---
layout: collection-browser-doc
title: Configuration Blocks and Attributes
category: reference
categories_url: reference
excerpt: >-
  Learn about all the blocks and attributes supported in the terragrunt configuration file.
tags: ["config"]
order: 403
nav_title: Documentation
nav_title_link: /docs/
---

The Terragrunt configuration file uses the same HCL syntax as Terraform itself in `terragrunt.hcl`.
Terragrunt also supports [JSON-serialized HCL](https://github.com/hashicorp/hcl/blob/hcl2/json/spec.md) in a `terragrunt.hcl.json` file:
where `terragrunt.hcl` is mentioned you can always use `terragrunt.hcl.json` instead.

The following is a reference of all the supported blocks and attributes in the configuration file:

## Blocks

- [terraform](#terraform)
- [remote_state](#remote_state)
- [include](#include)
- [locals](#locals)
- [dependency](#dependency)
- [dependencies](#dependencies)
- [generate](#generate)

### terraform

The `terraform` block is used to configure how Terragrunt will interact with Terraform. This includes specifying where
to find the Terraform configuration files, any extra arguments to pass to the `terraform` CLI, and any hooks to run
before or after calling Terraform.

The `terraform` block supports the following arguments:

- `source` (attribute): Specifies where to find Terraform configuration files. This parameter supports the exact same syntax as the
  [module source](https://www.terraform.io/docs/modules/sources.html) parameter for Terraform `module` blocks, including
  local file paths, Git URLs, and Git URLS with `ref` parameters. Terragrunt will download all the code in the repo
  (i.e. the part before the double-slash `//`) so that relative paths work correctly between modules in that repo.
- `extra_arguments` (block): Nested blocks used to specify extra CLI arguments to pass to the `terraform` CLI. Learn more
  about its usage in the [Keep your CLI flags DRY](/use-cases/keep-your-cli-flags-dry/) use case overview. Supports
  the following arguments:
    - `arguments` (required) : A list of CLI arguments to pass to `terraform`.
    - `commands` (required) : A list of `terraform` sub commands that the arguments will be passed to.
    - `env_vars` (optional) : A map of key value pairs to set as environment variables when calling `terraform`.
    - `required_var_files` (optional): A list of file paths to terraform vars files (`.tfvars`) that will be passed in to
      `terraform` as `-var-file=<your file>`.
    - `optional_var_files` (optional): A list of file paths to terraform vars files (`.tfvars`) that will be passed in to
      `terraform` like `required_var_files`, only any files that do not exist are ignored.

- `before_hook` (block): Nested blocks used to specify command hooks that should be run before `terraform` is called.
  Hooks run from the terragrunt configuration directory (the directory where `terragrunt.hcl` lives).
  Supports the following arguments:
    - `commands` (required) : A list of `terraform` sub commands for which the hook should run before.
    - `execute` (required) : A list of command and arguments that should be run as the hook. For example, if `execute` is set as
      `["echo", "Foo"]`, the command `echo Foo` will be run.
    - `run_on_error` (optional) : If set to true, this hook will run even if a previous hook hit an error, or in the
      case of "after" hooks, if the Terraform command hit an error. Default is false.
    - `init_from_module` and `init`: This is not an argument, but a special name you can use for hooks that run during
      initialization. There are two stages of initialization: one is to download [remote
      configurations](https://terragrunt.gruntwork.io/use-cases/keep-your-terraform-code-dry/) using `go-getter`; the
      other is [Auto-Init](https://terragrunt.gruntwork.io/docs/features/auto-init/), which configures the backend and
      downloads provider plugins and modules. If you wish to execute a hook when Terragrunt is using `go-getter` to
      download remote configurations, name the hook `init_from_module`. If you wish to execute a hook when Terragrunt is
      using terraform `init` for Auto-Init, name the hook `init`.


- `after_hook` (block): Nested blocks used to specify command hooks that should be run after `terraform` is called.
  Hooks run from the terragrunt configuration directory (the directory where `terragrunt.hcl` lives). Supports the same
  arguments as `before_hook`.

Example:

```hcl
terraform {
  # Pull the terraform configuration at the github repo "acme/infrastructure-modules", under the subdirectory
  # "networking/vpc", using the git tag "v0.0.1".
  source = "git::git@github.com:acme/infrastructure-modules.git//networking/vpc?ref=v0.0.1"

  # For any terraform commands that use locking, make sure to configure a lock timeout of 20 minutes.
  extra_arguments "retry_lock" {
    commands  = get_terraform_commands_that_need_locking()
    arguments = ["-lock-timeout=20m"]
  }

  # You can also specify multiple extra arguments for each use case. Here we configure terragrunt to always pass in the
  # `common.tfvars` var file located by the parent terragrunt config.
  extra_arguments "custom_vars" {
    commands = [
      "apply",
      "plan",
      "import",
      "push",
      "refresh"
    ]

    required_var_files = ["${get_parent_terragrunt_dir()}/common.tfvars"]
  }

  # The following are examples of how to specify hooks

  # Before apply or plan, run "echo Foo".
  before_hook "before_hook_1" {
    commands     = ["apply", "plan"]
    execute      = ["echo", "Foo"]
  }

  # Before apply, run "echo Bar". Note that blocks are ordered, so this hook will run after the previous hook to
  # "echo Foo". In this case, always "echo Bar" even if the previous hook failed.
  before_hook "before_hook_2" {
    commands     = ["apply"]
    execute      = ["echo", "Bar"]
    run_on_error = true
  }

  # Note that you can use interpolations in subblocks. Here, we configure it so that before apply or plan, print out the
  # environment variable "HOME".
  before_hook "interpolation_hook_1" {
    commands     = ["apply", "plan"]
    execute      = ["echo", get_env("HOME", "HelloWorld")]
    run_on_error = false
  }

  # After running apply or plan, run "echo Baz". This hook is configured so that it will always run, even if the apply
  # or plan failed.
  after_hook "after_hook_1" {
    commands     = ["apply", "plan"]
    execute      = ["echo", "Baz"]
    run_on_error = true
  }

  # A special after hook to always run after the init-from-module step of the Terragrunt pipeline. In this case, we will
  # copy the "foo.tf" file located by the parent terragrunt.hcl file to the current working directory.
  after_hook "init_from_module" {
    commands = ["init-from-module"]
    execute  = ["cp", "${get_parent_terragrunt_dir()}/foo.tf", "."]
  }

  # A special after_hook. Use this hook if you wish to run commands immediately after terragrunt finishes loading its
  # configurations. If "terragrunt-read-config" is defined as a before_hook, it will be ignored as this config would
  # not be loaded before the action is done.
  after_hook "terragrunt-read-config" {
    commands = ["terragrunt-read-config"]
    execute  = ["bash", "script/get_aws_credentials.sh"]
  }
}
```


### remote_state

The `remote_state` block is used to configure how Terragrunt will set up the remote state configuration of your
Terraform code. You can read more about Terragrunt's remote state functionality in [Keep your remote state configuration
DRY](/use-cases/keep-your-remote-state-configuration-dry) use case overview.

The `remote_state` block supports the following arguments:

- `backend` (attribute): Specifies which remote state backend will be configured. This should be one of the
  [backend types](https://www.terraform.io/docs/backends/types/index.html) that Terraform supports.

- `disable_init` (attribute): When `true`, skip automatic initialization of the backend by Terragrunt. Some backends
  have support in Terragrunt to be automatically created if the storage does not exist. Currently `s3` and `gcs` are the
  two backends with support for automatic creation. Defaults to `false`.

- `generate` (attribute): Configure Terragrunt to automatically generate a `.tf` file that configures the remote state
  backend. This is a map that expects two properties:
    - `path`: The path where the generated file should be written. If a relative path, it'll be relative to the Terragrunt
      working dir (where the terraform code lives).
    - `if_exists` (attribute): What to do if a file already exists at `path`. Valid values are: `overwrite` (overwrite the
      existing file), `overwrite_terragrunt` (overwrite the existing file if it was generated by terragrunt; otherwise,
      error) `skip` (skip code generation and leave the existing file as-is), `error` (exit with an error).

- `config` (attribute): An arbitrary map that is used to fill in the backend configuration in Terraform. All the
  properties will automatically be included in the Terraform backend block (with a few exceptions: see below). For
  example, if you had the following `remote_state` block:

    ```hcl
    remote_state {
      backend = "s3"
      config = {
        bucket = "mybucket"
        key    = "path/to/my/key"
        region = "us-east-1"
      }
    }
    ```

  This is equivalent to the following `terraform` code:

    ```hcl
    terraform {
      backend "s3" {
        bucket = "mybucket"
        key    = "path/to/my/key"
        region = "us-east-1"
      }
    }
    ```

Note that Terragrunt does special processing of the `config` attribute for the `s3` and `gcs` remote state backends, and
supports additional keys that are used to configure the automatic initialization feature of Terragrunt.

For the `s3` backend, the following additional properties are supported in the `config` attribute:

- `region` - (Optional) The region of the S3 bucket.
- `profile` - (Optional) This is the AWS profile name as set in the shared credentials file.
- `endpoint` - (Optional) A custom endpoint for the S3 API.
- `encrypt` - (Optional) Whether to enable server side encryption of the state file.
- `role_arn` - (Optional) The role to be assumed.
- `shared_credentials_file` - (Optional) This is the path to the shared credentials file. If this is not set and a profile is specified, `~/.aws/credentials` will be used.
- `external_id` - (Optional) The external ID to use when assuming the role.
- `session_name` - (Optional) The session name to use when assuming the role.
- `dynamodb_table` - (Optional) The name of a DynamoDB table to use for state locking and consistency. The table must have a primary key named LockID. If not present, locking will be disabled.
- `skip_bucket_versioning`: When `true`, the S3 bucket that is created to store the state will not be versioned.
- `skip_bucket_ssencryption`: When `true`, the S3 bucket that is created to store the state will not be configured with server-side encryption.
- `skip_bucket_accesslogging`: When `true`, the S3 bucket that is created to store the state will not be configured with
  access logging.
- `skip_bucket_root_access`: When `true`, the S3 bucket that is created will not be configured with bucket policies that allow access to the root AWS user.
- `enable_lock_table_ssencryption`: When `true`, the synchronization lock table in DynamoDB used for remote state concurrent access will not be configured with server side encryption.
- `s3_bucket_tags`: A map of key value pairs to associate as tags on the created S3 bucket.
- `dynamodb_table_tags`: A map of key value pairs to associate as tags on the created DynamoDB remote state lock table.
- `disable_aws_client_checksums`: When `true`, disable computing and checking checksums on the request and response,
  such as the CRC32 check for DynamoDB. This can be used to workaround
  https://github.com/gruntwork-io/terragrunt/issues/1059.

For the `gcs` backend, the following additional properties are supported in the `config` attribute:

- `skip_bucket_creation`: When `true`, Terragrunt will skip the auto initialization routine for setting up the GCS
  bucket for use with remote state.
- `skip_bucket_versioning`: When `true`, the GCS bucket that is created to store the state will not be versioned.
- `enable_bucket_policy_only`: When `true`, the GCS bucket that is created to store the state will be configured to use uniform bucket-level access.
- `project`: The GCP project where the bucket will be created.
- `location`: The GCP location where the bucket will be created.
- `gcs_bucket_labels`: A map of key value pairs to associate as labels on the created GCS bucket.

Example with S3:

```hcl
# Configure terraform state to be stored in S3, in the bucket "my-terraform-state" in us-east-1 under a key that is
# relative to included terragrunt config. For example, if you had the following folder structure:
#
# .
# ├── terragrunt.hcl
# └── child
#     └── terragrunt.hcl
#
# And the following is defined in the root terragrunt.hcl config that is included in the child, the state file for the
# child module will be stored at the key "child/terraform.tfstate".
#
# Note that since we are not using any of the skip args, this will automatically create the S3 bucket
# "my-terraform-state" and DynamoDB table "my-lock-table" if it does not already exist.
remote_state {
  backend = "s3"
  config = {
    bucket         = "my-terraform-state"
    key            = "${path_relative_to_include()}/terraform.tfstate"
    region         = "us-east-1"
    encrypt        = true
    dynamodb_table = "my-lock-table"
  }
}
```

Example with GCS:

```hcl
# Configure terraform state to be stored in GCS, in the bucket "my-terraform-state" in the "my-terraform" GCP project in
# the eu region under a key that is relative to included terragrunt config. This will also apply the labels
# "owner=terragrunt_test" and "name=terraform_state_storage" to the bucket if it is created by Terragrunt.
#
# For example, if you had the following folder structure:
#
# .
# ├── terragrunt.hcl
# └── child
#     └── terragrunt.hcl
#
# And the following is defined in the root terragrunt.hcl config that is included in the child, the state file for the
# child module will be stored at the key "child/terraform.tfstate".
#
# Note that since we are not using any of the skip args, this will automatically create the GCS bucket
# "my-terraform-state" if it does not already exist.
remote_state {
  backend = "gcs"

  config = {
    project  = "my-terraform"
    location = "eu"
    bucket   = "my-terraform-state"
    prefix   = "${path_relative_to_include()}/terraform.tfstate"

    gcs_bucket_labels = {
      owner = "terragrunt_test"
      name  = "terraform_state_storage"
    }
  }
}
```



### include

The `include` block is used to specify inheritance of Terragrunt configuration files. The included config (also called
the `parent`) will be merged with the current configuration (also called the `child`) before processing. You can learn
more about the inheritance properties of Terragrunt in the [Filling in remote state settings with Terragrunt
section](/use-cases/keep-your-remote-state-configuration-dry/#filling-in-remote-state-settings-with-terragrunt) of the
"Keep your remote state configuration DRY" use case overview.

The `include` block supports the following arguments:

- `path` (attribute): Specifies the path to a Terragrunt configuration file (the `parent` config) that should be merged
  with this configuration (the `child` config).

Example:

```hcl
# If you have the following folder structure, and the following contents for ./child/terragrunt.hcl, this will include
# and merge the items in the terragrunt.hcl file at the root.
#
# .
# ├── terragrunt.hcl
# └── child
#     └── terragrunt.hcl
include {
  path = find_in_parent_folders()
}
```


### locals

The `locals` block is used to define aliases for Terragrunt expressions that can be referenced within the configuration.
You can learn more about locals in the [feature overview](/docs/features/locals/).

The `locals` block does not have a defined set of arguments that are supported. Instead, all the arguments passed into
`locals` are available under the reference `local.ARG_NAME` throughout the Terragrunt configuration.

Example:

```hcl
# Make the AWS region a reusable variable within the configuration
locals {
  aws_region = "us-east-1"
}

inputs = {
  region = local.aws_region
  name   = "${local.aws_region}-bucket"
}
```


### dependency

The `dependency` block is used to configure module dependencies. Each dependency block exports the outputs of the target
module as block attributes you can reference throughout the configuration. You can learn more about `dependency` blocks
in the [Dependencies between modules
section](/use-cases/execute-terraform-commands-on-multiple-modules-at-once/#dependencies-between-modules) of the
"Execute Terraform commands on multiple modules at once" use case overview.

You can define more than one `dependency` block. Each label you provide to the block identifies another `dependency`
that you can reference in your config.

The `dependency` block supports the following arguments:

- `name` (label): You can define multiple `dependency` blocks in a single terragrunt config. As such, each block needs a
  name to differentiate between the other blocks, which is what the first label of the block is used for. You can
  reference the specific dependency output by the name. E.g if you had a block `dependency "vpc"`, you can reference the
  outputs of this dependency with the expression `dependency.vpc.outputs`.
- `config_path` (attribute): Path to a Terragrunt module (folder with a `terragrunt.hcl` file) that should be included
  as a dependency in this configuration.
- `skip_outputs` (attribute): When `true`, skip calling `terragrunt output` when processing this dependency. If
  `mock_outputs` is configured, set `outputs` to the value of `mock_outputs`. Otherwise, `outputs` will be set to an
  empty map.
- `mock_outputs` (attribute): A map of arbitrary key value pairs to use as the `outputs` attribute when no outputs are
  available from the target module, or if `skip_outputs` is `true`.
- `mock_outputs_allowed_terraform_commands` (attribute): A list of Terraform commands for which `mock_outputs` are
  allowed. If a command is used where `mock_outputs` is not allowed, and no outputs are available in the target module,
  Terragrunt will throw an error when processing this dependency.

Example:

```hcl
# Run `terragrunt output` on the module at the relative path `../vpc` and expose them under the attribute
# `dependency.vpc.outputs`
dependency "vpc" {
  config_path = "../vpc"

  # Configure mock outputs for the `validate` command that are returned when there are no outputs available (e.g the
  # module hasn't been applied yet.
  mock_outputs_allowed_terraform_commands = ["validate"]
  mock_outputs = {
    vpc_id = "fake-vpc-id"
  }
}

# Another dependency, available under the attribute `dependency.rds.outputs`
dependency "rds" {
  config_path = "../rds"
}

inputs = {
  vpc_id = dependency.vpc.outputs.vpc_id
  db_url = dependency.rds.outputs.db_url
}
```


### dependencies

The `dependencies` block is used to enumerate all the Terragrunt modules that need to be applied in order for this
module to be able to apply. Note that this is purely for ordering the operations when using `xxx-all` commands of
Terraform. This does not expose or pull in the outputs like `dependency` blocks.

The `dependencies` block supports the following arguments:

- `paths` (attribute): A list of paths to modules that should be marked as a dependency.

Example:

```hcl
# When applying this terragrunt config in an `xxx-all` command, make sure the modules at "../vpc" and "../rds" are
# handled first.
dependencies {
  paths = ["../vpc", "../rds"]
}
```


### generate

The `generate` block can be used to arbitrarily generate a file in the terragrunt working directory (where `terraform`
is called). This can be used to generate common terraform configurations that are shared across multiple terraform
modules. For example, you can use `generate` to generate the provider blocks in a consistent fashion by defining a
`generate` block in the parent terragrunt config.

The `generate` block supports the following arguments:

- `name` (label): You can define multiple `generate` blocks in a single terragrunt config. As such, each block needs a
  name to differentiate between the other blocks.
- `path` (attribute): The path where the generated file should be written. If a relative path, it'll be relative to the
  Terragrunt working dir (where the terraform code lives).
- `if_exists` (attribute): What to do if a file already exists at `path`. Valid values are: `overwrite` (overwrite the
  existing file), `overwrite_terragrunt` (overwrite the existing file if it was generated by terragrunt; otherwise,
  error) `skip` (skip code generation and leave the existing file as-is), `error` (exit with an error).
- `comment_prefix` (attribute): A prefix that can be used to indicate comments in the generated file. This is used by
  terragrunt to write out a signature for knowing which files were generated by terragrunt. Defaults to `# `. Optional.
- `contents` (attribute): The contents of the generated file.

Example:

```hcl
# When using this terragrunt config, terragrunt will generate the file "provider.tf" with the aws provider block before
# calling to terraform. Note that this will overwrite the `provider.tf` file if it already exists.
generate "provider" {
  path      = "provider.tf"
  if_exists = "overwrite"
  contents = <<EOF
provider "aws" {
  region              = "us-east-1"
  version             = "= 2.3.1"
  allowed_account_ids = ["1234567890"]
}
EOF
}
```


## Attributes

- [inputs](#inputs)
- [download_dir](#download_dir)
- [prevent_destroy](#prevent_destroy)
- [skip](#skip)
- [iam_role](#iam_role)
- [terraform_binary](#terraform_binary)
- [terraform_version_constraint](#terraform_version_constraint)


### inputs

The `inputs` attribute is a map that is used to specify the input variables and their values to pass in to Terraform.
Each entry of the map will be passed to Terraform using [the environment variable
mechanism](https://www.terraform.io/docs/configuration/variables.html#environment-variables). This means that each input
will be set using the form `TF_VAR_variablename`, with the value in `json` encoded format.

Note that because the values are being passed in with environment variables and `json`, the type information is lost
when crossing the boundary between Terragrunt and Terraform. You must specify the proper [type
constraint](https://www.terraform.io/docs/configuration/variables.html#type-constraints) on the variable in Terraform in
order for Terraform to process the inputs to the right type.

Example:

```hcl
inputs = {
  string      = "string"
  number      = 42
  bool        = true
  list_string = ["a", "b", "c"]
  list_number = [1, 2, 3]
  list_bool   = [true, false]

  map_string = {
    foo = "bar"
  }

  map_number = {
    foo = 42
    bar = 12345
  }

  map_bool = {
    foo = true
    bar = false
    baz = true
  }

  object = {
    str  = "string"
    num  = 42
    list = [1, 2, 3]

    map = {
      foo = "bar"
    }
  }

  from_env = get_env("FROM_ENV", "default")
}
```


### download_dir

The terragrunt `download_dir` string option can be used to override the default download directory.

The precedence is as follows: `--terragrunt-download-dir` command line option → `TERRAGRUNT_DOWNLOAD` env variable →
`download_dir` attribute of the `terragrunt.hcl` file in the module directory → `download_dir` attribute of the included
`terragrunt.hcl`.

It supports all terragrunt functions, i.e. `path_relative_from_include()`.


### prevent_destroy

Terragrunt `prevent_destroy` boolean flag allows you to protect selected Terraform module. It will prevent `destroy` or
`destroy-all` command to actually destroy resources of the protected module. This is useful for modules you want to
carefully protect, such as a database, or a module that provides auth.

Example:

```hcl
terraform {
  source = "git::git@github.com:foo/modules.git//app?ref=v0.0.3"
}

prevent_destroy = true
```

### skip

The terragrunt `skip` boolean flag can be used to protect modules you don’t want any changes to or just to skip modules
that don’t define any infrastructure by themselves. When set to true, all terragrunt commands will skip the selected
module.

Consider the following file structure:

    root
    ├── terragrunt.hcl
    ├── prod
    │   └── terragrunt.hcl
    ├── dev
    │   └── terragrunt.hcl
    └── qa
        └── terragrunt.hcl

In some cases, the root level `terragrunt.hcl` file is solely used to DRY up your Terraform configuration by being
included in the other `terragrunt.hcl` files. In this case, you do not want the `xxx-all` commands to process the root
level `terragrunt.hcl` since it does not define any infrastructure by itself. To make the `xxx-all` commands skip the
root level `terragrunt.hcl` file, you can set `skip = true`:

``` hcl
skip = true
```

The `skip` flag must be set explicitly in terragrunt modules that should be skipped. If you set `skip = true` in a
`terragrunt.hcl` file that is included by another `terragrunt.hcl` file, only the `terragrunt.hcl` file that explicitly
set `skip = true` will be skipped.


### iam_role

The `iam_role` attribute can be used to specify an IAM role that Terragrunt should assume prior to invoking Terraform.

The precedence is as follows: `--terragrunt-iam-role` command line option → `TERRAGRUNT_IAM_ROLE` env variable →
`iam_role` attribute of the `terragrunt.hcl` file in the module directory → `iam_role` attribute of the included
`terragrunt.hcl`.

Example:

```hcl
iam_role = "arn:aws:iam::ACCOUNT_ID:role/ROLE_NAME"
```


### terraform_binary

The terragrunt `terraform_binary` string option can be used to override the default terraform binary path (which is
`terraform`).

The precedence is as follows: `--terragrunt-tfpath` command line option → `TERRAGRUNT_TFPATH` env variable →
`terragrunt.hcl` in the module directory → included `terragrunt.hcl`


### terraform_version_constraint

The terragrunt `terraform_version_constraint` string overrides the default minimum supported version of terraform.
Terragrunt only officially supports the latest version of terraform, however in some cases an old terraform is needed.

Example:

```hcl
terraform_version_constraint = ">= 0.11"
```
