I have xfce running in display 0 (accessible via Ctrl + Alt + F1). I press Ctrl + Alt + F2 and type startx (attempting to run more than one window manager at the same time) and receive the error "another session manager is already running xinit".
I have also installed Xephyr and ran in a bash console startx -- /usr/bin/Xephyr :1, but receive the same error as above except this time in an existing desktop environment.
How do I run more than one window environment at once? Preferably, I would do this within two different GeTTY's (i.e., Ctrl + Alt + F1 takes me to my first environment, while Ctrl + Alt + F2 takes me to my second, etc).