Macondo: Yet Another Raspberry Pi Cluster

There are some practical reasons motivating this exercise; however, the main reason is just for fun... Why not?

Hardware

• 5 (or any other number) Raspberry Pi 3 Model B+
• A 32 GB micro SD card for each Raspberry Pi (I used a SanDisk ultra class 10, manufacturer number: SDSQUAR-032G-GN6TA)
• An ethernet switch (I used this 8-port 100 Mbps Renkforce Network Switch )
• A USB power supply with enough wattage (I used this ANKER 60W 10-Port)
• Micro-USB and ethernet cables
• A Raspberry Pi cluster case

Setup

Bootstrap and Configuration

The SD cards must be flashed (e.g. with raspbian), ssh enabled (by creating an empty file called "ssh" in the boot partition: touch /mount-point/boot/ssh), and the cluster turned on (of course) before starting with the configuration. Ansible was used to automate the configuration; in this way, the configuration can be done simultaneously on all devices.

• nmap or similar can be used to discover the devices IP addresses (in this example within the network 172.16.0.0/24). The IP addresses can be listed in an Ansible inventory.cfg.

  sudo nmap -sn 172.16.0.0-255 |grep rasp -i  -B 2

• The ansible playbooks are located in the ansible folder, and support the following tasks:

  • Creating a new user (e.g. macondo), deploying an ssh public key, and, finally, deleting the old user pi:

    ansible-playbook playbooks/create_user.yml -i inventory.cfg --user pi --ask-pass  -e user_name=macondo  -e ssh_key=FULL_PATH_TO_ID_RSA_PUB 
    
    ansible-playbook playbooks/remove_user.yml -i inventory.cfg --user macondo --ask-become-pass -e user_name=pi

  • [Optional] Devices hostnames can be changed. This playbook has to be applied to each individual device, for instance:

    ansible-playbook playbooks/change_hostname.yml -i "172.16.0.178," --user macondo --ask-become-pass -e hostname=remedios 

  My cluster nodes are called: ursula, amaranta, rebeca, pilar and remedios.

Additional Ansible Scripts

Shutdown and Reboot

ansible-playbook playbooks/shutdown.yml -i inventory.cfg --user macondo --ask-become-pass

ansible-playbook playbooks/reboot.yml -i inventory.cfg --user macondo --ask-become-pass

Adhoc commands

For instance:

ansible all -m ping -i inventory.cfg -u macondo

Conclusions

Ansible is cool. Most of the steps described previously scale well, baptizing individual nodes is just a matter of personal taste.

Credits

• https://github.com/garthvh/ansible-raspi-playbooks
• https://github.com/vicchi/ansible-pi-lockdown
• Image source