Add etcd configuration steps for RHEL and CentOS

Closes-Bug: #1740233

Change-Id: I59de4a7bf009a866c978512c6466803ba850f9c1
Signed-off-by: blkart <blkart.org@gmail.com>

doc/install-guide/source/environment-etcd-rdo.rst

@@ -0,0 +1,51 @@
+Etcd for RHEL and CentOS
+~~~~~~~~~~~~~~~~~~~~~~~~
+
+OpenStack services may use Etcd, a distributed reliable key-value store
+for distributed key locking, storing configuration, keeping track of service
+live-ness and other scenarios.
+
+Install and configure components
+--------------------------------
+
+#. Install the package:
+
+   .. code-block:: console
+
+      # yum install etcd
+
+   .. end
+
+2. Edit the ``/etc/etcd/etcd.conf`` file and set the ``ETCD_INITIAL_CLUSTER``,
+   ``ETCD_INITIAL_ADVERTISE_PEER_URLS``, ``ETCD_ADVERTISE_CLIENT_URLS``,
+   ``ETCD_LISTEN_CLIENT_URLS`` to the management IP address of the controller
+   node to enable access by other nodes via the management network:
+
+   .. code-block:: ini
+
+      #[Member]
+      ETCD_DATA_DIR="/var/lib/etcd/default.etcd"
+      ETCD_LISTEN_PEER_URLS="http://10.0.0.11:2380"
+      ETCD_LISTEN_CLIENT_URLS="http://10.0.0.11:2379"
+      ETCD_NAME="controller"
+      #[Clustering]
+      ETCD_INITIAL_ADVERTISE_PEER_URLS="http://10.0.0.11:2380"
+      ETCD_ADVERTISE_CLIENT_URLS="http://10.0.0.11:2379"
+      ETCD_INITIAL_CLUSTER="controller=http://10.0.0.11:2380"
+      ETCD_INITIAL_CLUSTER_TOKEN="etcd-cluster-01"
+      ETCD_INITIAL_CLUSTER_STATE="new"
+
+   .. end
+
+
+Finalize installation
+---------------------
+
+#. Enable and start the etcd service:
+
+   .. code-block:: console
+
+      # systemctl enable etcd
+      # systemctl start etcd
+
+   .. end