Suam

Hello everybody. I' ve just downloaded and installed Debian 8 Jessie desktop for Banana Pi pro. It works so fine but I don't know how to deactivate X envirnoment on demand. I want to have desktop envirnoment but not always and I' d want be able to start and stop it. Which service is that start X? I' ve tried to stop a lot of them but I didn't get it. Thanks in advance. Best regards, Suam.-