KodeKloud Notes

The generate block in Terragrunt automates file creation within your working directory. It’s essential for maintaining DRY (Don't Repeat Yourself) Terraform configurations across multiple modules, boosting consistency and simplifying management.

Key Use Cases

Centralize provider and backend configurations
Enforce version constraints on Terraform providers
Generate any auxiliary .tf or other configuration files

Note

Use the generate block to share common Terraform setup and reduce duplication across your modules.

generate Block Attributes

Attribute	Description
name	Identifier for the generate block, useful when defining multiple blocks.
path	Relative output path for the generated file in the Terragrunt working directory.
if_exists	Action if the file already exists. See values in the table below.
comment_prefix	Prefix for comments in the generated file (default: `#`).
disable_signature	When `true`, suppresses the Terragrunt signature comment in the generated file.
contents	The file content, supporting HEREDOC.
disable	When `true`, disables the entire generate block.

if_exists Options

Value	Behavior
overwrite	Unconditionally overwrite the existing file.
overwrite_terragrunt	Terragrunt overwrites its own generated signature section only.
skip	Leave the existing file untouched.
error	Throw an error if the file already exists, halting execution.

Warning

Overwriting files may lead to unintended changes. Review your if_exists setting to prevent data loss.

Example 1: Generate AWS Provider Configuration

This example demonstrates how to generate a providers.tf file for AWS in every module, alongside an S3 remote state configuration.

remote_state {
  backend = "s3"
  config = {
    bucket         = "kodekloud-terragrunt-remote-state"
    key            = "${path_relative_to_include()}/terraform.tfstate"
    region         = "eu-west-1"
    encrypt        = true
    dynamodb_table = "terraform-locks"
  }
}

generate "backend" {
  path      = "backend.tf"
  if_exists = "overwrite_terragrunt"
}

generate "provider" {
  path      = "providers.tf"
  if_exists = "overwrite_terragrunt"
  contents  = <<EOF
provider "aws" {
  region = "eu-west-1"
}
EOF
}

Example 2: Enforce Provider Version Constraints

To ensure all modules use AWS provider version ~> 5.0, add a versions.tf file:

generate "provider_version" {
  path      = "versions.tf"
  if_exists = "overwrite_terragrunt"
  contents  = <<EOF
terraform {
  required_providers {
    aws = {
      source  = "hashicorp/aws"
      version = "~> 5.0"
    }
  }
}
EOF
}

Combine this with the previous blocks to automate both provider and version file generation.

Best Practices

Practice	Benefit
Centralize common configs	Ensures uniformity across modules
Use dynamic content and external files	Provides flexibility and adaptability
Carefully choose `if_exists` behavior	Prevents accidental overwrites and operational issues

References

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