Step-00: Introduction
- v1: Input Variables - Basics
- v2: Provide Input Variables when prompted during terraform plan or apply
- v3: Override default variable values using CLI argument
-var
- v4: Override default variable values using Environment Variables
- v5: Provide Input Variables using
terraform.tfvars files
- v6: Provide Input Variables using
<any-name>.tfvars file with CLI
argument -var-file
- v7: Provide Input Variables using
auto.tfvars files
- v8-01: Implement complex type constructors like
list
- v8-02: Implement complex type constructors like
maps
- v9: Implement Custom Validation Rules in Variables
- v10: Protect Sensitive Input Variables
- v11: Understand about
File function
Pre-requisite
- Create a new EC2 Key pair with name as
terraform-key
- In all the templates listed below V1 to V12, we will be using
key_name = "terraform-key" incase if you want to login to EC2 Instance you can use this key
- Reference Sub folder: v1-Input-Variables-Basic
- Create / Review the terraform manifests
- c1-versions.tf
- c2-variables.tf
- c3-security-groups.tf
- c4-ec2-instance.tf
- We are going to define
c3-variables.tf and define the below listed variables
- aws_region is a variable of type
string
- ec2_ami_id is a variable of type
string
- ec2_instance_count is a variable of type
number
# Initialize Terraform
terraform init
# Validate Terraform configuration files
terraform validate
# Format Terraform configuration files
terraform fmt
# Review the terraform plan
terraform plan
# Create Resources
terraform apply
# Access Application
http://<Public-IP-Address>
# Clean-Up
terraform destroy -auto-approve
rm -rf .terraform*
rm -rf terraform.tfstate*
- Reference Sub folder: v2-Input-Variables-Assign-when-prompted
- Add a new variable in
variables.tf named ec2_instance_type without any default value.
- As the variable doesn't have any default value when you execute
terraform plan or terraform apply it will prompt for the variable.
# Initialize Terraform
terraform init
# Validate Terraform configuration files
terraform validate
# Format Terraform configuration files
terraform fmt
# Review the terraform plan
terraform plan
- Reference Sub folder: v3-Input-Variables-Override-default-with-cli
- We are going to override the default values defined in
variables.tf by providing new values using the -var argument using CLI
# Initialize Terraform
terraform init
# Validate Terraform configuration files
terraform validate
# Format Terraform configuration files
terraform fmt
# Option-1 (Always provide -var for both plan and apply)
# Review the terraform plan
terraform plan -var="ec2_instance_type=t3.large" -var="ec2_instance_count=1"
# Create Resources (optional)
terraform apply -var="ec2_instance_type=t3.large" -var="ec2_instance_count=1"
# Option-2 (Generate plan file with -var and use that with apply)
# Generate Terraform plan file
terraform plan -var="ec2_instance_type=t3.large" -var="ec2_instance_count=1" -out v3out.plan
# Create / Deploy Terraform Resources using Plan file
terraform apply v3out.plan
- Reference Sub folder: v4-Input-Variables-Override-with-Environment-Variables
- Set environment variables and execute
terraform plan to see if it overrides default values
# Sample
export TF_VAR_variable_name=value
# SET Environment Variables
export TF_VAR_ec2_instance_count=1
export TF_VAR_ec2_instance_type=t3.large
echo $TF_VAR_ec2_instance_count, $TF_VAR_ec2_instance_type
# Initialize Terraform
terraform init
# Validate Terraform configuration files
terraform validate
# Format Terraform configuration files
terraform fmt
# Review the terraform plan
terraform plan
# UNSET Environment Variables after demo
unset TF_VAR_ec2_instance_count
unset TF_VAR_ec2_instance_type
echo $TF_VAR_ec2_instance_count, $TF_VAR_ec2_instance_type
- Reference Sub folder: v5-Input-Variables-Assign-with-terraform-tfvars
- Create a file named
terraform.tfvars and define variables
- If the file name is
terraform.tfvars, terraform will auto-load the variables present in this file by overriding the default values in variables.tf
# Initialize Terraform
terraform init
# Validate Terraform configuration files
terraform validate
# Format Terraform configuration files
terraform fmt
# Review the terraform plan
terraform plan
# Create Resources
terraform apply
# Access Application
http://<Elastic-IP-Address>
- Reference Sub folder: v6-Input-Variables-Assign-with-tfvars-var-file
- If we plan to use different names for
.tfvars files, then we need to explicitly provide the argument -var-file during the terraform plan or apply
- We will use following things in this example
- c2-variables.tf: aws_region variable will be picked with default value
- terraform.tfvars: ec2_instance_count variable will be picked from this file
- web.tfvars: ec2_instance_type variable will be picked from this file
- app.tfvars: ec2_instance_type variable will be picked from this file
# Initialize Terraform
terraform init
# Validate Terraform configuration files
terraform validate
# Format Terraform configuration files
terraform fmt
# Review the terraform plan
terraform plan -var-file="web.tfvars"
terraform plan -var-file="app.tfvars"
- Reference Sub folder: v7-Input-Variables-Assign-with-auto-tfvars
- We will create a file with extension as
.auto.tfvars.
- With this extension, whatever may be the file name, the variables inside these files will be auto loaded during
terraform plan or apply
# Initialize Terraform
terraform init
# Validate Terraform configuration files
terraform validate
# Format Terraform configuration files
terraform fmt
# Review the terraform plan
terraform plan
Step-08: Implement complex type cosntructors like list and maps
Step-08-01: Implement Vairable Type as List
- list (or tuple): a sequence of values, like ["us-west-1a", "us-west-1c"]. Elements in a list or tuple are identified by consecutive whole numbers, starting with zero.
- Implement List function for variable
ec2_instance_type
# Implement List Function in variables.tf
variable "ec2_instance_type" {
description = "EC2 Instance Type"
type = list(string)
default = ["t3.micro", "t3.small", "t3.medium"]
}
# Reference Values from List in ec2-instance.tf
instance_type = var.ec2_instance_type[0] --> t3.micro
instance_type = var.ec2_instance_type[1] --> t3.small
instance_type = var.ec2_instance_type[2] --> t3.medium
# Initialize Terraform
terraform init
# Validate Terraform configuration files
terraform validate
# Format Terraform configuration files
terraform fmt
# Review the terraform plan
terraform plan
Step-08-02: Implement Vairable Type as Map
- map (or object): a group of values identified by named labels, like {name = "Mabel", age = 52}.
- Implement Map function for variable
ec2_instance_tags
# Implement Map Function for tags
variable "ec2_instance_tags" {
description = "EC2 Instance Tags"
type = map(string)
default = {
"Name" = "ec2-web"
"Tier" = "Web"
}
# Reference Values from Map in ec2-instance.tf
tags = var.ec2_instance_tags
# Implement Map Function for Instance Type
# Important Note: comment "ec2_instance_type" variable with list function
variable "ec2_instance_type_map" {
description = "EC2 Instance Type using maps"
type = map(string)
default = {
"small-apps" = "t3.micro"
"medium-apps" = "t3.medium"
"big-apps" = "t3.large"
}
# Reference Instance Type from Maps Variables
instance_type = var.ec2_instance_type_map["small-apps"]
instance_type = var.ec2_instance_type_map["medium-apps"]
instance_type = var.ec2_instance_type_map["big-apps"]
# Initialize Terraform
terraform init
# Validate Terraform configuration files
terraform validate
# Format Terraform configuration files
terraform fmt
# Review the terraform plan
terraform plan
Step-09: Implement Custom Validation Rules in Variables
- Reference Sub folder: v9-Input-Variables-Validation-Rules
- Understand and implement custom validation rules in variables
- Terraform Console
- The
terraform console command provides an interactive console for evaluating expressions.
# Go to Terraform Console
terraform console
# Test length function
Template: length()
length("hi")
length("hello")
length(["a", "b", "c"]) # List
length({"key" = "value"}) # Map
length({"key1" = "value1", "key2" = "value2" }) #Map
# Go to Terraform Console
terraform console
# Test substr function
Template: substr(string, offset, length)
substr("stack simplify", 1, 4)
substr("stack simplify", 0, 6)
substr("stack simplify", 0, 1)
substr("stack simplify", 0, 0)
substr("stack simplify", 0, 10)
Step-09-03: Implement Validation Rule for ec2_ami_id variable
variable "ec2_ami_id" {
description = "AMI ID"
type = string
default = "ami-0be2609ba883822ec"
validation {
condition = length(var.ec2_ami_id) > 4 && substr(var.ec2_ami_id, 0, 4) == "ami-"
error_message = "The ec2_ami_id value must be a valid AMI id, starting with \"ami-\"."
}
}
# Initialize Terraform
terraform init
# Validate Terraform configuration files
terraform validate
# Format Terraform configuration files
terraform fmt
# Review the terraform plan
terraform plan
- Reference Sub folder: v10-Sensitive-Input-Variables
- AWS RDS DB Instance
- Vault Provider
- When using environment variables to set sensitive values, keep in mind that those values will be in your environment and command-line history
Example: export TF_VAR_db_username=admin TF_VAR_db_password=adifferentpassword
- When you use sensitive variables in your Terraform configuration, you can use them as you would any other variable.
- Terraform will
redact these values in command output and log files, and raise an error when it detects that they will be exposed in other ways.
- Important Note-1: Never check-in
secrets.tfvars to git repositories
- Important Note-2: Terraform state file contains values for these sensitive variables
terraform.tfstate. You must keep your state file secure to avoid exposing this data.
# Initialize Terraform
terraform init
# Validate Terraform configuration files
terraform validate
# Format Terraform configuration files
terraform fmt
# Review the terraform plan
terraform plan -var-file="secrets.tfvars"
# Create Resources
terraform apply -var-file="secrets.tfvars"
# Verify Terraform State files
grep password terraform.tfstate
grep username terraform.tfstate
# Destroy Resources
terraform destroy var-file="secrets.tfvars"
# Clean-Up
rm -rf .terraform*
rm -rf terraform.tfstate*
Variable Definition Precedence
Step-11: Understand about File function
# Initialize Terraform
terraform init
# Validate Terraform configuration files
terraform validate
# Format Terraform configuration files
terraform fmt
# Review the terraform plan
terraform plan
# Create Resources
terraform apply
# Access Application
http://<Public-IP>
# Destroy Resources
terraform destroy -auto-approve
References