The database connection settings is passed using DJANGO_DB_URL environment variable which conforms to django-environ standards You can find documentation here: https://django-environ.readthedocs.io/en/latest/#django-environ

Container build includes drivers for SQLite and PostgreSQL (psycopg2)

DB in docker-compose

The easiest way when running inside a container - run a stack with docker-compose which includes PostgreSQL container.
For this you specify a service named db, and link to it using connection string DJANGO_DB_URL=postgres://postgres@db:5432/postgres Mount PostgreSQL data folder to named volume or bind mount.

Using named volume

version: '3'
services:
  server:
    image: guacozy/guacozy-server
    restart: always
    depends_on:
      - db
    environment:
    - DJANGO_DB_URL=postgres://postgres@db:5432/postgres
...
  db:
    image: postgres:10.4-alpine
    restart: always
    volumes:
    - postgres-data:/var/lib/postgresql/data
...
volumes:
  postgres-data:

Using bind mount

Bind mount postgresql data to directory ./data/postgres

version: '3'
services:
  server:
    image: guacozy/guacozy-server
    restart: always
    depends_on:
      - db
    environment:
    - DJANGO_DB_URL=postgres://postgres@db:5432/postgres
...
  db:
    image: postgres:10.4-alpine
    restart: always
    volumes:
    - ./data/postgres:/var/lib/postgresql/data

Connection string examples

SQLite

SQLite file guacozydb.sqlite3 located in the same directory as guacozy_server manage.py

sqlite:///guacozydb.sqlite3

SQLite file guacozydb.sqlite3 located under /datafiles/ (note the four slashes)

sqlite:////datafiles/guacozydb.sqlite3

PostgreSQL

PostgreSQL located on server db, listening on port 5432, using user postgres , no password and database name postgres

DJANGO_DB_URL=postgres://postgres@db:5432/postgres

PostgreSQL located on server postdb.example.com, listening on port 5432, using user guacozy_app , password Passw0rd and database name guacozy_db

DJANGO_DB_URL=postgres://guacozy_app:Passw0rd@postdb.example.com:5432/guacozy_db