docs:cdiwadkar16-patch-4 - added best practices and explicit clarifications

Added best practices for firewall and data protections.
Added explicit hostnames (fqdn) in cluster set up examples for clarity.

docs-en/10-cluster/01-deploy.md

@@ -6,29 +6,35 @@ title: Deployment
 
 ### Step 1
 
-The FQDN of all hosts needs to be setup properly, all the FQDNs need to be configured in the /etc/hosts of each host. It must be confirmed that each FQDN can be accessed (by ping, for example) from any other hosts.
+The FQDN of all hosts must be setup properly. For e.g. FQDNs may have to be configured in the /etc/hosts file on each host. You must confirm that each FQDN can be accessed from any other host. For e.g. you can do this by using the `ping` command. 
 
-On each host the command `hostname -f` can be executed to get the hostname. `ping` command can be executed on each host to check whether any other host is accessible from it. If any host is not accessible, the network configuration, like /etc/hosts or DNS configuration, need to be checked and revised to make any two hosts accessible to each other.
+To get the hostname on any host, the command `hostname -f` can be executed. `ping <FQDN>` command can be executed on each host to check whether any other host is accessible from it. If any host is not accessible, the network configuration, like /etc/hosts or DNS configuration, needs to be checked and revised, to make any two hosts accessible to each other.
 
 :::note
 
 - The host where the client program runs also needs to be configured properly for FQDN, to make sure all hosts for client or server can be accessed from any other. In other words, the hosts where the client is running are also considered as a part of the cluster.
 
-- It's suggested to disable the firewall for all hosts in the cluster. At least TCP/UDP for port 6030~6042 need to be open if a firewall is enabled.
+- Please ensure that your firewall rules do not block TCP/UDP on ports 6030-6042 on all hosts in the cluster.
 
 :::
 
 ### Step 2
 
-If any previous version of TDengine has been installed and configured on any host, the installation needs to be removed and the data needs to be cleaned up. For details about uninstalling please refer to [Install and Uninstall](/operation/pkg-install). To clean up the data, please use `rm -rf /var/lib/taos/\*` assuming the `dataDir` is configured as `/var/lib/taos`.
+If any previous version of TDengine has been installed and configured on any host, the installation needs to be removed and the data needs to be cleaned up. For details about uninstalling please refer to [Install and Uninstall](/operation/pkg-install). To clean up the data, please use `rm -rf /var/lib/taos/\*` assuming the `dataDir` is configured as `/var/lib/taos`. 
+
+:::note
+
+As a best practice, before cleaning up any data files or directories, please ensure that your data has been backed up correctly, if required by your data integrity, backup, security, or other standard operating protocols (SOP).
+
+:::
 
 ### Step 3
 
-Now it's time to install TDengine on all hosts without starting `taosd`, the versions on all hosts should be same. If it's prompted to input the existing TDengine cluster, simply press carriage return to ignore it. `install.sh -e no` can also be used to disable this prompt. For details please refer to [Install and Uninstall](/operation/pkg-install).
+Now it's time to install TDengine on all hosts but without starting `taosd`. Note that the versions on all hosts should be same. If you are prompted to input the existing TDengine cluster, simply press carriage return to ignore the prompt. `install.sh -e no` can also be used to disable this prompt. For details please refer to [Install and Uninstall](/operation/pkg-install).
 
 ### Step 4
 
-Now each physical node (referred to as `dnode` hereinafter, it's abbreviation for "data node") of TDengine needs to be configured properly. Please note that one dnode doesn't stand for one host, multiple TDengine nodes can be started on single host as long as they are configured properly without conflicting. More specifically each instance of the configuration file `taos.cfg` stands for a dnode. Assuming the first dnode of TDengine cluster is "h1.taosdata.com:6030", its `taos.cfg` is configured as following.
+Now each physical node (referred to, hereinafter, as `dnode` which is an abbreviation for "data node") of TDengine needs to be configured properly. Please note that one dnode doesn't stand for one host. Multiple TDengine dnodes can be started on a single host as long as they are configured properly without conflicting. More specifically each instance of the configuration file `taos.cfg` stands for a dnode. Assuming the first dnode of TDengine cluster is "h1.taosdata.com:6030", its `taos.cfg` is configured as following.
 
 ```c
 // firstEp is the end point to connect to when any dnode starts
@@ -67,9 +73,11 @@ Prior to version 2.0.19.0, besides the above parameters, `locale` and `charset`
 
 ## Start Cluster
 
+In the following example we assume that first dnode has FQDN h1.taosdata.com and the second dnode has FQDN h2.taosdata.com.
+
 ### Start The First DNODE
 
-The first dnode can be started following the instructions in [Get Started](/get-started/), for example h1.taosdata.com. Then TDengine CLI `taos` can be launched to execute command `show dnodes`, the output is as following for example:
+The first dnode can be started following the instructions in [Get Started](/get-started/). Then TDengine CLI `taos` can be launched to execute command `show dnodes`, the output is as following for example:
 
 ```
 Welcome to the TDengine shell from Linux, Client Version:2.0.0.0
@@ -80,27 +88,41 @@ Copyright (c) 2017 by TAOS Data, Inc. All rights reserved.
 taos> show dnodes;
  id |       end_point    | vnodes | cores | status | role |      create_time        |
 =====================================================================================
-  1 |  h1.taos.com:6030  |      0 |     2 |  ready |  any | 2020-07-31 03:49:29.202 |
+  1 |  h1.taosdata.com:6030  |      0 |     2 |  ready |  any | 2020-07-31 03:49:29.202 |
 Query OK, 1 row(s) in set (0.006385s)
 
 taos>
 ```
 
-From the above output, it is shown that the end point of the started dnode is "h1.taos.com:6030", which is the `firstEp` of the cluster.
+From the above output, it is shown that the end point of the started dnode is "h1.taosdata.com:6030", which is the `firstEp` of the cluster.
 
 ### Start Other DNODEs
 
 There are a few steps necessary to add other dnodes in the cluster.
 
-First, start `taosd` as instructed in [Get Started](/get-started/), assuming it's for the second dnode. Before starting `taosd`, please making sure the configuration is correct, especially `firstEp`, `FQDN` and `serverPort`, `firstEp` must be same as the dnode shown in the section "Start First DNODE", i.e. "h1.taosdata.com" in this example.
+Let's assume we are starting the second dnode with FQDN, h2.taosdata.com. First we make sure the configuration is correct.
+
+```c
+// firstEp is the end point to connect to when any dnode starts
+firstEp               h1.taosdata.com:6030
+
+// must be configured to the FQDN of the host where the dnode is launched
+fqdn                  h2.taosdata.com
+
+// the port used by the dnode, default is 6030
+serverPort            6030
+
+```
+
+Second, we can start `taosd` as instructed in [Get Started](/get-started/).
 
-Then, on the first dnode, use TDengine CLI `taos` to execute below command to add the end point of the dnode in the cluster. In the command "fqdn:port" should be quoted using double quotes.
+Then, on the first dnode i.e. h1.taosdata.com in our example, use TDengine CLI `taos` to execute the following command to add the end point of the dnode in the cluster. In the command "fqdn:port" should be quoted using double quotes.
 
 ```sql
 CREATE DNODE "h2.taos.com:6030";
 ```
 
-Then on the first dnode, execute `show dnodes` in `taos` to show whether the second dnode has been added in the cluster successfully or not.
+Then on the first dnode h1.taosdata.com, execute `show dnodes` in `taos` to show whether the second dnode has been added in the cluster successfully or not.
 
 ```sql
 SHOW DNODES;