Terraformer — Reverse-Engineer Existing Cloud Infrastructure to Terraform

What it is

Terraformer is a CLI tool originally developed at Google that reads existing cloud infrastructure and generates corresponding Terraform HCL configuration files and state files. It supports AWS, GCP, Azure, and over 30 additional providers. The primary use case is adopting infrastructure-as-code on brownfield environments where cloud resources were created manually or through other tools.

Terraformer targets DevOps engineers and platform teams who need to bring existing cloud infrastructure under Terraform management without manually writing HCL for every resource.

How it saves time or tokens

Manually writing Terraform configurations for existing infrastructure is tedious and error-prone. A typical AWS account might have hundreds of resources across VPCs, security groups, EC2 instances, RDS databases, and IAM policies. Terraformer scans all resources for a given provider and service, then generates the HCL files and imports the state in one command. This turns weeks of manual work into minutes.

For AI-assisted infrastructure management, Terraformer's output provides a machine-readable snapshot of your cloud infrastructure that an LLM can analyze for cost optimization, security review, or architecture documentation.

How to use

1. Install Terraformer: download the binary from GitHub releases or use brew install terraformer on macOS.
2. Ensure you have the corresponding Terraform provider installed and valid cloud credentials configured (AWS CLI, gcloud, etc.).
3. Run Terraformer to import resources: terraformer import aws --resources=vpc,subnet,sg --regions=us-east-1. The generated HCL and state files appear in a generated/ directory.

Example

# Import all AWS VPC resources in us-east-1
terraformer import aws \
  --resources=vpc,subnet,security_group,route_table \
  --regions=us-east-1 \
  --profile=production

# Output structure:
# generated/
#   aws/
#     vpc/
#       vpc.tf
#       terraform.tfstate
#     subnet/
#       subnet.tf
#       terraform.tfstate

Each resource type gets its own directory with the generated HCL and a corresponding state file.

Related on TokRepo

• DevOps tools — Infrastructure and deployment tools
• Automation tools — Infrastructure automation solutions

Common pitfalls

• Terraformer generates one state file per resource type. You likely need to reorganize the generated code and merge state files into your team's existing Terraform structure.
• Generated HCL uses hard-coded IDs and ARNs. You should refactor the output to use variables, data sources, and module references for maintainable code.
• Some resource types have complex dependencies that Terraformer may not fully capture. Review the generated code for missing cross-references between resources.