owner@Ubuntu-desktop:~$ cvt 1024 768
# 1024x768 59.92 Hz (CVT 0.79M3) hsync: 47.82 kHz; pclk: 63.50 MHz
Modeline "1024x768_60.00"   63.50  1024 1072 1176 1328  768 771 775 798 -hsync +vsync
owner@Ubuntu-desktop:~$ xrandr --newmode "1024x768_60.00"   63.50  1024 1072 1176 1328  768 771 775 798 -hsync +vsync
owner@Ubuntu-desktop:~$ xrandr --addmode default 1024X768_60.00
xrandr: cannot find mode "1024X768_60.00"
owner@Ubuntu-desktop:~$