Yesterday, I updated my os (#manjaro, at the moment), rebooted my computer, and got only a black screen. Ctrl+Alt+F2 yielded full-screen tty. Startx from there got me nowhere. my graphics card drivers were erroring out.
To fix it, I had to educate myself on the hardware driver situation used in manjaro: mhwd. It's pretty slick once you get the hang of it, but what wasn't clear was that I had to use mhwd to upgrade my linux kernel, then remove the old one, and only then would the tool allow me to install the correct graphics card driver. From there it just worked, but it's a good thing I had a full day to spare to get my machine working again.