Terraform

                                           

Terraform is not a cloud-agnostic tool It’s not a magic wand that gives you power over all clouds and systems. It embraces all major Cloud Providers and provides a common language to orchestrate your infrastructure resources.

                                        Terraform

 ● A provisioning declarative tool that based on Infrastructure as a Code paradigm 

● Uses own syntax - HCL (Hashicorp Configuration Language)

 ● Written in Golang

● Helps to evolve you infrastructure, safely and predictably

 ● Applies Graph Theory to IaaC 

● Terraform is a multipurpose composition tool: 

○ Composes multiple tiers (SaaS/PaaS/IaaS)

○ A plugin-based architecture model

 ● Open-source. Backed by Hashicorp company and Hashicorp Tao (Guide/Principles/Design)

Terraform Core: Init

 1. This command will never delete your existing configuration or state. 

2. Checkpoint → https://checkpoint.hashicorp.com/ 

3. .terraformrc → enable plugin_cache_dir, disable checkpoint 

4. Parsing configurations, a syntax check

 5. Checking for provisioners/providers (by precedence, only once)→ “.”, terraform_bin_dir, terraform.d/plugins/linux_amd64 .terraform/plugins/linux_amd64

 6. File lock.json contains sha-512 plugin hashes (.terraform) 

7. Loading backend config ( if it’s available, local instead ) Backend Initialization: Storage for Terraform state file. example 

Terraform Core: Plan + Apply

 1. Starting Plugins: Provisioners/Providers 

2. Building graph a. Terraform core traverses each vertex and requests each provider using parallelism 3. Providers syntax check: resource validation

 4. If backend == , use local

 5. If “-out file. plan” provided - save to file - the file is not encrypted 

6. Terraform Core calculates the difference between the last-known state and the current state

 7. Presents this difference as the output of the terraform plan operation to users in their terminal 

Terraform Core: Destroy

 1. Measure twice, cut once 

2. Consider -target flag

 3. Avoid running on production 

4. No “Retain” flag - Remove a resource from the state file instead 

5. terraform destroy tries to evaluate outputs that can refer to non-existing resources #18026 

6. prevent_destroy should let you succeed #3874 

7. You can’t destroy a single resource with the count in the list Terraform Backends

 ● Locking

 ● Workspaces (former known as environments) 

● Encryption at rest

 ● Versioning 

● Note: Backend configuration doesn’t support interpolations.