docker postgres with initial data is not persisted over commits

Question

I created a rails app in a docker environment and it links to a postgres instance. I edited the postgres container to add initial data (by running rake db:setup from the rai

Answer 1

For keeping permanent data such as databases, you should define these data volumes as external, therefore it will not be removed or created automatically every time you run docker-compose up or down commands, or redeploy your stack to the swarm.

...
volumes:
  db-data:
    external: true
...

then you should create this volume:

docker volume create db-data

and use it as data volume for your databse:

...
db:
  image: postgres:latest
  volumes:
    - db-data:/var/lib/postgresql/data
  ports:
    - 5432:5432
...

In production, there are many factors to consider when using docker for keeping permanent data safely, specially in swarm mode, or in kubernetes cluster.