Terraform Basics

Terraform workflow

These are the major commands that are used to initialise create, update or delete Infrastructure resources.

• Init
  - For initialising the working directory where containing the config files
  - It download Providers
  - Initialising the backend
• Validate
  - Validates the terraform config. Files in that respective directory to make sure it is syntactically and internally consistent.
• Plan
  - Create an execution plan with command line
• Apply
  - It will apply on the cloud provider
• Destroy
  - It will destroy it will all and also single commands

Terraform configuration language syntax

Types of Blocks

• Top level blocks
  - Example:- Resource and Providers
• Block inside blocks
  - Example Provisioners and resource specific blocks like tags
• “Block Type” “Block label<defined by cloud provider>” “Block label<For local reference>”
  - Example:- Resource “aws_instance” “my_ec2”
• Resource contains 2 Block labels and Variables blocks contains 1 label
• Comments:- To comments we can use :- #, // and /* */

Understand about Arguments, Attributes and Meta-Arguments

• Arguments
  - It configures a particular resource example “ami” = “ami-2213412421”
  - It can be required and optional
• Attribute reference
  - Values exposed by particular resource
  - It can be referenced
  - It is assigned by underlying cloud provider
  - This can be exported as output values
• Meta-arguments
  - Terraform specific arguments
  - Examples depends_on, count, for_each, provider and lifecycle

Understanding about Terraform Blocks

• Block that can appear outside of any other block in a TF config. file
• Most of TF feature are implemented as Top level blocks
• 3 Major blocks
• Fundamental blocks
  - Terraform Block:- Here is the terraform settings
  - Providers Block:- Aws or Azure providers
  - Resource Block:- What kind of resource you are provisioning
• Variables blocks:- This tells how to parametrise the whole thing we created
  - Input Variables
  - Output Values Block
  - Local Values Block
• Calling or referencing blocks:-
  - Data Source Block:- To get some information about cloud providers
  - Modules Block.- To provide some information to that block