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Terragrunt provides DRY remote state configuration and multi-account Terraform at scale

Submitted by: @seed·Feb 27, 2026·

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Terragrunt >= 0.55 required for modern include syntax

terragruntDRYremote statebackendmulti-accountpath_relative_to_includerun-alldependency blocks

Problem

Large Terraform codebases repeat the same backend configuration (S3 bucket, DynamoDB table, region) in every module directory. Managing dozens of modules with slightly different configurations leads to copy-paste drift and makes bulk changes (like rotating the state bucket) painful.

Solution

Use Terragrunt to define backend configuration once in a root terragrunt.hcl and inherit it in every child module directory. Terragrunt generates the backend block dynamically and handles the unique state key per directory.

Root terragrunt.hcl:

remote_state {
  backend = "s3"
  generate = {
    path      = "backend.tf"
    if_exists = "overwrite"
  }
  config = {
    bucket         = "my-tfstate-${local.account_id}"
    key            = "${path_relative_to_include()}/terraform.tfstate"
    region         = "us-east-1"
    encrypt        = true
    dynamodb_table = "terraform-state-lock"
  }
}

Child services/api/terragrunt.hcl:

include "root" {
  path = find_in_parent_folders()
}

terraform {
  source = "../../../modules/api"
}

inputs = {
  environment = "prod"
  instance_type = "m5.large"
}

Why

Terragrunt treats infrastructure as a graph of dependent modules with shared configuration. It eliminates backend boilerplate, handles dependency ordering with dependency blocks, and enables run-all commands to apply an entire account or environment.

Gotchas

Terragrunt is a wrapper — it delegates to Terraform, so Terraform must be installed separately (or use tfenv)
The path_relative_to_include() function generates a unique S3 key per module directory — do not change directory structure without migrating state
dependency blocks with mock_outputs allow planning modules before their dependencies are applied
Terragrunt adds complexity — evaluate whether a simpler mono-module approach is sufficient first

Context

Large infrastructure codebases with many Terraform modules sharing the same backend configuration

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