Ansible Playbooks for creating EC2 boxes ready to host Rails apps.
Full instructions on http://wp.me/plrKl-mN
The basic command needed to create a new instance from scratch is this:
ansible-playbook provisioning.yml --extra-vars "rails_env=staging site=example.com" -i localhostprovisioning.yml is the main provisioning playbook. The configurable parameters are rails_env and site, which are self explanatory. We use localhost as the inventory because we do not yet know the remote hosts which we will use (we are creating it).
The configuration of the machines are stored in the file roles/ec2_creation/vars/main.yml and they follow a hierarchical pattern. The variable default_values has the default and most used parameters. Then we have two dictionaries, one for staging and one for production, each one with the different machines, and their specific options and overrides (for example, the elastic_ip which has to be unique). Finally, there is a key instance_values that serves as a shortcut variable. It will hold the calculated final options of the machine to be created based on the values read from the command line. It uses some Jinja 2 black magic to get them, which you can read about in http://docs.ansible.com/playbooks_variables.html.
The common stuff to be configured and installed on the instances is in the common role. You can find the different system values used in the roles/common/vars/main.yml file, such as the minimum yum packages to install, or the ruby and passenger versions to be used.
The ssh keys are set up in the common role. The list of public ssh keys to use is in the roles/common/files/ssh_keys folder and they are named using the user name.
The actual ssh authorized_keys configuration is done on the task roles/common/tasks/rails_user.yml and is marked with the tag ssh_keys so it can be run individually.
To add a new ssh user access, the key must be added as a separate file on the mentioned folder and also added to the items list on the task. Maybe in the future we can change the task so it uses all files from that folder automatically.
After having modified the playbook, you can run this command to add the new key (COMMENT TO BE REVIEW):
ansible-playbook -i production provisioning.yml --tags ssh_keys