I recently installed Debian 8 with a hi-dpi monitor on a MacBook Pro or a Retina Display as Apple calls it. I used a very tiny netinst installer, but it leaves you with nothing but a Linux text console right after the download.
There’s a solution for this, luckily. First, squint and login your eyes and set the font to: setfont Uni3-Terminus32x16
To make that change permanent, edit /etc/default/console-setup and make the following three variables look like this: CODESET="Uni3" FONTFACE="Terminus" FONTSIZE="32x16"
You can now enjoy a readable font size that will be added to each boot.