In the era of the cloud, we can create and destroy entire data centers' worth of infrastructure with a few clicks in a web console. But clicking around in a UI is not a scalable, repeatable, or safe way to manage your production environment. A small misconfiguration can lead to downtime or a security breach.

The modern solution to this problem is Infrastructure as Code (IaC).

What is Infrastructure as Code?

Infrastructure as Code is the practice of managing and provisioning your IT infrastructure (like virtual machines, networks, and databases) through machine-readable definition files, rather than through physical hardware configuration or interactive configuration tools. In simple terms, you write code to manage your infrastructure.

This code is then stored in a version control system (like Git), just like your application code. This allows you to apply the same DevOps practices to your infrastructure that you apply to your software: versioning, code reviews, and automated testing and deployment.

The Problem: Manual Configuration and Configuration Drift

Before IaC, system administrators would manually set up and configure servers. This process was:

• Slow: It could take days or weeks to provision a new server.
• Error-Prone: Humans make mistakes. A small, manual error could lead to major problems.
• Inconsistent: Each server could be slightly different, leading to a problem known as configuration drift, where the configuration of your production environment slowly drifts away from the original baseline. This makes it hard to reproduce issues and even harder to recover from a disaster.

The IaC Solution: Automation and Repeatability

IaC solves these problems by treating infrastructure configuration as a software development problem.

Key benefits of IaC include:

• Speed and Automation: You can spin up an entire production environment in minutes by running a script. This allows you to create and destroy environments for development, testing, and production on demand.
• Consistency: Because your infrastructure is defined in code, you can be sure that every environment you create is identical. This eliminates configuration drift.
• Version Control: By storing your infrastructure code in Git, you get a full audit trail of every change that has ever been made. You can see who changed what, when, and why. If a change causes a problem, you can easily revert to a previous, known-good configuration.
• Collaboration: With your infrastructure defined as code, your team can collaborate on it using the same tools and processes they use for application code, like pull requests and code reviews.

Declarative vs. Imperative Approaches

There are two main approaches to writing IaC:

1. Declarative (The "What"): You define the desired state of your system, and the IaC tool is responsible for figuring out how to achieve that state. You tell it what you want, not how to do it. This is the most common approach.

   • Example Tool: Terraform. You write a file that says, "I want one virtual machine of this size and one database of this size," and Terraform makes the necessary API calls to create them.

2. Imperative (The "How"): You write scripts that specify the exact steps to take to get to the desired state. You are responsible for the logic of how to create and configure the resources.

   • Example Tool: A custom script using the AWS SDK. You would write code that says, "First, call the CreateVM API, then wait for it to be ready, then call the CreateDatabase API."

For most use cases, the declarative approach is preferred as it is simpler and less error-prone.

Conclusion

Infrastructure as Code is a fundamental practice of modern DevOps and cloud computing. It brings the power of software development best practices to infrastructure management, enabling teams to build and manage their infrastructure in a way that is fast, reliable, and repeatable. By codifying and versioning your infrastructure, you create a system that is more transparent, more consistent, and easier to manage at scale.