Setting up a Raspberry Pi Kubernetes Cluster with Ubuntu 20.04

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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 efficiency you can use to run tasks without breaking the bank. Canonical recently released Ubuntu 20.04, with full support for the Raspberry Pi. In this video, we take a look at how to create a Pi-powered Kubernetes cluster based on Ubuntu.

Relevant Links
Original Video
Ubuntu 20.04 Download (Pi Version)

What You'll Need

  • At least two Raspberry Pi 4 boards
  • A Raspberry-certified power supply for each
  • An SD card with decent speed
  • SD card flashed with Ubuntu 20.04 for each


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/firmware/cmdline.txt and add:

cgroup_enable=cpuset cgroup_enable=memory cgroup_memory=1 swapaccount=1

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
Reboot

Reboot each Pi:

 sudo reboot
Create a user for yourself
 sudo adduser jay
 usermod -aG sudo jay
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 nano /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
Test that docker is working properly

Check docker daemon:

 systemctl status docker

Run the hello-world container:

 docker run hello-world
Add Kubernetes repository
 sudo nano /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

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
pod.yml
 apiVersion: v1
 kind: Pod
 metadata:
   name: nginx-example
   labels:
     app: nginx
 spec:
   containers:
     - name: nginx
       image: linuxserver/nginx
       ports:
         - containerPort: 80
           name: "nginx-http"
service-nodeport.yml
 apiVersion: v1
 kind: Service
 metadata:
   name: nginx-example
 spec:
   type: NodePort
   ports:
     - name: http
       port: 80
       nodePort: 30080
       targetPort: nginx-http
   selector:
     app: nginx
Apply the pod yaml file
 kubectl apply -f pod.yml

Check the status with:

 kubectl get pods

Check the status with more info:

 kubectl get pods -o wide


Apply the service yaml file
 kubectl apply -f service-nodeport.yml

Check the status with:

 kubectl get service