Modify README.rst

Modify README document to keep the same as Build Guide.

Story: 2005440
Task: 30482

Change-Id: I445d3e8dcf7c6ed3edea688a591c8534e955ca13
Signed-off-by: hutianhao <hu.tianhao@99cloud.net>

README.rst

@@ -39,7 +39,7 @@ alter the default settings. This is a sample of a ``localrc`` file:
 .. code-block:: bash
 
     # tbuilder localrc
-    MYUNAME=$USER
+    MYUNAME=<your user name>
     PROJECT=starlingx
     HOST_PREFIX=$HOME/starlingx/workspace
     HOST_MIRROR_DIR=$HOME/starlingx/mirror
@@ -88,6 +88,7 @@ required to download a group of RPMs, SRPMs, source code packages and
 so forth. These tools live inside ``centos-mirror-tools`` directory.
 
 .. code-block :: bash
+
     $ cd centos-mirror-tools
 
 All items included in this directory must be visble inside the container
@@ -104,19 +105,44 @@ folder name should be used to define the volume. The container will
 start to run and populate ``logs`` and ``output`` folders in this
 directory.
 
-Run the ``download_mirror.sh`` script
+Download packages
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+~~~~~~~~~~~~~~~~~
 
-Once inside the container, run the downloader script
+Inside the Docker container, enter the following commands to download
+the required packages to populate the CentOS mirror repository:
 
 .. code-block :: bash
 
     $ cd localdisk && bash download_mirror.sh
 
-NOTE: in case there are some downloading failures due to network
+Monitor the download of packages until it is complete. When the download
-instability or timeouts, you should download them manually, to assure
+is complete, the following message appears:
-you get all RPMs listed in "rpms\_from\_3rd\_parties.lst" and
+
-"rpms\_from\_centos\_repo.lst".
+.. code-block :: bash
+
+    totally 17 files are downloaded!
+    step #3: done successfully
+    IMPORTANT: The following 3 files are just bootstrap versions. Based on them, the workable images
+    for StarlingX could be generated by running "update-pxe-network-installer" command after "build-iso"
+        - out/stx-r1/CentOS/pike/Binary/LiveOS/squashfs.img
+        - out/stx-r1/CentOS/pike/Binary/images/pxeboot/initrd.img
+        - out/stx-r1/CentOS/pike/Binary/images/pxeboot/vmlinuz
+
+Verify packages
+~~~~~~~~~~~~~~~
+
+Verify no missing or failed packages exist:
+
+.. code-block :: bash
+
+    $ cat logs/*_missing_*.log
+    $ cat logs/*_failmove_*.log
+
+In case missing or failed packages do exist, which is usually caused by
+network instability (or timeout), you need to download the packages
+manually.
+Doing so assures you get all RPMs listed in
+*rpms_3rdparties.lst*/*rpms_centos.lst*/*rpms_centos3rdparties.lst*.
 
 Copy the files to the mirror
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~
@@ -140,22 +166,6 @@ NOTE: You do not need to do the following step if you've synced the latest codeb
 Go into the StarlingX build system (i.e. *another* container that hosts the
 cgcs build system) and perform the following steps:
 
-Debugging issues
-~~~~~~~~~~~~~~~~
-
-The ``download_mirror.sh`` script will create log files in the form of
-``centos_rpms_*.txt``. After the download is complete, it's recommended
-to check the content of these files to see if everything was downloaded
-correctly.
-
-A quick look into these files could be:
-
-.. code-block :: bash
-
-    $ cd logs
-    $ cat *_missing_*log
-    $ cat *_failmove_*log
-
 Build packages/ISO creation
 ---------------------------