The default location for the docker data directory, when using overlay2 storage driver is /var/lib/docker. Maybe you want to move it to another location, and it’s actually pretty easy.

1. Stop the docker service:
   sudo systemctl stop docker.service
2. Copy the docker folder to the new location:
   sudo cp -rp /var/lib/docker /path/to/new/location
   The p in -rp will preserve ownership, permissions and timestamps
3. Tell the docker daemon about the new location by editing the /etc/docker/daemon.json file with the following:

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

4. Start the docker service:
sudo systemctl start docker.service

Thats it, the docker directory has been moved.

The above guide is tested on Ubuntu 20.04, but will probably be very much alike on other flavours.