Stupid Mac and it's automatic-apply. Once on my Mac side, I accidentally clicked on Startup Disk when I was aiming for something else in preferences, and because I used my Windows side to launch the Live Ubuntu Preview, and installed Ubuntu over my Windows side, wiping it; instead of Boot Camp, Mac recognizes my Ubuntu partition, yet it's grayed out on Disk Utility and when I click Mount, literally nothing happens. And that specific partition is not an option under Startup Disk.
Of course I can still get into Ubuntu by holding down Alt, but I reeeeeeealy hate having to press Alt at the PERFECT time every time I start up. I was digging around through my Mac system files and Google, looking for a way to force my computer to automatically boot into sda4 (my Ubuntu partition), and ended up learning a lot about the famous BootX file. I have no idea how I'd acces or edit it, nor do I know if it would fix my problem.
But anyway, I need some help with this. How do I FORCE Mac to boot into a hidden partition???