RedHat AS4.0花屏问题
在虚拟机上安装RedHat Linux AS4.0后，由于视频配置时选择颜色深度太高，把16位色配置为24位色，导致打开图形界面时出现花屏，屏幕宽度非常大，严重变形，不能操作。
既然是显卡配置部分出现问题，就必须修改该部分的配置信息。在这种情况下，这些应该进入单用户模式下完成：
首先重新启动机器，在出现 grub 后，按字母“e”，然后会出现 grub 的配置文件，再按键盘移动光标到第二行“Kernal……”，再按“e”，然后在编辑界面输入 single，回车。然后按“b”重启，就进入了“单用户模式”
进入后在提示符 # 后敲入：vi /etc/X11/xorg.conf，然后会打开这个视频配置文件，再输入“/Screen”(注意S是大写)检索到 Screen 部分，会显示相关的配置的地方。
然后您按“i”键进入Vi编辑器的插入模式，把光标移动到“24”的位置，把这里的 24 改为 16，然后按 ESC 键返回命令模式，按冒号“:”，输入 wq，回车，保存、退出。键入 reboot 命令，回车，重新启动，图形界面就出来了！
以下是一个正确的 xorg.conf 文件的内容：
# XFree86 4 configuration created by pyxf86config
Section "ServerLayout"
Identifier "Default Layout"
Screen 0 "Screen0" 0 0
InputDevice "Mouse0" "CorePointer"
InputDevice "Keyboard0" "CoreKeyboard"
EndSection
Section "Files"
# RgbPath is the location of the RGB database. Note, this is the name of the
# file minus the extension (like ".txt" or ".db"). There is normally
# no need to change the default.
# Multiple FontPath entries are allowed (they are concatenated together)
# By default, Red Hat 6.0 and later now use a font server independent of
# the X server to render fonts.
RgbPath "/usr/X11R6/lib/X11/rgb"
FontPath "unix/:7100"
EndSection
Section "Module"
Load "dbe"
Load "extmod"
Load "fbdevhw"
Load "glx"
Load "record"
Load "freetype"
Load "type1"
Load "dri"
EndSection
Section "InputDevice"
# Specify which keyboard LEDs can be user-controlled (eg, with xset(1))
# Option "Xleds" "1 2 3"
# To disable the XKEYBOARD extension, uncomment XkbDisable.
# Option "XkbDisable"
# To customise the XKB settings to suit your keyboard, modify the
# lines below (which are the defaults). For example, for a non-U.S.
# keyboard, you will probably want to use:
# Option "XkbModel" "pc102"
# If you have a US Microsoft Natural keyboard, you can use:
# Option "XkbModel" "microsoft"
#
# Then to change the language, change the Layout setting.
# For example, a german layout can be obtained with:
# Option "XkbLayout" "de"
# or:
# Option "XkbLayout" "de"
# Option "XkbVariant" "nodeadkeys"
#
# If you'd like to switch the positions of your capslock and
# control keys, use:
# Option "XkbOptions" "ctrl:swapcaps"
# Or if you just want both to be control, use:
# Option "XkbOptions" "ctrl:nocaps"
#
Identifier "Keyboard0"
Driver "kbd"
Option "XkbModel" "pc105"
Option "XkbLayout" "us"
EndSection
Section "InputDevice"
Identifier "Mouse0"
Driver "mouse"
Option "Protocol" "IMPS/2"
Option "Device" "/dev/input/mice"
Option "ZAxisMapping" "4 5"
Option "Emulate3Buttons" "yes"
EndSection
Section "Monitor"
Identifier "Monitor0"
VendorName "Monitor Vendor"
ModelName "Unknown monitor"
HorizSync 31.5 - 37.9
VertRefresh 50.0 - 70.0
Option "dpms"
EndSection
Section "Device"
Identifier "Videocard0"
Driver "s3"
VendorName "Videocard vendor"
BoardName "S3 Trio64 (generic)"
EndSection
Section "Screen"
Identifier "Screen0"
Device "Videocard0"
Monitor "Monitor0"
DefaultDepth 16
SubSection "Display"
Viewport 0 0
Depth 16
Modes "800x600" "640x480"
EndSubSection
SubSection "Display"
Viewport 0 0
Depth 16
Modes "800x600" "640x480"
EndSubSection
EndSection
Section "DRI"
Group 0
Mode 0666
EndSection
注意以上的 Section "Screen"……EndSection 部分，正是我们需要关心的地方。在实际中笔者发现，DefaultDepth 16 莫名其妙的变为了 DefaultDepth 16161616161616161616。SubSection "Display" 部分的两个 16 都变为了 24，需要全部变回来。这里表明是有2个显示器的情况。