Playbooks

Playbooks are a description of policies that you want to apply to your systems. They consist of a listing of modules and the arguments that will run on your system so that ansible gets to know the current state. They are written in YAML. They begin with “—”, followed by the group name of the hosts where the playbook would be run.

Example:

---
hosts: localhost

- name: install nginx
  yum: name=nginx state=installed

The example above will install Nginx on our systems. Let us also install pip, flask and our flask app.

---
hosts: localhost

- name: install nginx
  yum: name=nginx state=installed

- name: install pip
  yum: name=python-pip state=installed

- name: install flask
  pip: name=flask

- name: fetch application
  git: repo=https://gist.github.com/c454e2e839fcb20605a3.git dest=flask-demo

Now we should also copy the config file for Nginx and systemd service file for our flask app. We will also define a couple of handlers. Handlers are executed if there is any change in state of the task which is supposed to notifies them.

When we will be done with the workshop, our final playbook will look something like this:

---
- hosts: localhost
  remote_user: fedora
  become: yes
  become_method: sudo
  vars:
    - server_port: 8080

  tasks:
    - name: install nginx
      yum: name=nginx state=installed

    - name: serve nginx config
      template: src=../files/flask.conf dest=/etc/nginx/conf.d/
      notify:
      - restart nginx

    - name: install pip
      yum: name=python-pip state=installed

    - name: install flask
      pip: name=flask

    - name: serve flask app systemd unit file
      copy: src=../files/flask-demo.service dest=/etc/systemd/system/

    - name: fetch application
      git: repo=https://gist.github.com/c454e2e839fcb20605a3.git dest=/opt/flask-demo
      notify:
        - restart flask app

    - name: set selinux to permissive for demo
      selinux: policy=targeted state=permissive

    handlers:
    - name: restart nginx
      service: name=nginx state=restarted

    - name: restart flask app
      service: name=flask-demo state=restarted

We can also skip a particular task or make a task execute only if a condition is met using the When statement.

tasks:
  - shell: yum provides */elinks
    when: ansible_os_family == "RedHat"

Suppose we have a list of items we have to iterate on for a particular task, we can use loops like the following

- name: add ssh users
  user:
    name: "{{ item }}"
    state: present
    generate_ssh_key: yes
  with_items:
     - sshuser1
     - sshuser2
     - sshuser3

We can also run certain tasks from a playbook by tagging them -

---
- hosts: localhost
  become: yes

  tasks:
  - name: install nginx
    yum: name=nginx state=present
    tags:
      - system

  - name: install pip
    yum: name=python-pip state=present
    tags:
      - system

  - name: install flask
    pip: name=flask
    tags:
      - dev

We can run the system tagged tasks by running ansible-playbook playbook.yml –ask-become-pass –tags system

We can skip the system tagges tasks by running ansible-playbook playbook.yml –ask-become-pass –skip-tags system