Change the "data-root" from the "docker" service, with the goal to reduce utilization on the "/var" partition.

docker-change-data-root.sh

# Motivation: As the "/var" partition (Linux Debian) could have a limited size
# and "docker" by default set volumes and images inside of "/var/lib" the partition
# could run out ouf space soon.
#
# My approach is to modify the "data-root" argument from the docker daemon, and move
# all the data into a partition with more free space ("home" in my case).

> docker version

Client:
 Version:           20.10.12
 API version:       1.41
 Go version:        go1.16.2
 Git commit:        20.10.12-0ubuntu2~20.04.1
 Built:             Wed Apr  6 02:14:38 2022
 OS/Arch:           linux/amd64
 Context:           default
 Experimental:      true

# Steps:
> sudo su

> service docker status | stop
# If the docker is still runing becaouse of the docker.socket.
> systemctl stop docker.socket

# On my case "/home/diuble-lig/docker/" is my folder destination.
> rsync -a /var/lib/docker/* /home/diuble-lig/docker/
# Wait some minutes until the folder finish the creation

> nano /lib/systemd/system/docker.service

# Add --data-root parameter
ExecStart=/usr/bin/dockerd --data-root /home/diuble-lig/docker -H fd://

> systemctl daemon-reload
> service docker restart
> service docker status

# Pull a docker hello world image or some another images, for my test case "busybox".
> docker run -it --rm busybox

# Ref: https://docs.docker.com/engine/reference/commandline/dockerd/#daemon
# Ref: https://stackoverflow.com/questions/32070113/how-do-i-change-the-default-docker-container-location