安装数据库Typical path for xclock: /usr/X11R6/bin/xclock 错误问题

[oracle@localhost database]$ ./runInstaller
Starting Oracle Universal Installer...

Checking Temp space: must be greater than 120 MB. Actual 2847 MB Passed
Checking swap space: must be greater than 150 MB. Actual 2047 MB Passed
Checking monitor: must be configured to display at least 256 colors
>>> Could not execute auto check for display colors using command /usr/bin/xdpyinfo. Check if the DISPLAY variable is set. Failed <<<<

Some requirement checks failed. You must fulfill these requirements before

continuing with the installation,

Continue? (y/n) [n] y

>>> Ignoring required pre-requisite failures. Continuing...
Preparing to launch Oracle Universal Installer from /tmp/OraInstall2019-06-05_12-05-20AM. Please wait ...
DISPLAY not set. Please set the DISPLAY and try again.
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.
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':
% <full path to xclock.. see below>
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

DISPLAY变量是用来设置将图形显示到何处.比如CENTOS,你用图形界面登录进去,DISPLAY自动设置为DISPLAY=:0.0表示显式到本地监视器,那么通过终端工具(例如:xshell)进去,运行图形界面的程序,如果没有设置,系统是不允许程序启动的。
在执行xhost +命令（使得所有客户都可以访问）

正常返回信息为：
access control disabled,clients can connect from any host

如果xhost +不能执行，报错：xhost ：  unable to open display ""

可以输入命令export DISPLAY=:0执行一下

再执行xhost +  

就可以安装oracle了，但是如果没有安装成功 重启linux，还会包上面这个错，再重新执行一下就好了