A crucial aspect to Docker is the concept of the copy-on-write layered filesystems. There is a significant amount of documentation on this upstream:

Docker Engine Storage docs

docker-storage-setup is a script to configure the devicemapper or overlayfs backends, part of the Project Atomic suite of container projects. It is run via a systemd service docker-storage-setup.service before the Docker daemon, ensuring storage is provisioned according to configuration in /etc/sysconfig/docker-storage-setup.

You should typically set the contents of that file during system bootstrap, e.g. in a cloud-init bootcmd: hook, or via kickstart %post.

Also, in a cloud (OpenStack/AWS/etc.) scenario with the devicemapper backend, docker-storage-setup can also expand the root volume group to fill the space allocated for the root disk if GROWPART=true is set.

For more information on configuration, see man docker-storage-setup.