After upgrading to 17.10 like a true pioneer, I found the old CtrlAltF1 no longer switches between console mode and GUI, and a quick Google search brought up nothing useful. Was this feature removed entirely?
The actual used
tty consoles have changed around with the introduction of Wayland and 17.10. Now
tty1 always contains the login screen, and
tty2 contains your actual loaded session.
So use Ctrl+Alt+F3 up to Ctrl+Alt+F7 for getting to an actual unused
tty and use Ctrl+Alt+F2 to go back to GUI.
From the 17.10 Release Notes:
- GDM has replaced LightDM as the default display manager. The login screen now uses virtual terminal 1 instead of virtual terminal 7.
Also see Why is my GDM at a different TTY than my desktop environment? for more about the origin of this change.