How to upgrade Docker on Ubuntu 14.04 ?

http://askubuntu.com/questions/472412/how-do-i-upgrade-docker
http://xmodulo.com/2014/05/manage-linux-containers-docker-ubuntu.html
http://xmodulo.com/2014/05/docker-containers-centos-fedora.html
https://fredjean.net/running-docker-under-linux-mint-16/

Suppose it is Ubuntu Trusty (14.04) release, which has 0.9.1 officially

Update to 0.11.1 release

If you want to upgrade in this release, see new launchpad https://launchpad.net/~docker-maint/+archive/testing, better use ppa installation.

sudo add-apt-repository ppa:docker-maint/testing
sudo apt-get update
sudo apt-get install docker.io

Now I get the latest one

$ docker -v
Docker version 0.11.1, build fb99f99

Be aware, with the 1.0 GA release, this method may be changed

Update to latest release(now 1.1.1)

This is the way stated to install docker for 12.04 LTS in official document and noticed inubuntuupdates.org, which looks work for 14.04 as well.

Refer the command to Getting Docker Installed on Ubuntu 12.04 LTS as well

$ wget -qO- https://get.docker.io/gpg | sudo apt-key add -
$ sudo sh -c "echo deb http://get.docker.io/ubuntu docker main > /etc/apt/sources.list.d/docker.list"
$ sudo apt-get update
$ sudo apt-get install lxc-docker

Now I get

$ docker -v
Docker version 1.1.1, build bd609d2

lxc-docker will remove old docker package, therefore please backup the configuration in advance.