Terraform.tfvars file - Step-by-Step Execution

Process Flow - Terraform.tfvars file

Create variables.tf file

↓

Define variables with defaults or no defaults

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Create terraform.tfvars file

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Assign values to variables in terraform.tfvars

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Run terraform plan/apply

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Terraform reads terraform.tfvars and applies values

This flow shows how Terraform uses a terraform.tfvars file to assign values to variables defined in variables.tf during deployment.

Execution Sample

Terraform

variable "region" {
  description = "Cloud region"
  type        = string
}

# terraform.tfvars
region = "us-west-2"

Defines a variable 'region' and assigns it a value in terraform.tfvars for Terraform to use.

Process Table

Step	Action	File Read	Variable	Value Assigned	Effect
1	Terraform starts	variables.tf	region	no value yet	Variable declared, no value assigned
2	Terraform reads terraform.tfvars	terraform.tfvars	region	"us-west-2"	Value assigned to variable
3	Terraform plan/apply uses variable	N/A	region	"us-west-2"	Deployment uses assigned value
4	Execution ends	N/A	region	"us-west-2"	Process complete with variable set

💡 terraform.tfvars values loaded, variables assigned, deployment proceeds

Status Tracker

Variable	Start	After terraform.tfvars read	Final
region	undefined	"us-west-2"	"us-west-2"

Key Moments - 2 Insights

Why doesn't the variable have a value before terraform.tfvars is read?

Because variables are declared but not assigned until terraform.tfvars or other input sources provide values, as shown in step 1 and 2 of the execution_table.

What happens if terraform.tfvars does not include a variable value?

Terraform uses the default value if defined in variables.tf, or prompts the user if no default exists, since terraform.tfvars is just one way to assign values.

Visual Quiz - 3 Questions

Look at the execution_table, what value does 'region' have after reading terraform.tfvars?

A undefined

B "us-west-2"

C "us-east-1"

D null

💡 Hint

Check Step 2 in execution_table where terraform.tfvars is read and value assigned

At which step does Terraform use the variable value for deployment?

A Step 1

B Step 2

C Step 3

D Step 4

💡 Hint

Look at the 'Effect' column in execution_table for when deployment uses the variable

If the terraform.tfvars file is missing, what will happen to the variable 'region'?

A It will remain undefined unless a default is set or user input is provided

B Terraform will assign a random value

C It will be assigned the value from terraform.tfvars anyway

D Terraform will fail immediately without any prompt

💡 Hint

Refer to key_moments about what happens if terraform.tfvars does not include a variable

Concept Snapshot

Terraform.tfvars file stores variable values separately from code.
Variables declared in variables.tf get values from terraform.tfvars.
Terraform reads terraform.tfvars automatically during plan/apply.
This separates config from code for easier management.
Missing values use defaults or prompt user.

Full Transcript

Terraform uses variables to customize deployments. Variables are declared in variables.tf files but start without values. The terraform.tfvars file assigns values to these variables. When Terraform runs, it reads variables.tf to know what variables exist, then reads terraform.tfvars to get their values. This process is shown step-by-step: first variables are declared, then terraform.tfvars is read to assign values, then Terraform uses these values to deploy resources. If terraform.tfvars is missing a variable, Terraform uses a default value if set or asks the user. This separation helps keep code clean and configuration flexible.