ERROR: Unable to verify the graphical display setup.

  VNC环境下Oracle安装图形界面安装：

[oracle@chengyu ~]$ cd /home/softwares/oracle/19c/
[oracle@chengyu 19c]$ ./runInstaller
ERROR: Unable to verify the graphical display setup. This application requires X display. Make sure that xdpyinfo exist under PATH variable.
No X11 DISPLAY variable was set, but this program performed an operation which requires it.

  确定连接的vnc是几号号桌面，这里是3号桌面：

[root@chengyu ~]# vncserver

Warning: chengyu:1 is taken because of /tmp/.X11-unix/X1
Remove this file if there is no X server chengyu:1

New 'chengyu:3 (root)' desktop is chengyu:3

Starting applications specified in /root/.vnc/xstartup
Log file is /root/.vnc/chengyu:3.log

  解决：

[oracle@chengyu ~]$ export DISPLAY=":3.0"
[oracle@chengyu ~]$ echo $DISPLAY
:3.0
[oracle@chengyu ~]$ xhost +
access control disabled, clients can connect from any host
[oracle@chengyu 19c]$ xdpyinfo | head
name of display:    :3.0
version number:    11.0
vendor string:    The X.Org Foundation
vendor release number:    12001000
X.Org version: 1.20.1
maximum request size:  16777212 bytes
motion buffer size:  256
bitmap unit, bit order, padding:    32, LSBFirst, 32
image byte order:    LSBFirst
number of supported pixmap formats:    6
[oracle@chengyu ~]$ cd /home/softwares/oracle/19c/
[oracle@chengyu 19c]$ ./runInstaller 
Launching Oracle Database Setup Wizard...

  OK：

  其实，可以在安装Oracle之前通过xclock来验证是否能够正常弹出安装界面：

  [root@chengyu ~]# yum -y install xorg-x11-apps

  [root@slave oracle]# xclock