Ansible variables

The concept of variables in Ansible is similar to that of variables in any programming language.

Ansible uses variables to manage differences between systems. With Ansible, you can execute tasks and playbooks on multiple different systems with a single command. To represent the variations among those different systems, you can create variables with standard YAML syntax, including lists and dictionaries. You can define these variables in your playbooks, in your inventory , in reusable files or roles , or at the command line. You can also create variables during a playbook run by registering the return value or values of a task as a new variable. The ansible-examples GitHub repository contains many examples of using variables in Ansible.

Ansible variables

Ansible variables are dynamic values used within Ansible playbooks and roles to enable customization, flexibility, and reusability of configurations. They are very similar to variables in programming languages, helping you manage complex tasks more efficiently by allowing the same playbook or role to be applied across different environments, systems, or contexts without the need for hardcoding specific information. This blog post deep dives into Ansible Variables, which allow us to parametrize different Ansible components. Variables store values for reuse inside an Ansible project. If you are still learning how to use Ansible, you might also find helpful the introductory Ansible Tutorial or Working with Ansible Playbooks blog posts. The use of variables simplifies the management of dynamic values throughout an Ansible project and can potentially reduce the number of human errors. We have a convenient way to handle variations and differences between different environments and systems with variables. Another advantage of variables in Ansible is that we have the flexibility to define them in multiple places with different precedence according to our use case. We can also register new variables in our playbooks by using the returned value of a task. Ansible facts are a special type of variables that Ansible retrieves from any remote host for us to leverage them in Ansible projects. Ansible has a strict set of rules to create valid variable names. Variable names can contain only letters, numbers, and underscores and must start with a letter or underscore. The simplest use case of variables is to define a variable name with a single value using standard YAML syntax. Although this pattern can be used in many places, we will show an example in a playbook for simplicity. In the above example, after the vars block, we define the variable username , and assign the value bob.

You can define these variables in your playbooks, ansible variables your inventoryin reusable files or rolesor at the command line.

You can pass host names at the command line, but most Ansible users create inventory files. Your inventory defines the managed nodes you automate, with groups so you can run automation tasks on multiple hosts at the same time. Once your inventory is defined, you use patterns to select the hosts or groups you want Ansible to run against. The simplest inventory is a single file with a list of hosts and groups. Ansible Inventory plugins supports a range of formats and sources to make your inventory flexible and customizable.

Ansible uses variables to manage differences between systems. With Ansible, you can execute tasks and playbooks on multiple different systems with a single command. To represent the variations among those different systems, you can create variables with standard YAML syntax, including lists and dictionaries. You can define these variables in your playbooks, in your inventory , in reusable files or roles , or at the command line. You can also create variables during a playbook run by registering the return value or values of a task as a new variable. The ansible-examples GitHub repository contains many examples of using variables in Ansible. Once you understand the concepts and examples on this page, read about Ansible facts , which are variables you retrieve from remote systems. Creating valid variable names.

Ansible variables

With Ansible you can retrieve or discover certain variables containing information about your remote systems or about Ansible itself. Variables related to remote systems are called facts. With facts, you can use the behavior or state of one system as a configuration on other systems. For example, you can use the IP address of one system as a configuration value on another system. Variables related to Ansible are called magic variables. Package requirements for fact gathering.

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In defining variables, some strings are reserved for special purposes and cannot qualify as valid variable names. Check Available Servers. By default, Ansible gathers facts at the beginning of each play. These variables include facts, connection variables, and magic variables. You can define variables when you run your playbook by passing variables at the command line using the --extra-vars or -e argument. Author: Randy Romero Red Hat. You can define more complex variables using YAML dictionaries. All rights reserved. The larger the number, the later it will be merged, giving it higher priority. Search docs:. In addition, you can further narrow down and print out the value of a specific key. Write and test a script to generate the JSON data you want. Anything in the vars directory of the role overrides previous versions of that variable in the namespace. Registering Variables. Useful to configure a ProxyCommand for a certain host or group.

Ansible is not a full-fledged programming language, but it does have several programming language features, and one of the most important of these is variable substitution.

Facts are information derived from speaking with your remote systems. Non-SSH based types are described in the next section. You must use either bracket notation or dot notation. This will only work inside a role. Anything in the vars directory of the role overrides previous versions of that variable in namespace. You can define variables when you run your playbook by passing variables at the command line using the --extra-vars or -e argument. Also as it is used in the msg tab, it will print the value of the output variable. You must either cache facts or gather facts for those hosts before the task that fills out the template. For a complete list of options and their hierarchy, look at the official documentation Understanding variable precedence. The action again is a Ansible keyword used in yaml. Note Ansible does not expose a channel to allow communication between the user and the ssh process to accept a password manually to decrypt an ssh key when using the ssh connection plugin which is the default. A better approach would be to create a simple loop that iterates through the list of names. Users can also write custom facts modules, as described in the API guide.