Terraform Block

terraform {

  cloud {
    organization = "devshark"
    workspaces {
      name = "Example-Workspace"
    }
  }

  required_providers {
    aws = {
      source  = "hashicorp/aws"
      version = "~> 3.27"
    }
  }

  required_version = ">= 0.14.9"
}

terraform {} block contains Terraform settings
- including the required providers Terraform will use to provision your infrastructure.
For each provider, the source attribute defines an optional hostname, a namespace, and the provider type
Terraform installs providers from the Terraform Registry by default
hashicorp/aws => registry.terraform.io/hashicorp/aws
required_providers set a version constraint for each provider
version attribute is optional, but we recommend using it to constrain the provider version so that Terraform does not install a version of the provider that does not work with your configuration
- If you do not specify a provider version, Terraform will automatically download the most recent version during initialization
- https://www.terraform.io/language/providers/requirements

Providers Block

provider "aws" {
  profile = "terraform"
  region  = "us-west-2"
}

provider block configures the specified provider, such as aws . A provider is a plugin that Terraform uses to create and manage your resources.
profile attribute in the aws provider block refers Terraform to the AWS credentials stored in your AWS configuration file
You can use multiple provider blocks in your Terraform configuration to manage resources from different providers
You can even use different providers together. For example, you could pass the IP address of your AWS EC2 instance to a monitoring resource from DataDog.

Resources

resource "aws_instance" "app_server" {
  ami           = "ami-830c94e3"
  instance_type = "t2.micro"

  tags = {
    Name = "ExampleAppServerInstance"
  }
}

resource blocks to define components of your infrastructure.
A resource might be a physical or virtual component such as an EC2 instance, or it can be a logical resource such as a Heroku application.
Resource blocks have two strings before the block
- resource type
- resource name
- For example:
  - resource type is aws_instance
  - name is app_server
The prefix of the type maps to the name of the provider.
- In the example configuration, Terraform manages the aws_instance resource with the aws provider.
Together, the resource type and resource name form a unique ID for the resource
- For example, the ID for your EC2 instance is aws_instance.app_server
Resource blocks contain arguments which you use to configure the resource. Arguments can include things like machine sizes, disk image names, or VPC IDs.

Initialize the directory

Initializing a configuration directory downloads and installs the providers defined in the configuration, which in this case is the aws provider.

terraform init

Format and validate configuration

terraform fmt
terraform validate

Create/Apply infrastructure

terraform apply

The output has a + next to aws_instance.app_server, meaning that Terraform will create this resource
When the value displayed is (known after apply), it means that the value will not be known until the resource is created

Inspect state

When you applied your configuration, Terraform wrote data into a file called terraform.tfstate

terraform show

Tip: If your configuration fails to apply, you may have customized your region or removed your default VPC. Refer to the troubleshooting section at the bottom of this tutorial for help.

Manually Managing state

terraform state list

Change Infrastructure

Destroy Infrastructure

terraform destroy

Define Input Variables

Create new file variables.tf
Update main.tf with variables
Apply changed configuration

Now apply the configuration again, this time overriding the default instance name by passing in a variable using the -var flag. Terraform will update the instance's Name tag with the new name. Respond to the confirmation prompt with yes

terraform apply -var "instance_name=YetAnotherName"

Query data with output

Create new file outputs.tf
Add the configuration below to outputs.tf

output "instance_id" {
  description = "ID of the EC2 instance"
  value       = aws_instance.app_server.id
}

output "instance_public_ip" {
  description = "Public IP address of the EC2 instance"
  value       = aws_instance.app_server.public_ip
}

Apply configuration
Query the outputs with the terraform out command

Store remote state

In production environments you should keep your state secure and encrypted, where your teammates can access it to collaborate on infrastructure
The best way to do this is by running Terraform in a remote environment with shared access to state.
Terraform Cloud allows teams to easily version, audit, and collaborate on infrastructure changes. It also securely stores variables, including API tokens and access keys, and provides a safe, stable environment for long-running Terraform processes.

Set up Terraform Cloud

Create new account https://app.terraform.io/signup
Create new Organization and workspace
Next, modify main.tf to add a cloud block to your Terraform Configuration

  cloud {
    organization = "devshark"
    workspaces {
      name = "Example-Workspace"
    }
  }

Note: Because the cloud block is not supported by older versions of Terraform, you must use 1.1.0 or higher in order to follow this tutorial. Previous versions can use the remote backend block to configure the CLI workflow and migrate state.

Login to Terraform Cloud

Create new Token https://app.terraform.io/app/settings/tokens
Login to Terraform Cloud with terraform login

Initialize Terraform

terraform init

Now that Terraform has migrated the state file to Terraform Cloud, delete the local state file.

rm terraform.tfstate

Set workspace variables

Apply configutation with terraform apply command
Destroy your configuration

Terraform language

Blocks are containers for other content and usually represent the configuration of some kind of object, like a resource. Blocks have a block type, can have zero or more labels, and have a body that contains any number of arguments and nested blocks. Most of Terraform's features are controlled by top-level blocks in a configuration file.
Arguments assign a value to a name. They appear within blocks.
Expressions represent a value, either literally or by referencing and combining other values. They appear as values for arguments, or within other expressions.

Providers

Provider registry https://registry.terraform.io/browse/providers

hungbang/learn-terraform-aws-instance