Q: iMac boot from linux partition on external drive I have the following "setup:"
iMac (no internal drive/dead) --------- (Firewire) ------- [[MAC OS X]]
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(USB)
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[[MISC STORAGE PARTITION] [MISC STORAGE PARTITION] [EXT2 UBUNTU PARTITION]]

I routinely use the firewire drive to boot MAC OS X.
However, I would like to boot from the linux partition of the USB drive. This linux partition had linux installed on it from a live cd, and during that process, I told the installer to install GRUB on the usb drive (which happened to be /dev/sdd).
My question is, how do I get this disk to show up during the iMac option-boot? Currently, only the firewire MAC OS X option shows up. I have read about rEFIT, but that appears to install it to the Mac OS X disk (would that still work?)...
Also mentioned was installing rEFIT to the internal EFI system partition, but I don't know if that is wise.

A: This is the most useful link I have found for Ubuntu on an iMac using USB. 
I just swapped Karmic for Lucid. You boot holding down the Option key. I used a 16 GB SanDisk stick for Ubuntu and never had to touch my iMac's hard drive.
Installation of Ubuntu Karmic Koala for a MacBook Pro 3,1 on a USB stick | Linux on your Apple Mac

A: I don't think there's any good way to install Linux on Mac using Boot Camp, but you can tell Boot Camp to create a Windows entry and then install Linux to it.
I don't think you can rescue it at this point, so you might need to redo the process.
(Source)
If you install it using Boot Camp as a Windows partition, then you should be good. This isn't exactly a direct answer to your question, but I don't know what else you can do at this point... you have to trick the Mac to do anything not officially supported, that's kinda how it is.
