1. Update common.nix

In particular, don't forget:

• to configure your wifi
• to change the admin user able to connect through ssh

2. Build the image

Zero 2 W:

nix build -L .#nixosConfigurations.zero2w.config.system.build.sdImage

Or for Pi 4:

nix build -L .#nixosConfigurations.pi4.config.system.build.sdImage

3. Copy the image in your sd card

DEVICE=/dev/disk5 # Whatever your sd card reader is
sudo dd if=result/sd-image/pi.img of=$DEVICE bs=1M conv=fsync status=progress

4. Boot your Pi
5. Get your IP

ifconfig wlan0

6. From another machine, rebuild the system:

ZERO2_IP=<the-zero2-ip>
SSH_USER=<the-admin-user-in-the-pi>

For Zero 2 W:

nix run github:serokell/deploy-rs .#zero2w -- --ssh-user $SSH_USER --hostname $ZERO2_IP

For Pi 4:

nix run github:serokell/deploy-rs .#pi4 -- --ssh-user $SSH_USER --hostname $ZERO2_IP

• Various features are much better supported on the Pi 4 than on the Zero 2 W because the Pi 4 has a nixos-hardware profile.
• The Zero 2 doesn't have enough RAM to build itself. An initial lead was to create a swap partition, but it turns out it was a bad idea, as it would have decreased the sd card lifetime (sd cards don't like many write operations). A zram swap is not big enough to work. Hence the use of deploy-rs.
  • Note that nixos-rebuild --target-host would work instead of using deploy-rs. but as nixos-rebuild is not available on Darwin, I'm using deploy-rs that works both on NixOS and Darwin.
• I still couldn't find a way to use boot.kernelPackages = pkgs.linuxKernel.packages.linux_rpi3.
• the sdImage.extraFirmwareConfig option is not ideal as it cannot update config.txt after it is created in the sd image.

• this issue
• this gist