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Ansible

Ioannis Moustakis

This blog post explores the concept of Ansible roles, their structure, and how we can combine them with our playbooks. We will analyze their functionality and usage along with ways to create new roles and retrieve public shared roles from Ansible Galaxy, a public repository for Ansible resources.
If you are new to Ansible, you might also find these tutorials helpful <a href="https://spacelift.io/blog/ansible-tutorial" target="_blank" rel="noopener">Ansible Tutorial for Beginners</a>, <a href="https://spacelift.io/blog/ansible-playbooks" target="_blank" rel="noopener">Working with Ansible Playbooks</a>, and <a href="https://spacelift.io/blog/ansible-variables" target="_blank" rel="noopener">How to Use Different Types of Ansible Variables</a>.

Ansible Roles provide a well-defined framework and structure for setting your tasks, variables, handlers, metadata, templates, and other files. They enable us to reuse and share our Ansible code efficiently. This way, we can reference and call them in our playbooks with just a few lines of code while we can reuse the same roles over many projects without the need to duplicate our code.

When starting with Ansible, it’s pretty common to focus on writing playbooks to automate repeating tasks quickly. As new users automate more and more tasks with playbooks and their Ansible skills mature, they reach a point where using just Ansible playbooks is limiting. Ansible Roles to the rescue!
Since we have our code grouped and structured according to the Ansible standards, it is quite straightforward to share it with others. We will see an example of how we can accomplish that later with Ansible Galaxy. 
Organizing our Ansible content into roles provides us with a structure that is more manageable than just using playbooks. This might not be evident in minimal projects but as the number of playbooks grows, so does the complexity of our projects. 
Lastly, placing our Ansible code into roles lets us organize our automation projects into logical groupings and follow the separation of concerns design principle. Collaboration and velocity are also improved since different users can work on separate roles in parallel without modifying the same playbooks simultaneously.

Let’s have a look at the standard role directory structure. For each role, we define a directory with the same name. Inside, files are grouped into subdirectories according to their function. A role must include at least one of these standard directories and can omit any that isn’t actively used.
To assist us with quickly creating a well-defined role directory structure skeleton, we can leverage the command ansible-galaxy init &lt;your_role_name&gt;. The ansible-galaxy command comes bundled with Ansible, so there is no need to install extra packages.
Create a skeleton structure for a role named test_role:

image4-18

test_role

This command generates this directory structure:

image5-16

Directory structure

Ansible checks for main.yml files, possible variations, and relevant content in each subdirectory. It’s possible to include additional YAML files in some directories. For instance, you can group your tasks in separate YAML files according to some characteristic.
<ul>
<li aria-level="1">defaults &#8211;  Includes default values for variables of the role. Here we define some sane default variables, but they have the lowest priority and are usually overridden by other methods to customize the role.</li>
<li aria-level="1">files  &#8211; Contains static and custom files that the role uses to perform various tasks.</li>
<li aria-level="1">handlers &#8211; A set of <a href="https://docs.ansible.com/ansible/latest/user_guide/playbooks_handlers.html" target="_blank" rel="nofollow noopener">handlers</a> that are triggered by tasks of the role. </li>
<li aria-level="1">meta &#8211; Includes metadata information for the role, its dependencies, the author, license, available platform, etc.</li>
<li aria-level="1">tasks &#8211; A list of tasks to be executed by the role. This part could be considered similar to the task section of a playbook.</li>
<li aria-level="1">templates &#8211; Contains <a href="https://docs.ansible.com/ansible/latest/user_guide/playbooks_templating.html" target="_blank" rel="nofollow noopener">Jinja2</a> template files used by tasks of the role. (<span data-sheets-value="{&quot;1&quot;:2,&quot;2&quot;:&quot;Read more about how to create an Ansible template.&quot;}" data-sheets-userformat="{&quot;2&quot;:513,&quot;3&quot;:{&quot;1&quot;:0},&quot;12&quot;:0}">Read more about <a href="https://spacelift.io/blog/ansible-template" target="_blank" rel="noopener">how to create an Ansible template</a>.)</li>
<li aria-level="1">tests &#8211; Includes configuration files related to role testing.</li>
<li aria-level="1">vars &#8211; Contains variables defined for the role. These have quite a high <a href="https://docs.ansible.com/ansible/latest/user_guide/playbooks_templating.html" target="_blank" rel="nofollow noopener">precedence</a> in Ansible.</li>
</ul>
Another directory that wasn’t automatically generated by the ansible-galaxy init command but is mentioned in the official Ansible docs, and you might find helpful in some cases, is the library directory. Inside it, we define any custom modules and plugins that we have written and used by the role. Finally, we also have a preconfigured README.md file that we can fill with details and useful information about our role.

<ul>
<li><a href="https://spacelift.io/blog/using-terraform-and-ansible-together" target="_blank" rel="noopener">Using Terraform &amp; Ansible together</a></li>
<li><a href="https://spacelift.io/blog/spacelift-ansible-integration-beta" target="_blank" rel="noopener">How to better manage Ansible and overcome challenges</a></li>
<li><a href="https://spacelift.io/blog/ansible-best-practices" target="_blank" rel="noopener"><span data-sheets-value="{&quot;1&quot;:2,&quot;2&quot;:&quot;44 Ansible Best Practices to Follow [Tips &amp; Tricks]&quot;}" data-sheets-userformat="{&quot;2&quot;:513,&quot;3&quot;:{&quot;1&quot;:0},&quot;12&quot;:0}">44 Ansible best practices to follow</a></li>
</ul>

A common tactic is to refactor an Ansible playbook into a role. To achieve that, we have to decompose the different parts of a playbook and stitch them together into an Ansible role using the directories we’ve just seen in the previous section. 
This section will go through an example of creating a new role for installing and configuring a minimal Nginx web server from scratch. If you wish to follow along, you will need <a href="https://www.virtualbox.org/" target="_blank" rel="nofollow noopener">VirtualBox</a>, <a href="https://docs.ansible.com/ansible/latest/installation_guide/intro_installation.html" target="_blank" rel="nofollow noopener">Ansible</a>, and <a href="https://www.vagrantup.com/" target="_blank" rel="nofollow noopener">Vagrant</a> installed locally.
Ansible searches for referenced roles in common paths like the orchestrating playbook’s directory, the roles/ directory, or the configured <a href="https://docs.ansible.com/ansible/latest/reference_appendices/config.html#default-roles-path" target="_blank" rel="nofollow noopener">roles_path</a> configuration value. It’s also possible to set a custom path when referencing a role:

Using the ansible-galaxy init command, we generate the initial directory structure for a role named webserver inside a parent directory named roles. Let’s go ahead and delete the tests directory since we won’t be using it. We will see how to utilize all the other directories during our demo. 
The final structure of our role looks like this:

image2-23

The final structure of our role

First, let’s define the most fundamental part of our role, its tasks. Head to the tasks directory and edit the main.yml file.
roles/webserver/tasks/main.yml

Here, we define a handful of tasks that update the operating system, install an Nginx web server, and set up a minimal custom configuration for demo purposes.
Next, we move to the defaults directory, where we will set default values for the variables used in the tasks. If there is no other definition for these variables, they will be picked up and used by the role, but usually, they are meant to be easily overwritten.
roles/webserver/defaults/main.yml

Moving on to our vars directory, we define values with higher precedence that aren’t meant to be overridden at the play level. Here, we override the default variable that defines the Nginx custom directory.
roles/webserver/vars/main.yml

In the handlers directory, we define any handler that is triggered by our tasks. One of our tasks includes a notify keyword since it needs to trigger our Restart the Nginx service handler.
roles/webserver/handlers/main.yml

In the templates directory, we leverage a Jinja2 template file for the Nginx configuration that gets the Nginx custom directory value from one of our previously defined variables.
roles/webserver/templates/nginx.conf.j2

In the files directory, we define a static file index.html that will serve as our static demo webpage.
roles/webserver/files/index.html

We use the meta directory to add metadata and information about the role. Any role dependencies by other roles go here as well.
roles/webservers/meta/main.yml

Lastly, we update the README.md file accordingly. The autogenerated file provided by the ansible-galaxy init command includes many pointers and guidance on filling this nicely. 
roles/webserver/README.md

Once we have defined all the necessary parts of our role, it’s time to use it in plays. The classic and most obvious way is to reference a role at the play level with the roles option:

With this option, each role defined in our playbook is executed before any other tasks defined in the play.
This is an example play to try out our new webserver role. Let’s go ahead and execute this play. To follow along, you should first run the <code>vagrant up</code> command from the top directory of <a href="https://github.com/spacelift-io-blog-posts/Blog-Technical-Content/tree/master/ansible-roles" target="_blank" rel="nofollow noopener">this repository</a> to create our target remote host.

image3-20

webserver role

Sweet! All the tasks have been completed successfully. Let’s also validate that we have configured our Ngnix web server correctly.
Use the command <code>vagrant ssh host1</code> to connect to our demo Vagrant host. Then execute <code>systemctl status nginx</code> to verify that Nginx service is up and running. Finally, run the command <code>curl localhost</code> to check if the web server responds with the custom page that we configured.

image1-24

vagrant ssh host1

When using the roles option at the play level, we can override any of the default role’s variables or pass other keywords, like tags. <a href="https://spacelift.io/blog/ansible-tags" target="_blank" rel="noopener">Ansible tags</a> are added to all tasks within the role.

Here, we override the default variable nginx_version with another version.
Apart from defining roles at the play level with the roles option, we can use them also at the tasks level with the options include_role dynamically and import_role statically. These are useful when we would like to run our role tasks in a specific order and not necessarily before any other playbook tasks. This way, roles run in the order they are defined in plays.

Check the <a href="https://docs.ansible.com/ansible/latest/user_guide/playbooks_reuse_roles.html#using-roles" target="_blank" rel="nofollow noopener">official docs</a> for achieving more fine-grained control of your role’s task execution order. 
Even if we define a role multiple times, Ansible will execute it only once. Occasionally, we might want to run a role multiple times but with different parameters. Passing a different set of parameters to the same roles allows executing the role more than once. 
Example of executing the role test three times:

<a href="https://galaxy.ansible.com/" target="_blank" rel="nofollow noopener">Ansible Galaxy</a> is an online open-source, public repository of Ansible content. There, we can search, download and use any shared roles and leverage the power of its community. We have already used its client, ansible-galaxy, which comes bundled with Ansible and provides a framework for creating well-structured roles.
You can use Ansible Galaxy to browse for roles that fit your use case and save time by using them instead of writing everything from scratch. For each role, you can see its code repository, documentation, and even a rating from other users. Before running any role, check its code repository to ensure it’s safe and does what you expect. Here’s a blog post on <a href="https://www.jeffgeerling.com/blog/2019/how-evaluate-community-ansible-roles-your-playbooks" target="_blank" rel="noopener">How to evaluate community Ansible roles</a>. If you are curious about Galaxy, check out its <a href="https://galaxy.ansible.com/docs/" target="_blank" rel="nofollow noopener">official documentation</a> page for more details.
To download and install a role from Galaxy, use the ansible-galaxy install command. You can usually find the installation command necessary for the role on Galaxy. For example, look at <a href="https://galaxy.ansible.com/geerlingguy/postgresql" target="_blank" rel="nofollow noopener">this role that installs a PostgreSQL server</a>.
Install the role with:

Then use it in a playbook while overriding the default role variable postgresql_users to create an example user for us.

This section gathers some tips and tricks that might help you along your journey with Ansible roles.
<ul>
<li style="font-weight: 400;" aria-level="1">Always use descriptive names for your roles, tasks, and variables. Document the intent and the purpose of your roles thoroughly and point out any variables that the user has to set. Set sane defaults and simplify your roles as much as possible to allow users to get onboarded quickly.</li>
<li style="font-weight: 400;" aria-level="1">Never place secrets and sensitive data in your roles YAML files. Secret values should be passed to the role at execution time by the play as a variable and should never be stored in any code repository.</li>
<li style="font-weight: 400;" aria-level="1">At first, it might be tempting to define a role that handles many responsibilities. For instance, we could create a role that installs multiple components, a common anti-pattern. Try to follow the separation of concerns design principle as much as possible and separate your roles based on different functionalities or technical components.</li>
<li style="font-weight: 400;" aria-level="1">Try to keep your roles as loosely coupled as possible and avoid adding too many dependencies. </li>
<li style="font-weight: 400;" aria-level="1">To control the execution order of roles and tasks, use the import_role or Include_role tasks instead of the classic roles keyword.</li>
<li style="font-weight: 400;" aria-level="1">When it makes sense, group your tasks in separate task files for improved clarity and organization.</li>
</ul>
To learn more, check out the <a href="https://spacelift.io/blog/ansible-best-practices" target="_blank" rel="noopener">44 Ansible Best Practices to Follow</a>.

<a href="https://spacelift.io/" target="_blank" rel="noopener">Spacelift</a>’s vibrant ecosystem and excellent GitOps flow can greatly assist you in managing and orchestrating Ansible. By introducing Spacelift on top of Ansible, you can then easily <a href="https://docs.spacelift.io/concepts/policy/trigger-policy" target="_blank" rel="noopener">create custom workflows</a> based on pull requests and apply any necessary <a href="https://docs.spacelift.io/concepts/policy/terraform-plan-policy" target="_blank" rel="noopener">compliance checks</a> for your organization. Another great advantage of using Spacelift is that you can manage different infrastructure tools like Ansible, Terraform, Pulumi, AWS CloudFormation, and even Kubernetes from the same place and combine their <a href="https://docs.spacelift.io/concepts/stack/" target="_blank" rel="noopener">Stacks</a> with building workflows across tools.
If you want to learn more about Spacelift working with Ansible, check our <a href="https://docs.spacelift.io/vendors/ansible/" target="_blank" rel="noopener">documentation</a>, read our <a href="https://spacelift.io/blog/spacelift-ansible-integration-beta" target="_blank" rel="noopener">Ansible guide</a> or <a href="https://spacelift.io/schedule-demo" target="_blank" rel="noopener">book a demo with one of our engineers</a>.

We deep-dived into Ansible Roles and their utility and saw how to refactor our playbooks into roles or generate them from scratch. We went through a complete example of creating and using a role and explored how we can benefit from the Ansible Galaxy community.
Thank you for reading, and I hope you enjoyed this “Ansible Roles” blog post as much as I did.

Spacelift helps you manage the complexities and compliance challenges of using Ansible. It brings with it a GitOps flow, so your infrastructure repository is synced with your Ansible Stacks, and pull requests show you a preview of what they’re planning to change. It also has an extensive selection of policies, which lets you automate compliance checks and build complex multi-stack workflows.

Terraform vs. Ansible : Key Differences and Comparison of Tools

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Ansible Loops : How To Use, Tutorial & Examples

Explore the concept of Ansible roles, their structure, and how we can refactor our playbooks into roles or generate them from scratch.

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Manage and orchestrate Ansible with Spacelift’s vibrant ecosystem and excellent GitOps flow. Create powerful custom workflows combining multiple IaC tools.

Ioannis is a Cloud Architect with a background in DevOps &amp; Site Reliability Engineering interested in Cloud Infrastructure, Automation, CI/CD Pipelines &amp; Containerization. In his free time, he curates a personal blog at <a href="https://devopsmadness.com" rel="noopener nofollow">devopsmadness.com</a> and <a href="https://moustakisioannis.medium.com" rel="noopener nofollow">moustakisioannis.medium.com</a>. Opinions expressed are solely his own.

Flavius Dinu

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 the introductory <a href="https://spacelift.io/blog/ansible-tutorial" target="_blank" rel="noopener">Ansible Tutorial</a> or <a href="https://spacelift.io/blog/ansible-playbooks" target="_blank" rel="noopener">Working with Ansible Playbooks</a> blog posts helpful. You can find this article&#8217;s code on this <a href="https://github.com/spacelift-io-blog-posts/Blog-Technical-Content/tree/master/ansible-variables" target="_blank" rel="nofollow noopener">repository</a> if you wish to follow along.
What we will cover:
<ol>
<li><a href="https://spacelift.io/blog/ansible-variables#what-are-ansible-variables">What are Ansible variables?</a></li>
<li><a href="https://spacelift.io/blog/ansible-variables#variable-naming-rules">Variable naming rules</a></li>
<li><a href="https://spacelift.io/blog/ansible-variables#types-of-variables-in-ansible">Types of variables in Ansible</a></li>
<li><a href="https://spacelift.io/blog/ansible-variables#simple-variables">Simple variables</a></li>
<li><a href="https://spacelift.io/blog/ansible-variables#list-dictionary--nested-variables">List, dictionary &amp; nested variables</a></li>
<li><a href="https://spacelift.io/blog/ansible-variables#special-variables">Special variables</a></li>
<li><a href="https://spacelift.io/blog/ansible-variables#registering-variables">Registering variables</a></li>
<li><a href="https://spacelift.io/blog/ansible-variables#environment-variables">Environment variables</a></li>
<li><a href="https://spacelift.io/blog/ansible-variables#how-to-share-and-reuse-ansible-variables">How to share and reuse Ansible variables?</a></li>
<li><a href="https://spacelift.io/blog/ansible-variables#variable-scope">Variable scope</a></li>
<li><a href="https://spacelift.io/blog/ansible-variables#where-to-set-ansible-variables">Where to set Ansible variables?</a></li>
<li><a href="https://spacelift.io/blog/ansible-variables#variables-precedence">Variables precedence</a></li>
<li><a href="https://spacelift.io/blog/ansible-variables#best-practices-for-managing-ansible-variables">Best practices for managing Ansible variables</a></li>
</ol>

<dfn>Ansible variables</dfn> 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.
<h3>Why are variables useful in Ansible?</h3>
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 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. Some strings are reserved for other purposes and aren’t valid variable names, such as <a href="https://docs.python.org/3/reference/lexical_analysis.html#keywords" target="_blank" rel="nofollow noopener">Python Keywords</a> or <a href="https://docs.ansible.com/ansible/latest/reference_appendices/playbooks_keywords.html#playbook-keywords" target="_blank" rel="nofollow noopener">Playbook Keywords</a>.
Apart from these, as for every programming language and configuration language, the variable names should be short and meaningful, because otherwise, you will have a hard time with debugging them, especially in a complex playbook.
Good variable names:
<ul>
<li style="font-weight: 400;" aria-level="1">web_server_port</li>
<li style="font-weight: 400;" aria-level="1">db_connection_timeout</li>
<li style="font-weight: 400;" aria-level="1">ssh_private_key</li>
<li style="font-weight: 400;" aria-level="1">max_attempts_retry</li>
</ul>
All of the above variable names make sense and are very easy to understand, even without seeing them used in the code.
Bad variable names:
<ul>
<li style="font-weight: 400;" aria-level="1">my_var – even though it is valid, you don’t understand what this is doing without seeing it in the code</li>
<li style="font-weight: 400;" aria-level="1">tm@p%$2 – this contains special characters, so it is invalid</li>
<li style="font-weight: 400;" aria-level="1">1var – this starts with a number, so it is invalid</li>
</ul>

Variables in Ansible can come from different sources and can be used in playbooks, roles, inventory files, and even within modules. 
Here are the variable types you may encounter while using Ansible:
<ul>
<li>Playbook variables – These variables are used to pass values into playbooks and roles and can be defined inline in playbooks or included in external files.</li>
<li>Task variables – These variables are specific to individual tasks within a playbook. These can override other variable types for the scope of the task in which they are defined.</li>
<li>Host variables – Specific to hosts, these variables are defined in the inventory or loaded from external files or scripts and can be used to set attributes that differ between hosts.</li>
<li>Group variables – Similar to host variables but used for a group of hosts and are defined in the inventory or separate files in the group_vars directory.</li>
<li>Inventory variables – These variables are defined in the inventory file itself and can be applied at different levels (host, group, all groups).</li>
<li>Fact variables – Gathered by Ansible from the target machines, facts are a rich set of variables (including IP addresses, operating system, disk space, etc.) that represent the current state of the system and are automatically discovered by Ansible.</li>
<li>Role variables – Defined within a role, these variables are usually part of the role&#8217;s default variables (defaults/main.yaml file) or variables intended to be set by the role user (vars/main.yaml file) and are used to enable reusable and configurable roles.</li>
<li>Extra variables – Passed to Ansible at runtime using the -e or &#8211;extra-vars command-line option. They have the highest precedence and can be used to override other variables or to pass data that might change between executions.</li>
<li>Magic variables – Special variables such as hostvars, group_names, groups, inventory_hostname, and ansible_playbook_python, provide information about the execution context and allow access to inventory data programmatically.</li>
<li>Environment variables –  Used within Ansible playbooks to access environment variables from the system running the playbook or from remote systems.</li>
</ul>

The simplest use case of variables is to define a variable name with a single value using standard <a href="https://spacelift.io/blog/yaml" target="_blank" rel="noopener">YAML syntax</a>. 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. Later, to reference the value in the task, we use <a href="https://docs.ansible.com/ansible/latest/user_guide/playbooks_templating.html" target="_blank" rel="nofollow noopener">Jinja2 syntax</a> like this &#8220;{{ username }}&#8221; 
If a variable&#8217;s value starts with curly braces, <a href="https://docs.ansible.com/ansible/latest/user_guide/playbooks_variables.html#when-to-quote-variables-a-yaml-gotcha" target="_blank" rel="nofollow noopener">we must quote the whole expression</a> to allow YAML to interpret the syntax correctly.

There are many other options to define more complex variables like lists, dictionaries, and nested structures. To create a variable with multiple values, we can use YAML lists syntax:

To reference a specific value from the list we must select the correct field. For example, to access the third value v3:

Another useful option is to store key-value pairs in variables as dictionaries. For example:

Similarly, to reference the third field from the dictionary, use the bracket or dot notation:

Note that the bracket notation is preferred as you might encounter problems using the dot notation in special cases.
Sometimes, we have to create or use nested variable structures. For example, facts are nested data structures. We have to use a bracket or dot notation to reference nested variables.

Ansible special variables are a set of predefined variables that contain information about the system data, inventory, or execution context inside an Ansible playbook or role. These include magic variables, connection variables, and facts. The names of these variables are reserved. 
<h3>Magic variables</h3>
<a href="https://docs.ansible.com/ansible/latest/reference_appendices/special_variables.html#magic-variables" target="_blank" rel="nofollow noopener">Magic variables</a> are automatically created by Ansible and cannot be changed by a user. These variables will always reflect the internal state of Ansible, so they can be used only as they are.

In the above playbook, we are defining a playbook that uses the inventory_hostname magic variable. We are using this variable to get the name of the host on which Ansible runs and print a message with it as shown below.

Apart from inventory_hostname, some other essential magic variables are:
<ul>
<li style="font-weight: 400;" aria-level="1">hostvars → leveraged for getting information about other hosts in the inventory, including any variables that are associated with them. 
</li>
<li style="font-weight: 400;" aria-level="1">play_hosts → lists all the hosts that are targeted by the current play.</li>
<li style="font-weight: 400;" aria-level="1">group_names → contains a list of groups names to which the current host belongs in the inventory.</li>
<li style="font-weight: 400;" aria-level="1">groups → key/value pair of all the groups in the inventory with all the hosts that belong to each group.</li>
</ul>
<h3>Ansible facts</h3>
<a href="https://docs.ansible.com/ansible/latest/reference_appendices/special_variables.html#facts" target="_blank" rel="nofollow noopener">Ansible facts</a> are leveraged for getting system and hardware facts gathered about the current host during playbook execution. This data is often utilized for creating dynamic inventories, templating, or making decisions based on host-specific attributes. The gathered facts can be accessed using the ansible_facts variable, allowing you to reference specific information like the operating system, IP address, or CPU architecture.
To collect facts about a specific host, you can run the following command:

Also, you can add the <code>gather_facts: yes</code> option to your playbook to ensure facts are collected after executing tasks.
With Ansible facts, you have the option to filter for specific facts like os or even the IP address. This can be done with:

<h4>What is the difference between variables and facts in Ansible?</h4>
Variables are defined by the user, whereas facts are discovered directly from the target machines. While variables are used for playbook and role customization, facts provide insight into the current state of the target machines based on real-time system information. Variables can be modified and even overridden in various parts of playbooks and roles and even on the run-time, while facts are considered to be read-only system snapshots.
<h3>Connection variables</h3>
<a href="https://docs.ansible.com/ansible/latest/reference_appendices/special_variables.html#connection-variables" target="_blank" rel="nofollow noopener">Connection variables</a> are used to define how the machine that runs Ansible connects to remote hosts during the execution of tasks and playbooks. These variables provide flexibility in managing various connection types, authentication methods, and host-specific configurations.

In the above example, we are using the connection variable, to show the connection type on a run as shown below:

During our plays, we might find it handy to utilize the output of a task as a variable that we can use in the following tasks. We can use the keyword register to create our own custom variables from task output.

In the above example, we register the output of the command find /etc/hosts, and we showcase how we can use the variable in the next task by printing its value.

image3-12

Registering Variables

A powerful pattern is to combine registered variables with conditionals to create tasks that will only be executed when certain custom conditions are true.

Here, we registered in the variable hosts_contents the contents of /etc/hosts file, and we execute the second task only if the file contains the word localhost.

image2-14

Registered Variables localhost

Since registered variables are stored in memory, it’s not possible to use them in future plays, and they are only available for the current playbook run.

<ul>
<li><a href="https://spacelift.io/blog/using-terraform-and-ansible-together" target="_blank" rel="noopener">Using Terraform &amp; Ansible together</a></li>
<li><a href="https://spacelift.io/blog/ansible-use-cases" target="_blank" rel="noopener">7 Ansible use cases for management &amp; automation</a></li>
<li><a href="https://spacelift.io/blog/ansible-best-practices" target="_blank" rel="noopener"><span data-sheets-value="{&quot;1&quot;:2,&quot;2&quot;:&quot;44 Ansible Best Practices to Follow [Tips &amp; Tricks]&quot;}" data-sheets-userformat="{&quot;2&quot;:513,&quot;3&quot;:{&quot;1&quot;:0},&quot;12&quot;:0}">44 Ansible best practices to follow</a></li>
</ul>

Environment variables are a powerful way to influence the behavior of playbooks and tasks by passing external values into the Ansible runtime environment. These can be system environment variables available where Ansible is executed or on the managed nodes.
You should be cautious when using environment variables for sensitive data, as their values might be logged or exposed in debugging output, and relying on them will affect the overall portability and reusability of your playbook. Setting environment variables within tasks or plays will override those of the same name in the system environment for the duration of the task or play execution.

When we want to reuse and share variables, we can leverage YAML anchors and aliases. They provide us with great flexibility in handling shared variables and help us reduce the repetition of data. Learn more in our <a href="https://spacelift.io/blog/yaml" target="_blank" rel="noopener">Complete YAML Guide</a>.
Anchors are defined with &amp;, and then referenced with an alias denoted with *. Let’s go and check a hands-on example in a playbook.

Here, since some options are shared between users, instead of rewriting the same values, we share the common ones with the anchor &amp;user_info. For every subsequent user declaration, we use the alias *user_info to avoid repeating ourselves as much as possible.
The values for state and create_home are the same for all the users, while name and groups are replaced using the merge operator &lt;&lt;. 
Similarly, we reuse the user_groups declaration in the definition of the user_info anchor. This way, we don&#8217;t have to type the same groups again for user_2 while we still have the flexibility to override the groups, as we do for user_3. 
The result is that user_1 and user_2 are added to groups devs and support, while user_3 is added only to the support group.

image4-11

Share variables with YAML anchors and aliases

Ansible provides many options on setting variables, and the ultimate decision on where to set them lies with us based on the scope we would like them to have. Conceptually, there are three main options available for scoping variables. 
First, we have the global scope where the values are set for all hosts. This can be defined by the Ansible configuration, environment variables, and command line. 
We set values for a particular host or group of hosts using the host scope. For example, there is an option to define some variables per host in the inventory file.
Lastly, we have the play scope, where values are set for all hosts in the context of a play. An example would be the vars section we have seen in previous examples in each playbook.

Variables can be defined with Ansible in many different places. There are options to set variables in playbooks, roles, inventory, var files, and command line. Let’s go and explore some of these options. 
<h3>1. Vars block</h3>
As we have previously seen, the most straightforward way is to define variables in a play with the vars section.

<h3>2. Inventory files</h3>
Another option is to define variables in the inventory file. We can set variables per host or set shared variables for groups. This example defines a different ansible user to connect for each host as a host variable and the same HTTP port for all web servers as a group variable.

To better organize our variables, we could gather them in separate host and group variables files. In the same directory where we keep our <a href="https://spacelift.io/blog/ansible-variables" target="_blank" rel="noopener">Ansible inventory</a> or playbook files, we can create two folders named group_vars and host_vars that would contain our variable files. For example:

<h3>3. Custom var files</h3>
Variables can also be set in custom var files. Let’s check an example that uses variables from an external file and the group_vars and host_vars directories.

The vars/variables.yml file:

The group_vars/webservers file:

The host_vars/host1 file:

The host_vars/host2 file:

The inventory file contains a group named webservers that includes our two hosts, host1 and host2:

If we run this playbook, we notice the same value is used in both hosts for the group variable http_port but a different one for the host variable app_version.

image1-14

Variable setting options & precedence

A good use case for having separate variables files is that you can keep in them sensitive values without storing them in playbooks or source control systems.
Occasionally we might find it helpful to define or override variables at runtime by passing them at the command line with &#8211;extra-vars or &#8211;e argument. For example:

Since variables can be set in multiple places, Ansible applies variable precedence to select the variable value according to some hierarchy. The general rule is that variables defined with a more explicit scope have higher priority.
For example, role defaults are overridden by mostly every other option. Variables are also flattened to each host before each play, so all group and hosts variables are merged. Host variables have higher priority than group variables. 
Explicit variable definitions like the vars directory or an include_vars task override variables from the inventory. Finally, extra vars defined at runtime always win precedence. For a complete list of options and their hierarchy, look at the official documentation <a href="https://docs.ansible.com/ansible/latest/user_guide/playbooks_variables.html#understanding-variable-precedence" target="_blank" rel="nofollow noopener">Understanding variable precedence</a>.

Since Ansible provides a plethora of options to define variables, it might be a bit confusing to figure out the best way and place to set them. Let’s go and check some common &amp; best practices around setting variables that might help us better organize our Ansible projects.
<ul>
<li style="font-weight: 400;" aria-level="1">Always give descriptive and clear names to your variables. Taking a moment to properly think about how to name variables always pays off long-term.</li>
<li style="font-weight: 400;" aria-level="1">If there are default values for common variables, set them in group_vars/all</li>
<li style="font-weight: 400;" aria-level="1">Prefer setting group and host vars in group_vars and host_vars directories instead of in the inventory file.</li>
<li style="font-weight: 400;" aria-level="1">If variables related to geography or behavior are tied to a specific group, prefer to set them as group variables.</li>
<li style="font-weight: 400;" aria-level="1">If you are using roles, always set default role variables in roles/your_role/defaults/main.yml</li>
<li style="font-weight: 400;" aria-level="1">When you call roles, pass variables that you wish to override as parameters to make your plays easier to read.</li>
</ul>

<ul>
<li style="font-weight: 400;" aria-level="1">You can always use &#8211;extra-vars or &#8211;e to override every other option.</li>
<li style="font-weight: 400;" aria-level="1">Don’t store sensitive variables in your source code repository in plain text. You can leverage <a href="https://spacelift.io/blog/ansible-vault#encrypting-sensitive-info-with-ansible-vault" target="_blank" rel="noopener">Ansible Vault</a> in these cases.</li>
</ul>
In general, try to keep variable usage as simple as possible. You don’t have to use all the existing options and spread variables definition all over the place because that makes debugging your Ansible projects difficult. Try to find a structure that suits your needs best and stick to it! 
To learn more, check out the <a href="https://spacelift.io/blog/ansible-best-practices" target="_blank" rel="noopener">44 Ansible Best Practices to Follow</a>.

In this article, we deep-dived into Ansible Variables and saw how we can define and use them in playbooks. Moreover, we explored different options for sharing, setting, and referencing them, along with some guidelines and best practices to make our Ansible journey easier.
Thank you for reading, and I hope you enjoyed this “Ansible Variables” article as much as I did.

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