Update README

Author: adammck

README.md

@@ -1,8 +1,8 @@
 # Terraformed Inventory
 
 This is a little Go app which generates an dynamic [Ansible] [ansible] inventory
-from a [Terraform] [tf] state file. It allows one to spawn a bunch of VMs with
-Terraform, then (re-)provision them with Ansible. It's pretty neat. 
+from a [Terraform] [tf] state file. It allows one to spawn a bunch of instances
+with Terraform, then (re-)provision them with Ansible. It's pretty neat. 
 
 Currently, only **AWS** and **DigitalOcean** are supported.
 
@@ -19,13 +19,44 @@ add it, if you think that would be useful.
 
 ## Usage
 
-Ansible doesn't (seem to) support calling the inventory script with parameters,
-so you can specify the path to the state file using the `TF_STATE` environment
-variable, like so:
+If your Terraform state file is named `terraform.tfstate` (the default), `cd` to
+it and run:
+
+	ansible-playbook --inventory-file=terraform-inventory deploy/playbook.yml
+
+This will provide the resource names and IP addresses of any instances found in
+the state file to Ansible, which can then be used as hosts patterns in your
+playbooks. For example, given for the following Terraform config:
+
+	resource "digitalocean_droplet" "my-web-server" {
+	  image = "centos-7-0-x64"
+	  name = "web-1"
+	  region = "nyc1"
+	  size = "512mb"
+	}
+
+The corresponding playbook might look like:
+
+	- hosts: my-web-server
+	  tasks:
+	    - yum: name=cowsay
+	    - command: cowsay hello, world!
+
+Note that the instance was identified by its _resource name_ from the Terraform
+config, not its _instance name_ from the provider.
+
+
+## More Usage
+
+Ansible doesn't seem to support calling a dynamic inventory script with params,
+so if you need to specify the location of your state file, set the `TF_STATE`
+environment variable before running `ansible-playbook`, like:
 
 	TF_STATE=deploy/terraform.tfstate ansible-playbook --inventory-file=terraform-inventory deploy/playbook.yml
 
-Alternately, you can create a little shell script and call that. Something like:
+Alternately, if you need to do something fancier (like downloading your state
+file from S3 before running), you might wrap this tool with a shell script, and
+call that instead. Something like:
 
 	#!/bin/bash
 	terraform-inventory $@ deploy/terraform.tfstate
@@ -49,7 +80,8 @@ To test against an example statefile, run:
 	terraform-inventory --host=web-aws fixtures/example.tfstate
 
 To update the fixtures, populate `fixtures/secrets.tfvars` with your DO and AWS
-account details, and run `fixtures/update`. You probably don't need to do this.
+account details, and run `fixtures/update`. You almost certainly don't need to
+do this.
 
 
 ## License