Using a docker volume with postgresql to verify it is saving on the hosts filesystem

I am trying to get docker volumes working.

I have defined a volume in my Dockerfile as follows:

version: "3"

services:
redis:
image: redis:alpine
ports:
- "6379:6379"

db:
image: postgres:9.4
#container_name: db
volumes:
- "db-data:/var/lib/postgresql/data"


volumes:
db-data:


Now my question is, when I do a docker-compose up I don't see my data persisted on my local laptop (or server).

I just want to test/verify that my data is saving to the host's filesystem, so if I start/stop docker when it restarts it reads from the database file on the host.

1 Answer
1

That construct saves data in a named volume; if you look under /var/lib/docker/volumes as root you should be able to see it there (though mucking around in /var/lib/docker generally isn't advisable; and I believe this is one of the things where Docker Compose will change the name to try to make it unique).

/var/lib/docker/volumes

/var/lib/docker

If you want the data to be saved in a host directory, change the volume declaration to explicitly have a relative or absolute path. You won't need the explicit volume declaration, and for this you can remove the volumes block entirely. That would leave you with a docker-compose.yml that looks like:

docker-compose.yml

version: "3"
services:
db:
image: postgres:9.4
volumes:
- "./db-data:/var/lib/postgresql/data"


docker-compose.yml

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