Force gdm login screen to the primary monitor
For newer versions of Ubuntu such as 13.10 or upgraded 13.04 using Gnome 3.8, this procedure is different because the X configuration file no longer controls the monitor layout. You must do the following:
Set the monitor layout correctly as a logged-in user (see Permanantly set monitor as primary)
Copy the configuration file over to the gdm settings
cp ~/.config/monitors.xml ~gdm/.config/
For more details, see https://bbs.archlinux.org/viewtopic.php?id=161903
- Within the monitors.xml file there are tags labeled:
<primary>something</primary>
For the monitor you want to be primary put a 'yes' in between the tags and a 'no' for all other screens.
ex: <primary>yes</primary>