Comment 13 for bug 1886152

Reviewed: https://review.opendev.org/742119
Committed: https://git.openstack.org/cgit/starlingx/ansible-playbooks/commit/?id=8345f30dfae16f71bb798a4d5c8c7b17400bd757
Submitter: Zuul
Branch: master

commit 8345f30dfae16f71bb798a4d5c8c7b17400bd757
Author: Dan Voiculeasa <email address hidden>
Date: Thu Jul 16 17:31:31 2020 +0300

    B&R: Backup user images from local registry.

    The procedure is optional and is activated by setting
    backup_user_local_registry=true for the backup playbook.

    An user image is one that is not a platform or an app image.
    Information about platform images is kept in the playbooks.
    Information about apps images is retrieved through sysinv-utils.
    In fact apps images are filtered out in sysinv-utils by passing
    `--no-apps` arg.

    Save user images to local filesystem using docker pull.
    Check if there is enough disk space for the archive to be saved.
    Export to a tar archive using docker save.

    For remote play the copy of user images generated archive is not
    implemented yet.

    Partial-Bug: 1886152
    Depends-On: Ic3f7a82171dccaa15a76b2578135163dc78201f3
    Depends-On: I0852702be7d47cd5173a7815f33812e75332c63a
    Change-Id: I4644784ea4164134f163d218e69dc4ceb148985a
    Signed-off-by: Dan Voiculeasa <email address hidden>