In text mode, press the left Alt-F1 to Alt-F12 to select the consoles tty1 to tty12; Right Alt-F1 gives tty13 and so on. To switch out of X you must press Ctrl-Alt-F1, etc; Alt-F5
or whatever will switch back.
However, If you have a non-PC compatible system, please see the note below.
If you want to use a VC for ordinary login, it must be listed in /etc/inittab, which controls which terminals and virtual consoles have login prompts. The X Window System needs at least one free VC in order to start.
[Note: The key sequence is actually Ctrl—Meta— FN. On PC compatible systems, the right and left Alt keys are really synonymous with the keysymbols Meta_L and Meta_R. If the binding is different, you can determine what keys produce Meta_L and Meta_R with xkeycaps or a similar application.]