Demo Resource Dependencies

This lesson demonstrates how to manage resource dependencies in OpenTofu, covering both explicit and implicit approaches using depends_on and attribute references.

Understanding Resource Dependencies
Generating a TLS Private Key
Writing the Key to a Local File
Cleanup
Explicit Dependency with depends_on
Links and References

Understanding Resource Dependencies

OpenTofu resources can depend on each other in two ways:

Dependency Type	Definition	Syntax Example
Explicit	Resource A waits for Resource B without accessing its attributes directly.	`depends_on = [local_file.krill]`
Implicit	Resource A references Resource B’s attribute in its arguments.	`content = tls_private_key.pvtkey.private_key_pem`

First, we set an explicit dependency using the depends_on argument when Resource A does not reference Resource B’s attributes:

The image shows a Visual Studio Code editor with a welcome message for KodeKloud OpenTofu Lab on the right, and a multiple-choice question about dependencies on the left.

Next, an implicit dependency is created by referencing one resource’s attributes inside another:

The image shows a KodeKloud OpenTofu Lab interface with a Visual Studio Code editor on the right, displaying a welcome message and terminal, and a quiz question on the left about implicit dependency.

Generating a TLS Private Key

Navigate to your project’s key-generator directory and create key.tf:

resource "tls_private_key" "pvtkey" {
  algorithm = "RSA"
  rsa_bits  = 4096
}

Initialize, plan, and apply the configuration:

opentofu init
opentofu plan
opentofu apply
# Type "yes" to confirm

Inspect the generated key:

opentofu show tls_private_key.pvtkey

Storing private keys in plain text can pose a security risk. Never commit sensitive key material to version control.

Writing the Key to a Local File

Update key.tf to include a local_file resource:

resource "tls_private_key" "pvtkey" {
  algorithm = "RSA"
  rsa_bits  = 4096
}

resource "local_file" "key_details" {
  filename = "/root/key.txt"
  content  = tls_private_key.pvtkey.private_key_pem
}

Re-run OpenTofu:

opentofu init
opentofu plan
opentofu apply
# Confirm with "yes"

Verify that /root/key.txt contains your PEM-encoded private key.

Cleanup

When you’re done, destroy both resources:

opentofu destroy
# Confirm with "yes"

Explicit Dependency with depends_on

Create a new directory (e.g., /root/explicit-dependency) and add main.tf:

resource "local_file" "krill" {
  filename = "/root/krill.txt"
  content  = "krill"
}

resource "local_file" "whale" {
  filename   = "/root/whale.txt"
  content    = "whale"
  depends_on = [local_file.krill]
}

Here, whale will only be created after krill, illustrating an explicit dependency without attribute references. Apply this configuration:

opentofu init
opentofu plan
opentofu apply
# Enter "yes" to proceed

Course Introduction

Introduction to Infrastructure as Code

OpenTofu Basics

OpenTofu State

Working with OpenTofu

Remote State

OpenTofu Provisioners

OpenTofu Import, Tainting Resources and Deubugging

OpenTofu Modules

OpenTofu Functions and Conditional Expressions

OpenTofu: Beyond Basics

Course Conclusion

Getting Started with OpenTofu

Demo Resource Dependencies

Table of Contents

Understanding Resource Dependencies

Generating a TLS Private Key

Writing the Key to a Local File

Cleanup

Explicit Dependency with depends_on

Links and References

Watch Video

Practice Lab

​Table of Contents

​Understanding Resource Dependencies

​Generating a TLS Private Key

​Writing the Key to a Local File

​Cleanup

​Explicit Dependency with depends_on

​Links and References

Watch Video

Practice Lab

Table of Contents

Understanding Resource Dependencies

Generating a TLS Private Key

Writing the Key to a Local File

Cleanup

Explicit Dependency with depends_on

Links and References