How to get back into Debian?

I have Amibian on my SD card, and it works well, and I boot into the Amiga interface. I would really like to get into Debian at times. So, can anyone tell me if I can do either of the

following:

1. Is there some startup file or something that I could edit and perhaps comment out the stuff which causes it to boot up the Amiga interface at startup and which would therefore leave me in Debian?

2. Or, once I am up and running in the Amiga interface, is there a way that I can toggle back into Debian and/or some way to quit/kill the Amiga interface and get back to Debian (and if this is a quit/kill thing how to restart the Amiga interface when I am finished with Debian)?

Thanks.