On Sep 19,  4:28pm, Joel CARNAT wrote:
} 
} I decided to try to connect to my firewall using xdm/Xnest.

     I advise against this.  A machine acting as a firewall should be a
dedicated machine.  It should have no unnecessary services running, and
xdm is not required for a firewall to operate.  If you're going to run
a whole bunch of services on it and have users, then you should realise
that it is really a general purpose sever and will be less secure then
a true firewall.

} My FW has no screen, no keyboard, no mouse connected.
} I boot it with serial console enabled.
} 
} I used "XFree86 -configure" to set XF86Config.

     This is strictly for configuring the XFree86 X server.  You're not
interested in an X server, so ignore both XFree86 and XF86Config.

     You need to configure xdm.  You will find the config files for it
in either /etc/X11/xdm or /usr/X11R6/lib/X11/xdm.  There are several
files you need to modify.  First, you need to modify Xaccess to specify
which X terminals are allowed to use your xdm (see the comments in the
file).  Then, you need to comment out the line in Xservers that tells
it to start a server on the console (it should be the last line).
Finally, you need to comment the line in xdm-config that says,
"DisplayManager.requestPort:      0" (should be the last line) in order
to allow xdm to listen to the network.

}-- End of excerpt from Joel CARNAT