How to backup EteSync data when using Postgres?

[King-of-penguins]

Hello.
I'm using EteBase docker-container with Postgres, just like in your example.
I found an instruction of how to backup EteSync data without using a container.
Only I did not understand how best to backup EteSync data when using Postgres container?
As I understand I should backup secret.txt file. I can copy this file to my host machine by command: docker cp <name-of-my-etebase-app-container>:/data/secret.txt ~/
And as I understand I should make dump of Postgres to backup data with my calendars, tasks and contacts and copy this dump to my host machine. But I don't know how to do this.
Could you give me an example on how to do this?
Am I going to use a good backup method? Maybe there is an easier and more convenient method?

[King-of-penguins]

I have switched to the use of Etebase with SQLite database.
Here my docker-compose.yml file. Perhaps will be useful for someone.

version: '3'

volumes:
  etebase_static:

services:
  etebase:
    image: victorrds/etebase:latest
    container_name: "etebase-app"
    volumes:
      - /path/to/EteBase/storage/:/data:rw
      - etebase_static:${STATIC_PATH}:rw
    environment:
      SERVER: asgi
      SUPER_USER: ${ADMIN_USER}
      SUPER_PASS: ${ADMIN_PASS}
      DB_ENGINE: sqlite
      DATABASE_NAME: /data/etesync-sqlite-db.sqlite3
    restart: always

  nginx:
    image: nginx:stable-alpine
    container_name: "etebase-nginx"
    volumes:
      - etebase_static:${STATIC_PATH}:ro
      - ./nginx/default-ssl.conf:/etc/nginx/conf.d/default.conf
      - ./nginx/certs:/certs:ro
    ports:
      - "443:443"
    depends_on:
      - etebase
    restart: always