Comment 5 for bug 1939106

I hit similar problem (my distro is ubuntu 18.04), and I followed this guide to switch my storage driver from aufs to overlay2: https://docs.docker.com/storage/storagedriver/overlayfs-driver/ , then the upgrade worked.

Migrating docker images from one storage driver to another is a really painful process: you have to save your images as tar files, switch the storage driver, then load them back one after another. An upgrade requiring so much manual intervention like this should never happen in an LTS release.