In order to use this script, first export the AWS credentials enviroment variables, then add the correct .pem file to your ssh agent and call the ansible-playbook on the site.yml file.

```
export AWS_ACCESS_KEY_ID='XXX'
export AWS_SECRET_ACCESS_KEY='XXX'

ssh-agent bash
ssh-add ~/.ssh/keypair.pem

ansible-playbook site.yml
```

This playbook will recognize the right ubuntu hosts because they are tagged with role=webservers or role=dbservers through the AWS interface.