12. Writing Playbooks: Loops and Conditional Statements in Ansible

In the previous article, we discussed how to define and manage tasks. In this article, we’ll delve deeper into using loops and conditional statements in Ansible Playbooks to enhance the flexibility and adaptability of your automation scripts.

Using Loops

Loops are a powerful mechanism for controlling task execution in Ansible—commonly used to process lists or dictionaries. Below, we’ll explore how to use loops in Playbooks.

Example: Using with_items

Suppose you need to install the same set of software packages across multiple servers. You can achieve this efficiently using the with_items loop. Here’s a Playbook example that installs common packages:

- name: Install common packages
  hosts: all
  tasks:
    - name: Install packages
      apt:
        name: "{{ item }}"
        state: present
      with_items:
        - vim
        - git
        - curl

In this Playbook, the apt module processes each package in the with_items list sequentially. This approach significantly simplifies task definition.

Example: Using with_dict

For dictionary-type data, Ansible provides the with_dict loop. The following example assigns a specific IP address to each host based on its hostname:

- name: Assign IP addresses to hosts
  hosts: all
  tasks:
    - name: Set IP based on hostname
      command: echo "The IP for {{ item.key }} is {{ item.value }}"
      with_dict:
        server1: 192.168.1.10
        server2: 192.168.1.11

In this example, item.key and item.value correspond to the dictionary’s key (hostname) and value (IP address), respectively. Ansible automatically substitutes these placeholders during each iteration.

Using Conditional Statements

Conditional statements allow you to determine whether a task should execute based on specific criteria. Ansible uses the when keyword to implement conditional logic.

Example: Conditional Execution Based on Variable Values

The following example demonstrates how to conditionally install Nginx depending on the operating system family:

- name: Check package installation
  hosts: all
  tasks:
    - name: Install nginx
      apt:
        name: nginx
        state: present
      when: ansible_os_family == "Debian"  # Install nginx only on Debian-based systems

Here, the task executes only if the ansible_os_family variable equals "Debian". This ensures your Playbook behaves appropriately across diverse environments.

Example: Combining Loops and Conditions

Combining loops with conditionals is a common and powerful pattern. The following example shows how to install packages only if they are not already present on the target system:

- name: Install specific packages based on conditions
  hosts: all
  tasks:
    - name: Install packages only if they are not already installed
      apt:
        name: "{{ item }}"
        state: present
      with_items:
        - git
        - vim
        - curl
      when: ansible_facts.packages[item] is not defined

In this case, the task runs only when the specified package is absent from the system—avoiding redundant installations.

Summary

In this article, we explored how to use loops and conditional statements in Ansible Playbooks to increase the flexibility and robustness of automation workflows. Through concrete examples, we demonstrated practical applications of these features—equipping you with valuable techniques for writing more sophisticated Playbooks.

In the next article, we’ll cover how to configure basic Inventory files—a foundational step for managing heterogeneous host environments. By combining well-structured Inventory definitions with the looping and conditional capabilities covered here, you can dramatically improve both the efficiency and maintainability of your automation infrastructure.