How can one create a bootable Linux USB key that works on Mac (Intel 64 bit CPU) hardware?

Question

I'm trying to create a bootable USB key with Linux (debian) and that can be booted on Macintel hardware.

I have read that MAC's EFI can only boot GPT GUID formatted disks. I'm desperately trying to find a good tutorial which explains how to create such a key.

Here what I have done so far:

• create a GUID partition on te key using Linux GNU parted
• create a HFS+ or ext3 partition on the key, with the boot flag on
• install a Linux .iso with unetbootin

While all steps were successfull and in some cases I could even boot on a PC, the step of booting on Macintel software failed (on a macbook). I need to precise that I holded the "alt" key while booting the mac and the only visible bootable disk was the hard disk.

PS: I have tried with rEFIt as well. In one case I had a "Windows" icon but it then failed to boot with a message like "no system found"

Answer 1

From Boot Linux from USB on MacBook Pro 17″ :

It works! Can now boot Linux on an unmodified MacBook Pro (5,2) from a single USB stick (or external hard drive). I created a small 25MB partition as the first partition, formated it as Mac OS X Journaled and installed rEFIt to it, then followed that partition with a 100 MB boot partition, and then a root partition on a thumb drive (if using an external hard drive you could create swap as well, but I don’t do that on thumb drives so they don’t get worn out). Install linux normally (debootstrap is how I do it) onto the second and third partitions. Make sure Grub is installed to the MBR of the drive and points to the /boot partition as the second partition. Then take the USB drive to a MacBook Pro and insert it. Turn on the MBP and hold down the Alt/Option key until you see a boot menu offering Mac OS X or rEFIt. Choose rEFIt. After that you’ll be give a menu to choose OS X again or Linux. Here, choose Linux. Tada, now comes the Grub boot screen and then on into the Linux of your choice. Congrats and enjoy…

Some other useful articles that contain detailed instructions :

How to create an Ubuntu live USB for both Mac and PC
Installation of Ubuntu Karmic Koala for a MacBook Pro 3,1 on a USB stick

Answer 2

I have found that a standard ubuntu/fedora and even debian install disc, live cd or usb key will boot fine on a mac. With a CD you may need to hold down the 'c' key to boot. But I have no problems with usb installs.

I would warn that I only have linux installed on my macbook now. I installed ubuntu with a live cd a while ago, now rocking Fedora. Once there is no more OSX any linux distribution will boot without much trouble.

I'm not sure what happens when you boot a usb key and OSX is still on the machine though. I would recommend looking up key combinations to hold down to boot from USB 'c' might be enough.

I hope that helps