Terragrunt Validator Overview This skill provides comprehensive validation, linting, and testing capabilities for Terragrunt configurations. Terragrunt is a thin wrapper for Terraform/OpenTofu that provides extra tools for keeping configurations DRY (Don't Repeat Yourself), working with multiple modules, and managing remote state. Use this skill when: Validating Terragrunt HCL files (*.hcl, terragrunt.hcl, terragrunt.stack.hcl) Working with Terragrunt Stacks (unit/stack blocks, terragrunt stack generate/run ) Performing dry-run testing with terragrunt plan Linting Terragrunt/Terraform code for best practices Detecting and researching custom providers or modules Debugging Terragrunt configuration issues Checking dependency graphs Formatting HCL files Running security scans on infrastructure code (Trivy, Checkov) Generating run reports and summaries Terragrunt Version Compatibility This skill is designed for Terragrunt 0.93+ which includes the new CLI redesign. CLI Command Migration Reference Deprecated Command New Command run-all run --all hclfmt hcl fmt hclvalidate hcl validate validate-inputs hcl validate --inputs graph-dependencies dag graph render-json render --json -w terragrunt-info info print plan-all , apply-all run --all plan , run --all apply Key Changes in 0.93+: terragrunt run --all replaces terragrunt run-all for multi-module operations terragrunt dag graph replaces terragrunt graph-dependencies for dependency visualization terragrunt hcl validate --inputs replaces validate-inputs for input validation HCL syntax validation via terragrunt hcl fmt --check or terragrunt hcl validate Full validation requires terragrunt init && terragrunt validate If using an older Terragrunt version, some commands may need adjustment. Core Capabilities 1. Comprehensive Validation Suite Run the comprehensive validation script to perform all checks at once: bash scripts/validate_terragrunt.sh [ TARGET_DIR ] What it validates: HCL formatting ( terragrunt hcl fmt --check ) HCL input validation ( terragrunt hcl validate --inputs ) Terragrunt configuration syntax Terraform configuration validation Linting with tflint Security scanning with Trivy (or legacy tfsec) Dependency graph validation Dry-run planning Environment variables: SKIP_PLAN=true - Skip terragrunt plan step SKIP_SECURITY=true - Skip security scanning (Trivy/tfsec) SKIP_LINT=true - Skip tflint linting SKIP_INIT=true - Skip terragrunt init before validation SKIP_BACKEND_INIT=true - Run init with -backend=false (useful in CI/offline) SOFT_FAIL_SECURITY=true - Report security findings without failing TG_STRICT_MODE=true - Enable strict mode (errors on deprecated features) Example usage:
Full validation
bash scripts/validate_terragrunt.sh ./infrastructure/prod
Skip plan generation (faster)
SKIP_PLAN
true bash scripts/validate_terragrunt.sh ./infrastructure
Only validate, skip linting and security
SKIP_LINT
true SKIP_SECURITY = true bash scripts/validate_terragrunt.sh 2. Custom Provider and Module Detection Use the detection script to identify custom providers and modules that may require documentation lookup: python3 scripts/detect_custom_resources.py [ DIRECTORY ] [ --format text | json ] What it detects: Custom Terraform providers (non-HashiCorp) Remote modules (Git, Terraform Registry, HTTP) Provider versions Module versions and sources Output formats: text - Human-readable report with search recommendations json - Machine-readable format for automation When custom resources are detected: CRITICAL: You MUST look up documentation for EVERY detected custom resource (both providers AND modules). Do NOT skip any. This is mandatory, not optional. For custom providers: Option A - WebSearch: Search for provider documentation Query format: "{provider_source} terraform provider documentation version {version}" Example: "mongodb/mongodbatlas terraform provider documentation version 1.14.0" Option B - Context7 MCP (Preferred): Use Context7 for structured documentation lookup Step 1: Resolve library ID: mcp__context7__resolve-library-id with provider name (e.g., "datadog terraform provider") Step 2: REQUIRED - Fetch docs via mcp__context7__query-docs with the resolved library ID Use queries like "authentication requirements" and "configuration examples" For custom modules (EQUALLY IMPORTANT - DO NOT SKIP): Terraform Registry modules: Use Context7: mcp__context7__resolve-library-id with module name (e.g., "terraform-aws-modules vpc") Then fetch docs with mcp__context7__query-docs Or visit https://registry.terraform.io/modules/{source}/{version} Git modules: Use WebSearch with the repository URL to find README or documentation HTTP modules: Investigate the source URL for documentation Pay attention to version compatibility with your Terraform/Terragrunt version Documentation lookup workflow (MANDATORY for ALL detected resources): a) Run detect_custom_resources.py b) For EACH custom provider/module: - Note the exact version - Use Context7 MCP: 1. mcp__context7__resolve-library-id with libraryName: "{provider/module name}" 2. mcp__context7__query-docs with: - libraryId: "{resolved ID}" - query: "authentication requirements" (for auth requirements) 3. mcp__context7__query-docs with: - libraryId: "{resolved ID}" - query: "configuration examples" (for setup requirements) - OR use WebSearch with version-specific queries - Review documentation for: * Required configuration blocks * Authentication requirements (API keys, credentials) * Available resources/data sources * Known issues or breaking changes in the version c) Apply learnings to validation/troubleshooting d) Document findings if issues are encountered Example using Context7 MCP:
1. Detect custom resources
python3 scripts/detect_custom_resources.py ./infrastructure
Output: Provider: datadog/datadog, Version: 3.30.0
2. Resolve library ID
mcp__context7__resolve-library-id with libraryName: "datadog terraform provider"
Result: /datadog/terraform-provider-datadog
3. Fetch authentication docs (REQUIRED)
mcp__context7__query-docs with: libraryId: "/datadog/terraform-provider-datadog" query: "authentication requirements"
4. Fetch configuration docs
mcp__context7__query-docs with: libraryId: "/datadog/terraform-provider-datadog" query: "configuration examples" Example using WebSearch:
Detect custom resources
python3 scripts/detect_custom_resources.py ./infrastructure
Then search for documentation:
WebSearch: "datadog terraform provider 3.30.0 authentication configuration"
WebSearch: "datadog terraform provider api_key app_key setup"
- Step-by-Step Validation
For manual or granular validation, use these individual commands:
Format Validation
cd
<
target-directory
terragrunt hcl fmt --check
To auto-fix formatting
terragrunt hcl fmt Configuration Validation
Check HCL syntax and formatting
terragrunt hcl fmt --check
Note: In Terragrunt 0.93+, for deeper configuration validation,
initialize and validate (requires actual resources/credentials):
terragrunt init && terragrunt validate
Terraform Validation
Initialize if needed
terragrunt init
Validate
terragrunt validate Linting with tflint
Initialize tflint (if .tflint.hcl exists)
tflint --init
Run linting
tflint --recursive Security Scanning with Trivy (Recommended) Note: tfsec has been merged into Trivy and is no longer actively maintained. Use Trivy for all new projects.
Using Trivy (recommended)
trivy config . --severity HIGH,CRITICAL
With tfvars file
trivy config --tf-vars terraform.tfvars .
Exclude downloaded modules
trivy config --tf-exclude-downloaded-modules .
Legacy: Using tfsec (deprecated)
tfsec . --soft-fail Alternative: Security Scanning with Checkov
Scan directory
checkov -d . --framework terraform
Scan with specific checks
checkov -d . --check CKV_AWS_21
Output as JSON
checkov -d . --output json Dependency Graph Validation
Note: graph-dependencies command replaced with 'dag graph' in Terragrunt 0.93+
Validate and display dependency graph
terragrunt dag graph
Visualize dependencies (requires graphviz)
terragrunt dag graph | dot -Tpng
dependencies.png Dry-Run Planning
Single module
terragrunt plan
All modules (new syntax - Terragrunt 0.93+)
terragrunt run --all plan
Legacy syntax (deprecated)
terragrunt run-all plan
- Multi-Module Operations For projects with multiple Terragrunt modules, use run --all (replaces deprecated run-all ):
Validate all modules
terragrunt run --all validate
Plan all modules
terragrunt run --all plan
Apply all modules
terragrunt run --all apply
Destroy all modules
terragrunt run --all destroy
Format all HCL files
terragrunt hcl fmt
With parallelism
terragrunt run --all plan --parallelism 4
With strict mode (errors on deprecated features)
terragrunt --strict-mode run --all plan
Or via environment variable
TG_STRICT_MODE
true terragrunt run --all plan 5. HCL Input Validation (New in 0.93+) Validate that all required inputs are set and no unused inputs exist:
Validate inputs
terragrunt hcl validate --inputs
Show paths of invalid files
terragrunt hcl validate --show-config-path
Combine with run --all to exclude invalid files
terragrunt run --all plan --queue-excludes-file < ( terragrunt hcl validate --show-config-path || true ) 6. Strict Mode Enable strict mode to catch deprecated features early:
Via CLI flag
terragrunt --strict-mode run --all plan
Via environment variable (recommended for CI/CD)
export TG_STRICT_MODE = true terragrunt run --all plan
Check available strict controls
terragrunt info strict Specific Strict Controls: For finer-grained control, use --strict-control to enable specific controls:
Enable specific strict controls
terragrunt run --all plan --strict-control cli-redesign --strict-control deprecated-commands
Via environment variable (comma-separated)
TG_STRICT_CONTROL
'cli-redesign,deprecated-commands' terragrunt run --all plan
Available strict controls:
- cli-redesign: Errors on deprecated CLI syntax
- deprecated-commands: Errors on deprecated commands (run-all, hclfmt, etc.)
- root-terragrunt-hcl: Errors when using root terragrunt.hcl (use root.hcl instead)
- skip-dependencies-inputs: Improves performance by not reading dependency inputs
- bare-include: Errors on bare include blocks (use named includes)
- New CLI Commands (0.93+) Render Configuration
Render configuration to JSON
terragrunt render --json
Render and write to file
terragrunt render --json --write
Output goes to terragrunt.rendered.json
Info Print (replaces terragrunt-info)
Get contextual information about current configuration
terragrunt info print
Output includes:
- config_path
- download_dir
- terraform_binary
- working_dir
Find and List Units
Find all units/stacks in directory
terragrunt find
Output as JSON
terragrunt find --json
Include dependency information
terragrunt find --json --dag
List units (simpler output)
terragrunt list Run Summary and Reports
Run with summary output (default in newer versions)
terragrunt run --all plan
Disable summary output
terragrunt run --all plan --summary-disable
Generate detailed report file
terragrunt run --all plan --report-file = report.json
CSV format report
terragrunt run --all plan --report-file = report.csv 8. Terragrunt Stacks (GA in v0.78.0+) Terragrunt Stacks provide declarative infrastructure generation using terragrunt.stack.hcl files. Stack File Structure
terragrunt.stack.hcl
locals { environment = "dev" aws_region = "us-east-1" }
Define a unit (generates a single terragrunt.hcl)
unit "vpc" { source = "git::git@github.com:acme/infra-catalog.git//units/vpc?ref=v0.0.1" path = "vpc" values = { environment = local.environment cidr = "10.0.0.0/16" } } unit "database" { source = "git::git@github.com:acme/infra-catalog.git//units/database?ref=v0.0.1" path = "database" values = { environment = local.environment vpc_path = "../vpc" } }
Include reusable stacks
stack "monitoring" { source = "git::git@github.com:acme/infra-catalog.git//stacks/monitoring?ref=v0.0.1" path = "monitoring" values = { environment = local.environment } } Stack Commands
Generate stack (creates .terragrunt-stack directory)
terragrunt stack generate
Generate stack without validation
terragrunt stack generate --no-stack-validate
Run command on all stack units
terragrunt stack run plan terragrunt stack run apply
Clean generated stack directories
terragrunt stack clean
Get stack outputs
terragrunt stack output Stack Validation Control Use no_validation attribute to skip validation for specific units: unit "experimental" { source = "git::git@github.com:acme/infra-catalog.git//units/experimental?ref=v0.0.1" path = "experimental"
Skip validation for this unit (useful for incomplete/experimental units)
no_validation
- true
- values
- =
- {
- environment
- =
- local.environment
- }
- }
- Benefits of Stacks
- Clean working directory
-
- Generated code in hidden
- .terragrunt-stack
- directory
- Reusable patterns
-
- Define infrastructure patterns once, deploy many times
- Version pinning
-
- Different environments can pin different versions
- Atomic updates
- Easy rollbacks of both modules and configurations 9. Exec Command (Run Arbitrary Programs) The exec command allows you to run arbitrary programs against units with Terragrunt context. This is useful for integrating other tools like tflint, checkov, or AWS CLI with Terragrunt's configuration.
Run tflint with unit context (TF_VAR_ env vars available)
terragrunt exec -- tflint
Run checkov against specific unit
terragrunt exec -- checkov -d .
Run AWS CLI with unit's configuration
terragrunt exec -- aws s3 ls s3://my-bucket
Run custom scripts with Terragrunt context
terragrunt exec -- ./scripts/validate_terragrunt.sh
Run across all units
terragrunt run --all exec -- tflint Key Features: Terragrunt loads the inputs for the unit and makes them available as TF_VAR_ prefixed environment variables Works with any program that can use environment variables Integrates with Terragrunt's authentication context (e.g., AWS profiles) Can be combined with run --all for multi-unit operations Use Cases: Running security scanners (checkov, trivy) with unit context Executing linters (tflint) per unit Running operational commands (AWS CLI) with correct credentials Custom validation scripts that need Terragrunt inputs 10. Feature Flags (Production Feature) Terragrunt supports first-class Feature Flags for safe infrastructure changes. Feature flags allow you to integrate incomplete work without risk, decouple release from deployment, and codify IaC evolution. Defining Feature Flags
terragrunt.hcl
feature "enable_monitoring" { default = false } feature "use_new_vpc" { default = true } inputs = { monitoring_enabled = feature.enable_monitoring.value vpc_version = feature.use_new_vpc.value ? "v2" : "v1" } Using Feature Flags via CLI
Enable a feature flag
terragrunt plan --feature enable_monitoring = true
Enable multiple feature flags
terragrunt plan --feature enable_monitoring = true --feature use_new_vpc = false
Via environment variable
TG_FEATURE
'enable_monitoring=true' terragrunt plan Feature Flags with run --all
Apply feature flag across all units
- terragrunt run
- --all
- plan
- --feature
- enable_monitoring
- =
- true
- Benefits:
- Safe rollouts
-
- Test changes on subset of infrastructure
- Gradual migrations
-
- Enable new features incrementally
- A/B testing
-
- Compare infrastructure configurations
- Emergency rollbacks
- Quickly disable problematic features 11. Experiments (Opt-in Unstable Features) Terragrunt provides an experiments system for trying unstable features before they're GA:
Enable all experiments (not recommended for production)
terragrunt --experiment-mode run --all plan
Enable specific experiment
terragrunt --experiment symlinks run --all plan
Enable CAS (Content Addressable Storage) for faster cloning
terragrunt --experiment cas run --all plan Available Experiments: symlinks - Support symlink resolution for Terragrunt units cas - Content Addressable Storage for faster Git/module cloning filter-flag - Advanced filtering capabilities (coming in 1.0) Validation Workflow Follow this workflow when validating Terragrunt configurations: Canonical Executable Workflow (Default Path) Use one executable path so docs and scripts stay aligned:
Main validation
bash scripts/validate_terragrunt.sh < target-directory
Deterministic fixture tests (required after script changes)
python3 test/test_detect_custom_resources.py bash test/test_validate_terragrunt.sh Execution expectations: Fixture tests should be deterministic (stable pass/fail outcomes). Validation/security failures must surface as non-zero exits. Step 0: Read Best Practices Reference (MANDATORY FIRST STEP) You MUST read the best practices reference file BEFORE starting validation. This is not optional.
Read the best practices reference file first
if [ -f references/best_practices.md ] ; then cat references/best_practices.md else echo "WARNING: references/best_practices.md not found; continue with built-in checklist below." fi This ensures you understand the patterns, anti-patterns, and checklists you will verify. Initial Assessment Understand the structure: tree -L 3 < infrastructure-directory
Identify Terragrunt files: find . -name "*.hcl" -o -name "terragrunt.hcl" Detect custom resources: python3 scripts/detect_custom_resources.py . Documentation Lookup (MANDATORY for ALL detected custom resources) CRITICAL: If ANY custom providers or modules are detected, you MUST look up documentation for EACH ONE. Do not skip any. For EACH detected custom provider - look up documentation: Use Context7 MCP (preferred): mcp__context7__resolve-library-id with provider name mcp__context7__query-docs with query: "authentication requirements" mcp__context7__query-docs with query: "configuration examples" OR use WebSearch: "{provider} terraform provider {version} documentation" For EACH detected custom module - look up documentation: Use Context7 MCP for Terraform Registry modules: mcp__context7__resolve-library-id with module name (e.g., "terraform-aws-modules vpc") mcp__context7__query-docs with relevant configuration query For Git modules: Use WebSearch with repository URL For HTTP modules: Investigate source URL for documentation Document findings for each resource: Required configuration blocks Authentication requirements Known issues or breaking changes in the version Validation Execution Run comprehensive validation: bash scripts/validate_terragrunt.sh < target-directory
Review output for errors: Format errors → Fix with terragrunt hcl fmt Configuration errors → Check terragrunt.hcl syntax and inputs Terraform validation errors → Check .tf files or generated configs Linting issues → Review tflint output and fix Security issues → Review Trivy/Checkov/tfsec output and address Dependency errors → Check dependency blocks and paths Plan errors → Review Terraform configuration and provider setup Best Practices Check (REQUIRED - Must Complete All Checklists) You MUST verify each checklist item below and document the result (✅ pass or ❌ fail). Incomplete verification is not acceptable. Perform explicit best practices verification using references/best_practices.md : Configuration Pattern Checklist - verify each item: [ ] Include blocks: Child modules use
include "root" { path = find_in_parent_folders("root.hcl") }[ ] Named includes: All include blocks have names (not bareinclude {}) [ ] Root file naming: Root config is namedroot.hcl(notterragrunt.hcl) [ ] Environment configs: Environment-level configs namedenv.hcl(notterragrunt.hcl) [ ] Common variables: Shared variables incommon.hclread viaread_terragrunt_config()Dependency Management Checklist: [ ] Mock outputs: ALL dependency blocks have mock_outputs for validation [ ] Mock allowed commands: mock_outputs_allowed_terraform_commands includes ["validate", "plan", "init"] [ ] Explicit paths: Dependency config_path uses relative paths ("../vpc" not absolute) [ ] No circular deps: Runterragrunt dag graphto verify no cycles Security Checklist: [ ] State encryption: remote_state config hasencrypt = true[ ] State locking: DynamoDB table configured for S3 backend [ ] No hardcoded credentials: Search for patterns like "AKIA", "password =", account IDs [ ] Sensitive variables: Passwords/keys usesensitive = truein variable blocks [ ] IAM roles: Provider uses assume_role instead of static credentials DRY Principle Checklist: [ ] Generate blocks: Provider and backend configs usegenerateblocks [ ] Version constraints: terragrunt_version_constraint and terraform_version_constraint set [ ] Reusable locals: Common values in shared files, not duplicated [ ] if_exists: Generate blocks use appropriate if_exists strategy Quick grep checks to run:
Check for hardcoded AWS account IDs
grep -r "[0-9]{12}" --include = "*.hcl" . | grep -v mock
Check for potential credentials
grep -ri "password\s=" --include = ".hcl" . grep -ri "api_key\s=" --include = ".hcl" .
Check for dependencies without mock_outputs
grep -l "dependency\s" --include = "*.hcl" -r . | xargs grep -L "mock_outputs"
Check for terragrunt.hcl files in non-module directories (anti-pattern)
find . -name "terragrunt.hcl" -not -path "/.terragrunt-cache/" | head -20 Troubleshooting Common issues and resolutions: Issue: Module not found rm -rf .terragrunt-cache terragrunt init Issue: Provider authentication errors Check provider configuration in generated files Verify environment variables or credentials Review provider documentation from WebSearch Issue: Dependency errors Check dependency paths are correct Ensure mock_outputs are provided for validation Review dependency graph with terragrunt dag graph Issue: State locking errors terragrunt force-unlock < LOCK_ID
Issue: S3 backend dynamodb_table deprecation warning Recent Terraform versions may warn that dynamodb_table is deprecated for S3 backends. Prefer use_lockfile = true in backend config when compatible with your workflow. Keep dynamodb_table only for legacy compatibility needs. Issue: Unknown provider or module parameters Re-run custom resource detection Use WebSearch to look up current documentation Check version compatibility Issue: Generate block conflicts (file already exists) ERROR: The file path ./versions.tf already exists and was not generated by terragrunt. Can not generate terraform file: ./versions.tf already exists Solution: This occurs when static .tf files exist that conflict with Terragrunt's generate blocks. Either: Remove the conflicting static files ( versions.tf , provider.tf , backend.tf ) Or use if_exists = "skip" in the generate block to not overwrite existing files
Remove conflicting files
rm
-f
versions.tf provider.tf backend.tf
rm
-rf
.terragrunt-cache
Issue: Root terragrunt.hcl anti-pattern warning
WARN: Using terragrunt.hcl as the root of Terragrunt configurations is an anti-pattern
Solution:
In Terragrunt 0.93+, the root configuration file should be named
root.hcl
instead of
terragrunt.hcl
. Rename the file:
mv
terragrunt.hcl root.hcl
Update include blocks in child modules to reference root.hcl
Best Practices Integration Reference the comprehensive best practices guide for detailed recommendations:
Read the best practices reference
if [ -f references/best_practices.md ] ; then cat references/best_practices.md else echo "WARNING: references/best_practices.md not found; continue with checklist in this document." fi Key best practices to check: ✅ Use include for shared configuration ✅ Provide mock_outputs for dependencies ✅ Use generate blocks for provider config ✅ Enable state encryption and locking ✅ Use environment variables for dynamic values ✅ Specify version constraints ✅ Avoid hardcoded values ✅ Use meaningful directory structure ✅ Enable security features (encryption, IAM roles) When validating, check for anti-patterns: ❌ Hardcoded credentials or account IDs ❌ Missing mock outputs ❌ Overly deep directory nesting ❌ Duplicated configuration across modules ❌ Missing version constraints ❌ Unencrypted state Refer to references/best_practices.md for complete examples and detailed guidance. Tool Requirements Required: terragrunt (>= 0.93.0 recommended for new CLI) terraform or opentofu (>= 1.6.0 recommended) Optional but recommended: tflint - HCL linting trivy - Security scanning (replaces tfsec) checkov - Alternative security scanner (750+ built-in policies) graphviz (dot) - Dependency visualization jq - JSON parsing python3 - For custom resource detection script Deprecated tools: tfsec - Merged into Trivy, no longer actively maintained Installation commands:
macOS
brew install terragrunt terraform tflint trivy graphviz jq
Install Trivy (recommended security scanner)
brew install trivy
Install Checkov (alternative security scanner)
pip3 install checkov
Legacy tfsec (deprecated - use trivy instead)
brew install tfsec
Linux - Trivy
curl -sfL https://raw.githubusercontent.com/aquasecurity/trivy/main/contrib/install.sh | sh -s -- -b /usr/local/bin
Linux - Checkov
pip3 install checkov
Verify installations
terragrunt --version trivy --version checkov --version Integration with Context7 MCP If Context7 MCP is available, use it for provider/module documentation lookup: Resolve library ID: mcp__context7__resolve-library-id with libraryName: "mongodb/mongodbatlas" Query documentation: mcp__context7__query-docs with libraryId: "/mongodb/mongodbatlas" and query: "authentication requirements" This provides version-aware documentation directly, as an alternative to WebSearch. Automated Workflows CI/CD Integration Use the deterministic skill-level CI gate as the blocking check: bash scripts/run_ci_checks.sh --require-shellcheck This gate runs: Shell syntax checks ( bash -n ) Python syntax checks ( python3 -m py_compile ) Python regression tests ( test/test_detect_custom_resources.py ) Shell regression tests ( test/test_validate_terragrunt.sh ) ShellCheck linting (required in CI when --require-shellcheck is set) After that gate passes, run environment-dependent validation in jobs that have Terragrunt/Terraform credentials configured:
!/bin/bash
ci-validate.sh
set -euo pipefail echo "Running deterministic validator checks..." bash scripts/run_ci_checks.sh --require-shellcheck echo "Installing dependencies..."
Install terragrunt, terraform, tflint, trivy/checkov
echo "Detecting custom resources..." python3 scripts/detect_custom_resources.py . --format json
custom_resources.json
Could integrate with automated documentation lookup here
echo "Running validation suite..." SKIP_PLAN = true SKIP_BACKEND_INIT = true bash scripts/validate_terragrunt.sh . echo "Validation complete!" Pre-commit Hook Example pre-commit hook for local development:
!/bin/bash
.git/hooks/pre-commit
Format check
terragrunt hcl fmt --check || { echo "HCL formatting issues found. Run: terragrunt hcl fmt" exit 1 }
Quick HCL syntax validation (Terragrunt 0.93+)
Note: For full validation, use: terragrunt init && terragrunt validate
But that requires credentials. HCL format check catches syntax errors.
echo "Pre-commit validation passed!" Troubleshooting Guide Validation Modes and Exit Semantics validate_terragrunt.sh derives mode from the target directory and changes the Terragrunt command path accordingly: Mode Directory shape Terragrunt HCL check Terraform check Exit semantics single terragrunt.hcl (or terragrunt.stack.hcl ) in target dir terragrunt hcl validate terragrunt validate (with terragrunt init unless skipped) Any syntax/validate failure exits non-zero multi Nested units exist below target terragrunt hcl validate --all (fallback to plain hcl validate if --all is unsupported) terragrunt run --all validate (with run --all init unless skipped) Any unit failure exits non-zero root-only root.hcl only, no unit in target dir Warn and skip Warn and skip Returns success (0) for these skipped steps none No recognized Terragrunt config files Error Error Returns non-zero Debug Mode Enable debug output for troubleshooting:
Terragrunt debug
TERRAGRUNT_DEBUG
1 terragrunt plan
Terraform trace
TF_LOG
TRACE terragrunt plan
Common Error Patterns
"Error: Module not found"
Clear cache:
rm -rf .terragrunt-cache
Re-initialize:
terragrunt init
"Error: Provider not found"
Check provider configuration
Run custom resource detection
Use WebSearch to find correct provider source and version
Verify required_providers block
"Error: Invalid function call"
Check Terragrunt version compatibility
Review function syntax in documentation
"Cycle detected in dependency graph"
Review dependency chains
Consider refactoring into single module
Use data sources instead of dependencies
"Error acquiring state lock"
Check if another process is running
Verify DynamoDB table (for S3 backend)
Force unlock if safe:
terragrunt force-unlock
Example: exclude specific rules
Dependency Graph Analysis Analyze complex dependency chains:
Generate detailed graph (Terragrunt 0.93+ syntax)
terragrunt dag graph
graph.dot
Convert to visual format
dot -Tpng graph.dot
graph.png dot -Tsvg graph.dot
graph.svg
Analyze for circular dependencies
grep -A5 "cycle" < ( terragrunt dag graph 2
&1 ) Resources Scripts scripts/validate_terragrunt.sh - Comprehensive validation suite scripts/detect_custom_resources.py - Custom provider/module detector References references/best_practices.md - Comprehensive best practices guide covering: Directory structure patterns DRY principles and configuration sharing Dependency management Security best practices Testing and validation workflows Common anti-patterns to avoid Troubleshooting guides External Documentation Terragrunt Documentation Terraform Best Practices Terraform Registry Done Criteria Docs and scripts agree on one canonical executable workflow. Fixture runs are deterministic via: python3 test/test_detect_custom_resources.py bash test/test_validate_terragrunt.sh Validation and security failures are reported with correct non-zero exits.