data lost while restarting postgres with docker

Question

I was running a postgres instance with following docker-compose.yml-

postgres:
  restart: always
  image: postgres:latest
  volumes:
    - /data:/var/lib/postgresql
  ports:
    - "5432:5432"
  environment:
    - POSTGRES_USER=admin
    - POSTGRES_PASSWORD=123456
    - POSTGRES_DB=mydb
    - PGDATA=/var/lib/postgresql/data

I had added some tables with few rows. I made a small change in the file, adding container_name: postgres, and restarted with docker-compose up -d

and now when i login to the database, I don't see any tables/data.

psql -h ###### -p 5432 -d mydb -U admin --password

The data directory is added as volumes and is intact.

Is it something to do with initializing postgres?

UPDATE 2016/10/02

Please note that /data is an external hard drive mounted on host docker-machine.

UPDATE 2016/10/02

Also I noticed that when I change the rename the location of docker-compose.yml (from /home/ubuntu/dev/docker-storage/docker-compose.yml to /home/ubuntu/dev/storage/docker-compose.yml), and do a docker-compose up -d, I get an error saying

ERROR: for postgres  Conflict. The name "/postgres" is already in use by container 6de8378a8156ec368748194f8912836a7b5e3212fbb69627093d0f6114b82f0d. 
You have to remove (or rename) that container to be able to reuse that name.

Is that where problem is coming from? I might have removed the original container.

UPDATE 2016/10/06

This seems to be working now. For some weird reason, I had to mount both /var/lib/postgresql and /var/lib/postgresql/data

postgres:
    restart: always
    image: postgres:latest
    container_name: postgres
    volumes:
      - /data/postgresql:/var/lib/postgresql
      - /data/postgresql/data:/var/lib/postgresql/data
    ports:
      - "5432:5432"
    environment:
      - POSTGRES_USER=admin
      - POSTGRES_PASSWORD=123456
      - POSTGRES_DB=mydb

Answer 1

What you did is a hack! The official way to do it, is to have a environment variable named PGDATA, same as the container volume path

here you go:

postgres:
    restart: always
    image: postgres:latest
    container_name: postgres
    volumes:
      - ${PATH_TO_STORAGE}:/var/lib/postgresql/data/:rw <--- check this out
    ports:
      - "5432:5432"
    environment:
      POSTGRES_USER: ${POSTGRES_USER}
      POSTGRES_PASSWORD: ${POSTGRES_PASSWORD}
      PGDATA: /var/lib/postgresql/data/ <--- Check this out

Hope this helps :)