linux平台安装oracle时的xhost问题

今天在RHEL上安装oracle 10g RAC的clusterware时，出现如下错误：
[oracle@node1 clusterware]$ ./runInstaller -ignoreSysPrereqs
********************************************************************************
Please run the script rootpre.sh as root on all machines/nodes. The script can be found at the toplevel of the CD or stage-area. Once you have run the script, please type Y to proceed
Answer 'y' if root has run 'rootpre.sh' so you can proceed with Oracle Clusterware installation.
Answer 'n' to abort installation and then ask root to run 'rootpre.sh'.
********************************************************************************
Has 'rootpre.sh' been run by root? [y/n] (n)
y
Starting Oracle Universal Installer...
Checking installer requirements...
Checking operating system version: must be redhat-3, SuSE-9, redhat-4, UnitedLinux-1.0, asianux-1 or asianux-2
                                      Failed <<<<

>>> Ignoring required pre-requisite failures. Continuing...
Preparing to launch Oracle Universal Installer from /tmp/OraInstall2011-05-17_09-25-53PM. Please wait ...[oracle@node1 clusterware]$ Oracle Universal Installer, Version 10.2.0.1.0 Production
Copyright (C) 1999, 2005, Oracle. All rights reserved.
Xlib: connection to ":0.0" refused by server
Xlib: No protocol specified
Can't connect to X11 window server using ':0.0' as the value of the DISPLAY variable.
:0.0
:0.0
OUI-10025:Unable to start an interactive install session because of the following error:Can't connect to X11 window server using ':0.0' as the value of the DISPLAY variable. The DISPLAY environment variable should be set to :, where the is usually '0.0'.
OUI-10026:Depending on the Unix Shell, you can use one of the following commands as examples to set the DISPLAY environment variable:
- For csh:                      % setenv DISPLAY 192.168.1.128:0.0
- For sh, ksh and bash:         $ DISPLAY=192.168.1.128:0.0; export DISPLAY
Use the following command to see what shell is being used:
        echo $SHELL
Use the following command to view the current DISPLAY environment variable setting:
        echo $DISPLAY
- Make sure that client users are authorized to connect to the X Server.
OUI-10027:To enable client users to access the X Server, open an xterm, dtterm or xconsole as the user that started the session and type the following command:
% xhost +
To test that the DISPLAY environment variable is set correctly, run a X11 based program that comes with the native operating system such as 'xclock':
        %
If you are not able to run xclock successfully, please refer to your PC-X Server or OS vendor for further assistance.
Typical path for 'xclock': '/usr/X11R6/bin/xclock'


没有用远程管理工具管理桌面，后来定位是xhost的问题，解决方法如下：
1 利用root用户登陆，查看DISPLAY变量----echo $DISPLAY，确保为“:0.0”；
2 运行xclock，确保能弹出时钟；
3 运行"xhost +"，该命令的解释：
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因为Xserver默认情况下不允许别的用户的图形程序的图形显示在当前屏幕上. 如果需要别的用户的图形显示在当前屏幕上, 则应以当前登陆的用户, 也就是切换身份前的用户执行如下命令
        xhost +
    这个命令将允许别的用户启动的图形程序将图形显示在当前屏幕上.

xhost 是用来控制X server访问权限的。
通常当你从hostA登陆到hostB上运行hostB上的应用程序时，
做为应用程序来说，hostA是client,但是作为图形来说，
是在hostA上显示的，需要使用hostA的Xserver,所以hostA是
server.因此在登陆到hostB前，需要在hostA上运行xhost +
来使其它用户能够访问hostA的Xserver.
xhost + 是使所有用户都能访问Xserver.
xhost + ip使ip上的用户能够访问Xserver.
xhost + nis:user@domain使domain上的nis用户user能够访问
xhost + inet:user@domain使domain上的inet用户能够访问。
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4 切换到oracle，运行./runInstall即可安装。