{
  systemd.services.backlight-permissions = {
    wantedBy = [ "multi-user.target" ];
    serviceConfig.Type = "oneshot";
    script = let
      glob = "/sys/class/backlight/*/brightness";
    in ''
      chown :video ${glob}
      chmod g+w ${glob}
    '';
  };
}

    ./backlight-permissions.nix