Simple Raspberry Pi Cluster Setup

I needed to create a 5xPi cluster to run some distributed Erlang.

The stuff here gets me to that point.

Create the Bootable SD Cards

We're going to make sure we can ssh in, and that it will connect to your local network.

1. Download a Raspian Stretch image into images/ and unzip it.

2. Mount it, and

   a. touch an empty file called ssh in the /boot filesystem b. update the ssid and password in wpa_supplicant.wpa and copy it into the same filesystem.

3. Unmount it, and burn the image onto an SD card for each Pi.

   dd bs=1m conv=sync if=2018-03-13-raspbian-stretch-lite.img of=/dev/rdisk5
   

Bootstrap the Ansible Environment

Load the SD cards into the Pis (I numbered mine with a sharpie). Power them up one at a time. Using your router's management screen or nmap, find its WiFi ipaddress.

If you want to confirm it, try

$ ssh pi@192.168.0.xxx
Password:  raspberry

Now go into the ansible directory.

For each pi, run the following:

ansible-playbook -i "192.168.0.xx," -u pi -k playbooks/00-initial-setup.yml -e "ip=11 host=n1"

The IP address following the -i option is the WiFi address of the Pi being set up. The ip= parameter is the static IP address that will be assigned to the hardwired eth0 interface (the prefix will be 192.168.3.). The host= parameter sets the hostname for that card.

Double check the interface was set by ssh-ing in to pi@192.168.3.11 (or whatever IP you used). I'm using a MacBook, so I had to manually set the IP address on my Thunderbolt interface and enable internet sharing.

Repeat for each Pi in your cluster.

Do the Final Setup

Now we'll use Ansible to load up the rest of the environments.

1. Create an inventory file. I call mine hosts

    n2
    n3
    n4
    n5
   
    [builder]
    n1
   

The n1, n2... are the names of my nodes (set using the host= parameter to ansible_playbook above. I nominate one machine to be the build server for deployments.

2. Tell ansible the IP addresses of each node. Create a file host_vars/«nodename».yml for each one. For example, here's my n1.yml

   ---
   ansible_host: "192.168.3.11"
   

3. Run the playbooks:

   ansible-playbook -i hosts  -v -t d  playbooks/01-install-collectd.yml
   ansible-playbook -i hosts  -v -t d  playbooks/02-erlang.yml
   

Do something cool

. . .