Boot iMac to Terminal

Question

I'm trying to fix the display problem on an older iMac (2009) that is discussed in this link: 14.04 gets black screen unless radeon.modeset=0

But, I cannot figure out how to boot my iMac to a terminal window. Instead I always get the dead screen.

How do I boot to a terminal prompt that I can see?

Answer 1

I solved this by using the option button to boot back to the USB installation stick. Then I modified the file one edits from grub by adding nomodeset to the linux line.