How to deploy without losing database data using capistrano 3 (deploy rails)?

Question

Ruby on Rails

Good afternoon.
Tell me, how do you deploy the rails app?
I use capistrano (I have little experience with deployment), every time I deploy an application from scratch (from scratch - the database is migrated and of course the database is empty). Trying the commands that are in cap -T, using the brute-force method - the update / update commands - the result is the same, each time the database is clean.
As I understand it, you need to make a backup of the database and, or other files, and specify the path. Do I understand correctly?
I can't find in the documentation where these actions are described.
How to "correctly" configure the rails app using capitrano 3, or what to read / watch to understand this process? Tell me please.

Answer 1

https://gorails.com/deploy/ubuntu/16.04