DBMS backup inside Docker, how to organize it correctly?

Question

Database administration

Let's say I have a web application that uses a DBMS that lives inside a Docker container. Well, something is written there, something is read.
Transferring database files to the host system does not seem to be a very beautiful solution. Docker is advertised as a containerization solution, where the application, along with the entire environment, is packaged in a container that is isolated from the host system, and which can be transferred from one server to another with one command. In addition, I want to deal with a "black box" that you can connect to via TCP, and I don't want to figure out what particular DBMS is running inside, much less how it organizes data storage.
If you don't move the files to the host system, then all the data will live in the read-write layer of the container, if I understand correctly. In this case, it is not clear how to backup them? Do container commits regularly? It seems that the number of layers in AUFS is limited (and a bunch of meaningless tags will not look very nice). It turns out that it is necessary to pack some other scripts inside the container that will backup the database?