Error code 6 is already used by https://github.com/Kobo-InkBox/rootfs/blob/2c45339df177aae26fcdc321484806ad5ec793b8/etc/init.d/inkbox_gui#L100-L103

Let me tell you, this was a nightmare.

It's not perfect, it OOPS fairly often (when restarting QPA), but it is indeed better!