http://www.tldp.org/HOWTO/XWindow-User-HOWTO/runningx.html
Search for "servers" in /etc/X11/gdm/gdm.conf
Example below starts 2
servers
0=Standard
1=Standard
Search bottom in /etc/X11/xdm/Xservers
Example below starts 2
:0 local /usr/X11R6/bin/X
:1 local /usr/X11R6/bin/X
Search for "servers" in /etc/X11/gdm/gdm.conf
Example below starts 2
servers
0=Standard
1=Standard
Search bottom in /etc/X11/xdm/Xservers
Example below starts 2
:0 local /usr/X11R6/bin/X
:1 local /usr/X11R6/bin/X