Hello I have a laptop 15' and was going to use 23' external monitor.

I attached it and they both were working fine. But what I wanted is
just to use only one monitor and leave laptop's display to be turned off.

I couldn't find a way to do it and after playing with settings I turned first monitor off
hoping that system decides to use the second one as main monitor.

However they both are now showing black.

I am having to detach my second monitor and restart my machine (from another terminal's console)

What I want..is just turn laptops monitor off and use 23' one when it's attached.

I would also be quite happy if you would tell me where does Ubuntu store settings about monitors.

I also would to at least to be able to use two monitors at the same time (i.e revoke my last change)