Here’s the first in a series of building a robust docker swarm of raspberry pi hosts. This installment goes through installing the Pi(s), modifiying the Docker Daemon config, and starting up a test to verify that everyone can join the cluster.
The cluster which I am using consists of
• Raspberry Pi B+ x 5
• Raspberry Pi 2 B x 5
In order to verify that the cluster is working properly, there should be ten (10) members, five (5) of which have 4 cores.
Obtaining the OS and Setup
The wonderful folks at Hypriot have produced a raspberry image based on Raspbian, but with Docker 1.5.0. The image and instructions can be found at Heavily ARMed after major upgrade: Raspberry Pi with Docker 1.5.0 – Docker Pirates ARMed with explosive stuff.
Note: The image resizes itself to fit the card upon the first boot and then reboots. This takes a little bit (minutes at most). Just don’t be surprised when it reboots.
In order for this to work properly, the hosts need a unique name. It’s sometimes possible to configure DHCP to do this, but I went ahead and edited /etc/hostname myself since I wanted the most portability possible.
Like all good sysadmins, I am lazy. Doing the same thing over and over is boring. Besides, that’s what computers are for. So I wrote a script to make copies of the image and then edit the hostnames. Once that’s done I can then proceed to write the images to the SD cards.
The following script takes one argument, the location of the image you wish to modify — this should work for more than just Hypriot; it should work for just about any Rasberry Pi image. At present, it creates 10 instances and the NAME starts with apis-rpi- — you will likely want to change those. I may make the file a bit more generic at some point.
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