Ansible tasks

Tasks

The tasks folder contains a ‘main.yml’ file, and possibly other YAML files, to define the tasks needed to realise the role. A task is an action that needs to be taken to change the state. This takes the form of a module and parameters.

Tasks to execute, in the shape of a YAML file. This contains a main.yml file, which in turn may include other files if it makes sense to split into multiple sections.

It’s good manners to start the tasks/main.yml file with a prolog. A simple description can help maintain focus for the task declarations.

---
# This role deploys P and configures Q.

You can then add the steps to achieve this.

Installing packages

Using package managers via Ansible is trivial. Declare a task to install the software you require.

- name: Install yum packages wingnut and shamalangadingdong
  yum: name= state=present
  with_items:
  - wingnut
  - shamalangadingdong

What this does is use the ‘yum’ module with each of the listed items, to change their state to ‘present’. If they are already there, no action is needed.

If the yum module is unable to change the state to present then the task fails.

Interestingly, this results in a build that only works on yum-based distributions. Similarly, using ‘apt’ also produces a non-portable role. It’s advised to use ‘package’ instead, which is then farmed out to apt, yum, or other package managers depending on the target system.

Removing software is just as easy - create a task to manage packages with the state set to ‘absent’ to ensure that the items are not present on the target system.

- name: Remove packages sendmail and postfix
  package: name= state=absent
  with_items:
  - sendmail
  - postfix

When we declare ‘state=absent’ it tells the module to take action to remove the package. Ansible is happy so long as the package isn’t installed, or even if it doesn’t exist at all.

You’ll need to add ‘absent’ state entries to clean up later when software is no longer needed - you can’t just remove the install entry because old systems would have the package installed, and new systems would not. Be consistent, be explicit.

Creating a file using a template

This will be covered in more detail later, but a general pattern for this is to use the ‘template’ module with a source and destination.

- name: Configure the etc hosts file
  template: src=etc.hosts.j2 dest=/etc/hosts

Ansible will find the template in the ‘templates’ folder, and use variables to generate the content to render the output file.

Service management

We can look after system services, start them, and set them to start at boot using the ‘service’ module.

- name: Start the Wingnut service
  service: name=wingnut state=started enabled=yes

This will start the service immediately, and configure the system to start this service if the machine is rebooted. Naturally we can set state to stop the service, or disable it at boot time.