Introduction

XDMCP is a remote desktop protocol. With XDMCP, one computer A running X11 can connecting computer B running X11, and interact with computer B as if one were physically at computer B. XDMCP is integrated into X.org.

To Configure

1. Add the following to /etc/gdm/custom.conf

   [xdmcp]
   Enable=true
   
   [security]
   DisallowTCP=false
   AllowRemoteRoot=true
   

2. Restart X:

   [root@racnode1 ~]# init 3
   [root@racnode1 ~]# init 5
   

3. Run gdmsetup
4. Restart GDM: /usr/sbin/gdm-restart

References

1. http://www.idevelopment.info/data/Unix/Linux/LINUX_ConfiguringXDMCPRedHa...
2. http://dvradmin.blogspot.com/2013/04/configuring-xdmcp-on-rhel-6.html
3. https://wiki.ubuntu.com/xdmcp