Editer le fichier /etc/default/docker. Attention: le changement de répertoire efface toutes les données des images et conteneurs précedemment utilisés.
Exemple de configuration:
# Docker Upstart and SysVinit configuration file
# Customize location of Docker binary (especially for development testing).
#DOCKER="/usr/local/bin/docker"
# Use DOCKER_OPTS to modify the daemon startup options.
#DOCKER_OPTS="--dns 8.8.8.8 --dns 8.8.4.4"
DOCKER_OPTS="--storage-driver=overlay -D -g /mnt/hdd1/docker-files/"
# If you need Docker to use an HTTP proxy, it can also be specified here.
#export http_proxy="http://127.0.0.1:3128/"
# This is also a handy place to tweak where Docker's temporary files go.
export TMPDIR="/mnt/hdd1/docker-files/temp-files/"