What is Infrastructure as Code (IaC)?

Managing and provisioning IT infrastructure through machine-readable definition files instead of manual configuration, so that applying the code puts the infrastructure into the described state.

With IaC you write down how servers, networks and services should be configured in files. A tool then applies that code to the real infrastructure and makes sure it actually is in that state. The benefits are more efficiency and more consistency.

Two properties of the language matter:

• Machine-readable, so a tool can apply it.
• Human-readable, so people can understand the current state and change it easily.

Ansible playbooks are an example: YAML files that a human can read and that Ansible can execute.

Go deeper:

• What is Infrastructure as Code? (Red Hat) — declarative vs imperative IaC, reducing drift, immutable infrastructure.
• What is Infrastructure as Code? (IBM Technology) — short lightboard explainer of the idea and its benefits.
• Infrastructure as code (Wikipedia) — definition, history and the main approaches and tools.