DevOps Classroom notes 08/Nov/2025

Terraform contd

Google Style Guide for Terraform

• official style guide
• Prompt for using style guide

According to Terraform style guide over here https://developer.hashicorp.com/terraform/language/style. How should i name variables

• Google style guide and best practices

Terraform input variables

• Terraform allows to define variables and use them (which is better than hardcoding)
• Syntax

variable "<LABEL>" {
  type        = <TYPE>
  default     = <DEFAULT_VALUE>
  description = "<DESCRIPTION>"
  sensitive   = <true|false>
  nullable    = <true|false>

}

• Lets create a new tf file called as inputs.tf

variable "vpc_cidr" {
    type = string
    description = "vpc cidr"
    default = "192.168.0.0/16"
}

# -------------------
# Web Subnet Variables
# -------------------

variable "web_subnet_cidr" {
    type = string
    description = "web subnet cidr"
    default = "192.168.0.0/24"
}

variable "web_subnet_az" {
    type = string
    description = "web subnet az"
    default = "ap-south-1a"
}

# -------------------
# App Subnet Variables
# -------------------
variable "app_subnet_cidr" {
  type        = string
  description = "App subnet CIDR block"
  default     = "192.168.1.0/24"
}

variable "app_subnet_az" {
  type        = string
  description = "App subnet Availability Zone"
  default     = "ap-south-1b"
}

# -------------------
# DB Subnet Variables
# -------------------
variable "db_subnet_cidr" {
  type        = string
  description = "DB subnet CIDR block"
  default     = "192.168.2.0/24"
}

variable "db_subnet_az" {
  type        = string
  description = "DB subnet Availability Zone"
  default     = "ap-south-1c"
}

• default values will be picked up when we dont pass the value
• variable values can be passed by terraform commands

terraform apply -var 'vpc_cidr=10.0.0.0/16' -var 'web_subnet_cidr=10.0.0.0/24'

• When we have many variables to pass the above command line becomes difficult to manage. so terraform allows to pass a file with variables which has an extension of .tfvars
• ideally a tfvars file per environment and execute

 terraform apply -var-file='default.tfvars'

• Refer Here for the changes done.

Terraform meta argument count

• Refer Here for official docs

Terraform functions

• Refer Here for functions
• Refer Here for example with list usage in variables and count