I just upgraded the lxc-docker package from 1.4.1 to 1.7.0 and was greeted with this afterwards:

Cannot connect to the Docker daemon. Is ‘docker -d’ running on this host?
Rebooting did not help. Trying to run docker manually I find out why:

$ sudo /usr/bin/docker -d
FATA[0000] Error starting daemon: error initializing graphdriver: “/var/lib/docker” contains other graphdrivers: devicemapper; Please cleanup or explicitly choose storage driver (-s )
Added the line as suggested by @renoirb to /etc/default/docker and issued a sudo service docker restart and all was fine.

DOCKER_OPTS=”-s aufs”
Not sure exactly why it was necessary but happy nonetheless.

https://meta.discourse.org/t/ubuntu-updates-intefere-with-docker-and-aufs/25039/15