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Configure SSH and X11 Forwarding

Installing the Oracle Enterprise Manager 12c components using the Oracle Universal Installer (OUI) GUI requires local or remote access to the server' console or a remote X Windows (X11) session. Please note that the only software requirements on the Linux Oracle Enterprise Manager host for remote X Windows (X11) sessions is the xauth RPM package. The xauth RPM package handles the X11 forwarding authentication. X-windows and xhost are not required on the Linux Oracle Enterprise Manager host for remote X Windows (X11) sessions. 
SSH and X11 forwarding enables the redirection of an X11 session from a remote Oracle Linux machine to a local desktop. For example, from a local desktop, ssh to a remote Oracle Linux server using X11 forwarding and run the Oracle Universal Installer, i.e. by typing “./runInstaller”. The Oracle Universal Installer will be displayed on the local desktop and the Oracle Enterprise Manager 12c components can be installed on the remote Oracle Linux server.  
On the Oracle Linux server, enable X11 forwarding in the /etc/ssh/sshd_config by adding "ForwardX11 yes" to the file as shown in the next example.
#X11Forwarding no
X11Forwarding yes
Once the "ForwardX11 yes" entry has been added to the /etc/ssh/sshd_config file, to enable X11 forwarding, as root, restart the ssh service by typing:
# service sshd restart
With X11 forwarding enabled, the Oracle Universal Installer (OUI) GUI can be exported from the Oracle Linux server to your local desktop.  
Tip: To aviod X11 challanges install the xauth and xorg-x11-apps RPMs on the Linux host. To check for the RPMs, as root type:
# rpm -qa | grep -i xauth and rpm -qa | grep -i xorg-x11-apps
To install xauth and the xorg-x11-apps RPMs, as root type:
# yum -y install xorg-x11-apps xauth. 
To enable X11 forwarding from a Linux desktop, use the "-X" switch with ssh. For example, type "ssh -X oracle@<ORACLE LINUX SERVER>" to create a ssh tunnel with X11 forwarding. Do not forget that -X enables X11 forwarding, and -x actually disables X11 forwarding. Also, using the su command within a SSH session with X11 forwarding breaks X11 authentication.
To test remote X Windows (X11), open a new ssh session with X11 forwarding enabled (ssh -X user@servername), and type xclock. The xclock application should open on your desktop. xclock is an X window client application that is included in the xorg-x11-apps RPM package. xclock is often used to test remote X Windows (X11) sessions.
Tip: To troubleshoot ssh connections, use ssh verbose mode, i.e. ssh -v -v -X user@servername
If your using a Windows PC, a PC X Server like XMing is required to run an X Windows session, along with an ssh client like putty that supports X11 forwarding.
If you get X11 forwarding request failed on channel 0 messages from an ssh connection, on the target Oracle Linux server edit the /etc/ssh/sshd_config file, and ensure that "X11Forwarding yes" is not commented, add "X11UseLocalhost no", and uncomment "AddressFamily any". Next, restart sshd by typing "service sshd restart", and your X11 apps will successfully run. 
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