The Linux console is the basic text entry and display device for system administration messages. It is the well known white on black display that is shown at boot when no desktop environment is installed.
How to access the Console
In Debian, there are already six default virtual Consoles ready to be used. They all can be accessed using the key combination Ctrl + Alt + FN#Console. For example, the Console #3 is accessed by pressing Ctrl + Alt + F3.
Note The Console #7 is usually allocated to the graphical environment (Xorg, etc.).
Locking the console
To completely lock the console and prevent virtual console switching, check out the vlock package.
Use logout to terminate your console session and go back to the login prompt.