Ansible Variable Precedence

 Ansible Variable Precedence

Ansible is an open-source automation platform that is used to automate IT tasks such as configuration management, application deployment, and orchestration. Ansible uses variables to store values that can be used in playbooks and templates. Variables can be defined in multiple places, and Ansible has a specific order of precedence for determining which variable will be used. In this blog, we will discuss Ansible variable precedence with examples. Ansible variable precedence is the order in which Ansible will look for variables when executing a playbook. The order of precedence is as follows: 1. Role defaults 2. Inventory file or script group vars 3. Inventory group vars 4. Playbook group vars 5. Host vars 6. Task vars 7. Extra vars Let's look at each of these in more detail. 1. Role defaults: Role defaults are variables that are defined in the role's defaults/main.yml file. These variables are used to set default values for the role. 2. Inventory file or script group vars: Group vars can be defined in the inventory file or in a script. These variables are used to set values for a specific group of hosts. 3. Inventory group vars: Group vars can also be defined in the inventory file. These variables are used to set values for a specific group of hosts. 4. Playbook group vars: Group vars can also be defined in the playbook. These variables are used to set values for a specific group of hosts. 5. Host vars: Host vars are variables that are defined in the inventory file for a specific host. These variables are used to set values for a specific host. 6. Task vars: Task vars are variables that are defined in the task. These variables are used to set values for a specific task. 7. Extra vars: Extra vars are variables that are passed in from the command line. These variables are used to set values for a specific task or playbook. To illustrate Ansible variable precedence, let's look at an example. Suppose we have a playbook that deploys an application to a group of hosts. We have defined a variable called "app_version" in the role defaults, inventory file, and playbook. We have also defined a variable called "app_name" in the inventory file and playbook. In this case, Ansible will use the "app_version" variable from the role defaults, since it has the highest precedence. The "app_name" variable will be taken from the inventory file, since it has the second highest precedence. In conclusion, Ansible variable precedence is the order in which Ansible will look for variables when executing a playbook. The order of precedence is role defaults, inventory file or script group vars, inventory group vars, playbook group vars, host vars, task vars, and extra vars. Understanding Ansible variable precedence is important for ensuring that the correct variables are used in playbooks and templates.