Simple, but confounding, X-terminal question

[Mark Phillips]

I use an old laptop as an x-terminal. The laptop boots up to Debian and a 
console prompt. I then login, issue the command 'X -broadcast' and I get my 
gdm login prompt from the server. I login and everything works as it should.

There is an option on the login screen for "disconnect". I had hoped it would 
allow me to disconnect from the server and drop back to the shell prompt on 
the laptop. However, it just blanks the screen and then up comes the gdm 
login prompt. 

Is there a setting somewhere that I can use to make the disconnect button on 
the gdm prompt stop the local X session? 

How do I kill the local X session without Ctrl-Alt-F2, logging in again, and 
killing it from the command line?

Thanks!

Mark Phillips