有关redhat调节屏幕分辨率的问题

我在网上查redhat调节屏幕分辨率，很多都是说修改/etc/X11/xorg.conf文件中的“Monitor”那一项，但我的这个文件中根本就没有这一项啊，下面是我的这个文件里的内容：
Section "ServerLayout"
Identifier "single head configuration"
Screen 0 "Screen0" 0 0
InputDevice "Keyboard0" "CoreKeyboard"
InputDevice "Synaptics" "CorePointer"
EndSection

Section "InputDevice"
Identifier "Keyboard0"
Driver "kbd"
Option "XkbModel" "pc105"
Option "XkbLayout" "us"
EndSection

Section "InputDevice"
Identifier "Synaptics"
Driver "synaptics"
Option "Device" "/dev/input/mice"
Option "Protocol" "auto-dev"
Option "Emulate3Buttons" "yes"
EndSection

Section "Device"
Identifier "Videocard0"
Driver "vesa"
EndSection

Section "Screen"
Identifier "Screen0"
Device "Videocard0"
DefaultDepth 24
SubSection "Display"
Viewport 0 0
Depth 24
EndSubSection
EndSection

请问我该怎么修改屏幕的分辨率？？