Applying changes to xorg.conf without restarting

Try this from the command line:

sudo restart lightdm

or alternatively

 sudo service lightdm restart

I am not sure what will happen if you are already running X, but it should restart it, so better close out all windows first.

See Restart X Server Ubuntu 12.04 Without Rebooting and How to kill and to start the X server? for more information.

Always a good idea to keep a copy of any configuration file before you modify it so that you can easily restore it if something goes awry.

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