In order to effectively run ansible, the target machine needs to have a python interpreter. Coreos machines are minimal and do not ship with any version of python. To get around this limitation we can install pypy, a lightweight python interpreter. The coreos-bootstrap role will install pypy for us and we will update our inventory file to use the installed python interpreter.

ansible-galaxy install defunctzombie.coreos-bootstrap

Unlike a typical role, you need to configure Ansible to use an alternative python interpreter for coreos hosts. This can be done by adding a coreos group to your inventory file and setting the group's vars to use the new python interpreter. This way, you can use ansible to manage CoreOS and non-CoreOS hosts. Simply put every host that has CoreOS into the coreos inventory group and it will automatically use the specified python interpreter.

[coreos]
host-01
host-02

[coreos:vars]
ansible_ssh_user=core
ansible_python_interpreter="PATH=/home/core/bin:$PATH python"

This will configure ansible to use the python interpreter at /home/core/bin/python which will be created by the coreos-bootstrap role.

Now you can simply add the following to your playbook file and include it in your site.yml so that it runs on all hosts in the coreos group.

- hosts: coreos
  gather_facts: False
  roles:
    - defunctzombie.coreos-bootstrap

Make sure that gather_facts is set to false, otherwise ansible will try to first gather system facts using python which is not yet installed!

After bootstrap, you can use ansible as usual to manage system services, install python modules (via pip), and run containers. Below is a basic example that starts the etcd service, installs the docker-py module and then uses the ansible docker module to pull and start a basic nginx container.

- name: Nginx Example
  hosts: web
  sudo: true
  tasks:
    - name: Start etcd
      service: name=etcd.service state=started

    - name: Install docker-py
      pip: name=docker-py

    - name: pull container
      raw: docker pull nginx:1.7.1

    - name: launch nginx container
      docker:
        image="nginx:1.7.1"
        name="example-nginx"
        ports="8080:80"
        state=running

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