Update DFC documentation

Change-Id: I95befc4a6b597f67672797d44561de41af9c480d
Signed-off-by: Chengkai Yan <martin.c.yan@est.tech>
Issue-ID: DCAEGEN2-876
diff --git a/docs/sections/services/dfc/installation.rst b/docs/sections/services/dfc/installation.rst
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+.. This work is licensed under a Creative Commons Attribution 4.0 International License.

+.. http://creativecommons.org/licenses/by/4.0

+

+Installation

+============

+

+An environment suitable for running docker containers is recommended.

+

+As a docker container

+---------------------

+

+**datafile** is delivered as a docker container based on openjdk:8-jre-alpine.  The

+host or VM that will run this container must have the docker application

+loaded and available to the userID that will be running the DFC container.

+

+Also required is a working DMAAP/MR and DMAAP/DR environment.  datafile

+subscribes to DMAAP/MR fileReady event as JSON messages and publishes the downloaded files to the DMAAP/DR.

+

+Installation

+^^^^^^^^^^^^

+

+The following command will download the latest datafile container from

+nexus and launch it in the container named "datafile":

+

+    ``docker run -d -p 8100:8100 -p 8433:8433  nexus3.onap.org:10001/onap/org.onap.dcaegen2.collectors.datafile``