docker.io (20.10.2-0ubuntu2) hirsute; urgency=medium

  As of version 20.10.2-0ubuntu2, upgrading the docker.io package will fail if
  any containers are still using AUFS. It will be necessary to take some
  measures to move existing containers away from aufs and delete the directory
  /var/lib/docker/aufs before upgrading can succeed. See the previous NEWS
  entry for instructions on moving away from AUFS.

  Note: Option 3 from the previous NEWS entry is no longer going to be a valid
        option moving forward. Users will have to either migrate their
        containers to a supported storage driver or maintain their own kernel
        builds with AUFS support.

 -- William 'jawn-smith' Wilson <william.wilson@canonical.com>  Wed, 24 Feb 2021 16:06:03 -0600

docker.io (1.8.3~ds1-3) unstable; urgency=medium

  As of src:linux 4.0+ (specifically, >= 3.18-1~exp1), AUFS support is no longer
  included in official Debian-compiled kernels.  What this means to Docker users
  is that if your existing images are stored within the "AUFS" graph driver that
  once you update your kernel, your images (and containers) will become
  inaccessible (due to the kernel not having the necessary aufs modules to mount
  them).  To recover from this, there are a couple options (detailed below).

  1. Use the included nuke script to blow away your existing "/var/lib/docker"
     contents and start fresh with Linux 4.0+:

       service docker stop
       /usr/share/docker.io/contrib/nuke-graph-directory.sh /var/lib/docker
       service docker start

  2. Use "docker save" (see "docker help save" for usage) before booting 4.0+ to
     preserve your images on-disk as tar files, then follow the nuke step from
     the previous option followed by using "docker load" to re-load your images.

  3. Update to src:linux >= 4.1.1-1~exp1 ("aufs: Apply patches to enable
     building aufs out-of-tree"), and then compile the aufs modules out-of-tree
     (a package for doing this module compilation automatically doesn't yet
     exist at the time of this writing, but might in the future).

 -- Tianon Gravi <tianon@debian.org>  Tue, 01 Dec 2015 01:02:44 -0800
