FATA[0000] Cannot connect to the Docker daemon. Is 'docker -d' running on this host? 

# vim /etc/default/docker 

DOCKER_OPTS="-H unix:///var/run/docker.sock -H 0.0.0.0:5555" 

# service docker restart 

syx@syx-VB:~$ docker version 
Client version: 1.6.2 
Client API version: 1.18 
Go version (client): go1.3.3 
Git commit (client): 7c8fca2 
OS/Arch (client): linux/amd64 
Server version: 1.6.2 
Server API version: 1.18 
Go version (server): go1.3.3 
Git commit (server): 7c8fca2 
OS/Arch (server): linux/amd64 

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

root@syx-VB:~# apt-get install -y libdevmapper-dev 

root@syx-VB:~# service docker restart  
root@syx-VB:~# docker version  
root@syx-VB:~# docker version 
Client version: 1.7.0-dev 
Client API version: 1.19 
Go version (client): go1.4.2 
Git commit (client): 9234460 
OS/Arch (client): linux/amd64 
FATA[0000] Get http:///var/run/docker.sock/v1.19/version: read unix /var/run/docker.sock: connection reset by peer. Are you trying to connect to a TLS-enabled daemon without TLS? 

root@syx-VB:~# docker -d 
INFO[0000] Listening for HTTP on unix (/var/run/docker.sock) 
FATA[0000] Error starting daemon: error initializing graphdriver: "/var/lib/docker" contains other graphdrivers: devicemapper; Please cleanup or explicitly choose storage driver (-s <DRIVER>) 

root@syx-VB:/var/lib/docker# ls 
aufs containers devicemapper graph init linkgraph.db repositories-aufs repositories-devicemapper tmp trust volumes 

root@syx-VB:/var/lib/docker# rm -r devicemapper/ 

root@syx-VB:/var/lib/docker# docker version 
Client version: 1.7.0-dev 
Client API version: 1.19 
Go version (client): go1.4.2 
Git commit (client): 9234460 
OS/Arch (client): linux/amd64 
FATA[0000] Cannot connect to the Docker daemon. Is 'docker -d' running on this host? 

root@syx-VB:/var/lib/docker# service docker restart 
root@syx-VB:/var/lib/docker# docker version