Docker 1.9.0 がでましたね。
http://www.publickey1.jp/blog/15/docker_19docker_swarm.html

さっそく入れてみましたが
公式サイトのドキュメント通りだとうまくいかなかったのでメモを残しておきます


■kernel update

root@ubuntu:~# uname -a
Linux ubuntu 3.19.0-15-generic #15-Ubuntu SMP Thu Apr 16 23:32:37 UTC 2015 x86_64 x86_64 x86_64 GNU/Linux

root@ubuntu:~# apt-get update && apt-get upgrade -y 
root@ubuntu:~# apt-get dist-upgrade -y

root@ubuntu:~# reboot now
root@ubuntu:~# uname -r
3.19.0-32-generic


■Docker install

sudo apt-key adv --keyserver hkp://pgp.mit.edu:80 --recv-keys 58118E89F3A912897C070ADBF76221572C52609D

vi /etc/apt/sources.list.d/docker.list 

# Ubuntu Precise
deb https://apt.dockerproject.org/repo ubuntu-precise main
# Ubuntu Trusty
deb https://apt.dockerproject.org/repo ubuntu-trusty main
# Ubuntu Vivid
deb https://apt.dockerproject.org/repo ubuntu-vivid main
# Ubuntu Wily
deb https://apt.dockerproject.org/repo ubuntu-wily main

--------------


apt-get purge lxc-docker*
apt-get install apt-transport-https
apt-get update

sudo sed -i '/wily/d' /etc/apt/sources.list.d/docker.list
sudo sed -i '/trusty/d' /etc/apt/sources.list.d/docker.list
sudo sed -i '/precise/d' /etc/apt/sources.list.d/docker.list
sudo apt-get update
sudo apt-get install docker-engine



root@ubuntu:~# docker info
Containers: 0
Images: 0
Server Version: 1.9.0
Storage Driver: devicemapper
 Pool Name: docker-252:0-136125-pool
 Pool Blocksize: 65.54 kB
 Base Device Size: 107.4 GB
 Backing Filesystem: extfs
 Data file: /dev/loop0
 Metadata file: /dev/loop1
 Data Space Used: 1.821 GB
 Data Space Total: 107.4 GB
 Data Space Available: 20.78 GB
 Metadata Space Used: 1.479 MB
 Metadata Space Total: 2.147 GB
 Metadata Space Available: 2.146 GB
 Udev Sync Supported: true
 Deferred Removal Enabled: false
 Deferred Deletion Enabled: false
 Deferred Deleted Device Count: 0
 Data loop file: /var/lib/docker/devicemapper/devicemapper/data
 Metadata loop file: /var/lib/docker/devicemapper/devicemapper/metadata
 Library Version: 1.02.90 (2014-09-01)
Execution Driver: native-0.2
Logging Driver: json-file
Kernel Version: 3.19.0-32-generic
Operating System: Ubuntu 15.04
CPUs: 4
Total Memory: 9.766 GiB
Name: ubuntu
ID: 7LMS:3G5J:O3ZR:JXP4:XUDO:2XLC:P7OI:TFY5:2GYT:HAWO:6VTK:GHFD
WARNING: No swap limit support

■参考
https://docs.docker.com/engine/installation/ubuntulinux/
http://askubuntu.com/questions/686698/docker-installation-error-libdevmapper1-02-1-21-02-99