How can I increase text size in single-user mode?

I know this is really old but I thought I might share the answer with y'all. The way Apple implements characters in the boot video mode is in pixels. There is an array of 0s and 1s that correspond to white and black respectively. Now since the Retina display has such high resolution, the density of those pixels will have a direct coincide with the size of the characters. For example, this is the implementation of capital A:

1 1 1 1 1 1 1 1
1 1 1 1 1 1 1 1
1 0 0 0 0 0 1 1
0 0 1 1 1 0 0 1
0 0 1 1 1 0 0 1
0 0 1 1 1 0 0 1
0 0 0 0 0 0 0 1
0 0 1 1 1 0 0 1
0 0 1 1 1 0 0 1
0 0 1 1 1 0 0 1
0 0 1 1 1 0 0 1
0 0 1 1 1 0 0 1
1 1 1 1 1 1 1 1
1 1 1 1 1 1 1 1
1 1 1 1 1 1 1 1

I hope this answers your question, and as joshfindit said, Apple would need to redesign the boot video mode if they were to fix this.

This is going to be your experience with Single User mode until Apple rewrites the underlying code to allow it to understand what retina is.

Photo courtesy of Bev Sykes

Do you really need single-user mode? If so, why?

You should be able to use the Recovery partition to do much of the same, and possibly also dump the contents of that partition to make it PXE bootable for other Macs on your local LAN...

I tried some tricks by setting NVRAM boot-args instead of booting into single-user mode the usual way. There is the known kernel boot option:

"Graphics Mode"="<width>x<height>x<depth>@<frequency>"

but it doesn't seem to effect console mode. See http://www.tonymacx86.com/wiki/index.php/Org.chameleon.Boot.plist#System_Boot_Options for more info on boot-args

I couldn't find any command-line tools to set the resolution either, or even how to magnify the text (though this might be possible). There is virtually no information online about how to set Darwin's framebuffer resolution. You might find some related code on http://opensource.apple.com if you poked around enough. You could also try to patch the console mode display driver in OS X (probably XNU?) to handle this, or look at alternative boot loaders like Chameleon.

You may also be able to rewrite the EDID presented from your monitor to the Mac to make console mode use a lower resolution. This would require flashing the firmware of your display.