Static Inventory in Ansible
Introduction
In Ansible, an inventory is a collection of hosts that can be managed by Ansible. A static inventory is a simple and straightforward way to define your managed nodes. It is typically a text file that lists all the hosts and their groupings.
Basic Structure
The most basic form of a static inventory is a plain text file that lists the hostnames or IP addresses of the target machines. Here is an example:
inventory.txt
192.168.1.10
192.168.1.11
192.168.1.12
Grouping Hosts
Hosts can be grouped together to apply tasks to specific sets of servers. Groups are defined by enclosing the group name in square brackets. Here is an example of grouping hosts:
inventory.txt
[webservers]
192.168.1.10
192.168.1.11
[dbservers]
192.168.1.12
Defining Variables
You can define variables for hosts and groups within the inventory file. These variables can be used in your playbooks. Here is an example:
inventory.txt
[webservers]
192.168.1.10 http_port=80
192.168.1.11 http_port=8080
[dbservers]
192.168.1.12 db_port=3306
Host Variables
In addition to defining variables inline, you can also define host-specific variables in a separate file. Create a directory named host_vars and place your variable files there. Here is an example:
host_vars/192.168.1.10
http_port: 80
host_vars/192.168.1.11
http_port: 8080
Group Variables
Similar to host variables, you can define group-specific variables in a group_vars directory. Here is an example:
group_vars/webservers
common_http_port: 80
Using the Inventory in Playbooks
Once your inventory is defined, you can use it in your Ansible playbooks. Here is an example of a simple playbook that uses the static inventory:
simple_playbook.yml
- hosts: webservers
tasks:
- name: Ensure Apache is installed
yum:
name: httpd
state: present
Running the Playbook
To run the playbook with the static inventory, use the following command:
ansible-playbook -i inventory.txt simple_playbook.yml
Conclusion
Static inventories are a simple and effective way to define the hosts and groups for your Ansible automation. They are easy to set up and manage, making them ideal for small to medium-sized environments. With the knowledge of how to structure your inventory, define variables, and use them in playbooks, you can effectively manage your infrastructure using Ansible.