更新Docker版本

# add the new gpg key
$ apt-key adv --keyserver hkp://p80.pool.sks-keyservers.net:80 --recv-keys 58118E89F3A912897C070ADBF76221572C52609D

# edit your /etc/apt/sources.list.d/docker.list
$ vim /etc/apt/sources.list.d/docker.list

# remove the contents and replace with the following depending on your os and version:

# Ubuntu Trusty 
deb https://apt.dockerproject.org/repo ubuntu-trusty main

$ apt-get update

# remove the old
$ apt-get purge lxc-docker*

# install the new
$ apt-get install docker-engine