Starting from v1.10 docker uses content addressable IDs for the images and layers instead of using generated ones. This tool calculates SHA256 checksums for docker layer content, so that they don't need to be recalculated when the daemon starts for the first time.

The migration usually runs on daemon startup but it can be quite slow(usually 100-200MB/s) and daemon will not be able to accept requests during that time. You can run this tool instead while the old daemon is still running and skip checksum calculation on startup.

v1.10-migrator --help
Usage of v1.10-migrator:
  -g, --graph string            Docker root dir (default "/var/lib/docker")
  -s, --storage-driver string   Storage driver to migrate (default "auto")
      --storage-opt value       Set storage driver option (default [])

Supported storage drivers are aufs, overlay, btrfs, vfs and devicemapper. auto tries to automatically detect the driver from the root directory. zfs is currently not supported.

Copyright © 2016 Docker, Inc. All rights reserved, except as follows. Code is released under the Apache 2.0 license. The README.md file, and files in the "docs" folder are licensed under the Creative Commons Attribution 4.0 International License under the terms and conditions set forth in the file "LICENSE.docs". You may obtain a duplicate copy of the same license, titled CC-BY-SA-4.0, at http://creativecommons.org/licenses/by/4.0/.