Default [Q] Edit system.db and keep changes after reboot

Hi, I have an LG Optimus L9(P769) running 4.1.2. I used the tethering hack where you change the value in systems.db of tether_dun_required to 0. It works and allows me to tether. However, when I reboot my phone, the value changes back to 1. Changing the read write permissions prevents me from booting and so I'm out of ideas on how to do this. I've tried changing the value through SQLite debugger and through ADB, and both work, until I reboot.