This is an example of booting NixOS on a BPi-R3.

Build an SD-Image with:

$ nix build -L '.#nixosConfigurations.bpir3.config.system.build.sdImage'

Deriving random static MAC addresses for interfaces is done via patches applied in the custom u-boot of this repository. This can be pulled in as an input if desired.

{
  inputs = {
    bpir3.url = "github:nakato/nixos-bpir3-example";
  };

  # And used somewhere
  firmware = bpir3.packages.aarch64-linux.armTrustedFirmwareMT7986;
}

Updated u-boot builds use bootstd instead of distroboot to achieve extlinux booting. This change requires an update to the partition table of the SD card.

# nix shell nixpkgs#gptfdisk
# sgdisk -t 4:8300 -t 5:EF00 /dev/mmcblk0

After this is completed, bl2.img can be written to parition 1, and fip.bin to partition 4.