I'm trying to set up PostgreSQL 18 in Docker and want to store the database files on my host machine instead of within the container. This way, I could easily set up a new container using the same database. However, after configuring my Docker Compose setup, my host folder remains empty. Here's my setup:
```yaml
postgres:
image: docker.io/library/postgres:18
container_name: postgres
environment:
- POSTGRES_USER=user
- POSTGRES_PASSWORD=123456
- POSTGRES_DB=meshcentral
- PGDATA=/var/lib/postgresql/18/docker
volumes:
- ./postgres:/var/lib/postgresql
restart: unless-stopped
ports:
- "5332:5432"
networks:
- internal-database
healthcheck:
test: [ "CMD-SHELL", "pg_isready -d postgres" ]
interval: 30s
timeout: 10s
retries: 5
```
Even with and without setting PGDATA, I can still see the database files when I attach to the container, but they don't seem to be reflected on the host. Am I misunderstanding the way volumes work?
2 Answers
It sounds like you're not quite mapping the volume correctly. Double-check the path on the right side of your volume mapping. With PostgreSQL 18, you should map it to `/var/lib/postgresql/18/docker` since it's the new structure they introduced. Also, make sure your user has the right permissions for that host folder — it might be a permissions issue that’s causing the files not to show up on your host.
Just to add, it's important to ensure your Docker daemon is configured correctly, especially if you're using a VM or Docker Desktop. Sometimes using a relative path like `./postgres` can lead to unexpected results, and you might want to inspect the container with `docker inspect` to see where exactly it's mapping to on your host.
That’s a good point! I think something like `./postgres` could point to an unexpected location, especially in a VM setup. I'll definitely check my path mappings.