day-21

TERRAFORM VAR FILES:
these files used to store variables seperately on terraform.
if values havent declared on main.tf terraform will search for variable.tf and takes values from that file.

cat main.tf 
provider "aws" {
  region = "us-east-1"
}

resource "aws_instance" "one" {
  count         = var.instance_count
  ami           = var.ami_id
  instance_type = var.instance_type
  tags = {
    Name = var.instance_name
  }
}

cat variable.tf

variable "instance_count" {
  description = "*"
  type        = number
  default     = 3
}

variable "ami_id" {
  type    = string
  default = "ami-079db87dc4c10ac91"
}

variable "instance_type" {
  type    = string
  default = "t2.micro"
}

variable "instance_name" {
  type    = string
  default = "dev-server"
}

TERRAFORM REFRESH:
it will store the values when compared with real world infrastructure when we modified the terraform values in real world infrastructure it does not replicate to state file so we need to run the command called Terraform Refresh it will refresh the state file while refreshing state file it will compare original values with the state file values if the original values are modified or change it it will be replicated to state file after running terraform refresh command.


TERRAFORM TFVARS:


cat main.tf
provider "aws" {
  region = "us-east-1"
}

resource "aws_instance" "one" {
  count         = var.instance_count
  ami           = var.ami_id
  instance_type = var.instance_type
  tags = {
    Name = var.instance_name
  }
}

cat variable.tf
variable "instance_count" {
}

variable "ami_id" {
}

variable "instance_type" {
}

variable "instance_name" {
}

cat dev.tfvar

instance_count = 1

ami_id = "ami-036c2987dfef867fb"

instance_type = "t2.micro"

instance_name = "dev-server"

cat test.tfvar

instance_count = 2

ami_id = "ami-0c7217cdde317cfec"

instance_type = "t2.medium"

instance_name = "test-server"

terraform apply --auto-approve -var-file="test.tfvar"
terraform apply --auto-approve -var-file="dev.tfvar"

Note: In the above example first we created the testing infrastructure and later we created developing infrastructure 
but when developing infrastructure is created testing infrastructure had deleted.
The main reason is both of the values you are passing from single workspace.
when we work on single workspace previous values are going to be overrided and new values are going to be added for the current working infrastructure.
For this purpose in real time if you want to create multiple environments we use terraform workspace concept. 


WORKSPACES:
it is used to create infra for multiple env 
it will isolate each env
if we work on dev env it wont affect test env
the default workspace is default 
all the resource we create on terraform by default will store on default workspace

terraform workspace list	: to list the workspaces
terraform workspace new dev	: to create workspace
terraform workspace show	: to show current workspace
terraform workspace select dev	: to switch to dev workspace
terraform workspace delete dev	: to delete dev workspace


NOTE:
1. we need to empty the workspace befor delete
2. we cant delete current workspace, we can switch and delete
3. we cant delete default workspace


TERRAFORM OUTPUTS:
this is block used to print particular resource infromation.
when we create a resource the information will be stored on state file.
this output block will get required values from state file when it create resource.

provider "aws" {
  region = "us-east-1"
}

resource "aws_instance" "one" {
  count         = var.instance_count
  ami           = var.ami_id
  instance_type = var.instance_type
  tags = {
    Name = var.instance_name
  }
}

output "raham" {
value = [aws_instance.one[0].public_ip, aws_instance.one[0].private_ip, aws_instance.one[0].public_dns]
}

HISTORY:
   23  cd terraform/
   24  vim main.tf
   25  vim variable.tf
   26  terraform plan
   27  terraform validate
   28  vi main.tf
   29  vim variable.tf
   30  cat main.tf
   31  cat variable.tf
   32  terraform fmt
   33  cat main.tf
   34  cat variable.tf
   35  terraform plan
   36  terraform apply --auto-approve
   37  vim variable.tf
   38  terraform apply --auto-approve
   39  cat main.tf variable.tf
   40  terraform state list
   41  terraform refresh
   42  terraform state list
   43  ll
   44  terraform state list
   45  terraform refresh
   46  terraform state list
   47  ll
   48  cat terraform.tfstate
   49  terraform refresh
   50  cat terraform.tfstate
   51  terraform destroy --auto-approve
   52  vim variable.tf
   53  vim dev.tfvars
   54  mv dev.tfvars dev.tfvar
   55  vim test.tfvar
   56  cat main.tf
   57  cat variable.tf
   58  cat dev.tfvar
   59  cat test.tfvar
   60  terraform apply --auto-approve -var-file="test.tfvar"
   61  terraform apply --auto-approve -var-file="dev.tfvar"
   62  terraform workspace list
   63  terraform state list
   64  terraform destroy --auto-approve
   65  cat main.tf
   66  terraform destroy --auto-approve
   67  terraform workspace list
   68  terraform workspace new dev
   69  terraform workspace show
   70  terraform apply --auto-approve -var-file="dev.tfvar"
   71  ll
   72  terraform state list
   73  cat terraform.tfstate
   74  cat terraform.tfstate.backup
   75  terraform workspace new test
   76  ll
   77  terraform apply --auto-approve -var-file="tes.tfvar"
   78  terraform apply --auto-approve -var-file="test.tfvar"
   79  terraform workspace list
   80  terraform workspace show
   81  terraform workspace delete test
   82  terraform workspace select dev
   83  terraform workspace delete test
   84  terraform workspace select test
   85  terraform destroy --auto-approve -var-file="test.tfvar"
   86  terraform workspace select dev
   87  terraform workspace delete test
   88  terraform destroy --auto-approve -var-file="dev.tfvar"
   89  terraform workspace select default
   90  terraform workspace delete dev
   91  terraform workspace list
   92  vim main.tf
   93  terraform apply --auto-approve -var-file="dev.tfvar"
   94  vim main.tf
   95  terraform apply --auto-approve -var-file="dev.tfvar"
   96  cat main.tf
   97  terraform destroy --auto-approve -var-file="dev.tfvar"
   98  history