Source: http://pihalf.wordpress.com/2009/11/...e-with-xrandr/

For example my screen resolution is 1280x1024 and I want to change my refresh rate to 75 from 60:

Code:
$ xrandr
$ xrandr --output VGA1 --mode "1280x1024" -r 75
$ xrandr
First imput of xrandr:
Code:
Screen 0: minimum 320 x 200, current 1280 x 1024, maximum 4096 x 4096
LVDS1 connected (normal left inverted right x axis y axis)
   1024x600       59.5 +
   800x600        60.3     56.2  
   640x480        59.9  
VGA1 connected 1280x1024+0+0 (normal left inverted right x axis y axis) 338mm x 270mm
   1280x1024      60.0*+   75.0
   1280x960       60.0  
   1152x864       75.0     70.0  
   1024x768       75.1     70.1     60.0  
   832x624        74.6  
   800x600        72.2     75.0     60.3     56.2  
   640x480        72.8     75.0     66.7     60.0  
   720x400        70.1  
TV1 disconnected (normal left inverted right x axis y axis)
Second output of xrandr:
Code:
Screen 0: minimum 320 x 200, current 1280 x 1024, maximum 4096 x 4096
LVDS1 connected (normal left inverted right x axis y axis)
   1024x600       59.5 +
   800x600        60.3     56.2  
   640x480        59.9  
VGA1 connected 1280x1024+0+0 (normal left inverted right x axis y axis) 338mm x 270mm
   1280x1024      60.0 +   75.0* 
   1280x960       60.0  
   1152x864       75.0     70.0  
   1024x768       75.1     70.1     60.0  
   832x624        74.6  
   800x600        72.2     75.0     60.3     56.2  
   640x480        72.8     75.0     66.7     60.0  
   720x400        70.1   
TV1 disconnected (normal left inverted right x axis y axis)
If the resolution or the refresh rate is wrong at the reboot, you can modify the file monitors.xml in /etc/gnome-settings-daemon/xrandr/.
if it does not exist copy the file ~/.config/monitors.xml in /etc/gnome-settings-daemon/xrandr/ with superuser rights:
Code:
su
cp ~/.config/monitors.xml /etc/gnome-settings-daemon/xrandr/
nano /etc/gnome-settings-daemon/xrandr/monitors.xml
My modified monitors.xml:
Code:
<monitors version="1">
  <configuration>
      <clone>no</clone>
      <output name="LVDS1">
          <vendor>???</vendor>
          <product>0x0000</product>
          <serial>0x00000000</serial>
      </output>
      <output name="VGA1">
          <vendor>PHL</vendor>
          <product>0x081e</product>
          <serial>0x000028b8</serial>
          <width>1280</width>
          <height>1024</height>
          <rate>75</rate>
          <x>0</x>
          <y>0</y>
          <rotation>normal</rotation>
          <reflect_x>no</reflect_x>
          <reflect_y>no</reflect_y>
          <primary>yes</primary>
      </output>
      <output name="TV1">
      </output>
  </configuration>
</monitors>