terraform

Terraform

Workflow

1. init
2. validate
3. plan
4. apply
5. destroy

Configuration files

Terraform configuration files (aka terraform manifests) are files with .tf extension.

HCL

HCL HashiCorp Language:

• Blocks
• Arguments
• Identifiers
• Comments

Blocks

# Template
<BLOCK TYPE> "<BLOCK LABEL>" "<BLOCK LABEL>"   {
  # Block body
  <IDENTIFIER> = <EXPRESSION> # Argument
}

# AWS Example
resource "aws_instance" "ec2demo" { # BLOCK
  ami           = "ami-04d29b6f966df1537" # Argument
  instance_type = var.instance_type # Argument with value as expression (Variable value replaced from varibales.tf
}

Comments

# Line comment

// Line comment

/* Multi
line
comments*/

Arguments

An argument assigns a value to a particular name.

Meta-arguments

The meta-arguments within resource blocks allow to define the behavior of a resource behavior.

Top-level blocks

• Fundamental blocks
  • Terraform (settings) block: special block used to define some behaviors;
    • Required Terraform version
    • List required providers
    • Terraform backend
    • Only constant values can be used!
  • Provider block: Terraform relies on providers to ineract with remote systems;
  • Resource block: each resource block describes one or more infrastructure objects;
• Variable blocks
  • Input variables block
  • Output values block
  • Local values block
• Calling / Referencing blocks
  • Data sources block
  • Modules block

Terraform Settings (aka Terraform block)

Each Terraform block can contain a number of settings related to Terraform's behavior.

• Required Terraform version
• Required providers
• Terraform backend

Terraform Provider

Every Resource Type is implemented by a provider.

• Provider requirements
• Provider configuration
• Dependency lock file