change docker directory to another partition

docker_mv_dir.sh

turns out you don't need the bind mount. This works with current docker by just modifying the -g option in /etc/docker/defaults DOCKER_OPTS. I had previously tried this and maybe like you failed to get it to work, and looked to linking and bind mounting.

Tried on AWS EC2 VM on a Ubuntu 14.04 server, with a second block storage volume.

First prepare your new block storage, this will house the moved docker folder
First format and mount the new block storage device
mkfs.ext4 /dev/sdx
Mount it 
create a mount point
mkdir /mnt/diskX
mount the file or do equivalent mount in /etc/fstab
mount /dev/sdx1 /mnt/diskX
create a new folder to house docker
mkdir /mnt/diskX/docker
chmod 700 /mnt/diskX/docker

Setup the move
stop containers and docker daemon
docker ps -q | xargs docker kill
service docker stop
#if it exists
cd /var/lib/docker/devicemapper/mnt
umount ./*
move /var/lib/docker to the new mounted storage device 
mv didn't work with sudo, must be ROOT user! e.g. sudo bash first
root@foo# mv /var/lib/docker /mnt/diskX/docker
set the flag in /etc/default/docker to
e.g. DOCKER_OPTS="--dns 8.8.8.8 --dns 8.8.4.4 -g /mnt/diskX/dock