Ansible vs. Terraform in networks: similarities and differences

Ansible and Terraform are open-source automation tools well-known to DevOps teams. They can be used to perform similar tasks and share many features. Both of them have devoted communities and are used across organizations worldwide. However, they differ in many ways. The most significant difference is that Ansible is a configuration management tool, and Terraform is an infrastructure as code platform. While they excel in different areas, many professionals use them to complement each other.

This article highlights similarities between these tools, explores their differences, and provides use cases for Terraform and Ansible. 

Ansible

Ansible is an open-source automation tool with a product version provided by Red Hat. Its focus is configuration management. It can be used for deployment, configuration, and orchestration.

Ansible doesn’t require the installation of any software or agent on the managed nodes as it is agentless. It has modules working in both declarative and procedural programming approaches. Ansible is decentralized, using your existing OS credentials to control access to remote machines. It can also be integrated with LDAP, Kerberos, and other centralized systems. 

Ansible is a popular choice mainly because of its focus on simplicity and ease of use. It uses YAML syntax, which is easier to understand than other formats, such as XML or JSON, according to the Ansible documentation      .

Terraform

Terraform is an infrastructure as code tool provided by HashiCorp. It helps in infrastructure automation in various cloud and on-prem environments. It aims to provide easy-to-understand configuration files that can be versioned, reused, and shared. 

Terraform uses HCL - HashiCorp Configuration Language, which is human- and machine-friendly. Like Ansible, Terraform promises to be easy to use by network administrators, IT managers, and other professionals. It is a command-line-only tool, but it’s easily integrated with the popular public clouds. It is declarative - it strictly follows the infrastructure as code approach.

Terraform state is another crucial concept in the Terraform tool. It refers to the current and saved information about the resources and their configurations managed by Terraform for a specific infrastructure project. Terraform uses this state data to keep track of the resources it has created and manage their ongoing state.Terraform uses state data to understand what resources are part of your infrastructure, their current configuration, and their dependencies.

Common use cases for Terraform include Kubernetes management and multi-cloud infrastructure provisioning. It’s primarily used in public clouds, data centers, and SDN environments. 

One of Terraform’s significant advantages is that it is platform agnostic, and you can use it to manage a complex infrastructure across architectures. It can also be easily integrated with CI/CD pipelines. 

Terraform is nowadays also more and more used for configuration as code solutions, allowing not only for resource deployment but also for resource configuration, still benefiting from the Terraform state concept and Terraform declarative nature. 

Some users find that HCL has quite a learning curve, and debugging using Terraform is challenging. 

Ansible and Terraform: similarities

While these tools are quite different, they also share many similarities. Firstly, both of these products state that they focus on ease of use, which their users commonly admit in both cases. They both have command-line-only, open-source versions and product versions with enterprise features, like maintenance and support. They are agentless and can be used to solve similar use cases, such as setting up a new cloud infrastructure or carrying out remote commands for a new virtual machine. They can also work together, as they have plugins to cooperate with each other. 

Both of these tools are commonly used in network automation services.

A significant advantage shared by these tools is that there are many resources to help you use them. Ansible has a rich collection of pre-built modules and a vast community-created playbook library for various use cases. Terraform offers a wide range of provider plugins to interact with different cloud providers and services and a growing ecosystem of modules shared by the community.

Ansible vs. Terraform - the differences

They are different tools at the core - Ansible is a configuration management automation tool, and Terraform is an infrastructure as code tool. The difference between those is that configuration management tools focus on automating the configuration of resources, and IaC tools focus on resources’ provisioning. They are often compared because they can be used for the same use cases and perform mostly the same tasks. It’s important to note their differences because sometimes one might be a better choice than the other. Below, you can find a detailed list of their differences. 

Key features of Ansible and Terraform 

Let’s start with an overview of the key features to understand the primary differences between these tools. 

Comparison between Ansible and Terraform

Procedural vs. declarative

The first difference is that Terraform takes a declarative approach to infrastructure. That means the user creates a declarative file describing precisely what they want their end-state cloud footprint to look like, and Terraform always follows this file. That way, you have a single source of truth defining the end result. This approach works best for smaller environments because it becomes too complex with scaled infrastructure. Its biggest pro is easy deprovisioning, which lets you quickly tear down your resources, test something new, and so on.

Ansible uses an opposite approach: procedural. That means the tool is provided with a task list that is reiterated over each resource. This approach gives you better control and understanding of what the tool is doing and, therefore, easier troubleshooting. While this approach is great, sometimes it makes teardowns and deprovisioning cloud resources difficult and time consuming. You need to do it in a specific order. To overcome this challenge, Ansible allows you to call for Terraform or other declarative approach tools. 

Deletion of resources with Terraform is much easier than with Ansible. The “Terraform Destroy” command simply destroys all resources deployed thanks to Terraform state, while with Ansible, the deletion of the configuration has to be defined in the same manner as the configuration itself, which requires more work from an engineer. 

Orchestration vs. configuration management

Orchestration and configuration management are significant concepts of the DevOps methodology. Ansible is a configuration management tool that solves issues locally instead of replacing the entire system. This tool configures each action and instrument individually and ensures that they run smoothly without error, which, as a result, keeps the system healthy. While Ansible is a configuration management tool, it can also handle many orchestration tasks.

Orchestration involves the continuous maintenance of a system in its intended state. Terraform excels at achieving and sustaining the desired shape of infrastructure, making it a great choice for various orchestration tasks. With Terraform, you can effortlessly define and provision various infrastructure resources, making it well suited for scenarios where maintaining a consistent state is essential.

State Management

For Terraform operations, state management is key. This tool provides life cycle management for resources, and states are responsible for providing and monitoring configuration changes. Each configuration of an infrastructure resource is listed in the state file. These state files can then be used to import resources existing under Terraform management from external infrastructure. The state files also contain much data that can be queried to gain insights into infrastructure components and their characteristics. 

Ansible does not provide state files due to its procedural approach. It doesn’t have to list configurations because it relies on the task list described in the “Procedural vs. declarative” section above. 

Modules

In Terraform, modules allow the use and reuse of certain resources, as necessary. They serve as containers for resources grouped by a developer. The modules have input and output variables. The input variable accepts values from a calling module, and the output variable returns data to the calling module—modules calling each other speed up configurations. Users can access and discover modules from a centralized repository called the Terraform Registry. There is a public version available, which contains services that support API interactions for exposing and managing particular resources and community-sourced modules, and a private version, which enterprises use to store their internal modules. 

In Ansible, modules serve as models for the required system state. For example, if you want all endpoints to have a specific version of some software installed, Ansible’s modules will determine whether this state is true for all nodes. For the nodes with an older version, Ansible follows the steps to achieve the desired state, which in this case is to update the software. Each module of Ansible is prescribed a specific task (such as updating the software). If you want to automate a certain process, you need to find a module that best fits this process and configure it accordingly. Users can share Ansible modules by submitting them to the Ansible project.

Use cases compared

The best way to understand the differences between Ansible and Terraform is to learn about the use cases for each tool. Thanks to their unique features and characteristics, they excel in various fields.

Use cases for Ansible include:

• Configuration management

  Ansible can automate most configuration management tasks, including package installation, software configuration, file management, and user management.

• Application deployment

  Ansible is well suited for automating the deployment of applications and services on servers. It can handle tasks like deploying web applications, databases, and middleware

• Network operations automation

  You can use Ansible for network configuration, network upgrades, and more.

• Provisioning

  Ansible can be used to provision cloud platforms, virtualized hosts and hypervisors, applications, network devices, and bare-metal servers.

• Compliance

  You can use Ansible to enforce policies ensuring a common experience across public clouds or shut down instances out of compliance. 

• Cloud operations

  Ansible can be used to automate Day 2 operations in cloud infrastructure, such as application deployments, network devices management, and more.

• Cloud migration

  Ansible is useful in migrations from on-prem to a public cloud infrastructure.

• Automated troubleshooting

  When you become well acquainted with automation, you can introduce event-driven architecture, which results in faster response to accidents. 

• Continuous integration and continuous deployment (CI/CD)

  Ansible can be integrated into CI/CD pipelines to automate the deployment and configuration of application environments, making it easier to achieve consistency and reliability in deployments.

Terraform's use cases are:

• Infrastructure provisioning with an infrastructure as code approach

  Terraform's primary use case is provisioning and managing infrastructure resources, including virtual machines, networks, storage, and cloud services. It is excellent for creating, updating, and destroying infrastructure components in a consistent and repeatable manner.

• Multi-cloud and hybrid cloud

  Terraform can be used to manage infrastructure across multiple cloud providers or in hybrid cloud environments. It abstracts the differences between cloud APIs, allowing you to define infrastructure in a provider-agnostic way.

• Resources configuration / configuration as code

  Thanks to various providers, it is possible to configure different resources with Terraform and still benefit from the Terraform state. Merging that approach with infrastructure as code creates a unified method of resource management.

If you're looking for more information about Terraform, check out our previous article: Network automation tools comparison in code examples: Terraform, Ansible, and Python SDK.

Which one should you choose?

If you’re choosing between Ansible and Terraform, you should first determine what your expectations are and what you need from the chosen tool. While these tools can perform each other’s tasks, they do so in a limited and often time-consuming manner. It’s best to prioritize your requirements and choose the one that is more aligned with your needs and maybe, if necessary, go for both. 

Ansible is a better fit for configuration management. It is easily integrated with network operations. It’s procedural, so it’s easily adapted by network teams. However, it is stateless and procedural so the user needs to manage these aspects outside of Ansible. Like Terraform, it allows the creation of resources, but because it’s procedural and not declarative, it makes it more difficult over a longer time perspective. 

Terraform excels at infrastructure provisioning across multiple cloud platforms and containerized solutions within a cloud platform. Because it is declarative and keeps the state, it’s the best choice for resource provisioning. It uses providers to configure resources, so it ensures configuration management benefits from all of the Terraform advantages. However, Terraform's support sometimes falls short compared to Ansible’s. Resource configuration also turns out to be more complex to build than in Ansible. Terraform is compatible with many providers, including Docker, which makes up for Terraform’s lack of configuration management capabilities. However, to perform better, it might need other configuration management tools.

Conclusion

Terraform and Ansible are both powerful tools that can significantly speed up your workflow. Each of them is unique and works best for its own purpose. While they can perform each other’s tasks, it is usually not the optimal solution.

While deciding which one to choose, it’s good to also consider the option of using both of them simultaneously. In that case, you harness the power of both of these tools. In conclusion, the decision depends on your infrastructure’s needs.