nixos-raspberry-pi-cluster

A user-guide to create a Raspberry Pi (3B+, 4) cluster under NixOS and managed by NixOps.

In this guide, the nodes are all connected to a VPN server using Wireguard.

Table of contents

1. Installation
   1. Booting the Raspberry Pis
   2. First viable configuration
2. NixOps deployment
   1. Install NixOps
   2. Create the deployment
   3. Deploy the configurations

Installation

Booting the Raspberry Pis

4

For the Raspberry Pi 4, a Hydra job build a SD Image for it. You can find the job here, just pick the latest successful job and download the image.

3B+

In order to boot NixOS on a Raspberry Pi 3B+ you'll have to build your own image. Find its Nix expression at rpi3B+/sd-image.nix

First of all, if your main computer is not ARM-based, you have to emulate ARM on your system.

1. Add the following parameter to your NixOS configuration:

boot.binfmt.emulatedSystems = [ "aarch64-linux" ];

Then make sure to rebuild your system via nixos-rebuild switch

2. You can now build the image via this command (which might take a while depending on your computer)

nix-build '<nixpkgs/nixos>' -A config.system.build.sdImage --argstr system aarch64-linux -I nixos-config=sd-image.nix

You might find useful information on this wiki post.

Uncompress the image and flash it

1. The image created will be compressed with the zst format, to decompress it use:

nix-shell -p zstd --run "unzstd nixos-sd-image-20.09pre242769.61525137fd1-aarch64-linux.img.zst

2. You can now flash the image to your SD card! Example with dd:

dd bs=4M if=nixos-sd-image-21.03pre262561.581232454fd-aarch64-linux.img of=/dev/mmcblk0 conv=fsync

Booting

Then, plug a keyboard and a screen via the HDMI/micro-HDMI ports.

To connect it to internet, either plug a Ethernet cable or connect to the wifi with:

wpa_supplicant -B -i wlan0 -c <(wpa_passphrase 'SSID' 'password')

First viable configuration

After booting on the Raspberry Pi, generate the configuration via:

nixos-generate-configuration

4

Then, you can pull the default configuration

curl https://raw.githubusercontent.com/hugolgst/nixos-raspberry-pi-cluster/master/rpi4/default-configuration.nix > /etc/nixos/configuration.nix

3B+

After successfully booting your RPI3B+, you have to pull the default configuration file in /etc/nixos/configuration.nix

curl https://raw.githubusercontent.com/hugolgst/nixos-raspberry-pi-cluster/master/rpi3B%2B/default-configuration.nix > /etc/nixos/configuration.nix

Rebuild

Then tweak the configuration file as you want and rebuild/reboot the system

nixos-rebuild switch
reboot

NixOps deployment

To manage the Raspberry Pi cluster, we can use NixOps.

Install NixOps

First of all make sure to have it installed on your system:

nix-env -iA nixos.nixops

or

nix-shell -p nixops

or add it to your system packages in /etc/nixos/configuration.nix.

Create the deployment

Create the deployment using this command

nixops create nixops/cluster.nix -d <your-deployment-name>

Then you can list all your deployments and check if yours is present with:

nixops list

To have more information about the commands available and the tool in general, check the manual.

Make sure to have your ssh public key in the root authorized keys!

users.extraUsers.root.openssh.authorizedKeys.keys = [
  "ssh-rsa ... host"
];

Deploy the configurations

You can tweak the configuration(s) in nixops/cluster.nix and the nixops/ files as you want.

In order to deploy the configuration you can use the deploy tag.

nixops deploy -d <your-deployment-name>