You can customize the mounted config.exs to extend the pleroma config outside the ones generated off environment variables
In `./volumes/pleroma/config.exs` you can append like so:
```
# cat volumes/pleroma/config.exs
import Config
config :pleroma, :instance,
registrations_open: true,
federating: true
```
The postgres database files are located in `./volumes/pleroma-db/pgdata`. You can also insert postgres startup scripts inside `./volumes/pleroma-db/pginit`