Docker Swarm node set up with Docker 1.12 RC on Raspberry Pi

I’ve been following through the steps in this article to set up a Docker swarm cluster on a pair of Raspberry Pis. Most of the steps work as-is from Mac OS, but for a few steps there’s a couple of variations.

This is most likely going to be part 1 of a few posts as I work through and get this working.

For example, to copy your ssh key to the Pis, instead of:

ssh-copy-id pirate@pi3.local

… you can do (from tip here):

cat ~/.ssh/ | ssh user@machine "mkdir ~/.ssh; cat >> ~/.ssh/authorized_keys"

To switch between remote hosts:

eval $(docker-machine env pi1)

where pi1 is the name of the remote host.

To switch back to the localhost (not entirely obvious but found the answer here):

eval "$(docker-machine env -u)"

After ‘swarm init’ and adding the other nodes to the cluster, ‘docker swarm ls’ lists the nodes in the cluster:

More to come in part 2:-)

Configuring a static IP on HypriotOS for the Raspberry Pi

How you configure a static IP on the Pi changed between Wheezy and Jessie, and it seems on Hypriot’s prebuilt images for running Docker on the Pi, it’s a slight variation.

Edit /etc/network/interfaces.d/eth0, comment out the DHCP line:

iface eth0 inet dhcp

and add:

iface eth0 inet static
address your-static-ip
gateway your-gateway-ip
#google dns servers


Spring Boot REST app in a Docker Container on the Raspberry Pi

Docker on the Raspberry Pi? Sure, with help from Hypriot who provide an iso image ready to go, getting docker up and running on the Pi is as simple as burning their image to an sd card and booting it up. Ok, so that part is simple.

Building an image to run on the Pi is not as straightforward as it sounds. Well, it’s no more complicated than building an image from a Dockerfile, but given that the Pi is ARM based and not x86, you have to build an image that is built/compiled with executables/libraries for ARM.

This makes complete sense when you think about it, you’re not going to get an image containing x86 executables and libraries to run on a Pi, but it’s rather sad that it isn’t possible to build an image for example from my Mac and and I can run on my Mac, or Linux, or on the Pi. Well, you can build the image on any architecture, but you can’t run an ARM compatible image on the Mac (or docker-machine/boot2docker).

Ok, so that in mind, there are a number of ARM compatible images on Docker Hub already – Hypriot also have base images ready to go. So to run Spring Boot in a container on the Pi, I need an ARM image with Java. Luckily, here’s one ready to go.

For a quick test, I took my simple Sprig Boot REST app I already have on GitHub, and threw together a Dockerfile using Alpine first to check it would run locally:

FROM java:openjdk-8-alpine

ADD SpringBootREST-0.0.1-SNAPSHOT.jar /opt/SpringBootREST-0.0.1-SNAPSHOT.jar


ENTRYPOINT ["java", "-jar", "/opt/SpringBootREST-0.0.1-SNAPSHOT.jar"]

This runs as expected in docker-machine on my Mac.

To push to the Pi, the only change is to replace the base image with an ARM compatible image with Java, so this looks like:

FROM hypriot/rpi-java

ADD SpringBootREST-0.0.1-SNAPSHOT.jar /opt/SpringBootREST-0.0.1-SNAPSHOT.jar


ENTRYPOINT ["java", "-jar", "/opt/SpringBootREST-0.0.1-SNAPSHOT.jar"]

To get it to my Pi, I set up a local Registry to push the image to, and then pulled it from the Pi. So tag the image to the registry:

docker tag spring-boot-rest-rpi registry-ip:5000/spring-boot-rest-rpi

…push to the registry:

docker push registry-ip:5000/spring-boot-rest-rpi

and then pull from the Pi:

docker pull registry-ip:5000/spring-boot-rest-rpi

And then fire it up!

docker run -it -p 8080:8080 registry-ip:5000/spring-boot-rest-rpi

Spring Boot in a Docker Container on the Pi!