By default Docker uses loopback mounted "devices" to store docker images and
metadata. This default storage configuration (100 GB for image storage) leads
to a rather lengthy start up phase of docker when initially launched.

When docker is enabled by default, such as in the Amazon Container Service
images for SUSE Linux Enterprise, the slow start up time of docker upon
instance creation provides a sub optimal user experience. Additionally other
services that depend on docker being operational may time out.

The script and systemd unit file in the docker-img-store-setup package address
the problem described above. The script creates a 100 GB device file that is
then formatted with btrfs. The mounted device allows docker to use the btrfs
storage driver and the start up process is very fast.

This update was imported from the SUSE:SLE-12:Update update project.