I have some all-in-one System76 workstations running Debian Jessie with XFCE. Whenever I add a second external monitor via DVI and reboot, the primary all-in-one monitor will go black, as if the brightness has been set to 0; even the System76 boot screen does not appear. Both screens work perfectly fine before rebooting.However, the machine seems to start up fine; the external monitor is usable, with a working mouse cursor and everything. Unplugging the external monitor then rebooting again fixes the internal screen.I suspect this is some problem with X11 but I really have no idea.
Dual monitors not working in Debian Jessie
linux;debian;x11;xfce