When you make changes in developer mode, those changes are written into the database associated with the company. One of the major advantages of this approach is that you do not have to write code in Python or create a custom module to implement simple customizations. You don't even have to restart the server. One of the major disadvantages, however, is that there is the potential for making an unwanted change, or one that is difficult to reverse.

Therefore, it is very important and highly recommended that you make backups of your database both before and after you make any customizations while in developer mode.

To back up your database, you must first log out of Odoo. After you have successfully logged out, click on the Manage Databases link on the login form. From this screen, you click on the Backup link in the top-left corner of the Database Management menu:

To back up your database, select the database from the pop-up menu and enter the master password for the Odoo installation (by default, the master password will be admin). Next, click on the Backup button.

After you click on the Backup button, Odoo will then save your database to your local drive. Depending on the browser you are using and its settings, the prompt you get to save your file will vary. The default filename will end with the .dump extension.

After you save your file, Odoo will download it into the directory you have specified. If this is the first time you have backed up your database, you should also take the time to verify that you can successfully restore the database. While this may seem like an unnecessary exercise, it is important to remember that a backup is only as good as your ability to successfully restore it.