> ## Documentation Index
> Fetch the complete documentation index at: https://notes.kodekloud.com/llms.txt
> Use this file to discover all available pages before exploring further.
# Demo Resource Dependencies
> This lesson demonstrates managing resource dependencies in OpenTofu using explicit and implicit approaches.
This lesson demonstrates how to manage resource dependencies in OpenTofu, covering both explicit and implicit approaches using `depends_on` and attribute references.
## Table of Contents
1. [Understanding Resource Dependencies](#understanding-resource-dependencies)
2. [Generating a TLS Private Key](#generating-a-tls-private-key)
3. [Writing the Key to a Local File](#writing-the-key-to-a-local-file)
4. [Cleanup](#cleanup)
5. [Explicit Dependency with depends\_on](#explicit-dependency-with-depends_on)
6. [Links and References](#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:
Next, an **implicit dependency** is created by referencing one resource’s attributes inside another:
## Generating a TLS Private Key
Navigate to your project’s `key-generator` directory and create `key.tf`:
```hcl theme={null}
resource "tls_private_key" "pvtkey" {
algorithm = "RSA"
rsa_bits = 4096
}
```
Initialize, plan, and apply the configuration:
```bash theme={null}
opentofu init
opentofu plan
opentofu apply
# Type "yes" to confirm
```
Inspect the generated key:
```bash theme={null}
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:
```hcl theme={null}
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:
```bash theme={null}
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:
```bash theme={null}
opentofu destroy
# Confirm with "yes"
```
## Explicit Dependency with depends\_on
Create a new directory (e.g., `/root/explicit-dependency`) and add `main.tf`:
```hcl theme={null}
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:
```bash theme={null}
opentofu init
opentofu plan
opentofu apply
# Enter "yes" to proceed
```
## Links and References
* [OpenTofu CLI Documentation](https://docs.opentofu.org/cli)
* [Terraform TLS Provider](https://registry.terraform.io/providers/hashicorp/tls/latest)
* [OpenTofu GitHub Repository](https://github.com/opentofu/opentofu)