Count for multiple instances in Terraform - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create multiple instances using count.

Terraform

resource "aws_instance" "example" {
  ami           = "ami-12345678"
  instance_type = "t2.micro"
  count         = [1]
}

Drag options to blanks, or click blank then click option'

A3

B1

C0

D"3"

Attempts:

3 left

💡 Hint

Common Mistakes

Using a string instead of a number for count.

Setting count to 0 which creates no instances.

The count argument expects a number to specify how many instances to create. Using 3 creates three instances.

2fill in blank

medium

Complete the code to reference the ID of the second instance created using count.

Terraform

output "second_instance_id" {
  value = aws_instance.example[[1]].id
}

Drag options to blanks, or click blank then click option'

A1

B2

C0

D"1"

Attempts:

3 left

💡 Hint

Common Mistakes

Using 2 instead of 1 for the second instance index.

Using a string index instead of a number.

Terraform uses zero-based indexing. The second instance is at index 1.

3fill in blank

hard

Fix the error in the count expression to create instances based on a variable.

Terraform

variable "instance_count" {
  type    = number
  default = 2
}

resource "aws_instance" "example" {
  ami           = "ami-12345678"
  instance_type = "t2.micro"
  count         = [1]
}

Drag options to blanks, or click blank then click option'

Ainstance_count

Bvar.instance_count

Cvar["instance_count"]

D"var.instance_count"

Attempts:

3 left

💡 Hint

Common Mistakes

Using the variable name without var. prefix.

Using quotes around the variable reference.

To use a variable in Terraform, prefix it with var.. So var.instance_count correctly references the variable.

4fill in blank

hard

Fill both blanks to create instances with different names using count and the index.

Terraform

resource "aws_instance" "example" {
  ami           = "ami-12345678"
  instance_type = "t2.micro"
  count         = 3
  tags = {
    Name = "example-$[1]"
    Env  = "$[2]"
  }
}

Drag options to blanks, or click blank then click option'

Acount.index

Bvar.environment

Ccount_index

Denvironment

Attempts:

3 left

💡 Hint

Common Mistakes

Using count_index instead of count.index.

Not using var. prefix for variables.

count.index gives the current instance number starting at 0, used to create unique names. var.environment references a variable for environment tagging.

5fill in blank

hard

Fill all three blanks to create a map of instance IDs keyed by their index using count.

Terraform

output "instance_ids_map" {
  value = { for i in range([1]) : i => aws_instance.example[[2]].id if i [3] 0 }
}

Drag options to blanks, or click blank then click option'

Avar.instance_count

Bi

C>

Dcount.index

Attempts:

3 left

💡 Hint

Common Mistakes

Using count.index instead of i inside the loop.

Using < instead of > in the condition.

range(var.instance_count) loops over the number of instances. i is the index used to access each instance. The condition i > 0 filters out the first instance.

Practice

1. What does the count argument do in a Terraform resource block?

easy

A. It deletes resources after creation.

B. It creates multiple copies of the resource based on the count value.

C. It renames the resource dynamically.

D. It pauses resource creation until manually resumed.

Solution

1. Step 1: Understand the purpose of count

   The count argument tells Terraform how many copies of a resource to create.

2. Step 2: Recognize the effect of count value

   If count is set to 3, Terraform creates 3 identical resources.

3. Final Answer:

   It creates multiple copies of the resource based on the count value. -> Option B

4. Quick Check:

   count creates copies = A [OK]

Hint: Count controls how many resource copies are made [OK]

Common Mistakes:

• Thinking count deletes resources
• Assuming count renames resources
• Believing count pauses creation

2. Which of the following is the correct syntax to create 4 instances of an AWS EC2 resource using count?

easy

A. resource "aws_instance" "example" { count = 4 }

B. resource "aws_instance" "example" { count = "four" }

C. resource "aws_instance" "example" { count = true }

D. resource "aws_instance" "example" { count = 1..4 }

Solution

1. Step 1: Check the count value type

   The count argument must be a number, not a string or boolean.

2. Step 2: Validate syntax correctness

   resource "aws_instance" "example" { count = 4 } uses count = 4, which is a valid number and correct syntax.

3. Final Answer:

   resource "aws_instance" "example" { count = 4 } -> Option A

4. Quick Check:

   count = number syntax = D [OK]

Hint: Count must be a number, not string or boolean [OK]

Common Mistakes:

• Using string instead of number for count
• Using boolean true/false for count
• Trying to use a range expression directly

3. Given this Terraform snippet:

resource "aws_s3_bucket" "bucket" {
  count = 3
  bucket = "my-bucket-${count.index}"
}

What will be the names of the created buckets?

medium

A. ["my-bucket", "my-bucket", "my-bucket"]

B. ["my-bucket-1", "my-bucket-2", "my-bucket-3"]

C. ["my-bucket-0", "my-bucket-1", "my-bucket-2"]

D. ["my-bucket-3"]

Solution

1. Step 1: Understand count.index usage

   The count.index starts at 0 and increments by 1 for each instance.

2. Step 2: Apply count.index to bucket names

   With count=3, bucket names become "my-bucket-0", "my-bucket-1", and "my-bucket-2".

3. Final Answer:

   ["my-bucket-0", "my-bucket-1", "my-bucket-2"] -> Option C

4. Quick Check:

   count.index starts at 0 = C [OK]

Hint: count.index starts at zero and increments [OK]

Common Mistakes:

• Starting count.index at 1 instead of 0
• Using same name for all instances
• Assuming only one bucket created

4. Identify the error in this Terraform resource block:

resource "aws_security_group" "sg" {
  count = 2
  name = "sg-${count}"
}

medium

A. Name attribute cannot use interpolation.

B. Missing required provider configuration.

C. Count cannot be used with security groups.

D. Using count instead of count.index in the name.

Solution

1. Step 1: Check usage of count in interpolation

   The variable count is not valid inside strings; count.index should be used.

2. Step 2: Confirm correct interpolation

   Replace "sg-${count}" with "sg-${count.index}" to get unique names.

3. Final Answer:

   Using count instead of count.index in the name. -> Option D

4. Quick Check:

   Use count.index for indexes in strings = A [OK]

Hint: Use count.index, not count, inside strings [OK]

Common Mistakes:

• Using count instead of count.index
• Assuming count cannot be used with this resource
• Thinking name interpolation is disallowed

5. You want to create multiple AWS EC2 instances with different instance types using count. Which approach correctly assigns instance types from a list?

hard

A. Use count with var.instance_types[count.index] to assign types.

B. Use count and assign a single instance type to all instances.

C. Use count with a fixed string for instance type.

D. Use count with a random instance type each time.

Solution

1. Step 1: Understand how to assign different values per instance

   Using count.index allows selecting different values from a list for each instance.

2. Step 2: Apply list indexing with count.index

   Accessing var.instance_types[count.index] assigns the correct instance type per resource copy.

3. Final Answer:

   Use count with var.instance_types[count.index] to assign types. -> Option A

4. Quick Check:

   List indexing with count.index assigns unique values = B [OK]

Hint: Index lists with count.index for unique resource values [OK]

Common Mistakes:

• Assigning same instance type to all
• Using fixed string ignoring count.index
• Expecting random assignment without code