Allegedly, on or about 04 July 2014, don fisher sent:
Do you know what file the setting are maintained in? I do not use Gnome and would like to be able to edit the appropriate files rather than being so dependent on GUI interfaces.
I have to say that there's a certain level of irony in avoiding using a graphical tool for configuring your graphical user interface...
I'm not sure if this file works with every type of desktop: ~/.config/monitors.xml
For system things, like GDM (the logon screen for Gnome), it goes into *that* thing's homespace, rather than /home/username:
i.e. /var/lib/gdm/.config/monitors.xml
KDM may do something similiar (it'll have a different path).
The file begins like this, and may have multiple sections, if you've switched monitors around:
<monitors version="1"> <configuration> <clone>no</clone> ...[snip]...
If each monitor clones each other, it has "yes" in there. Otherwise, "no" cloning spreads the picture across the monitors.