On Thu, Jan 28, 2016 at 10:30:03AM -0500, ken wrote:
When someone is sitting at their linux machine which is running gnome, and if that machine is running at 'init 5', and if they aren't yet logged in, they'll have something on their screen called the Greeter. If they successfully log in they'll have displayed on their monitor a 'gnome desktop'. If they've logged in before, normally gnome (or more properly 'gdm') will display those apps which were open that last time (at the time they logged out from gnome). By 'remote display' I mean that all of that, beginning with the Greeter, can be seen and used, it functions, not on the machine which one is sitting at, at that moment called the local machine, but another machine, a remote machine.
So, what you're asking for is to run XDMCP on the gdm on the centos5 system, which it does support, just add an [xdmcp] section to /etc/gdm/custom.conf.
However, the real question is how do you want to have clients contact gdm via XDMCP? X11 isn't a secure protocol, so just running 'X -query remotehost' isn't really the best idea. You'd have to open up the port on the server in the firewall too.
I wouldn't suggest using this. It'd probably be better to use VNC and forward all traffic over SSH.