Exercise 1.1 - Writing Your First Playbook | Red Hat

Exercise Description

Now that you’ve gotten a sense of how Red Hat Ansible Tower works, we are going to write our first Ansible playbook. The playbook is where you can take some of those ad hoc commands you just ran and put them into a repeatable set of plays and tasks.

A playbook can have multiple plays and a play can have one or multiple tasks. The goal of a play is to map a group of hosts. The goal of a task is to implement modules against those hosts.

Section 1: Running a pre-existing playbook from SCM

Let’s clone a source code repository locally to get the sample playbook.

ansible localhost -m git -a "repo=https://github.com/RedHatGov/workshop.artifacts.git dest=artifacts"

Now, let’s run a playbook. This playbook will open firewall ports on the remote node.

ansible-playbook -i hosts artifacts/playbooks/firewall-open-http.yml

Section 2: Creating a directory structure and files for your own playbook

For our first playbook, we are only going to write one play and two tasks.

There is a best practice regarding the preferred directory structures for playbooks. We strongly encourage you to read and understand these practices as you develop your Ansible ninja skills. That said, our playbook today is very basic, because creating a complex structure can create unnecessary challenges.

Instead, we are going to create a very simple directory structure for our playbook, and add just a couple of files to it.

Step 1: Create a directory

Create a directory called apache_basic in your home directory and change directories to it.

mkdir ~/apache_basic
cd ~/apache_basic

Step 2: Open the apache install

Use vi or vim to open a file called install_apache.yml

vim install_apache.yml

Section 2: Defining Your play

Now that you are editing install_apache.yml, let’s begin by defining the play. Then, we’ll take some time to understand what each line accomplishes.

---
- hosts: web
  name: Install the apache web service
  become: yes

--- Defines the beginning of YAML
hosts: web Defines the host group in your inventory on which this play will run against.
name: Install the apache web service This describes our play.
become: yes Enables user privilege escalation. The default is sudo, but su, pbrun, and several others are also supported.

Section 3: Adding tasks to your play

Now that we’ve defined your play, let’s add some tasks to get some things done. Align (vertically) the t in task with the b become.

Yes, it does actually matter. In fact, you should make sure all of your playbook statements are aligned, as shown here.

If you want to see the entire playbook for reference, skip to the bottom of this exercise.

tasks:
 - name: install apache
   package:
     name: httpd
     state: present

 - name: start httpd
   service:
     name: httpd
     state: started

tasks: This denotes that one or more tasks are about to be defined
- name: Each task requires a name, which will print to standard output when you run your playbook. Therefore, give your tasks a name that is short, sweet, and to the point

package:
  name: httpd
  state: present

These three lines are calling the Ansible module package to install httpd. Click here to see all options for the package module.

service:
  name: httpd
  state: started

The next few lines are using the ansible module service to start the httpd service. The service module is the preferred way of controlling services on remote hosts. Click here to learn more about the service module.

Section 4: Saving your playbook

Now that you’ve completed writing your playbook, it would be a shame not to keep it for later use.

Use the write/quit method in vi or vim to save your playbook, i.e. Esc :wq!

And that should do it. You should now have a fully written playbook called install_apache.yml. You are ready to automate!

Ansible (well, YAML really) can be a bit particular about formatting, especially around indentation/spacing. When you all get back to the office, read up on this YAML Syntax a bit more and it will save you some headaches later. In the meantime, your completed playbook should look like this. Take note of the spacing and alignment.

---
- hosts: web
  name: Install the apache web service
  become: yes

  tasks:
    - name: install apache
      package:
        name: httpd
        state: present

    - name: start httpd
      service:
        name: httpd
        state: started

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