Running two X servers in parallel, such working under graphical mode under root (is strongly discouraged),ensure that you have previously closed its user session or that you run a desktop management software different from its current session (KDE - Gnome-XFCE), etc ...
How to proceed
Simply launch a new console using the following combination of keys:
CTRL + ALT + F1
You will be prompted to enter a login and password. Log"yourself under your main identity with your password.
In prompt, run the GUI using the startx command, note that you must specify a new display:
#startx -- :1 <Enter>
Note that: there is a space between the startx and 2 dashes --, and between the 2 dashes
and 1, however there no space between : and the 1.
You can now navigate from a display to another through these combinations of keys: