How to persist data in a dockerized postgres database using volumes

Question

My docker compose file has three containers, web, nginx, and postgres. Postgres looks like this:

postgres:   container_name: postgres   restart: always   image: postgres:latest   volumes:     - ./database:/var/lib/postgresql   ports:     - 5432:5432 

My goal is to mount a volume which corresponds to a local folder called ./database inside the postgres container as /var/lib/postgres. When I start these containers and insert data into postgres, I verify that /var/lib/postgres/data/base/ is full of the data I'm adding (in the postgres container), but in my local system, ./database only gets a data folder in it, i.e. ./database/data is created, but it's empty. Why?

Notes:

• This suggests my above file should work.
• This person is using docker services which is interesting

UPDATE 1

Per Nick's suggestion, I did a docker inspect and found:

    "Mounts": [         {             "Source": "/Users/alex/Documents/MyApp/database",             "Destination": "/var/lib/postgresql",             "Mode": "rw",             "RW": true,             "Propagation": "rprivate"         },         {             "Name": "e5bf22471215db058127109053e72e0a423d97b05a2afb4824b411322efd2c35",             "Source": "/var/lib/docker/volumes/e5bf22471215db058127109053e72e0a423d97b05a2afb4824b411322efd2c35/_data",             "Destination": "/var/lib/postgresql/data",             "Driver": "local",             "Mode": "",             "RW": true,             "Propagation": ""         }     ], 

Which makes it seem like the data is being stolen by another volume I didn't code myself. Not sure why that is. Is the postgres image creating that volume for me? If so, is there some way to use that volume instead of the volume I'm mounting when I restart? Otherwise, is there a good way of disabling that other volume and using my own, ./database?

UPDATE 2

I found the solution, thanks to Nick! (and another friend) Answer below.

Answer 1

Strangely enough, the solution ended up being to change

volumes:   - ./postgres-data:/var/lib/postgresql 

to

volumes:   - ./postgres-data:/var/lib/postgresql/data 

Answer 2

You can create a common volume for all Postgres data

 docker volume create pgdata 

or you can set it to the compose file

   version: "3"    services:      db:        image: postgres        environment:          - POSTGRES_USER=postgres          - POSTGRES_PASSWORD=postgress          - POSTGRES_DB=postgres        ports:          - "5433:5432"        volumes:          - pgdata:/var/lib/postgresql/data        networks:          - suruse    volumes:       pgdata: 

It will create volume name pgdata and mount this volume to container's path.

You can inspect this volume

docker volume inspect pgdata  // output will be [     {         "Driver": "local",         "Labels": {},         "Mountpoint": "/var/lib/docker/volumes/pgdata/_data",         "Name": "pgdata",         "Options": {},         "Scope": "local"     } ]