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
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.
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
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