linux - Docker can't connect to docker daemon
After I update my Docker version to 0.8.0, I get an error message while entering sudo docker version:

Linux
The Post-installation steps for Linux documentation reveals the following steps:

Create the docker group.
sudo groupadd docker
Add the user to the docker group.
sudo usermod -aG docker $(whoami)
Log out and log back in to ensure docker runs with correct permissions.
Start docker.
sudo service docker start

Mac OS X
As Dayel Ostraco says is necessary to add environments variables:
docker-machine start # Start virtual machine for docker
docker-machine env  # It's helps to get environment variables
eval "$(docker-machine env default)" # Set environment variables

The docker-machine start command outputs the comments to guide the process.
