns-domain=mydomain.com

While that can work, it goes against the best practice for flannel. Source. Thank you to the viewer that brought this to my attention, but I cannot find his comment to credit him.

Once this runs, you will get some output that will include the join command, but don't join nodes yet. Copy this somewhere for later.

Set up config directory

The previous command will give you three additional commands to run, most likely these: 

 mkdir -p ~.kube
 sudo cp /etc/kubernetes/admin.conf ~/.kube/config
 sudo chown $(id -u):$(id -g) $HOME/.kube/config

Go ahead and run those, but if it recommends different commands, run those instead.

Install flannel network driver
 kubectl apply -f https://raw.githubusercontent.com/coreos/flannel/master/Documentation/kube-flannel.yml

Note: The lack of sudo is intentional

Make sure all the pods come up
kubectl get pods --all-namespaces
Join worker nodes to the cluster

Once all of the pods have come up, run the join command on each worker node. This command was provided in an earlier step.

Check status of nodes

See if the nodes have joined successfully, run the following command a few times until everything is ready: 

 kubectl get nodes
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