Ubuntu as main OS... How to restore to OSX?

Is Ubuntu still working? It seems to me, I had Ubuntu running on a seperate partition on my MBP for a while that there was a another piece of software required to swap from one boot system to another. I think it was called rEFInd and I take it because you were not dual booting you do not have that.
Try booting into Ubuntu with the OSX Disk in the drive and select the OSX disk as the Startup Disk in Ubuntu preferences, then reboot.
If this is unsuccessful you may have to download and install rEFInd. I am just brainstorming here, anyone else with an opinion on this??

I have a friend that is a programmer that uses it exclusively on his personal equipment. He loves it. I think is basically just a Unix based OS. Not everyone appreciates Mac OS.

It's beyond me. I tried running WARP on my old windows machine a while ago. That's when I realized, I'm not a computer guy and never will be. LOL. I don't mess with operating systems. They've gotten WAY too complicated for me to wrap my hear around.

ken