You cannot back up an Odoo DB without the records. I'm assuming you are asking this question because you created dummy data in order to test your instance and configure it the way you want; now you want to "save your configuration" without having the dummy data you created in order to start a production instance or something like that. This is not possible. The correct practice is to back up your database before doing something that could harm/pollute it (like creating dummy data or like installing a new app that you don't know the consequence of).

Now that you are in this situation, your only option is to start a new instance fresh. This means that you need to copy the configuration that you have in the original instance into your new instance (install the same apps, check the same checkboxes,...). Fortunately, this is only a couple hours work.

On backup page of Odoo you have two options for create a backup, 

1- zip (includes filestore)

2- pg_dump custom format (without filestore)

Seems that you are using the first, select the second to get a backup without data of attachments