Terraform-- IAC( Infrastructure as code)

Infrastructure is defined as code, but it is both human and machine readable.


for eg:

resource "aws_s3_bucket" "s3_bucket" {
  acl                    = "private"
  bucket_prefix   = "testbucket"
  region               = "us-east-1"
}

Moving from physical to cloud based technology

Physical:
- Physical servers purchased and racked
- virtual machine created on host servers
-Redundant power and storage provisions


Cloud
- Instances spun up in cloud and paid per unit of time
- No more hosts
- Redundancy is built in when cloud services are configured properly

IaC Examples:
-Terraform
- CloudFormation
-Azure Resource Manager
- Google Deployment Manager

What IaC is not:
(Configuration tools)
-Chef
- Puppet
- Ansible

Makes sure it stays and complies with the configuration after provisioning

Why Terraform ?

- Build infrastructure
- Change infrasture
- Version infrastructure

- You can do all 3 of the above while keeping a much tigher grip on compliance using modules
-Cloud agnostic- can work in aws, gcp or azure



Terraform state file:


--- terraform state is stored in a file called terraform.tfstate
-- stores state information from a terraform apply
-- doesn'tr track changes in your cloud environment not made by Terraform . For eg: changes made in the console

How to make changes to state:


- Configuration file
- Terraform state command
- Terraform import commands


The Workflow:

Example Terraform state list


terraform state list

-- module.my_logs_bucket.aws_s3_bucket.s3_bucket

example output of a terraform.tfstate file
- defines individual resources that have been provisioned
- excludes resources that did not provision

examples:

high level examples
making changes to state without configuration file


terraform import
terraform import aws_instance.example <instance-id>

Terraform taint
-marks resoures as tainted . will recreate the resource at the run of the next terraform apply

Terraform untaint:

- talk to the terraform.tfstate file to untaint the specific item
-prevents the recreation of resources during terraform apply

terrform untaint aws_security_group.allow_all

Terrform destroy

--looks at the state file and will say let's burn it all down
-destroys all resources in the terraform.tfstate file
terraform destroy