Document usage of subdomain, hostname and domain

Closes: #312

docs/installation_instructions.md

@@ -55,9 +55,9 @@ checkout the latest tagged version (currently `0.2.2`):
 > and you can proceed without any further actions.
 
 
-If you installed `virtualenv`, create a python virtual environment called "env"
-that uses python 3. This makes sure we do not change any of your other python
-projects. The second command "activates" the virtualenv.
+Create a python virtual environment called "env" that uses python 3. This makes
+sure we do not change any of your other python projects. The second command
+"activates" the virtualenv.
 
 > **NOTE:** Activating the virtualenv means you will use that environment to
 > install and run python programs instead of your global environment. If you
@@ -71,10 +71,6 @@ Next, install the OpenAppStack CLI client by running the following commands:
 
     $ pip3 install -r requirements.txt
 
-> *Hint:* if the `pip3 install` command results in a [segmentation
-> fault](https://bitbucket.org/cffi/cffi/issues/272/segfault-while-installing-via-pip),
-> you can add `--no-use-wheel` to it.
-
 Now you can run the OpenAppStack CLI as follows:
 
     $ python -m openappstack CLUSTER_NAME <command>
@@ -154,7 +150,7 @@ There are two options to create a cluster:
      more information*
 - In both cases you need to provide the `DOMAIN_NAME` positional argument.
 
-  If you use a subdomain (e.g. oas.yourdomain.com), use the `--subdomain`
+  If you use a subdomain (e.g. `oas.yourdomain.com`), use the `--subdomain`
   command as follows:
 
   ```
@@ -188,10 +184,18 @@ If you want to follow this step, we assume you already have a VPS. You'll need
 its *hostname* and its *IP address*. Also check that your VPS meets our
 [prerequisites](#prerequisites).
 
-> **NOTE:** You can use the `--acme-staging` argument for testing purposes This
-> ensures you use "staging" certificates from Let's Encrypt, to reduce the
-> stress on their servers. However, ONLYOFFICE integration requires valid (live)
-> certificates to work.
+> **NOTE:** You can use the `--acme-staging` argument for testing purposes. If
+> you are automating this, please use this to ensure you use "staging"
+> certificates from Let's Encrypt, to > reduce the stress on their servers.
+> However, ONLYOFFICE integration requires valid (live) certificates to work
+> properly so please don't use this option by default.
+
+If you want your cluster to be reachable under the fully qualified domain name
+(`FQDN`) `my-cluster.oas.example.org`, the corresponding parameters would be:
+
+* `--hostname`: `my-cluster`
+* `--subdomain`: `oas`
+* the `DOMAIN`: `example.org`
 
 Create the OpenAppStack settings for your VPS by running the following command:
 
@@ -199,10 +203,6 @@ Create the OpenAppStack settings for your VPS by running the following command:
 $ python -m openappstack my-cluster create --ip-address IP_ADDRESS --hostname HOSTNAME --subdomain oas example.org
 ```
 
-> **NOTE:** If you are automating this, please add the --acme-staging`
-> argument. This ensures you use "staging" certificates from Let's Encrypt, to
-> reduce the stress on their servers.
-
 ### DNS entries
 
 Before you continue, if you have not made DNS entries with the CLI tool, you