How to Have More Than One X Server Running at Once

If you need to test something in a different resolution or run an X session for more than one user at the same time, you may be interested to know that you can indeed run multiple X servers.

To do so, simply execute the following command, replacing n with whatever you want the display number to be:

startx -- :n

As switching to the 7th virtual console (for me) using Alt-F7 gets you to your first X server, Alt-F8 will be your second, et cetera.