[oracle@localhost ~]$ /u01/database/./runInstaller
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
Passed


All installer requirements met.

Preparing to launch Oracle Universal Installer from /tmp/OraInstall2011-12-03_02-44-22AM. Please wait ...[oracle@localhost ~]$ Xlib: connection to ":0.0" refused by server
Xlib: No protocol specified

Exception in thread "main" java.lang.InternalError: Can't connect to X11 window server using ':0.0' as the value of the DISPLAY variable.
at sun.awt.X11GraphicsEnvironment.initDisplay(Native Method)
at sun.awt.X11GraphicsEnvironment.<clinit>(Unknown Source)
at java.lang.Class.forName0(Native Method)
at java.lang.Class.forName(Unknown Source)
at java.awt.GraphicsEnvironment.getLocalGraphicsEnvironment(Unknown Source)
at java.awt.Window.init(Unknown Source)
at java.awt.Window.<init>(Unknown Source)
at java.awt.Frame.<init>(Unknown Source)
at oracle.ewt.popup.PopupFrame.<init>(Unknown Source)
at oracle.ewt.lwAWT.BufferedFrame.<init>(Unknown Source)
at oracle.sysman.oio.oioc.OiocOneClickInstaller.<init>(OiocOneClickInstaller.java:378)
at oracle.sysman.oio.oioc.OiocOneClickInstaller.main(OiocOneClickInstaller.java:2091)

Hi

I dont know much about oracle 10g but from the error message, it seems to be looking for an X server/session.
Try running it from a terminal after you log in to your Gnome (or KDE or any desktop) you have.

This has been asked (and answered) MANY times on this site...a quick search will bring up lots of answers. This is also covered on Oracle's knowledgebase, and in RedHat's knowledegebase...since you're paying for these two commercial products, you have access to them and their tech support lines, and can get assistance quicker that way.

You say nothing about how you're running this, in what environment, or give details about the hardware/network, but your local workstation needs to be running an X server (or X server emulator), and allow incoming X connections from your Oracle server. Once you do that, the installer should come right up. You can also install via text-mode, and don't need a GUI.

It wants to display a graphical window and can't. Either log in graphically, or of this is over SSH, configure/enable X forwarding.