There seems to be another, easy way to setup a triple-boot Mac (with Mac OS X, Windows 7 and Ubuntu 12.04) without even using an additional bootloader such as rEFIt or rEFInd! You can just use the built-in Mac bootmanager and GRUB. It's really simple!
I haven't tested this yet, I've just read about it in an article that was published in a german computer science magazine. But it seems to work! :-)
Here are the necessary steps in short:
- BACKUP everything! ;-)
- create two additional partitions using the Disk Utility that comes with Mac OS X (the last partition will be used for Linux, the one in the middle for Windows - format it as MS-DOS (FAT) and name it "Windows" -> the Disk Utility will create two entries for that partition: One in the GPT and one in the MBR)
- start the Windows 7 installation from a DVD or USB flash drive (hold down the alt-key while booting your Mac). Make sure you select the right partition for Windows.
- install Ubuntu from DVD or USB flash drive.
During the installation, delete the partition you've created for Ubuntu and create new partitions instead: A small one (just 1 MB) for the use as a "reserved BIOS boot partition" (some of the grub code will be stored there) and one or more for your Linux system.
- if you start your Mac now while holding down the alt-key, you should see three hard drive icons in the bootmanager labelled "Mac OS", "Windows" and "Recovery". If you select the "Windows" entry, the grub bootloader should show up where you can chose between booting Windows or Ubuntu.
That's all! :-)
You don't even need to install rEFIt or rEFInd which makes everything simpler.
Please let me know if this works for you!