Docker镜像类似于操作系统镜像，是启动Docker容器的基础。
Docker采用传统的client-server架构模式。
Docker通过cgroups实现资源限制
Docker通过namespace实现资源隔离
Docker在官网定义是：Accelerate how you build, share, and run applications. Docker helps developers build, share, run, and verify applications anywhere — without tedious environment configuration or management.
