In Ubuntu 14.04 if I unplug my monitor from HDMI and open my laptop, the built-in LCD doesn't come on. Only after hard rebooting am I able to get back to a state where my laptop screen is the primary monitor.
I tried setting "mirroring" on the Ubuntu display settings. Unfortunately, this had the same effect.
Recently, to solve another issue I created an xorg.conf file that specified which backlight functionality to use:
Section "Device" Identifier "card0" Driver "intel" Option "Backlight" "intel_backlight" BusID "PCI:0:2:0"EndSection
Could adding this file have caused the issue?
Is there a keyboard shortcut or anything I could do to get the main monitor to come back without resorting to hard rebooting the system?