mjhjmtu

I pressed something and accidentally swapped my two screens. My left one is actually considered as the right one, and vice versa. How can I swap them back?

Edit - Specifically, I'm using Gnome, though we might also want to keep this question generic.

Edit 2 - It appears that my driver isn't compatible with xrandr. I'm attaching log of /var/log/Xorg.0.log here

Your desktop environment probably has a way, but you don't say which one you're using (if any).

If your display driver is compatible with the XRandR extension, which is the standard X.org method for managing display resolutions and arrangements, you can use the command-line utility xrandr. I think the proprietary NVidia driver bypasses XRandR, so if you're using it, you'll have to use a dedicated NVidia tool.

Run xrandr (with no argument) to see your monitor (screen) arrangement. You'll see lines like these:

DVI-0 connected 1600x1200+1600+0 (normal left inverted right x axis y axis) 408mm x 306mm
DVI-1 connected 1600x1200+0+0 (normal left inverted right x axis y axis) 408mm x 306mm

This example means that I have two monitors called DVI-0 and DVI-1, and DVI-1 is at the top left (position +0+0) while DVI-0 is to its right (position +1600+0). To swap them, I would run

xrandr --output DVI-0 --left-of DVI-1

I used the native Gnome Monitor Manager (from the System->Preferences menu) and it worked like a charm.