generate

Usage

Generate a stack of units based on configurations in a terragrunt.stack.hcl file.

Examples

Generate stacks of units using the configurations in all terragrunt.stack.hcl files found, starting in the current directory.

terragrunt stack generate

Generating a stack

terragrunt.stack.hcl

unit "mother" {
  source = "units/chicken"
  path   = "mother"
}

unit "father" {
  source = "./units/chicken"
  path   = "father"
}

unit "chick_1" {
  source = "./units/chick"
  path   = "chicks/chick-1"
}

unit "chick_2" {
  source = "units/chick"
  path   = "chicks/chick-2"
}

Running the following:

terragrunt stack generate

Generates the following stack:

• terragrunt.stack.hcl
• Directory.terragrunt-stack

  • Directorymother

    • terragrunt.hcl
  • Directoryfather

    • terragrunt.hcl
  • Directorychicks

    • Directorychick-1

      • terragrunt.hcl
    • Directorychick-2

      • terragrunt.hcl

Note

Parallel Execution: Stack generation runs concurrently to improve performance. The number of parallel tasks is determined by the GOMAXPROCS environment variable and can be explicitly controlled using the --parallelism flag:

terragrunt stack generate --parallelism 4

Automatic Discovery: The command automatically discovers all terragrunt.stack.hcl files within the directory structure and generates them in parallel.

Validation of Units and Stacks: During the stack generation, the system will validate that each unit and stack’s target directory contains the appropriate configuration file (terragrunt.hcl for units and terragrunt.stack.hcl for stacks). This ensures the directories are correctly structured before proceeding with the stack generation. To skip this validation, you can use the --no-stack-validate flag:

terragrunt stack generate --no-stack-validate

Caution

Path Restrictions: If an absolute path is provided as an argument, generate will throw an error. Only relative paths within the working directory are supported.

Caution

Recreating the stack directory and cleaning stale files: By default, terragrunt stack generate does not delete files in .terragrunt-stack that are no longer produced by the current terragrunt.stack.hcl. If you removed or changed values or units and still see old files (e.g., a lingering terragrunt.values.hcl), regenerate from a clean state by either refreshing sources or cleaning the directory first:

# Refresh sources and regenerate from a clean copy
terragrunt stack generate --source-update

# Or explicitly remove the generated directory first
terragrunt stack clean && terragrunt stack generate

You can also pass --source-update when running commands via stack run:

terragrunt stack run plan --source-update

Flags

--filter

Filter configurations using a flexible query language

Filter Behavior for Stack Generate

The --filter flag works differently for stack generate compared to other commands. It requires that you explicitly target stacks using the type=stack attribute.

Examples:

# Filter by name
terragrunt stack generate --filter 'name=prod | type=stack'

Attribute-Based Filtering

Match stacks by their configuration attributes:

# Filter by name
terragrunt stack generate --filter 'prod | type=stack'

# Filter by type
terragrunt stack generate --filter 'type=stack'

# Filter by path
terragrunt stack generate --filter './envs/prod/** | type=stack'

Negation

Exclude paths using the ! prefix:

# Exclude by path
terragrunt stack generate --filter '!./prod/** | type=stack'

Union (Multiple Filters)

Specify multiple --filter flags to combine results using OR logic:

# Generate the dev and prod stacks
terragrunt stack generate --filter 'dev | type=stack' --filter 'prod | type=stack'

Type: list(string)

--no-cas

Disable the CAS (Content Addressable Storage) feature.

When this flag is set, Terragrunt skips all CAS operations and clones sources directly.

Generation or runs error when update_source_with_cas = true is set on any unit, stack, or terraform block reachable from the current invocation, since relative sources rewritten by CAS cannot be resolved without it.

Type: bool

Environment Variables:

• TG_NO_CAS

--cas-clone-depth

When using CAS, pass this value to git clone --depth (default 1; -1 clones full history).

Experimental

This flag only has an effect when the cas experiment is enabled. Enable it with --experiment=cas or TG_EXPERIMENT=cas.

Controls the --depth value the CAS (Content Addressable Storage) uses when cloning a Git source. The default of 1 performs a shallow clone of the latest commit. Negative values clone the full history by omitting --depth entirely; zero is rejected because Git requires a positive depth.

When passing a negative value, use the --cas-clone-depth=-1 form so the leading dash isn’t parsed as a flag.

Type: integer

Default: 1

Environment Variables:

• TG_CAS_CLONE_DEPTH