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Using Ansible to populate config files with unique variables for various servers

Brice Willie

• 1 min read

This Ansible playbook is designed to update configuration files on multiple servers, ensuring each server has a unique configuration based on its specific variables, such as host_id and ip_addr.

How It Works:

  1. Inventory File: Lists all the target servers along with their unique variables (host_id and ansible_host which represents the IP address).
  2. Playbook: Uses Ansible’s template module to generate configuration files on each server, incorporating the host-specific variables.
  3. Looping with Variables: The playbook loops over the list of servers, dynamically assigning the host_id and ip_addr variables for each host and applying the configuration template accordingly.
  4. Template File: The Jinja2 template file defines the structure of the configuration file and includes placeholders for the variables.

Implementation Details:

  • Inventory File (hosts): Specifies the servers and their unique variables.
  • Playbook (playbook.yml): Defines tasks to apply the configuration template on each server using a loop.
  • Template File (config.j2): Contains the configuration structure, with placeholders for host_id and ip_addr.

Example Inventory File:

[servers]
server1 ip_addr=192.168.1.1 host_id=1
server2 ip_addr=192.168.1.2 host_id=2
server3 ip_addr=192.168.1.3 host_id=3

Example Playbook:

- name: Update configuration file on multiple servers
  hosts: localhost
  tasks:
    - name: Apply the configuration template on each server
      ansible.builtin.template:
        src: templates/config.j2
        dest: "{{ dest_path }}"
      loop: "{{ groups['servers'] }}"
      loop_control:
        loop_var: current_host
      vars:
        dest_path: /path/to/destination/config_file
        host_id: "{{ hostvars[current_host].host_id }}"
        ip_addr: "{{ hostvars[current_host].ansible_host }}"
      delegate_to: "{{ current_host }}"

Example Template File (config.j2):

# Configuration File

host_id = {{ host_id }}
ip_addr = {{ ip_addr }}

Running the Playbook:

Execute the playbook with the following command:

ansible-playbook -i hosts playbook.yml

This setup ensures that each server in the servers group receives a configuration file tailored to its specific host_id and ip_addr, maintaining consistency and reducing the potential for manual errors.

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