This was going to be my first Ubuntu install, aiming to triple boot from a Mac Book Air OS, W7 and Ubuntu. I used USB sticks for both the W7 and Ubuntu. After successfully partitioning using OS (it is apparently required to do it from OS because of the MBR/GPT issues) installing W7 and refit, and having a working dual boot, I proceeded with Ubuntu, following this tutorial.
I however missed the advanced button that would have allowed to specify that the boot loader should be installed in a non standard way, to the same partition into which Linux is being installed.
I restarted with no USB drive connected, expecting to see the refit menu with the three OSs, but there had been no change: only OS and W7 were selectable. That's when I noticed something was wrong. So I reconnected the USB drive with the Ubuntu installer and restarted with the intention of reinstalling. To my surprise I could now select Ubuntu from the hard drive, in which case it would boot correctly, or the USB installer, which instead of running normally showed a menu to select the OS to boot.
And now is when I made the big mistake: I destroyed the partition from OS and/or w7 thinking that would allow me to reinstall. Now whenever I connect the USB and select it in the refit menu a command prompt that says "error: no such device: 56756fb3-57a2-4f0c-8068-a9068cb88a18.", and in a new line: "grub rescue> ". I tried to find the Ubuntu file system with fs but none of the listed partitions that appear with the "ls" command were recognized. This does make sense since Ubuntu's file system was presumably destroyed with my hard formatting and destruction of the partition in which I had installed it. I have recreated a partition to no avail.
Obviously somewhere is stored that Linux was once installed, and I need to reset that in order to reinstall. My guess is I need to fix the MBR or the GPT, but I don't know how to accomplish such a feat or even if that is what I need to do.
I know this is very specific, but I believe might happen to other potential triple booters. Is there anyone who could please help me? Thanks in advance.