Move /var/lib/docker to a new location

switch_docker_image_library_path.sh

##
#  Update - no longer works. You need to also:
#  edit: /lib/systemd/system/docker.service
#  then run: sudo systemctl daemon-reload
#  see, https://medium.com/@ibrahimgunduz34/how-to-change-docker-data-folder-configuration-33d372669056
#
#  TODO: Fix this to use sed or similar to edit /lib/systemd/system/docker.service
##

# From: https://forums.docker.com/t/how-do-i-change-the-docker-image-installation-directory/1169

DOCKER_IMAGE_PATH="/mnt/docker"
BACKUP_PATH="/mnt"

sudo echo 'DOCKER_OPTS="-dns 8.8.8.8 -dns 8.8.4.4 -g ${DOCKER_IMAGE_PATH}"' >>/etc/default/docker && \
sudo service docker stop && \
tar -zcC /var/lib docker >${BACKUP_PATH}/var_lib_docker-backup-$(date +%s).tar.gz && \
sudo mv /var/lib/docker ${DOCKER_IMAGE_PATH} && \
sudo ln -s ${DOCKER_IMAGE_PATH} /var/lib/docker && \
sudo service docker start

Looks like there is a better way using data-root in /etc/docker/daemon.json now: https://www.guguweb.com/2019/02/07/how-to-move-docker-data-directory-to-another-location-on-ubuntu/