nixos/machines/serverle/hardware-configuration.nix

{ config, pkgs, lib, ... }:
{
  boot = {
    loader = {
      raspberryPi = {
        firmwareConfig = ''
          # Disable the ACT LED.
          dtparam=act_led_trigger=none
          dtparam=act_led_activelow=off
          # Disable the PWR LED.
          # somehow this changed in firmware settings: https://github.com/raspberrypi/firmware/issues/1742
          #dtparam=pwr_led_trigger=default-on
          dtparam=pwr_led_activelow=off

          # Disable ethernet port LEDs
          dtparam=eth0_led=4
          dtparam=eth1_led=4

          # Disable SD-Card pools
          dtparam=sd_pool_once=on
        '';

        # the bootloader has to be enabled for fat systems. for ext use the other one.
        enable = true;
        version = 4;
      };
      generic-extlinux-compatible.enable = false;
    };
    # Kernel configuration
    kernelParams = [ "cma=64M" "console=tty0" ];
  };
}