Opening session via XDMCP to GDM

I have a RHEL6 server which we connect via XDMCP. If I start xdm (xdm &) it works but the login screen is the old xdm simple login and not gdm. Our RHEL5 servers connect to gdm just fine. The problem is that GDM isn't running. When I try to launch GDM (gdm &) it gives me the following message: ** (gdm-binary:3229): WARNING **: Couldn't connect to system bus: Failed to connect to socket /var/run/dbus/system_bus_socket: No such file or directory I've also tried using (gdm-binary &) and get the same message. cat /etc/gdm/custom.conf # GDM configuration storage [daemon] [security] DisallowTCP=false AllowRemoteRoot=true [xdmcp] Enable=true [greeter] IncludeAll=true [chooser] [debug] In /etc/X11/xdm/Xaccess I have the following uncommented: * #any host can get a login window In /etc/X11/xdm/xdm-config I have tried commenting and uncommenting the following: DisplayManager.requestPort: 0 I've referenced several tutorials such as: http://www.yolinux.com/TUTORIALS/GDM_XDMCP.html http://kosala-linux.blogspot.com/2013/02/x-manager-configurations-for-rheloel.html