Day 3: Playbooks, plays and tasks

Yesterday:

• You created a repository and added the three files ansible.cfg, hosts, and group_vars/all.yml to the working directory.

• You tested and troubleshooted Ansible’s connection to the server.

Today you will create and execute your first playbook.

Create the playbook

The playbook is essentially the script we use to install the server. Create a file site.yml in your working directory with these contents:

---
- name: Install greeter server
  hosts: example.com
  tasks:
   - name: Install git
     apt: name=git

   - name: Install virtualenv
     apt: name=virtualenv

   - name: Install nginx
     apt: name=nginx-light

   - name: Install pillow
     apt: name=python3-pillow

You need to replace example.com with the actual name of your server (the one you have specified in the hosts file).

This is a playbook that consists of a single play, which consists of four tasks. We could add another play below it, but in this course we will only deal with a single play.

Execute the playbook

Next, enter this command to execute the playbook:

ansible-playbook site.yml

When you do this, Ansible logs on to the server and executes the tasks we specified in the playbook. The output is green for the tasks that had already been accomplished, and orange for those tasks for which the execution resulted in a modification of the server. Try running the command a second time to see the difference. So when you run the playbook on a server that is already setup, you should get no orange output, and in the end, when Ansible shows the summary of what it did, the “changed” part should be zero.

Anatomy of a task

Ansible has a library of modules. In contrast to Python, each Ansible module is just one command, a directive let’s say. And each directive accepts options. So the only option we are specifying here in the apt task is name (I’m talking about the name=git option in the apt line, not about the name of the task). If you created a shortcut on your browser as I told you two days ago, you should be able to visit the reference for the apt module very easily, so please do that and take a quick look at the page.

Your turn

Here is your assignment for tomorrow:

• Create a fifth task that will create a user.

• The task must do the equivalent of this command:

  adduser --system --home=/var/opt/greeter \
     --no-create-home --disabled-password --group \
     --shell=/bin/bash greeter
  

• Use the ansible user module.

• Ignore --disable-password and --group, as this is the default behavior of the module.

• Execute the playbook with ansible-playbook site.yml.

Don’t spend more than 5–10 minutes for it.

Tomorrow we will discuss the solution to this assignment and we will see three more examples of Ansible library modules.