Resource block syntax in Terraform - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Configuration

intermediate

Identify the correct resource block syntax for creating an AWS S3 bucket

Which resource block correctly defines an AWS S3 bucket named "my_bucket" with versioning enabled?

A

resource "aws_s3_bucket" "my_bucket" {
  bucket = "my_bucket"
  versioning = true
}

B

resource aws_s3_bucket my_bucket {
  bucket = "my_bucket"
  versioning = true
}

C

resource "aws_s3_bucket" "my_bucket" {
  name = "my_bucket"
  versioning = {
    enabled = true
  }
}

D

resource "aws_s3_bucket" "my_bucket" {
  bucket = "my_bucket"
  versioning {
    enabled = true
  }
}

💡 Hint

Remember that nested blocks like versioning require a block syntax, not just an attribute assignment.

Option D correctly uses the resource block syntax with the nested versioning block and the enabled attribute set to true. Option D misses quotes and uses incorrect versioning syntax. Option D uses name instead of bucket attribute. Option D incorrectly assigns versioning as a boolean instead of a block.

❓ service_behavior

intermediate

Effect of missing required attribute in resource block

What happens if you define an AWS EC2 instance resource block without specifying the required attribute "ami"?

Terraform

resource "aws_instance" "example" {
  instance_type = "t2.micro"
}

A Terraform will ignore the missing attribute and create the instance with instance_type only.

B Terraform will create the instance with a default AMI automatically.

C Terraform plan will fail with an error about missing required attribute "ami".

D Terraform will create the instance but it will be stopped by default.

💡 Hint

Think about how Terraform validates resource blocks before applying.

The ami attribute is required for aws_instance. Terraform validates resource blocks and will fail the plan phase if required attributes are missing. It does not provide defaults or partial creations.

❓ Architecture

advanced

Correct resource block to create a VPC with CIDR block and enable DNS support

Which resource block correctly creates an AWS VPC with CIDR block "10.0.0.0/16" and enables DNS support?

A

resource "aws_vpc" "main" {
  cidr = "10.0.0.0/16"
  enable_dns = true
}

B

resource "aws_vpc" "main" {
  cidr_block = "10.0.0.0/16"
  enable_dns_support = true
}

C

resource "aws_vpc" "main" {
  cidr_block = "10.0.0.0/16"
  dns_support = true
}

D

resource "aws_vpc" "main" {
  cidr_block = "10.0.0.0/16"
  enable_dns_hostnames = true
}

💡 Hint

Check the exact attribute names required by the AWS VPC resource.

Option B uses the correct attribute names cidr_block and enable_dns_support. Option B uses incorrect attribute names. Option B uses dns_support which is invalid. Option B enables DNS hostnames but not DNS support.

❓ security

advanced

Resource block to create a security group allowing inbound HTTP traffic

Which resource block correctly creates an AWS security group allowing inbound HTTP (port 80) traffic from anywhere?

A

resource "aws_security_group" "web_sg" {
  name = "web_sg"
  ingress {
    from_port = 80
    to_port = 80
    protocol = "tcp"
    cidr_blocks = ["0.0.0.0/0"]
  }
}

B

resource "aws_security_group" "web_sg" {
  name = "web_sg"
  ingress = [{
    from_port = 80
    to_port = 80
    protocol = "tcp"
    cidr_blocks = ["0.0.0.0/0"]
  }]
}

C

resource "aws_security_group" "web_sg" {
  name = "web_sg"
  ingress {
    port = 80
    protocol = "tcp"
    cidr_blocks = ["0.0.0.0/0"]
  }
}

D

resource "aws_security_group" "web_sg" {
  name = "web_sg"
  ingress {
    from_port = 80
    to_port = 80
    protocol = "tcp"
    cidr_block = "0.0.0.0/0"
  }
}

💡 Hint

Remember the correct attribute names and types for ingress rules.

Option A correctly uses the ingress block with from_port, to_port, protocol, and cidr_blocks as a list. Option A incorrectly assigns ingress as a list directly. Option A uses port which is invalid. Option A uses cidr_block instead of cidr_blocks list.

✅ Best Practice

expert

Correct way to reference another resource's attribute in a resource block

Given a resource "aws_vpc" "main" with attribute "id", which resource block correctly references this VPC ID when creating a subnet?

Terraform

resource "aws_vpc" "main" {
  cidr_block = "10.0.0.0/16"
}

resource "aws_subnet" "subnet1" {
  vpc_id = ???
  cidr_block = "10.0.1.0/24"
}

A vpc_id = aws_vpc.main.id

B vpc_id = "aws_vpc.main.id"

C vpc_id = ${aws_vpc.main.id}

D vpc_id = $aws_vpc.main.id

💡 Hint

Terraform 0.12+ allows direct references without interpolation syntax.

Option A uses the correct direct reference syntax. Option A treats the reference as a string literal. Option A uses deprecated interpolation syntax which is invalid without quotes. Option A uses invalid shell-style variable syntax.

Practice

1. What is the correct way to start a resource block in Terraform?

easy

A. resource "aws_instance" { example }

B. resource aws_instance example { }

C. resource "example" "aws_instance" { }

D. resource "aws_instance" "example" { }

Solution

1. Step 1: Understand resource block syntax

   A resource block starts with the keyword resource, followed by the resource type in quotes, then the resource name in quotes.

2. Step 2: Match the correct syntax

   resource "aws_instance" "example" { } correctly uses resource "aws_instance" "example" { }, which matches the required syntax.

3. Final Answer:

   resource "aws_instance" "example" { } -> Option D

4. Quick Check:

   Resource block syntax = resource "type" "name" { } [OK]

Hint: Resource block always uses resource "type" "name" [OK]

Common Mistakes:

• Omitting quotes around type or name
• Swapping type and name order
• Using braces incorrectly

2. Which of the following is a valid property assignment inside a Terraform resource block?

easy

A. instance_type = t2.micro

B. instance_type => "t2.micro"

C. instance_type = "t2.micro"

D. instance_type: "t2.micro"

Solution

1. Step 1: Identify correct property syntax

   Terraform uses = to assign values, and string values must be in quotes.

2. Step 2: Check each option

   instance_type = "t2.micro" uses instance_type = "t2.micro", which is correct. instance_type = t2.micro misses quotes, B and C use invalid assignment symbols.

3. Final Answer:

   instance_type = "t2.micro" -> Option C

4. Quick Check:

   Property assignment uses = and quotes for strings [OK]

Hint: Use = and quotes for string values inside resource blocks [OK]

Common Mistakes:

• Forgetting quotes around string values
• Using colon or arrow instead of =
• Missing equal sign

3. Given this resource block snippet, what will Terraform create?

resource "aws_s3_bucket" "mybucket" {
  bucket = "my-unique-bucket-123"
  acl    = "private"
}

medium

A. An S3 bucket named "mybucket" with public access

B. An S3 bucket named "my-unique-bucket-123" with private access

C. An S3 bucket named "aws_s3_bucket" with private access

D. A storage container with default public access

Solution

1. Step 1: Identify resource type and name

   The resource type is aws_s3_bucket, and the resource name is mybucket. The bucket property sets the actual bucket name.

2. Step 2: Understand properties

   The bucket property sets the bucket's real name to "my-unique-bucket-123". The acl is set to "private", meaning no public access.

3. Final Answer:

   An S3 bucket named "my-unique-bucket-123" with private access -> Option B

4. Quick Check:

   Bucket name = property value, ACL = private [OK]

Hint: Bucket name is from bucket property, not resource name [OK]

Common Mistakes:

• Confusing resource name with actual bucket name
• Assuming default ACL is public
• Ignoring property values inside the block

4. Identify the error in this Terraform resource block:

resource "aws_instance" "web" {
  ami = "ami-123456"
  instance_type = t2.micro
}

medium

A. Missing quotes around the instance_type value

B. Resource block missing closing brace

C. Incorrect resource type name

D. Missing resource name

Solution

1. Step 1: Check property value syntax

   The instance_type property value t2.micro is missing quotes, which is required for string values.

2. Step 2: Verify block structure

   The resource block has correct braces and resource type/name, so no errors there.

3. Final Answer:

   Missing quotes around the instance_type value -> Option A

4. Quick Check:

   String values must be quoted [OK]

Hint: Always quote string values inside resource blocks [OK]

Common Mistakes:

• Forgetting quotes around string properties
• Assuming braces are optional
• Mixing resource type and name order

5. You want to create two AWS EC2 instances with different names but the same AMI and instance type using resource blocks. Which is the best way to write this in Terraform?

hard

A. resource "aws_instance" "web1" {
ami = "ami-abc123"
instance_type = "t2.micro"
}
resource "aws_instance" "web2" {
ami = "ami-abc123"
instance_type = "t2.micro"
}

B. resource "aws_instance" "web" {
count = 2
ami = "ami-abc123"
instance_type = "t2.micro"
}

C. resource "aws_instance" "web" {
ami = "ami-abc123"
instance_type = "t2.micro"
name = ["web1", "web2"]
}

D. resource "aws_instance" "web" {
ami = "ami-abc123"
instance_type = "t2.micro"
for_each = ["web1", "web2"]
}

Solution

1. Step 1: Understand resource naming and duplication

   Each resource block must have a unique name.

   resource "aws_instance" "web1" {
     ami = "ami-abc123"
     instance_type = "t2.micro"
   }
   resource "aws_instance" "web2" {
     ami = "ami-abc123"
     instance_type = "t2.micro"
   }

   defines two separate resources with different names.

2. Step 2: Evaluate other options

   resource "aws_instance" "web" {
     count = 2
     ami = "ami-abc123"
     instance_type = "t2.micro"
   }

   uses count but does not differentiate names.

   resource "aws_instance" "web" {
     ami = "ami-abc123"
     instance_type = "t2.micro"
     name = ["web1", "web2"]
   }

   tries to assign a list to name property, which is invalid.

   resource "aws_instance" "web" {
     ami = "ami-abc123"
     instance_type = "t2.micro"
     for_each = ["web1", "web2"]
   }

   uses for_each incorrectly without mapping names.

3. Final Answer:

   Define two separate resource blocks with unique names -> Option A

4. Quick Check:

   Unique resource names needed for multiple instances [OK]

Hint: Use separate resource blocks with unique names for multiple instances [OK]

Common Mistakes:

• Using count without unique names
• Assigning list to single property
• Misusing for_each without proper keys