Introduction to Infrastructure as Code & Terraform

What is Infrastructure as Code (IaC)?

Infrastructure as Code (IaC) is the process of managing and provisioning computing infrastructure and resources through machine-readable definition files, rather than physical hardware configuration or interactive configuration tools.

Why IaC?

• Speed and Simplicity: Spin up an entire architecture just by running a script.
• Configuration Consistency: Standardize setup and eliminate configuration drift.
• Risk Minimization: Reduce human error that occurs during manual provisioning.
• Version Control: Manage infrastructure using the same tools as application code (e.g., Git).

Declarative vs Imperative

• Imperative: Focuses on how to achieve the desired state (e.g., “Run this command to create a VM, then run this to attach a disk”). Bash scripts and CLI commands are typically imperative.
• Declarative: Focuses on what the desired state should be (e.g., “I want a VM with this attached disk”). The tool figures out how to achieve it. Terraform is a declarative tool.

Introducing Terraform

Terraform is an open-source IaC tool created by HashiCorp. It allows you to define both cloud and on-premise resources in human-readable configuration files that you can version, reuse, and share.

The Core Workflow

1. Write: Author infrastructure as code in .tf files.
2. Init (terraform init): Initialize the working directory containing Terraform configuration files. This downloads necessary providers.
3. Plan (terraform plan): Generate an execution plan describing what Terraform will do to achieve the desired state.
4. Apply (terraform apply): Execute the actions proposed in the plan.