Why is the backup or copy of the graphRoot directory utilized by podman or Docker much larger than anticipated?

Solution Verified - Updated -

Issue

  • When using Red Hat Enterprise Linux or Red Hat OpenShift, and utilizing a container solution such as podman, docker, or cri-o that is using the overlayfs driver to store container images and container data, when attempting to copy everything from the graphRoot directory (by default located at /var/lib/containers/storage for podman and cri-o) the backup size is much larger than the tools within podman or docker report the combined size of container images and container data.
  • Why when I perform copies of this graphRoot directory is data duplicated, or much larger than the size reported by the tools that are using this directory?

Environment

  • Red Hat Enterprise Linux 7
  • Red Hat Enterprise Linux 8
  • Red Hat OpenShift 3
  • Red Hat OpenShift 4
  • Podman, Docker, or CRI-O using the overlay graph driver for storage

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