How to quit the X interface without quiting the system?
 

I mean I want to get back to the concole mode without shutdown the system.

How can I do that ?

Thanks!

ctrl - alt - backspace

telinit 3

Just a few of the many ways, etc. The first one will not work if you start X at bootup, as it will just kill and respawn X with those keystrokes.

If you use xinit/startx, you can generally just close your window manager and it will close your X session along with it, assuming that your window manager was not started as a background process.

Ctrl + Alt +(F1 to F6)
To return X press Alt + F7