This works in ubuntu if you want to set any other screen mode get the according screen line with cvt XRES YRES FREQUENCY
Also the device name may have to be modified but VGA1 is typical for an second monitor which is plugged in via VGA.

xrandr --newmode "1280x1024_60" 109.25 1280 1368 1496 1712 1024 1027 1034 1063 -hsync +vsync
xrandr --addmode VGA1 1280x1024_60
xrandr --output VGA1 --mode 1280x1024_60