terragrunt

name	terragrunt
description	Homelab infrastructure management with Terragrunt and OpenTofu. Use when: adding/modifying machines in inventory.hcl, creating or updating units and stacks, working with feature flags, running validation (fmt, validate, test, plan), understanding the units→stacks→modules architecture, or working with HCL configuration files. Triggers: "terragrunt", "terraform", "opentofu", "tofu", "infrastructure code", "IaC", "inventory.hcl", "networking.hcl", "HCL files", "add machine", "add node", "cluster provisioning", "bare metal", "talos config", "task tg:", "infrastructure plan", "infrastructure apply", "stacks", "units", "modules architecture"
user-invocable	false

Terragrunt Infrastructure Skill

Manage bare-metal Kubernetes infrastructure from PXE boot to running clusters.

For architecture overview (units vs modules, config centralization), see infrastructure/CLAUDE.md. For detailed unit patterns, see infrastructure/units/CLAUDE.md.

Task Commands (Always Use These)

# Validation (run in order)
task tg:fmt                    # Format HCL files
task tg:test-<module>          # Test specific module (e.g., task tg:test-config)
task tg:validate-<stack>       # Validate stack (e.g., task tg:validate-integration)

# Operations
task tg:list                   # List available stacks
task tg:plan-<stack>           # Plan (e.g., task tg:plan-integration)
task tg:apply-<stack>          # Apply (REQUIRES HUMAN APPROVAL)
task tg:gen-<stack>            # Generate stack files
task tg:clean-<stack>          # Clean generated files

NEVER run terragrunt or tofu directly—always use task commands.

How to Add a Machine

Edit inventory.hcl → run task tg:plan-live → review plan (config module auto-includes machines where cluster == "live") → request human approval before apply.

node50 = {
  cluster = "live"
  type    = "worker"
  install = {
    selector     = "disk.model == 'Samsung'"
    architecture = "amd64"
  }
  interfaces = [{
    id           = "eth0"
    hardwareAddr = "aa:bb:cc:dd:ee:ff"  # VERIFY correct
    addresses    = [{ ip = "192.168.10.50" }]  # VERIFY available
  }]
}

How to Add a Feature Flag

Add version to versions.hcl if needed → add feature detection in modules/config/main.tf (contains(var.features, "new-feature")) → enable in the stack's features list (features = ["gateway-api", "longhorn", "new-feature"]).

How to Create a New Unit

Create units/new-unit/terragrunt.hcl (include root, point to module source, declare dependency "config" with mock_outputs, set inputs = dependency.config.outputs.new_unit) → create modules/new-unit/ with variables.tf, main.tf, outputs.tf, versions.tf → add output from config module → add unit block to stacks that need it. See units.md for the full unit template.

For module tests, see the opentofu-modules skill. Run with task tg:test-config or task tg:test for all modules.

Important

• NEVER guess MAC addresses or IPs—verify against inventory.hcl
• NEVER commit .terragrunt-cache/ or .terragrunt-stack/
• NEVER manually edit Terraform state

State Operations

When removing state entries with indexed resources (e.g., this["rpi4"]), xargs strips the quotes causing errors. Use a while loop instead:

# WRONG - xargs mangles quotes in resource names
terragrunt state list | xargs -n 1 terragrunt state rm

# CORRECT - while loop preserves quotes
terragrunt state list | while read -r resource; do terragrunt state rm "$resource"; done

This applies to any state operation on resources with map keys like data.talos_machine_configuration.this["rpi4"].

Validation Checklist

task tg:fmt → task tg:test (if module tests exist) → task tg:validate-<stack> for ALL stacks → task tg:plan-<stack> reviewed (no unexpected destroys, network changes won't break connectivity).

References

• stacks.md - Detailed Terragrunt stacks documentation
• units.md - Detailed Terragrunt units documentation