Update English document

doc/getstarted/build_and_install/docker_install_en.rst

@@ -16,70 +16,66 @@ Developers can work on PaddlePaddle using Docker.  This allows
 developers to work on different platforms -- Linux, Mac OS X, and
 Windows -- in a consistent way.
 
-The general development workflow with Docker and CMake is as follows:
-
-1. Get the source code of Paddle:
+1. Build the Development Environment as a Docker Image
 
    .. code-block:: bash
 
-      git clone https://github.com/PaddlePaddle/Paddle.git
+   git clone --recursive https://github.com/PaddlePaddle/Paddle
+   cd Paddle
+   docker build -t paddle:dev -f paddle/scripts/docker/Dockerfile .
 
 
-2. Build a development Docker image :code:`paddle:dev` from the source
-   code.  This image contains all the development tools and
-   dependencies of PaddlePaddle.
+   Note that by default :code:`docker build` wouldn't import source
+   tree into the image and build it.  If we want to do that, we need
+   to set a build arg:
 
    .. code-block:: bash
 
-      cd paddle
-      docker build -t paddle:dev -f paddle/scripts/docker/Dockerfile .
-
-   Sometimes docker build might suffer from a slow network connection to the official Ubuntu apt-source servers. In such case, we can specify an apt-source mirror server that is geologically nearer to us. In the following example, we specified an apt-source server that responds fast in China.You can specify the UBUNTU MIRROR with :code:`--build-arg UBUNTU_MIRROR` like the example below.
+   docker build -t paddle:dev -f paddle/scripts/docker/Dockerfile --build-arg BUILD_AND_INSTALL=ON .
 
-   .. code-block:: bash
-
-      docker build \
-       --build-arg UBUNTU_MIRROR="http://mirrors.163.com" \
-       -t paddle:dev \
-       -f paddle/scripts/docker/Dockerfile .
 
+1. Run the Development Environment
 
-3. Run the image as a container and mounting local source code
-   directory into the container.  This allows us to change the code on
-   the host and build it within the container.
+   Once we got the image :code:`paddle:dev`, we can use it to develop
+   Paddle by mounting the local source code tree into a container that
+   runs the image:
 
    .. code-block:: bash
+   docker run -d -p 2202:22 -v $PWD:/paddle paddle:dev
+
+   This runs a container of the development environment Docker image
+   with the local source tree mounted to :code:`/paddle` of the
+   container.
 
-      docker run       \
-       -d              \
-       --name paddle   \
-       -p 2022:22      \
-       -v $PWD:/paddle \
-       paddle:dev
+   Note that the default entry-point of :code:`paddle:dev` is
+   :code:`sshd`, and above :code:`docker run` commands actually starts
+   an SSHD server listening on port 2202.  This allows us to log into
+   this container with:
 
-   where :code:`-d` makes the container running in background,
-   :code:`--name paddle` allows us to run a nginx container to serve
-   documents in this container, :code:`-p 2022:22` allows us to SSH
-   into this container, :code:`-v $PWD:/paddle` shares the source code
-   on the host with the container.
+   .. code-block:: bash
+   ssh root@localhost -p 2202
 
-4. SSH into the container:
+   Usually, I run above commands on my Mac.  I can also run them on a
+   GPU server :code:`xxx.yyy.zzz.www` and ssh from my Mac to it:
 
    .. code-block:: bash
+   my-mac$ ssh root@xxx.yyy.zzz.www -p 2202
 
-      ssh root@localhost -p 2022
+1. Build and Install Using the Development Environment
 
-5. We can edit the source code in the container or on this host.  Then
-   we can build using cmake
+   Once I am in the container, I can use
+   :code:`paddle/scripts/docker/build.sh` to build, install, and test
+   Paddle:
 
    .. code-block:: bash
+   /paddle/paddle/scripts/docker/build.sh
+
+   This builds everything about Paddle in :code:`/paddle/build`.  And
+   we can run unit tests there:
 
-      cd /paddle # where paddle source code has been mounted into the container
-      mkdir -p build
-      cd build
-      cmake -DWITH_TESTING=ON ..
-      make -j `nproc`
-      CTEST_OUTPUT_ON_FAILURE=1 ctest
+   .. code-block:: bash
+   cd /paddle/build
+   ctest
 
 
 CPU-only and GPU Images