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Install Kubernetes on Raspbian on a Raspberry Pi Cluster

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Instructions

Install Kubernetes on Raspbian on a Raspberry Pi Cluster

Kubernetes on (vanilla) Raspbian Lite

Yes - you can create a Kubernetes cluster with Raspberry Pis with the default Raspberry Pi operating system called Raspbian. This means you can carry on using all the tools and packages you're used to with the officially-supported OS.

This is part of a blog post Serverless Kubernetes home-lab with your Raspberry Pis written by Alex Ellis (https://blog.alexellis.io/serverless-kubernetes-on-raspberry-pi - 12 OCTOBER 2017 on raspberrypi, Raspberry PI, swarm, serverless, docker, arm, openfaas)

Copyright disclaimer: Please provide a link to the post and give attribution to the author if you plan to use this content in your own materials.

Update - k3s and docker

My current thinking is that k3s (https://github.com/teamserverless/k8s-on-raspbian#pick-k3s) from Rancher Labs is a better option than kubeadm to bootstrap a cluster. Whilst both create a compliant Kubernetes cluster, k3s uses fewer resources, is faster and doesn't run into some of the timing issues we've seen in the community with kubeadm.

You should also see my note on installing Docker on Raspbian Buster

Pre-reqs: To install and operate Kubernetes, you use only Raspberry Pi 3B, 3B+, or 4B I'm assuming you're using wired ethernet (Wi-Fi also works, but it's not recommended) Master node setup You can either follow the steps below, or use my flashing script which automates the below. The automated flashing script must be run on a Linux computer with an SD card writer or an RPi.

Flash with a Linux host Provision a Raspberry Pi SD card

Then run:

curl -sLSf https://gist.githubusercontent.com/alexellis/fdbc90de7691a1b9edb545c17da2d975/raw/125ad6eae27e40a235412c2b623285a089a08721/prep.sh | sudo sh Continue to flash manually Flash Raspbian to a fresh SD card. You can use Etcher.io to burn the SD card.

Before booting set up an empty file called ssh in /boot/ on the SD card.

Use Raspbian Stretch Lite

Update: I previously recommended downloading Raspbian Jessie instead of Stretch. At time of writing (3 Jan 2018) Stretch is now fully compatible.

https://www.raspberrypi.org/downloads/raspbian/

Change hostname Use the raspi-config utility to change the hostname to k8s-master-1 or similar and then reboot.

Set a static IP address It's not fun when your cluster breaks because the IP of your master changed. The master's certificates will be bound to the IP address, so let's fix that problem ahead of time:

cat » /etc/dhcpcd.conf Paste this block:

profile static_eth0 static ip_address=192.168.0.100/24 static routers=192.168.0.1 static domain_name_servers=8.8.8.8 Hit Control + D.

Change 100 for 101, 102, 103 etc.

You may also need to make a reservation on your router's DHCP table so these addresses don't get given out to other devices on your network.

Enable bridge-nf-call-iptables sudo sysctl net.bridge.bridge-nf-call-iptables=1 Install Docker This installs 17.12 or newer.

curl -sSL get.docker.com | sh

  1. Add current user to docker group:

sudo usermod pi -aG docker

  1. Refresh groups

newgrp docker Disable swap For Kubernetes 1.7 and onwards you will get an error if swap space is enabled.

Turn off swap:

$ sudo dphys-swapfile swapoff && \

 sudo dphys-swapfile uninstall && \
 sudo update-rc.d dphys-swapfile remove
For Debian, also run:

sudo systemctl disable dphys-swapfile This should now show no entries:

$ sudo swapon –summary Edit /boot/cmdline.txt Add this text at the end of the line, but don't create any new lines:

cgroup_enable=cpuset cgroup_memory=1 cgroup_enable=memory Now reboot - do not skip this step.

Add repo lists & install kubeadm $ curl -s https://packages.cloud.google.com/apt/doc/apt-key.gpg | sudo apt-key add - && \

 echo "deb http://apt.kubernetes.io/ kubernetes-xenial main" | sudo tee /etc/apt/sources.list.d/kubernetes.list && \
 sudo apt-get update -q && \
 sudo apt-get install -qy kubeadm
I realise this says 'xenial' in the apt listing, don't worry. It still works.

Initialize your master node You now have two new commands installed:

kubeadm - used to create new clusters or join an existing one

kubectl - the CLI administration tool for Kubernetes

Pre-pull images

kubeadm now has a command to pre-pull the requisites Docker images needed to run a Kubernetes master, type in:

$ sudo kubeadm config images pull -v3 If using Weave Net

Initialize your master node: $ sudo kubeadm init –token-ttl=0 If using Flannel:

Initialize your master node with a Pod network CIDR: $ sudo kubeadm init –token-ttl=0 –pod-network-cidr=10.244.0.0/16 We pass in –token-ttl=0 so that the token never expires - do not use this setting in production. The UX for kubeadm means it's currently very hard to get a join token later on after the initial token has expired.

Optionally also pass –apiserver-advertise-address=192.168.0.27 with the IP of the Pi as found by typing ifconfig.

Note: This step can take a long time, even up to 15 minutes.

Sometimes this stage can fail, if it does then you should patch the API Server to allow for a higher failure threshold during initialization around the time you see [controlplane] wrote Static Pod manifest for component kube-apiserver to “/etc/kubernetes/manifests/kube-apiserver.yaml”

sudo sed -i 's/failureThreshold: 8/failureThreshold: 20/g' /etc/kubernetes/manifests/kube-apiserver.yaml && \ sudo sed -i 's/initialDelaySeconds: [0-9]\+/initialDelaySeconds: 360/' /etc/kubernetes/manifests/kube-apiserver.yaml After the init is complete run the snippet given to you on the command-line: 

 mkdir -p $HOME/.kube
 sudo cp -i /etc/kubernetes/admin.conf $HOME/.kube/config
 sudo chown $(id -u):$(id -g) $HOME/.kube/config
This step takes the key generated for cluster administration and makes it available in a default location for use with kubectl.

Now save your join-token Your join token is valid for 24 hours, so save it into a text file. Here's an example of mine:

$ kubeadm join –token 9e700f.7dc97f5e3a45c9e5 192.168.0.27:6443 –discovery-token-ca-cert-hash sha256:95cbb9ee5536aa61ec0239d6edd8598af68758308d0a0425848ae1af28859bea Check everything worked: $ kubectl get pods –namespace=kube-system NAME READY STATUS RESTARTS AGE etcd-of-2 1/1 Running 0 12m kube-apiserver-of-2 1/1 Running 2 12m kube-controller-manager-of-2 1/1 Running 1 11m kube-dns-66ffd5c588-d8292 3/3 Running 0 11m kube-proxy-xcj5h 1/1 Running 0 11m kube-scheduler-of-2 1/1 Running 0 11m weave-net-zz9rz 2/2 Running 0 5m You should see the “READY” count showing as 1/1 for all services as above. DNS uses three pods, so you'll see 3/3 for that.

Setup networking with Weave Net or Flannel Some users have reported stability issues with Weave Net on ARMHF. These issues do not appear to affect x86_64 (regular PCs/VMs). You may want to try Flannel instead of Weave Net for your RPi cluster.

Weave Net Install Weave Net network driver

$ kubectl apply -f \

"https://cloud.weave.works/k8s/net?k8s-version=$(kubectl version | base64 | tr -d '\n')"
If you run into any issues with Weaveworks' networking then flannel is also a popular choice for the ARM platform.

Flannel (alternative) Apply the Flannel driver on the master:

$ kubectl apply -f https://raw.githubusercontent.com/coreos/flannel/master/Documentation/kube-flannel.yml On each node that joins including the master:

$ sudo sysctl net.bridge.bridge-nf-call-iptables=1 Join other nodes On the other RPis, repeat everything apart from kubeadm init.

Change hostname Use the raspi-config utility to change the hostname to k8s-worker-1 or similar and then reboot.

Join the cluster Replace the token / IP for the output you got from the master node, for example:

$ sudo kubeadm join –token 1fd0d8.67e7083ed7ec08f3 192.168.0.27:6443 You can now run this on the master:

$ kubectl get nodes NAME STATUS AGE VERSION k8s-1 Ready 5m v1.7.4 k8s-2 Ready 10m v1.7.4 Deploy a container This container will expose a HTTP port and convert Markdown to HTML. Just post a body to it via curl - follow the instructions below.

function.yml

apiVersion: v1 kind: Service metadata:

 name: markdownrender
 labels:
   app: markdownrender
spec:
 type: NodePort
 ports:
   - port: 8080
     protocol: TCP
     targetPort: 8080
     nodePort: 31118
 selector:
   app: markdownrender
— apiVersion: apps/v1 kind: Deployment metadata:
 name: markdownrender
 labels:
  app: markdownrender
spec:
 replicas: 1
 selector:
   matchLabels:
     app: markdownrender
 template:
   metadata:
     labels:
       app: markdownrender
   spec:
     containers:
     - name: markdownrender
       image: functions/markdownrender:latest-armhf
       imagePullPolicy: Always
       ports:
       - containerPort: 8080
         protocol: TCP
Deploy and test:

$ kubectl create -f function.yml Once the Docker image has been pulled from the hub and the Pod is running you can access it via curl:

$ curl -4 http://127.0.0.1:31118 -d “

  1. test”

<p><h1>test</h1></p> If you want to call the service from a remote machine such as your laptop then use the IP address of your Kubernetes master node and try the same again.

Start up the Kubernetes dashboard The dashboard can be useful for visualising the state and health of your system, but it does require the equivalent of “root” in the cluster. If you want to proceed you should first run in a ClusterRole from the docs.

echo -n 'apiVersion: rbac.authorization.k8s.io/v1beta1 kind: ClusterRoleBinding metadata:

 name: kubernetes-dashboard-head
 labels:
   k8s-app: kubernetes-dashboard-head
roleRef:
 apiGroup: rbac.authorization.k8s.io
 kind: ClusterRole
 name: cluster-admin
subjects: - kind: ServiceAccount
 name: kubernetes-dashboard-head
 namespace: kube-system' | kubectl apply -f -
This is the development/alternative dashboard which has TLS disabled and is easier to use.

$ kubectl apply -f https://raw.githubusercontent.com/kubernetes/dashboard/master/aio/deploy/alternative/kubernetes-dashboard-arm-head.yaml You can then find the IP and port via kubectl get svc -n kube-system. To access this from your laptop you will need to use kubectl proxy and navigate to http://localhost:8001/ on the master, or tunnel to this address with ssh.

See also: Kubernetes Dashboard docs.

Remove the test deployment Now on the Kubernetes master remove the test deployment:

$ kubectl delete -f function.yml Wrapping up You should now have an operational Kubernetes master and several worker nodes ready to accept workloads.

Now let's head back over to the tutorial and deploy OpenFaaS to put the cluster through its paces with Serverless functions.

See also: Kubernetes documentation

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