Reviewing playbooks and roles

Let's jump right into examining the master playbook that we created earlier to deploy Docker containers on CoreOS called ansible-coreos. The completed playbook and file, named base.yml, located in the root of the ansible-coreos directory, looks like this:

--- 
# This playbook deploys the ELK stack on CoreOS 
 
- name: Bootstrap CoreOS 
 hosts: coreos 
 gather_facts: False 
 roles: 
    - defunctzombie.coreos-bootstrap 
 
- name: Deploy ELK Stack 
 hosts: coreos 
 remote_user: core 
 become: false 
 tasks: 
    - name: Start etcd 
       service: name=etcd.service state=started 
       become: true 
 
    - name: Install docker-py 
       shell: /home/core/bin/pip install docker-py==1.9.0 docker-compose==1.8.0 
 
    - name: Pull Elasticsearch container 
       docker_image: name=elasticsearch 
 
    - name: Pull Kibana container 
       docker_image: name=kibana 
        
    - name: Pull Logstash container 
       docker_image: name=logstash 
 
    - name...