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Terraform is HashiCorp’s Infrastructure-as-Code (IaC) tool that enables you to define and provision infrastructure using a declarative configuration language. env zero provides comprehensive support for Terraform deployments across all major cloud providers and services.

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Terraform in env zero

env zero supports Terraform as an alternative to OpenTofu, allowing you to use HashiCorp’s official Terraform binary for your infrastructure deployments. While OpenTofu is the default, you can easily switch to Terraform when needed.

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Configuration options

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Terraform version selection

To use Terraform instead of OpenTofu:
  1. Navigate to your template settings
  2. Open the Advanced settings section
  3. Select Terraform from the TF binary dropdown
  4. Choose your preferred Terraform version
Terraform version selection in Advanced settings

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Working directory

Configure the working directory where your Terraform configuration files are located:
  • Root directory: Use the repository root (default)
  • Subdirectory: Specify a path relative to the repository root
If your Terraform files are in a subdirectory, specify the path in the Working Directory field under Advanced settings.

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Terraform-specific features

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State management

Terraform uses state files to track infrastructure resources:
  • Local state: Stored temporarily during deployment
  • Remote state: Recommended for production environments using backends
  • State locking: Prevents concurrent modifications using DynamoDB or similar
State persistenceenv zero stores the local state between deployments by default. For production environments, configure a remote backend in your Terraform configuration to ensure state persistence and team collaboration.

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Variable handling

Terraform supports multiple variable input methods with clear precedence:
  1. Command-line variables: -var flags (highest precedence)
  2. Environment variables: TF_VAR_* prefixed variables
  3. Variable files: .tfvars files
  4. Default values: Defined in variable blocks (lowest precedence)

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Provider configuration

Configure Terraform providers in your configuration files:
main.tf
terraform {
  required_providers {
    aws = {
      source  = "hashicorp/aws"
      version = "~> 5.0"
    }
  }
  required_version = ">= 1.0"
}

provider "aws" {
  region = var.aws_region
}

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Deployment workflow

env zero follows Terraform’s standard deployment workflow:
  1. Initialize: terraform init - Download providers and modules
  2. Plan: terraform plan - Generate execution plan
  3. Apply: terraform apply - Execute the planned changes
  4. Destroy: terraform destroy - Remove resources (when needed)

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Plan and apply process

The plan step generates a detailed execution plan showing what changes will be made. The apply step uses this plan to make the actual changes to your infrastructure.
env zero stores plan files between the plan and apply steps to ensure consistency and allow for review and approval workflows.

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Best practices

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Remote backend configuration

Configure a remote backend for state management:
backend.tf
terraform {
  backend "s3" {
    bucket         = "your-terraform-state-bucket"
    key            = "path/to/your/state.tfstate"
    region         = "us-west-2"
    encrypt        = true
    dynamodb_table = "terraform-state-lock"
  }
}

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Module usage

Organize your infrastructure using Terraform modules:
main.tf
module "vpc" {
  source = "terraform-aws-modules/vpc/aws"
  version = "~> 5.0"
  
  name = "my-vpc"
  cidr = "10.0.0.0/16"
  
  azs             = ["us-west-2a", "us-west-2b"]
  private_subnets = ["10.0.1.0/24", "10.0.2.0/24"]
  public_subnets  = ["10.0.101.0/24", "10.0.102.0/24"]
}

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Variable management

Use consistent variable naming and types:
variables.tf
variable "environment" {
  description = "Environment name"
  type        = string
  validation {
    condition     = contains(["dev", "staging", "prod"], var.environment)
    error_message = "Environment must be dev, staging, or prod."
  }
}

variable "instance_count" {
  description = "Number of instances to create"
  type        = number
  default     = 1
  validation {
    condition     = var.instance_count > 0
    error_message = "Instance count must be greater than 0."
  }
}

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Advanced features

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Workspaces

Terraform workspaces allow you to manage multiple environments: 
# Create a new workspace
terraform workspace new production

# List workspaces
terraform workspace list

# Switch workspaces
terraform workspace select production
env zero automatically manages Terraform workspaces based on your environment configuration.

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Data sources

Use data sources to fetch information about existing resources:
data.tf
data "aws_ami" "latest_amazon_linux" {
  most_recent = true
  owners      = ["amazon"]
  
  filter {
    name   = "name"
    values = ["amzn2-ami-hvm-*-x86_64-gp2"]
  }
}

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Outputs

Define outputs to expose important resource information:
outputs.tf
output "vpc_id" {
  description = "ID of the VPC"
  value       = module.vpc.vpc_id
}

output "private_subnets" {
  description = "List of IDs of private subnets"
  value       = module.vpc.private_subnets
}

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Troubleshooting

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Common issues

Provider version conflicts State file issues
  • Use remote backends for production environments
  • Enable state locking to prevent concurrent modifications
  • Regularly backup your state files
Variable resolution
  • Check variable precedence order
  • Verify environment variables are set correctly in env zero
  • Use terraform console to debug variable values

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Debugging deployments

Enable detailed logging by setting the TF_LOG environment variable:
  • TF_LOG=DEBUG - Most verbose logging
  • TF_LOG=INFO - Standard information level
  • TF_LOG=WARN - Warning and error messages only
Set the TF_LOG environment variable in your template’s environment variables section for detailed Terraform execution logs.

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Common error messages

“Error: No such file or directory”
  • Verify the working directory path is correct
  • Check that Terraform files exist in the specified location
“Error: Failed to get existing workspaces”
  • Ensure proper backend configuration
  • Check backend credentials and permissions
“Error: Provider configuration not present”
  • Verify required providers are declared
  • Check provider version constraints

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Migration considerations

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From OpenTofu to Terraform

If migrating from OpenTofu to Terraform:
  1. Configuration compatibility: Most configurations work without changes
  2. State files: Compatible format, but consider backing up first
  3. Provider versions: Verify compatibility with Terraform version
  4. Testing: Test in a non-production environment first
Migration planningAlways test migrations in a development environment before applying to production infrastructure.

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Additional resources

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