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Welcome to the Kubernetes on ARM project!

Kubernetes on a Raspberry Pi? Is that possible?

Yes, now it is.

Imagine... Your own testbed for Kubernetes with cheap Raspberry Pis and friends.

Image of Kubernetes and Raspberry Pi

Are you convinced too, like me, that cheap ARM boards and Kubernetes is a match made in heaven?

Then, lets go!

Important information

This project was published in September 2015 as the first fully working way to easily set up Kubernetes on ARM devices.

I worked on making it better non-stop until early 2016, when I started contributing the changes I've made back to Kubernetes core. I strongly think that most of these features belong to the core, so everyone may take advantage of it, and so Kubernetes can be ported to even more platforms.

So I opened kubernetes/kubernetes#17981 and started working on making Kubernetes cross-platform. To date I've ported the Kubernetes core to ARM, ARM 64-bit and PowerPC 64-bit Little-endian. Already in v1.2.0 binaries were released for ARM, and I used the official binaries in v0.7.0 in Kubernetes on ARM.

Since v1.3.0-alpha.3 the hyperkube image has been built for both arm and arm64, which have made it possible to run Kubernetes officially the "kick the tires way". So it has been possible to run v1.3.x Kubernetes on Raspberry Pi´s (or whatever arm or arm64 device that runs docker) with the docker-multinode deployment!

I've written a proposal about how to make Kubernetes available for multiple platforms here

And then I became a Kubernetes maintainer in April! 😄

This means I have not had any extra time for maintaining Kubernetes on ARM when I instead made these features available in the core.

So what should I use Kubernetes on ARM for now then?

Kubernetes on ARM will still serve as a out-of-the-box solution that builds upon the Kubernetes core features. For example: A SD Card writing process for Raspberry Pis with Kubernetes prebaked will never reach the core, but its a great feature here.

Also, addons will first be ported to ARM in this project, then proposed to the official project.

OK, are you ready now to put your ARM boards to work? Then let´s go!

Download and build a SD Card

The first thing you will do, is to create a SD Card for your Pi. Alternatively, you may use the .deb deployment

Supported OSes/boards:

  • Arch Linux ARM (archlinux)
    • Raspberry Pi 1 A, A+, B, B+, (ZERO,) armv6 (rpi)
    • Raspberry Pi 2 Model B, armv7 (rpi-2)
    • Raspberry Pi 3 Model B, armv8, armv7 rootfs (rpi-3)
    • Parallella armv7, read more (parallella)
    • Cubietruck, armv7 (cubietruck)
    • Banana Pro, armv7 (bananapro)
  • HypriotOS (hypriotos)
    • Raspberry Pi 1 A, A+, B, B+, armv6 (rpi)
    • Raspberry Pi 2 Model B, armv7 (rpi-2)
    • Raspberry Pi 3 Model B, armv8, armv7 rootfs (rpi-3)
# Go to our home folder, if you want
cd ~

# Install git if needed and download this project
# sudo apt-get install git
git clone https://github.com/luxas/kubernetes-on-arm

# Change to that directory
cd kubernetes-on-arm

# See which letter your newly inserted SD Card has:
sudo fdisk -l

# Another great command
lsblk

# Get some help text about supported options
sdcard/write.sh

# Template:
sudo sdcard/write.sh /dev/sdX [board] [os] [rootfs]

# Example: Write the SD Card for Raspberry Pi 2, Arch Linux ARM and include this project's Kubernetes scripts
sudo sdcard/write.sh /dev/sdX rpi-2 archlinux docker-multinode

# The installer will ask you if you want to erase all data on your card
# Answer y/n on that question
# Prepend the command with QUIET=1 if no security check should be made
# Requires an internet connection
# This script runs in 3-4 mins

The README for the docker-multinode rootfs is here

Setup your board from an SD Card

Boot your board and log into it.

Arch Linux users:

  • The user/password is: root/root or alarm/alarm
  • These scripts requires root. So if you login via alarm, then su root when you´re going to do some serious hacking :)

HypriotOS users:

  • The user/password is: pirate/hypriot
  • Remember to prepend all commands with sudo if you are the pirate user

Yes, I know. Root enabled via ssh isn´t that good. But the task to enhance ssh security is left as an exercise to the user.

# This script will install and setup docker etc.
kube-config install

# First, it will install docker, if not present
# Then it will download kube deploy

# It will ask for which hostname you want. Defaults to kubepi.

# The script will ask you for timezone. Defaults to Europe/Helsinki
# Run "timedatectl list-timezones" before to check for values

# It will ask you if it should create a 1 GB swapfile.

# Last question is whether you want to reboot
# You have to reboot in order to get the cgroups working

# If you want to run this script non-interactively, do this:
# TIMEZONE=Europe/Helsinki SWAP=1 NEW_HOSTNAME=mynewpi REBOOT=0 kube-config install
# This script runs in 2-3 mins

Start Kubernetes!

Hmm, starting a complex system like Kubernetes should be a complex task, right? Well, not this time.

enable-master runs master.sh enable-worker runs worker.sh

# To set up your board as both a master and a node, run
kube-config enable-master

# To set up your board as a node, run
kube-config enable-worker [master-ip]

Package deployment

If you have already made a SD Card and your device is up and running, what can you do instead? For that, I've made a .deb package, so you could install it easily

The README for the docker-multinode rootfs is here

If you already have set up your Pi with latest Raspbian OS for example, follow this guide.

Install the .deb package

Supported operating systems are HypriotOS, Raspbian, Arch Linux ARM and in some cases Debian/Ubuntu.

# Download the latest package
curl -sSL https://github.com/luxas/kubernetes-on-arm/releases/download/v0.8.0/docker-multinode.deb > docker-multinode.deb
# or
wget https://github.com/luxas/kubernetes-on-arm/releases/download/v0.8.0/docker-multinode.deb

# Requires dpkg, which is preinstalled in at least all Debian/Ubuntu OSes
sudo dpkg -i docker-multinode.deb

# Setup the enviroinment
# It will ask which board it's running on and which OS
# A reboot is required for it to function properly, but not for HypriotOS
kube-config install

## ----- REBOOT -----

# Start the master or worker
kube-config enable-master
kube-config enable-worker [master ip]

# Get some info about the node
kube-config info

Use Kubernetes (the fun part begins here)

Some notes on running Docker on ARM are here

# See which commands kubectl and kube-config has
kubectl
kube-config

# Get info about your machine and Kubernetes version
kube-config info

# Make an replication controller with an image
# Hopefully you will have some workers, so you is able to see how they spread across hosts
# The nginx-test image will be downloaded from Docker Hub and is a nginx server which only is serving the message: "<p>WELCOME TO NGINX</p>"
# Expose the replication controller "my-nginx" as a service
kubectl run my-nginx --image=luxas/nginx-test --replicas=3 --expose --port=80

# The above command will make a deployment since v1.2. The deployment will run a replica set (the "new" kind of replication contoller)
# You may also specify --hostport, e.g. --hostport=30001 for exposing the service on all nodes' port 30001

# The pull might take some minutes
# See when the nginx container is running
docker ps

# See which pods are running
kubectl get pods

# See which nodes we have
kubectl get nodes

# See which ip we may ping, by getting services
kubectl get svc

# See if the nginx container is working
# Replace $SERVICE_IP with the ip "kubectl get svc" returned 
curl $SERVICE_IP
# --> <p>WELCOME TO NGINX</p>

# See which internal cluster services that are running
kubectl --namespace=kube-system get pods,rc,svc

# Test dns
curl my-nginx.default.svc.cluster.local
# --> <p>WELCOME TO NGINX</p>

# By default, "search [domains]" is added to /etc/resolv.conf
# In this case, these domains are searched: "default.svc.cluster.local svc.cluster.local cluster.local"
# That means, that you may only write "my-nginx", and it will search in those domains
curl my-nginx
# --> <p>WELCOME TO NGINX</p>

# Start the registry
kube-config enable-addon registry

# Wait a minute for it to start
kubectl --namespace=kube-system get pods

# Tag an image
docker tag my-name/my-image localhost:5000/my-name/my-image

# And push it to the registry
docker push localhost:5000/my-name/my-image

# On another node, pull it
docker pull localhost:5000/my-name/my-image

# The master also proxies the services so that they are accessible from outside
# The -L flag is there because curl has to follow redirects
# You may also type this URL in a web browser
curl -L http://[master-ip]:8080/api/v1/proxy/namespaces/default/services/my-nginx

# Generic apiserver proxy URL
# curl -L http://[master-ip]:8080/api/v1/proxy/namespaces/[namespace]/services/[service-name]:[port-name]

# See which ports are open
netstat -nlp

# See cluster info
kubectl cluster-info

# See master health in a web browser
# cAdvisor in kubelet provides a web site that outputs all kind of stats in real time
# http://$MASTER_IP:4194

# Turndown Kubernetes on this node. This always reverts the "kube-config enable-*" commands
kube-config disable

Addons

To enable/disable addons is very easy: kube-config enable-addon [addon-name] and kube-config disable-addon [addon-name] README for the addons

Three addons are available for the moment:

  • Kubernetes DNS:
    • Every service gets the hostname: {{my-svc}}.{{my-namespace}}.svc.cluster.local
    • The default namespace is default (surprise), so unless you manually edit something it will land there
    • Kubernetes internal addon services runs in the namespace kube-system
    • Example: my-awesome-webserver.default.svc.cluster.local or just my-awesome-webserver may resolve to ip 10.0.0.154
    • Those DNS names is available both in containers and on the node itself (kube-config automatically adds the info to /etc/resolv.conf)
    • If you want to access the Kubernetes API easily, curl -k https://kubernetes or curl -k https://10.0.0.1 if you remember numbers better (-k stands for insecure as apiserver has no signed certs by default)
    • The DNS server itself has allocated ip 10.0.0.10
    • The DNS domain is cluster.local
    • This addon can't be disabled.
  • Kubernetes Dashboard:
    • The Kubernetes Dashboard project is here
    • Access the dashboard on: http://[master-ip]:8080/ui
    • This addon can't be disabled.
  • Central image registry:
    • A registry for storing cluster images if e.g. the cluster has no internet connection for a while
    • Or for cluster-specific images that one not want to publish on Docker Hub
    • This service is available at localhost:5000 on all nodes, which by default is a "trusted" location.
    • localhost:5000 forwards the traffic to the internal IP of the registry service.
    • Just tag your image: docker tag my-name/my-image localhost:5000/my-name/my-image
    • And push it to the registry: docker push localhost:5000/my-name/my-image
  • Service loadbalancer:
    • Documentation here
    • You have to label at least one node role=loadbalancer like this: kubectl label no [node_ip] role=loadbalancer
    • The loadbalancer will expose http services in the default namespace on http://[loadbalancer_ip]/[service_name]. Only http services on port 80 are tested in this release. It should be pretty easy to add https support though.
    • You may see haproxy stats on http://[loadbalancer_ip]:1936
    • Not recommended for heavy use. Will be replaced with ingress in coming releases.
  • Cluster monitoring with heapster, influxdb and grafana
    • When this addon is enabled, the dashboard will show usage graphs in the CPU and RAM columns.
    • All heapster data is stored in an InfluxDB database. Data is written once a minute. Access the graphical InfluxDB UI: http://[master-ip]:8080/api/v1/proxy/namespaces/kube-system/services/monitoring-influxdb:http and the raw api on: http://[master-ip]:8080/api/v1/proxy/namespaces/kube-system/services/monitoring-influxdb:api
    • A nice grafana web dashboard that shows resource usage for the whole cluster as for individual pods is accessible at: http://[master-ip]:8080/api/v1/proxy/namespaces/kube-system/services/monitoring-grafana. It may take some minutes for data to show up.

Access your cluster

Here is some ways to make your outside devices reach the services running in the cluster.

  • apiserver proxy:
    • This is enabled by default by apiserver
    • Type this URL in a browser or use curl
    • curl -L http://[master-ip]:8080/api/v1/proxy/namespaces/[namespace]/services/[service-name][:[port-name]]
    • You may build a proxy in front of this with nginx that forwards all requests to the apiserver proxy
  • Connect a computer to the flannel network
    • It's possible to start flannel and kube-proxy on another computer in the same network and access all services
    • Run these two commands from a amd64 machine with docker:
      • docker run --net=host -d --privileged -v /dev/net:/dev/net quay.io/coreos/flannel:0.6.1-amd64 /opt/bin/flanneld --etcd-endpoints=http://$MASTER_IP:2379
      • docker run --net=host -d --privileged gcr.io/google_containers/hyperkube-amd64:v1.3.6 /hyperkube proxy --master=http://$MASTER_IP:8080 --v=2'
    • Replace $MASTER_IP with the actual ip of your master node
    • The consuming amd64 computer can access all services
    • For example: curl -k https://10.0.0.1
  • Make a service with externalIP
    • Via kubectl: kubectl expose rc {some rc} --port={the port this service will listen on} --container-port={the port the container exposes} --external-ip={the host you want to listen on}
    • Example: kubectl expose rc my-nginx --port=9060 --container-port=80 --external-ip=192.168.200.100
    • This will make the service accessible at 192.168.200.100:9060
  • Service NodePort
    • If one sets Service .spec.type to NodePort, Kubernetes automatically exposes the service on a random port on every node

See node health via cAdvisor

Go to a web browser and type: {IP of your node}:4194 and a nice dashboard will be there and show you some nice real-time stats.

Configuration

There is a configuration file: /etc/kubernetes/k8s.conf, where you can customize some things:

  • K8S_MASTER_IP: Points to the master in the cluster. If the node is master, it uses 127.0.0.1 (aka localhost). Default: 127.0.0.1
  • The other options comes from docker-multinode

Note: You must change the values in k8s.conf before starting Kubernetes. Otherwise they won't have effect, just be able to harm your setup.

On Arch Linux, this file will override the default eth0 settings. If you have a special eth0 setup (or use some other network), edit this file to fit your use case: /etc/systemd/network/dns.network

Docker versions

Only docker-1.10 and higher is supported, docker-1.11 is recommended.

Troubleshooting

If your cluster won't start, try kube-config disable and choose to remove /var/lib/kubelet. That will remove all data you store in /var/lib/kubelet and kill most running docker images.

Reboots

Will not work in this version. It's in the roadmap to enable reboots again.

Contributing

I would be really glad to review your Pull Request! One thing would be good to remember though. I develop on the dev branch, so it would be great if you target that one instead of master

Thanks!

Beta version

This project is under development.
I develop things on the dev branch

Changelog

Future work

See the ROADMAP

License

MIT License

Goals for this project

This project ports Kubernetes to the ARM architecture. The primary boards used for testing is Raspberry Pi 2´s.

My goal for this project is that it should be as small as possible, while retaining its flexibility.
It should also be as easy as possible for people, who don´t know anything about Kubernetes, to get started.

I also have opened a proposal for Kubernetes on ARM: kubernetes/kubernetes#17981.
The long-term goal most of this functionality should be present in core Kubernetes.

It should be easy in the future to add support for new boards and operating systems.

Feel free to create an issue if you find a bug or think that something should be added or removed!