Day18: Ansible - Ad-hoc commands and playbooks

Introduction:

Ansible is a powerful automation tool that simplifies complex tasks in IT environments. In this blog post, we will explore Ansible ad-hoc commands and playbooks. Ad-hoc commands are a quick way to execute simple tasks on remote hosts, while playbooks allow you to create reusable and more complex automation workflows.

Setup

I had setup 1 Ubuntu ansible controller and 3 Debian ansible host machine.

Ansible Ad-hoc commands

Ad-hoc commands are a great way to perform quick tasks on your remote hosts without the need for a playbook. These commands are executed directly from the command line and are useful for simple tasks like checking the status of a service or creating a new user.

Here are some examples of Ansible ad-hoc commands:

Check if linux host are reachable

ansible linux-host -m ping

Check uptime of all the linux host

ansible linux-host -m command -a "uptime"

Use ansible/builtin.shell module

ansible linux-host -m ansible.builtin.shell -a 'echo $TERM'

Use ansible.builtin.copy module

ansible linux-host -m ansible.builtin.copy -a "src=/etc/hosts dest=/tmp/hosts"

Keep in mind that ad-hoc commands are not suitable for complex tasks, and their usage should be limited to simple and quick tasks.

Ansible Playbook

Playbooks are the core of Ansible’s automation capabilities. They are written in YAML and define a series of tasks to be executed on remote hosts. Playbooks can be easily shared, reused, and versioned, making them ideal for more complex tasks and workflows.

Here’s a simple example of an Ansible playbook that installs and configures the Apache web server on multiple Debian hosts under the “linux-host” group:

---
- name: Install and configure Apache on Debian hosts
  hosts: linux-host
  become: yes

  tasks:
    - name: Update package index
      apt:
        update_cache: yes

    - name: Install Apache
      apt:
        name: apache2
        state: present

    - name: Start and enable Apache service
      service:
        name: apache2
        state: started
        enabled: yes

  handlers:
    - name: Restart Apache
      service:
        name: apache2
        state: restarted

In this playbook, we first update the package index on all hosts in the “linux-host” group. Then, we install the Apache web server using the apt module. Finally, we start and enable the Apache service, and create a handler to restart the service if any changes are made.

To run this playbook, save it as apache_setup.yml and execute the following command:

ansible-playbook apache_setup.yml

This playbook will install and configure the Apache web server on all Debian hosts in the “linux-host” group.

Conclusion

In this blog post, we have explored Ansible ad-hoc commands and playbooks. Ad-hoc commands are useful for quick and simple tasks, while playbooks provide a more powerful and reusable way to automate complex tasks and workflows.

As you continue to learn and use Ansible, you’ll find that these tools can greatly simplify your IT automation tasks and improve your overall workflow.

Few more resources one can read:

• Introduction to ad hoc commands
• CI/CD concepts
• How to install software packages with an Ansible playbook