Loops in Ansible Playbook

To demonstrate the 'loop' in Ansible, let's take tasks from a playbook I used in another training to configure a Kubernetes cluster.

---
- name : Install the required packages, set the Selinux to permissive , disable the swap etc 
  hosts: all
  become : True
  tasks :
  
  - name: Ensure SELinux is set to permissive mode in the configuration file 
    lineinfile:
      path: /etc/selinux/config
      regexp: '^SELINUX='
      line: SELINUX=permissive
  
  - name: Put SELinux in permissive mode.
    ansible.posix.selinux:
      policy: targeted
      state: permissive

  - name: Configure required modules
    shell : modprobe overlay ; modprobe br_netfilter

Let's break down the playbook and then enhance the last task to utilize an Ansible loop.

  1. Setting SELinux to Permissive Mode:

    • The first two tasks focus on SELinux configuration.

    • In the lineinfile task, we ensure that the SELINUX line in the /etc/selinux/config file is set to permissive.

    • The ansible.posix.selinux task puts SELinux in permissive mode for the targeted policy.

  2. Configuring Required Modules:

    • The third task executes a shell command to load two kernel modules: overlay and br_netfilter.

    • These modules are essential for containerization and network filtering.

  3. Enhancing the Last Task with an Ansible Loop:

    • Instead of using a shell command directly, let's modify the last task to use an Ansible loop.

    • We'll use the loop keyword to iterate over a list of module names and load them.

    • Here's the updated task:

  • In this new task:

    • The shell module runs the modprobe command for each item in the loop.

    • The item variable represents the current module name (e.g., overlay, br_netfilter).

Now your playbook will dynamically load the specified modules using the Ansible loop!

One other section of the playbook that can be optimized with 'loop' is given below.

We'll consolidate this into a single task that iterates over the required parameters.

In this updated task:

  • The lineinfile module will add each parameter line to the specified file.

  • The loop iterates over the list of parameters, ensuring cleaner and more concise code.

Here is another instance of 'loop' in the same playbook, which should be self-explanatory. Like this, the playbooks can be simplified and enhanced with appropriate loops.

Reference

Loops — Ansible Community Documentation.

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