debe haber algun fallo,mira las respuestas
jaime@Jaime:~$ cvt 1024 968
# 1024x968 59.81 Hz (CVT) hsync: 60.11 kHz; pclk: 81.75 MHz
Modeline "1024x968_60.00" 81.75 1024 1088 1192 1360 968 971 981 1005 -hsync +vsync
jaime@Jaime:~$ # 1024x968 59.81 Hz (CVT) hsync: 60.11 kHz; pclk: 81.75 MHz
jaime@Jaime:~$ Modeline "1024x968_60.00" 81.75 1024 1088 1192 1360 968 971 981 1005 -hsync +vsync
Modeline: orden no encontrada
jaime@Jaime:~$ xrandr --newmode "1024x968_60.00" 81.75 1024 1088 1192 1360 968 971 981 1005 -hsync +vsync
xrandr: Failed to get size of gamma for output default
X Error of failed request: BadName (named color or font does not exist)
Major opcode of failed request: 151 (RANDR)
Minor opcode of failed request: 16 (RRCreateMode)
Serial number of failed request: 19
Current serial number in output stream: 19
jaime@Jaime:~$ xrandr --addmode default 1024x968_60.00
xrandr: Failed to get size of gamma for output default
jaime@Jaime:~$ xrandr --output default --mode 1024x968_60.00
xrandr: Failed to get size of gamma for output default
xrandr: Configure crtc 0 failed