How to change the docker image installation directory?

Question

With recent versions of Docker, you would set the value of the data-root parameter to your custom path, in /etc/docker/daemon.json (according to https://docs.docker.com/engine/reference/commandline/dockerd/#daemon-configuration-file).

With older versions, you can change Docker's storage base directory (where container and images go) using the -goption when starting the Docker daemon. (check docker --help). You can have this setting applied automatically when Docker starts by adding it to /etc/default/docker

Following advice from comments I utilize Docker systemd documentation to improve this answer. Below procedure doesn't require reboot and is much cleaner.

First create directory and file for custom configuration:

sudo mkdir -p /etc/systemd/system/docker.service.d
sudo $EDITOR /etc/systemd/system/docker.service.d/docker-storage.conf

For docker version before 17.06-ce paste:

[Service]
ExecStart=
ExecStart=/usr/bin/docker daemon -H fd:// --graph="/mnt"

For docker after 17.06-ce paste:

[Service]
ExecStart=
ExecStart=/usr/bin/dockerd -H fd:// --data-root="/mnt"

Alternative method through daemon.json

I recently tried above procedure with 17.09-ce on Fedora 25 and it seem to not work. Instead of that simple modification in /etc/docker/daemon.json do the trick:

{
    "graph": "/mnt",
    "storage-driver": "overlay"
}

Despite the method you have to reload configuration and restart Docker:

sudo systemctl daemon-reload
sudo systemctl restart docker

To confirm that Docker was reconfigured:

docker info|grep "loop file"

In recent version (17.03) different command is required:

docker info|grep "Docker Root Dir"

Output should look like this:

 Data loop file: /mnt/devicemapper/devicemapper/data
 Metadata loop file: /mnt/devicemapper/devicemapper/metadata

Or:

 Docker Root Dir: /mnt

Then you can safely remove old Docker storage:

rm -rf /var/lib/docker

For new docker versions we need to use data-root as graph is deprecated in v17.05.0: official deprecated docs

Edit /etc/docker/daemon.json (if it doesn’t exist, create it) and include:

{
  "data-root": "/new/path/to/docker-data"
}

Then restart Docker with:

sudo systemctl daemon-reload
sudo systemctl restart docker

• A more detailed step-by-step explanation (including moving data) using Docker Storage with data-root can be found in: Blog post
• In case of Windows a similar post Windows specific

Much easier way to do so:

Stop docker service

sudo systemctl stop docker

Move existing docker directory to new location

sudo mv /var/lib/docker/ /path/to/new/docker/

Create symbolic link

sudo ln -s /path/to/new/docker/ /var/lib/docker

Start docker service

sudo systemctl start docker