[Note,]由于docker的局限性，docker只能运行在64位的系统中
docker软件应用程序可以重复地运行在任何地方，因为它的容器包含了所有的环境依赖关系！
docker有三种方式运行
作为一个守护demo进程来管理你的linux主机上的LXC容器（sudo docker -d）
作为一个命令行的方式来告诉docker进程的程序接口来做什么（docker run ...）
作为一个仓库的客户端让你分享你搭建的环境(docker pull,docker commit)
built and shared in the Docker Hub Registry, a cloud-based collection of applications
Docker Engine consists of two parts: a daemon, a server process that manages all the containers, and a client, which acts as a remote control for the daemon
Docker Hub Registry, a cloud-based collection of application
can find them online at Docker Hub as well through the Docker Engine client command line
Container images can be downloaded easily using docker pull. For images in the Docker Hub Registry, the name you specify is constructed as <username>/<repository>
