Stop any instance that's currently running with the Odoo source you are about to update, and then make a backup of all of the databases you care about in case something goes wrong. This is obviously something you need to do for production databases. Refer to the Managing Odoo server databases recipe of this chapter for further instructions.

Next, make a note of the current version of the source you are running. The best way to do this is by creating a lightweight tag using the following command:

$ cd ~/odoo-dev/odoo
$ git checkout 12.0
$ git tag 12.0-before-update-$(date --iso)