Infrastructure as code, also referred to as IaC, is a type of IT setup wherein developers or operations teams automatically manage and provision the technology stack for an application through software, rather than using a manual process to configure discrete hardware devices and operating systems. Infrastructure as code is sometimes referred to as programmable or software-defined infrastructure.
Versatile and Adaptive Provisioning
Infrastructure as code uses higher-level or descriptive language to code more versatile and adaptive provisioning and deployment processes. For example, infrastructure-as-code capabilities included with Ansible can install Apache web server, verify that it is running properly, create user accounts and passwords, etc.
The code-based infrastructure automation process closely resembles software design practices in which developers carefully control code versions, test iterations, and limit deployment until the software is proven and approved for production. Software developers can use code to provision and deploy servers and applications, rather than rely on system administrators. A developer might write an infrastructure-as-code process to provision and deploy a new application for QA or experimental deployment before operations takes over for live deployment in production. With the infrastructure setup written as code, it can go through the same version control, automated testing, and other steps of a continuous integration and continuous delivery (CI/CD) pipeline that developers use for application code.
Infrastructure-as-code tools configure and automate the provisioning of infrastructure. These tools can automatically execute the deployment of infrastructure, such as servers, with orchestration functionality. They also can configure and monitor previously provisioned systems.
Infrastructure-as-code tools enforce the setup from the template via push or pull methods. In the push method, a centralized server sends the desired configuration to a specific system or systems. The pull method is initiated by a request to a centralized server from a system or systems in the infrastructure. These tools should also be able to roll back changes to the code, as in the event of unexpected problems from an update.
Examples of infrastructure-as-code tools include AWS CloudFormation, Red Hat Ansible, Chef, Puppet, SaltStack and HashiCorp Terraform. Some tools rely on a domain-specific language, while others use a standard template format, such as YAML and JSON. When selecting a tool, organizations should consider the target deployment. For example, AWS CloudFormation is designed to provision and manage infrastructure on AWS, and it works with other AWS offerings. Alternatively, Chef works with on-premises servers and multiple cloud provider infrastructure-as-a-service offerings.