Download ubuntu in the image file, with xrandr query only one resolution options, minimum value is the maximum resolution, 1680 * 1050, for example, I want to put into resolution of 1920 * 1080, tried a lot of ways, and are not set,
Xrandr, moreover, only in the graphics mode can be used, if if plain text mode (CTRL + Alt + f1), xrandr unusable,

Excuse me, how should adjust resolution?