I have a Macbook Pro (mid 2014) and want to run OS X, Windows and Ubuntu.
I installed Win 8.1 using Bootcamp in the standard way recommended by Apple. I set Windows as the default in Bootcamp, but pressed Option when I wanted OS X.
I then created a Ubuntu 14 installer flash drive, and installed Ubuntu 14 to another flash drive. I figured I could just boot from the USB when I needed Linux. But the installer also installed GRUB to the Macbook SSD (same happened to a colleague).
On the first few boots after this, I could boot with the Ubuntu flash disk in and it would offer a plain text (I assume GRUB) menu, which would enable me to choose between Ubuntu or Windows. If I booted without the flash disk I could hold Option, and could get into OS X.
Then behaviour changed. If I booted without the flash disk I got the GRUB command line with a flashing cursor. I assume booting into the flash Ubuntu put it there. Typing exit [enter] booted me into Windows. If I booted with the flash disk I got a Ubuntu menu that let me choose between Ubuntu and Windows. But I had lost OS X. I tried holding Option while typing exit into GRUB but it just booted into Windows.
Then behaviour changed again, possibly when I opened the Windows system tray Bootcamp assistant. Now, booting with Option held down offers the Bootcamp menu, with OS X or Windows. But I have lost Ubuntu on the flash disk!
Can I get my Macbook to simply boot from USB, like any Windows laptop could, by setting that in the BIOS? I tried holding C, but the Macbook doesn't seem to find the flash disk Ubuntu. Is triple boot possible, with eg, rEFInd? (Sources suggest it is with Bootcamp, too, but not in my experience.) I could re-install Ubuntu - is there a way of doing it without corrupting Bootcamp? How could I avoid losing Ubuntu again?
Is there some reason why Ubuntu won't co-exist with OS X? Is one EFI but the other not?
Help with understanding or diagnosis would be massively appreciated, let alone assistance with a solution.