I'm trying to dual boot linux on a 2006 iMac. I have tried Arch, Ubuntu, and Fedora.
I originally created the Arch USB installation media following the instructions in the Arch Beginner's Guide. Based on these instructions, I used dd to directly write the image to the USB drive. I was unable to get the iMac to boot properly from the USB media. So later on, I tried creating an Ubuntu live USB drive using dd. This was the least successful because, as I recall, the iMac bootloader wouldn't even show me an option to try to boot from the USB drive.
Most recently I tried creating a Fedora Live USB drive using the instructions provided by Fedora.
Essentially, I just did
sudo dd if=correct-fedora-name.iso of=/dev/rdisk1 bs=8m && sync
I originally tried with bs=1m, which also failed to properly boot.
So, with my Fedora Live USB media setup, I tried booting from the USB drive and I was at the bootloader screen, I selected the Fedora option, and after that it seemed to wait for a second before proceeding to boot into Mac OS. Nothing at all came up after I selected to boot from the USB drive, other than it booting into Mac OS as it does normally.
Using the same USB drive, I tested it on my MacBook Pro Late 2013, on which it booted fine, and I was able to use Fedora a bit on the live media.
I'm wondering why booting the Fedora media did not work on the iMac. At this point I don't care much about Arch or Ubuntu. However, the Arch beginner's guide has a section about restoring a USB drive for use after having imaged it. Something about it messing with the partition scheme. This confused me a bit, but I think it's safe to assume that it is no longer a factor, given that I have overwritten the drive completely multiple times at this point?