Script to completely reset docker on zfs after Ubuntu zsysd has completely fubared your docker installation

reset_docker_on_ubuntu_zfs.sh

# Ubuntu's zsysd creates snapshots within docker's zfs datasets, causing docker
# to fail to destroy them, which then completely wrecks the correspondance
# between zfs reality, docker's belief of zfs reality, and you are screwed.
# These are the commands I used to completely reset docker on zfs so it
# could be completely rebuilt.

# First things first: get rid of all the autozsys snapshots
service zsys stop
zfs list -H -o name -t snapshot | grep autozsys | xargs -n1 zfs destroy

# Try to persuade docker to remove everything it can
docker image prune -a
docker ps -a

# Remove all datasets created by docker. Do NOT run if you have other legacy zfs datasets!
service docker stop
zfs list | grep legacy | cut -d ' ' -f 1 | xargs -n1 zfs destroy -r

# Remove docker cache of zfs datasets
rm -rf /var/lib/docker/image/zfs/layerdb/sha256/*
service docker start

# You should now be able to completely rebuild your docker containers
# from scratch, and it won't error out