Volumes and Persistence

Part of the Docker course

Run a database in a container, add some rows, remove the container, start it again, and the rows are gone. Not corrupted, not hidden: gone, as though you had never typed them. This catches everyone once, and the fix is not a setting you switch on. It follows from how container storage is built, and once you can picture that, the rest of this lesson is obvious.

An image is a stack of read-only layers. Each instruction in a Dockerfile adds one, and because they never change they can be shared: ten containers from the same image share one copy of those layers on disk. ...