mac mini 2014 - boot from usb key/drive

Thanks Gary. Given your confirmation that it should be possible, I've taken the fact that the external drive doesn't appear as a choice in "startup disk" as an indication that my disk is the issue. I did try two alternatives method to get the .iso to disk given your hint,

The first, using UNetbootin rather than my linux distribution and it does come back with a message rather specific after it finishes: "The created USB device will not boot off a Mac. Insert it into a PC, and select the USB boot option in the BIOS boot menu".

The second, using Disk Utility but the restore section for the target volume doesn't seems interested in me dragging the .iso to the 'source' field.

And that's with two different OS's .iso. so assuming that's not the right alternative either.

Few questions from there if I may,

1. Is there anything special I should take care off while doing the formatting to boot from a mac (mini)? (I'd welcome any link to a validated method)
2. what do you do when you have a non mac keyboard? (I had used "C")
3. should the PXE method have worked as well on the mac mini?

(Thanks again for that first response Gary)

I gave up...

Burn the .iso on a cd-rom (bought just for that...) and boot from it (cd-rom selected from startup disk with my non mac keyboard).

This worked fine. Not answering the questions above but figured I would save myself some time...

Cheers.