infrastructure-terraform

Infrastructure Terraform

Expert knowledge for Infrastructure as Code using Terraform with focus on declarative HCL, state management, and resilient infrastructure.

When to Use This Skill

Use this skill when...	Use a tfc-* sibling instead when...
Writing or modifying Terraform HCL configuration locally	Inspecting Terraform Cloud run state via API (tfc-run-status)
Running terraform init/plan/apply/destroy against a backend	Reading TFC plan/apply log streams (tfc-run-logs)
Designing module structure, providers, or remote backends	Analyzing structured plan JSON from a TFC run (tfc-plan-json)
Debugging local state, drift, or import workflows	Listing or filtering TFC run history (tfc-list-runs, tfc-workspace-runs)

Core Expertise

Terraform & IaC

• Declarative Infrastructure: Clean, modular, and reusable HCL code
• State Management: Protecting and managing Terraform state with remote backends
• Providers & Modules: Leveraging community and custom providers/modules
• Execution Lifecycle: Mastering the plan -> review -> apply workflow

Infrastructure Provisioning Process

1. Plan First: Always generate terraform plan and review carefully before changes
2. Modularize: Break down infrastructure into reusable and composable modules
3. Secure State: Use remote backends with locking to protect state file
4. Parameterize: Use variables and outputs for flexible and configurable infrastructure
5. Destroy with Caution: Double-check plan before running terraform destroy

Essential Commands

# Core workflow
terraform init                   # Initialize working directory
terraform plan                   # Generate execution plan
terraform apply                  # Apply changes
terraform destroy               # Destroy infrastructure

# State management
terraform state list            # List all resources
terraform state show <resource> # Show specific resource
terraform state pull > backup.tfstate  # Backup state

# Validation and formatting
terraform validate              # Validate configuration
terraform fmt -recursive        # Format all files recursively
terraform fmt path/to/dir       # Format specific directory
terraform graph | dot -Tsvg > graph.svg  # Dependency graph

# Working with directories (use -chdir to stay in repo root)
terraform -chdir=gcp fmt        # Format files in gcp/ directory
terraform -chdir=gcp validate   # Validate gcp/ configuration
terraform -chdir=gcp plan       # Plan from specific directory
terraform -chdir=modules/vpc init  # Init module directory

# Debugging
export TF_LOG=DEBUG             # Enable debug logging
terraform plan -out=tfplan      # Save plan for review
terraform show tfplan           # View saved plan

Best Practices

Module Structure

module "vpc" {
  source  = "./modules/vpc"
  version = "1.0.0"

  vpc_cidr = var.vpc_cidr
  environment = var.environment
}

output "vpc_id" {
  value = module.vpc.vpc_id
}

Variable Configuration

variable "environment" {
  description = "Environment name"
  type        = string
  validation {
    condition     = contains(["dev", "staging", "prod"], var.environment)
    error_message = "Environment must be dev, staging, or prod."
  }
}

Remote State Backend

terraform {
  backend "s3" {
    bucket         = "my-terraform-state"
    key            = "prod/terraform.tfstate"
    region         = "us-east-1"
    encrypt        = true
    dynamodb_table = "terraform-locks"
  }
}

Provider Configuration

terraform {
  required_providers {
    aws = {
      source  = "hashicorp/aws"
      version = "~> 5.0"
    }
  }
  required_version = ">= 1.5"
}

Key Debugging Techniques

State Debugging

# State inspection
terraform state list
terraform state show aws_instance.web

# State recovery
terraform refresh
terraform plan -refresh-only
terraform import aws_instance.existing i-1234567890

Error Resolution

# Provider errors
terraform init -upgrade
terraform init -reconfigure

# Resource conflicts
terraform taint aws_instance.broken
terraform apply -target=aws_instance.web

Agentic Optimizations

Context	Command
Format directory	terraform -chdir=path/to/dir fmt
Check format (CI)	terraform fmt -check -recursive
Validate config	terraform -chdir=path/to/dir validate
Compact plan	terraform plan -compact-warnings
JSON plan output	terraform plan -out=plan.tfplan && terraform show -json plan.tfplan
List resources	terraform state list

Quick Reference

Flag	Description
-chdir=DIR	Change to DIR before running command
-recursive	Process directories recursively
-check	Check formatting without changes (CI)
-compact-warnings	Show warnings in compact form
-json	Output in JSON format
-out=FILE	Save plan to file
-target=RESOURCE	Target specific resource
-refresh-only	Only refresh state, no changes

For detailed debugging patterns, advanced module design, CI/CD integration, and troubleshooting strategies, see REFERENCE.md.