pass environement variables docker
sudo docker run -d -t -i -e REDIS_NAMESPACE='staging'
-e POSTGRES_ENV_POSTGRES_PASSWORD='foo'
-e POSTGRES_ENV_POSTGRES_USER='bar'
-e POSTGRES_ENV_DB_NAME='mysite_staging'
-e POSTGRES_PORT_5432_TCP_ADDR='docker-db-1.hidden.us-east-1.rds.amazonaws.com'
-e SITE_URL='staging.mysite.com'
-p 80:80
--link redis:redis
--name container_name dockerhub_id/image_name