Merge pull request #196 from ESGF/ansible-docs-update

The playbook and associated roles and variables are in [deploy/ansible/](../deploy/ansible/).

Please look at these files to understand exactly what the playbook is doing.

Ansible requires that you have `root` access on the hosts that you are deploying to.

For a complete list of all variables that are available, please look at the defaults for each

of the [playbook roles](../deploy/ansible/roles/). The defaults have extensive comments that

explain how to use these variables. This document describes how to apply some common

configurations.

**NOTE: The installation has a footprint of around 4GB. Please ensure there is enough disk

space before you run Ansible.**

<!-- TOC depthFrom:2 -->

- [Running the playbook](#running-the-playbook)

## Running the playbook

Before attempting to run the playbook, make sure that you have

[installed Ansible](https://docs.ansible.com/ansible/latest/installation_guide/intro_installation.html).

Before attempting to run the playbook, make sure that you have:

- [installed Ansible](https://docs.ansible.com/ansible/latest/installation_guide/intro_installation.html)

- `root` access on the target hosts where the services will be deployed

- checked that there is at least 4GB of free disk space on the target hosts

Next, make a configuration directory - this can be anywhere on your machine that is **not** under

`esgf-docker`. You can also place this directory under version control if you wish - this can be very