Before to start playing with the commands suggested here let me clarify my context:
- I had a Mac Book Pro with OSX Maverick with dual boot working with Ubuntu 14.04 through rEFInd boot loader.
- Today I upgraded OSX to Yosemite and after everything was updated rEFInd stopped working.
So my goal was to make able to have rEFInd working again to switch between operating systems. My primary OS is Linux so if you are in a similar situation this may help:
On a Twitter search I found someone linked the following solution:
That worked for me, I got a few warnings and I did not need to run the 'mount' command. Good luck!