I have attempted to install Debian to my external USB HDD (for which I had previously created a 150GB ext4 partition on it).
I have done these operations from my Macbook pro (on which I had installed rEFind)
Here are what I did:
1) Flashed Debian DVD install on a USB thumb
2) Booted on it
3) Proceed to install Debian
3a) I have selected "manual" at the disk step 3b) I have selected my 150GB ext4 partition to be mounted as '/' 3c) I did not chose any swap
4) The Debian install process finished and I was a bit worried because it did not ask me where to install GRUB ... (I want to install it on my external HDD master boot)
When I restarted the macbook instead of going to the usual rEFind screen it went straight to a grub error screen where it says device xxxxxxxx could not be found
I restarted again the Macbook by holding "alt" and thankfully the Mac boot manager appeared and I could boot into my OSX.
From there I have re installed rEFind, restarted and the rEFind screen appeared again (uufff!) and I could see both the OSX and Debian choice. (which by the way if I chose it with my HDD plugged in, boot perfectly fine into Debian)
Can I erase the debian entry on my primary drive master boot and put it on the external HDD instead?