Storage for Docker Containers

This was written using Alpine 3.18 and Docker 23.0.6. All the snippets below were correct at the time of writing ;-).

Where?

Where is the filesystem present in the container stored?

$ docker inspect 1097c009fe6b --format '{{.GraphDriver.Data.MergedDir }}'
/var/lib/docker/overlay2/5caf5b1ac4b7783d61cfee47c1b3b959d37459c0e6855da1a36754cdf4b207dc/merged

1097c009fe6b in the above example is the shortened hash of the running container, it may be substituted with the name of the container or the full hash. If the container is not running the UpperDir will contain the differences from the base image:

$ docker inspect e053591239bd --format '{{.GraphDriver.Data.UpperDir }}'
/var/lib/docker/overlay2/b30f69a1e579511cada4f1156d8d865dc1d69c467b17db377cc5de563f4a02d8/diff

These directories and the files within will have permissions for the container users... however those have been set-up.

Binds

If the container was started with any binding/volume arguments (-v) then dumping those might be useful also:

docker inspect e053591239bd --format '{{.HostConfig.Binds }}'