Update: Now that we have named volumes, you generally don’t want to use data containers at all.
Use the same image for the data container – in this case the Postgres image. You don’t leave data containers running, so it won’t consume resources.
Using the same image is important for several reasons:
- It will take up less space as you already have the image cached.
- The image gets a chance to seed the volume with data e.g. default files.
- The permissions and owner will be correct.
For more information see Data Only Container Madness.