Infrastructure as Code (IaC)
Infrastructure as Code (IaC) is the practice of defining and managing IT infrastructure – servers, networks, databases – through machine-readable configuration files instead of manual processes.
In the modern cloud world organizations manage hundreds or thousands of infrastructure resources – VMs, networks, databases, load balancers and more. Infrastructure as Code (IaC) replaces manual configuration with declarative or imperative code files that are versioned, tested and deployed automatically. Infrastructure is treated like application code: reproducible, traceable and less error-prone. IaC is a cornerstone of modern DevOps and essential for cloud-native architectures.
What is Infrastructure as Code (IaC)?
Infrastructure as Code (IaC) means defining, provisioning and managing IT infrastructure through code files instead of manual setup via GUIs or CLI. IaC tools such as Terraform (HashiCorp), AWS CloudFormation, Pulumi, Ansible or OpenTofu read configuration files and bring the actual infrastructure into the desired state. A distinction is made between declarative IaC (desired end state is described, the tool figures out changes – e.g. Terraform, CloudFormation) and imperative IaC (concrete steps are defined – e.g. Ansible playbooks, Bash scripts). IaC files are versioned in Git so every change is traceable and can be reviewed via pull requests. Concepts like state management, drift detection and plan/apply workflows ensure the real infrastructure matches the code. IaC also allows creating identical environments (dev, staging, production) from the same codebase and is the basis for GitOps workflows.
How does Infrastructure as Code (IaC) work?
A DevOps engineer defines the desired infrastructure in config files – e.g. HCL (Terraform), YAML (CloudFormation, Ansible) or TypeScript (Pulumi). In Terraform a .tf file declaratively describes which resources should exist (VMs, networks, DNS). The command terraform plan compares desired state with current state and shows planned changes. terraform apply executes the changes and updates the state file. Changes are versioned in Git: a developer opens a pull request, colleagues review the infrastructure changes, and after merge a CI/CD pipeline deploys them. Drift detection finds when manual changes have diverged the infrastructure from the code.
Practical Examples
Terraform project: A company defines its entire AWS infrastructure (VPCs, EC2, RDS, S3) in Terraform modules and deploys changes via a GitHub Actions pipeline.
Kubernetes cluster via IaC: A DevOps team creates GKE clusters with Terraform and configures workloads with Helm charts and ArgoCD as GitOps tool.
Multi-cloud setup: A financial services provider uses Terraform to provision identical infrastructure on AWS and Google Cloud – for disaster recovery and vendor diversification.
Ansible configuration: A sysadmin automates configuration of 200 Linux servers (packages, users, firewall rules) with Ansible playbooks instead of manual SSH.
Ephemeral environments: For each pull request a CI pipeline creates a full preview environment with Terraform – after merge it is torn down again.
Typical Use Cases
Cloud infrastructure management: Automated provisioning and management of cloud resources on AWS, Azure and Google Cloud
Environment consistency: Create identical dev, staging and production environments from the same codebase
Disaster recovery: Entire infrastructure can be rebuilt in another region in minutes instead of days after an outage
Compliance and audit: Every infrastructure change is documented in Git – ideal for audits and regulatory requirements
Team scaling: Infrastructure knowledge lives in code, not only in people's heads – new team members can contribute immediately
Advantages and Disadvantages
Advantages
- Reproducibility: Infrastructure is created deterministically from code – no manual drift between environments
- Versioning and audit trail: All changes are traceable in Git – who changed what, when and why
- Speed: New environments or regions are provisioned in minutes instead of days
- Fewer errors: Manual configuration is error-prone – IaC reduces human error through automation and code review
- Reusability: Terraform modules and Ansible roles encapsulate proven patterns for use across teams
Disadvantages
- Learning curve: Tools like Terraform, HCL syntax and state management require specialized knowledge
- State management: Terraform state files must be stored securely and protected from concurrent access (e.g. remote state in S3 with locking)
- Initial effort: Migrating existing manually configured infrastructure into IaC (import) is time-consuming
- Drift: Manual changes outside the IaC workflow cause drift that must be detected and resolved
Frequently Asked Questions about Infrastructure as Code (IaC)
Which IaC tool should I use?
What is the difference between IaC and configuration management?
How secure is Infrastructure as Code?
Related Terms
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