Because Jeff manually deleted the resource from the state file, Terraform was no longer aware of the virtual machine. When Jeff ran a terraform apply, it refreshed the state file and discovered that the configuration file declared a virtual machine but it was not in state, therefore Terraform needed to create a virtual machine so the provisioned infrastructure matched the desired configuration, which is the Terraform configuration file.

Hopefully, this isn't a tricky one but I thought it was good to test on, especially since terraform state commands are listed in Objective 4 of the exam. In this case, Jeff should NOT have removed the resource from the state file, but rather remove it from the configuration file and run a terraform plan/apply. In this scenario, Terraform would recognize that the virtual machine was no longer needed and would have destroyed it.

https://www.terraform.io/docs/commands/state/list.html

You can use methods such as static credentials, environment variables, share credentials/configuration file, or other methods. For example, the AWS provider can use many different options as seen here:

https://registry.terraform.io/providers/hashicorp/aws/latest/docs#authentication

Each provider is different, and you should check the documentation to see what is supported for each one you want to use.

Terraform state is required and there are many benefits that are outlined in this documentation:

https://www.terraform.io/docs/state/purpose.html

The following specifications apply to index values on modules and resources with multiple instances:

[N] where N is a 0-based numerical index into a resource with multiple instances specified by the count meta-argument. Omitting an index when addressing a resource where count > 1 means that the address references all instances.

["INDEX"] where INDEX is an alphanumerical key index into a resource with multiple instances specified by the for_each meta-argument.

https://www.terraform.io/docs/language/meta-arguments/for_each.html#referring-to-instances

Terraform Cloud offers many features, even in the free version, that organizations can quickly take advantage of. This is the best table that compares the features available in Terraform OSS vs. Terraform Cloud and Terraform Enterprise.

https://www.datocms-assets.com/2885/1602500234-terraform-full-feature-pricing-tablev2-1.pdf

The code above will create three subnets. The value of count is determined by the number of strings included in the private_subnet_names variable.

https://www.terraform.io/docs/configuration/functions/length.html

If the state has drifted from the last time Terraform ran,terraform plan -refresh-only or terraform apply -refresh-only allows drift to be detected.

https://www.hashicorp.com/blog/detecting-and-managing-drift-with-terraform

In this case, since there is a state file with resources, Terraform will match the desired state of no resources since the configuration file doesn't include any resources. Therefore, all resources defined in the state file will be destroyed.

https://www.terraform.io/docs/state/purpose.html

IaC makes changes idempotent, consistent, repeatable, and predictable. Without IaC, scaling up infrastructure to meet increased demand may require an operator to remotely connect to each machine and then manually provision and configure many servers by executing a series of commands/scripts. They might open multiple sessions and move between screens, which often results in skipped steps or slight variations between how work is completed, necessitating rollbacks. Perhaps a command was run incorrectly on one instance and reverted before being re-run correctly.

https://www.hashicorp.com/blog/infrastructure-as-code-in-a-private-or-public-cloud

The resource above will be created in the default region of us-east-1, since the resource does signify an alternative provider configuration. If the resource needs to be created in one of the other declared regions, it should have looked like this, where "aws" signifies the provider name and "west" signifies the alias name as such <PROVIDER NAME>.<ALIAS>:

resource "aws_instance" "vault" {

 provider                   = aws.west

 ami                        = data.aws_ami.amzlinux2.id

 instance_type              = "t3.micro"

 key_name                   = "ec2_key"

 vpc_security_group_ids     = var.vault_sg

 subnet_id                  = var.vault_subnet

 user_data                  = file("vault.sh")

 tags = {

   Name = "vault"

 }

}

https://www.terraform.io/docs/configuration/providers.html#selecting-alternate-provider-configurations