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K8s on Raspbian

K8s on (vanilla) Raspbian Lite

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

Pre-reqs:

  • You must use an RPi2 or 3 for Kubernetes
  • I'm assuming you're using wired ethernet (Wi-Fi also works)

Master node setup

  • 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 Jessie

https://downloads.raspberrypi.org/raspbian_lite/images/raspbian_lite-2017-07-05/

  • Change hostname

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

  • Install Docker

This installs 17.05 - the latest release for Jessie.

$ curl -sSL get.docker.com | sh && \
sudo usermod pi -aG docker
  • Disable swap

For Kubernetes 1.7 and newer 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

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_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.

  • 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

  • Initialize your master node:

$ sudo kubeadm init

Optionally also pass --apiserver-advertise-address=192.168.0.27 with the IP of the Pi.

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

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

Install Weave network driver

$ kubectl apply -f https://git.io/weave-kube-1.6

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:

$ 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

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/v1beta1 # for versions before 1.6.0 use extensions/v1beta1
kind: Deployment
metadata:
  name: markdownrender
spec:
  replicas: 1
  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
$ curl -4 http://localhost:31118 -d "# test"
<p><h1>test</h1></p>

From a remote machine such as your laptop use the IP address of your Kubernetes master and try the same again.

Start up the dashboard

This is the development dashboard which has TLS disabled and is easier to use.

$ curl -sSL https://raw.githubusercontent.com/kubernetes/dashboard/master/src/deploy/recommended/kubernetes-dashboard-arm.yaml | kubectl create -f -

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.

Remove the test deployment

Now on the Kubernetes master remove the test deployment:

$ kubectl delete -f function.yml

Moving on

Now head back over to the tutorial and deploy OpenFaaS

#!/bin/sh
# This installs the base instructions up to the point of joining / creating a cluster
curl -sSL get.docker.com | sh && \
sudo usermod pi -aG docker
sudo dphys-swapfile swapoff && \
sudo dphys-swapfile uninstall && \
sudo update-rc.d dphys-swapfile remove
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
echo Adding " cgroup_enable=cpuset cgroup_enable=memory" to /boot/cmdline.txt
sudo cp /boot/cmdline.txt /boot/cmdline_backup.txt
orig="$(head -n1 /boot/cmdline.txt) cgroup_enable=cpuset cgroup_enable=memory"
echo $orig | sudo tee /boot/cmdline.txt
echo Please reboot

Lewiscowles1986 commented Oct 12, 2017

This is great. It'd be very cool to have this operate unattended. (or as unattended as possible)

The swapfile turns back on when you reboot unless you

sudo dphys-swapfile swapoff
sudo dphys-swapfile uninstall
sudo update-rc.d dphys-swapfile remove

For this line curl localhost:31118 -d "# test" I had to use the full host name. Localhost is still 127.0.0.1 and it doesn't seem to be listening

Owner

alexellis commented Oct 25, 2017

Kubernetes please stop changing every other day 👎

olavt commented Oct 29, 2017

I followed the instructions and got everything installed on a 2x Raspberry PI 3 cluster (1 master and 1 node). But, I have not been able to get the Dashboard up and running.

olavt@k8s-master-1:~ $ kubectl get svc -n kube-system
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE
kube-dns ClusterIP 10.96.0.10 53/UDP,53/TCP 5h
kubernetes-dashboard ClusterIP 10.104.85.132 443/TCP 4h
olavt@k8s-master-1:~ $ kubectl proxy
Starting to serve on 127.0.0.1:8001

What is the Url I should use from my other computer to connect to the Dashboard?

Owner

alexellis commented Oct 30, 2017

OK for the dashboard you need to run kubectl on your own PC/laptop. Maybe an SSH tunnel would work?

ssh -L 8001:127.0.01:8001 pi@k8s-master-1.local

then try 127.0.0.1:8001 on your local machine

olavt commented Oct 30, 2017

That didn't work for me.

steini commented Nov 3, 2017

First of all thanks for the detailed setup process.

After updating raspbian i ran into the problem that sudo kubeadm join raised the error CGROUPS_MEMORY: missing. The boot option is no longer cgroup_enable=memory but cgroup_memory=1

See https://archlinuxarm.org/forum/viewtopic.php?f=15&t=12086#p57035 and raspberrypi/linux@ba742b5

movingbytes commented Nov 5, 2017

after installation the status of all pods in namespace kube-system is pending except kube-proxy (NodeLost). Any ideas?
Using docker 17.10 and K8S 1.8.2

borrillis commented Nov 15, 2017

My dashboard wouldn't work properly until I did:
kubectl create clusterrolebinding add-on-cluster-admin --clusterrole=cluster-admin --serviceaccou nt=kube-system:kubernetes-dashboard

I could get to the dashboard using kubectl proxy and opened the url http://localhost:8001/ui in a browser, but it couldn't get any data from the api.

@alexellis it should be cgroup_memory=1 not cgroup_enable=memory

krystan commented Dec 12, 2017

cgroup_enable=memory seems to be fine under kernel 4.9.35-v7.

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