Demo Count and for each

In this lab, you’ll learn how to leverage the count and for_each meta-arguments to create multiple resource instances dynamically in OpenTofu. We’ll work through a series of tasks:

• Inspecting a basic configuration
• Scaling with count
• Parameterizing with variables
• Ensuring uniqueness with for_each

Task 1: Inspect the Base Configuration

Navigate to your project directory:

cd /root/opentofu-projects/project-shade

Open the default main.tf:

resource "local_sensitive_file" "name" {
  filename = "/root/user-data"
  content  = "password: S3cr3tP@ssw0rd"
}

Since there’s only one resource block, running opentofu plan would create one file at /root/user-data.

Task 2: Create Multiple Instances with count

Add the count argument to generate three instances:

resource "local_sensitive_file" "name" {
  filename = "/root/user-data"
  content  = "password: S3cr3tP@ssw0rd"
  count    = 3
}

Initialize and preview:

opentofu init
opentofu plan

Expected plan excerpt:

# local_sensitive_file.name will be created with 3 instances
+ resource "local_sensitive_file" "name" {
    + count    = 3
    + filename = "/root/user-data"
    + content  = (sensitive)
  }

Apply the changes:

opentofu apply

All three instances target the same filepath, so you end up with just one actual file on disk.

Task 3: Accessing Resources by Index

Resources managed with count form a list. To view the ID of the second element (index 1):

opentofu state show local_sensitive_file.name[1]

Look for the id attribute in the output.

Task 4: Parameterize with Variables and count

Define variables in variables.tf:

variable "users" {
  type = list(string)
}

variable "content" {
  default = "password: S3Cr3tP@ssw0rd"
}

Update main.tf:

resource "local_sensitive_file" "name" {
  count    = length(var.users)
  filename = var.users[count.index]
  content  = var.content
}

Now each users element becomes a filename. Initialize and apply:

opentofu init
opentofu plan
opentofu apply

Task 5: Set Default Values for Variables

Add sensible defaults in variables.tf:

variable "users" {
  type    = list(string)
  default = ["/root/user1", "/root/user11", "/root/user12"]
}

variable "content" {
  default = "password: S3Cr3tP@ssw0rd"
}

Key points:

• Type of users: list(string)
• List vs. set: Lists allow duplicates; sets do not.

Example of a duplicate in a list (invalid for a set):

variable "users" {
  default = [
    "/root/user10",
    "/root/user1",
    "/root/user12",
    "/root/user10"  # duplicate
  ]
}

Task 6: Ensure Unique Instances with for_each

Refactor main.tf to use for_each on a set:

resource "local_sensitive_file" "name" {
  for_each = toset(var.users)
  filename = each.value
  content  = var.content
}

The toset() function removes duplicates, and for_each creates a map keyed by each unique filename.

Initialize and apply:

opentofu init
opentofu plan
opentofu apply

Expected output:

local_sensitive_file.name["/root/user10"]: Creating...
local_sensitive_file.name["/root/user11"]: Creating...
local_sensitive_file.name["/root/user12"]: Creating...
Apply complete! Resources: 3 added, 0 changed, 0 destroyed.

Comparing count vs. for_each

Q&A

1. What data structure does for_each produce?
   A map, keyed by each unique element.

2. How do you address the resource for /root/user11 with for_each?
   local_sensitive_file.name["/root/user11"]

Further Reading

• OpenTofu Documentation
• Terraform Meta-Arguments
• Understanding Lists and Sets

That’s a wrap for this lab. Happy automating!