Docs: Fix Starting Container Instructions for RocksDB Iroha (#1600)

Signed-off-by: Sara <lira.lemur@gmail.com>

Author: LiraLemur

docs/source/getting_started/index.rst

@@ -30,7 +30,10 @@ Starting Iroha Node
 
 Creating a Docker Network
 ^^^^^^^^^^^^^^^^^^^^^^^^^
-To operate, Iroha requires a ``PostgreSQL`` database.
+To operate, Iroha requires a ``PostgreSQL`` database or ``RocksDB``.
+If you prefer ``PostgreSQL``, you will need a container running it alongside Iroha.
+
+
 Let's start with creating a Docker network, so containers for Postgres and
 Iroha can run on the same virtual network and successfully communicate.
 In this guide we will call it ``iroha-network``, but you can use any name.
@@ -43,6 +46,8 @@ In your terminal write following command:
 Starting PostgreSQL Container
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
+.. note:: You do not need to start this container if your plan is to use Iroha with RocksDB and not PostgreSQL. Just skip to the next step. 
+
 Now we need to run ``PostgreSQL`` in a container, attach it to the network
 you have created before, and expose ports for communication:
 
@@ -114,6 +119,8 @@ Let's start Iroha node in Docker container with the following command:
   -e KEY='node0' \
   hyperledger/iroha:latest
 
+.. note:: If you are using Iroha with RocksDB, please add ``--entrypoint irohad`` to these parameters, to skip the PostgreSQL container check.
+
 If you started the node successfully you would see the container id in the same console where you started the container.
 
 Let's look in details what this command does: