Build Infrastructure | Terraform

With Terraform installed, you're ready to create your first infrastructure.

You will provision an Amazon Machine Image (AMI) on Amazon Web Services (AWS) in this tutorial, since AMIs are widely used.

»Prerequisites

To follow this tutorial you will need:

An AWS account
The AWS CLI installed
Your AWS credentials configured locally.
1. With your account created and the CLI installed configure the AWS CLI.
```
$ aws configure
```
1. Follow the prompts to input your AWS Access Key ID and Secret Access Key, which you'll find on this page.
The configuration process creates a file at ~/.aws/credentials on MacOS and Linux or %UserProfile%\.aws\credentials on Windows, where your credentials are stored.

Note: This tutorial will provision resources that qualify under the AWS free-tier. If your account doesn't qualify under the AWS free-tier, we're not responsible for any charges that you may incur.

»Write configuration

The set of files used to describe infrastructure in Terraform is known as a Terraform configuration. You'll write your first configuration now to launch a single AWS EC2 instance.

Each configuration should be in its own directory. Create a directory for the new configuration.

$ mkdir learn-terraform-aws-instance

Change into the directory.

$ cd learn-terraform-aws-instance

Create a file for the configuration code.

$ touch example.tf

Paste the configuration below into example.tf and save it. Terraform loads all files in the working directory that end in .tf.

terraform {
  required_providers {
    aws = {
      source  = "hashicorp/aws"
      version = "~> 2.70"
    }
  }
}

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

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

Tip: To use this snippet with Terraform 0.12, remove the terraform {} block.

This is a complete configuration that Terraform is ready to apply. In the following sections we'll review each block of the configuration in more detail.

»Terraform Block

The terraform {} block is required so Terraform knows which provider to download from the Terraform Registry. In the configuration above, the aws provider's source is defined as hashicorp/aws which is shorthand for registry.terraform.io/hashicorp/aws.

You can also assign a version to each provider defined in the required_providers block. The version argument is optional, but recommended. It is used to constrain the provider to a specific version or a range of versions in order to prevent downloading a new provider that may possibly contain breaking changes. If the version isn't specified, Terraform will automatically download the most recent provider during initialization.

To learn more, reference the provider source documentation.

»Providers

The provider block configures the named provider, in our case aws, which is responsible for creating and managing resources. A provider is a plugin that Terraform uses to translate the API interactions with the service. A provider is responsible for understanding API interactions and exposing resources. Because Terraform can interact with any API, you can represent almost any infrastructure type as a resource in Terraform.

The profile attribute in your provider block refers Terraform to the AWS credentials stored in your AWS Config File, which you created when you configured the AWS CLI. HashiCorp recommends that you never hard-code credentials into *.tf configuration files. We are explicitly defining the default AWS config profile here to illustrate how Terraform should access sensitive credentials.

Note: If you leave out your AWS credentials, Terraform will automatically search for saved API credentials (for example, in ~/.aws/credentials) or IAM instance profile credentials. This is cleaner when .tf files are checked into source control or if there is more than one admin user.

Multiple provider blocks can exist if a Terraform configuration manages resources from different providers. You can even use multiple providers together. For example you could pass the ID of an AWS instance to a monitoring resource from DataDog.

»Resources

The resource block defines a piece of infrastructure. A resource might be a physical component such as an EC2 instance, or it can be a logical resource such as a Heroku application.

The resource block has two strings before the block: the resource type and the resource name. In the example, the resource type is aws_instance and the name is example. The prefix of the type maps to the provider. In our case "aws_instance" automatically tells Terraform that it is managed by the "aws" provider.

The arguments for the resource are within the resource block. The arguments could be things like machine sizes, disk image names, or VPC IDs. Our providers reference documents the required and optional arguments for each resource provider. For your EC2 instance, you specified an AMI for Ubuntu, and requested a t2.micro instance so you qualify under the free tier.

»Initialize the directory

When you create a new configuration — or check out an existing configuration from version control — you need to initialize the directory with terraform init.

Terraform uses a plugin-based architecture to support hundreds of infrastructure and service providers. Initializing a configuration directory downloads and installs providers used in the configuration, which in this case is the aws provider. Subsequent commands will use local settings and data during initialization.

Initialize the directory.

$ terraform init
Initializing the backend...

Initializing provider plugins...
- Finding latest version of hashicorp/aws...
- Installing hashicorp/aws v2.70.0...
- Installed hashicorp/aws v2.70.0 (signed by HashiCorp)

The following providers do not have any version constraints in configuration,
so the latest version was installed.

To prevent automatic upgrades to new major versions that may contain breaking
changes, we recommend adding version constraints in a required_providers block
in your configuration, with the constraint strings suggested below.

* hashicorp/aws: version = "~> 2.70.0"

Terraform has been successfully initialized!

You may now begin working with Terraform. Try running "terraform plan" to see
any changes that are required for your infrastructure. All Terraform commands
should now work.

If you ever set or change modules or backend configuration for Terraform,
rerun this command to reinitialize your working directory. If you forget, other
commands will detect it and remind you to do so if necessary.

Terraform downloads the aws provider and installs it in a hidden subdirectory of the current working directory. The output shows which version of the plugin was installed.

»Format and validate the configuration

We recommend using consistent formatting in files and modules written by different teams. The terraform fmt command automatically updates configurations in the current directory for easy readability and consistency.

Format your configuration. Terraform will return the names of the files it formatted. In this case, your configuration file was already formatted correctly, so Terraform won't return any file names.

$ terraform fmt

If you are copying configuration snippets or just want to make sure your configuration is syntactically valid and internally consistent, the built in terraform validate command will check and report errors within modules, attribute names, and value types.

Validate your configuration. If your configuration is valid, Terraform will return a success message.

$ terraform validate
Success! The configuration is valid.

»Create infrastructure

In the same directory as the example.tf file you created, run terraform apply. You should see an output similar to the one shown below, though we've truncated some of the output to save space.

Note: Terraform 0.11 and earlier require running terraform plan before terraform apply. Use terraform version to confirm your running version.

$ terraform apply

## ... Output truncated ...

An execution plan has been generated and is shown below.
Resource actions are indicated with the following symbols:
  + create

Terraform will perform the following actions:

  # aws_instance.example will be created
  + resource "aws_instance" "example" {
      + ami                          = "ami-830c94e3"
      + arn                          = (known after apply)
      + associate_public_ip_address  = (known after apply)
      + availability_zone            = (known after apply)
      + cpu_core_count               = (known after apply)
      + cpu_threads_per_core         = (known after apply)
      + get_password_data            = false
      + host_id                      = (known after apply)
      + id                           = (known after apply)
      + instance_state               = (known after apply)
      + instance_type                = "t2.micro"
      + ipv6_address_count           = (known after apply)
      + ipv6_addresses               = (known after apply)

## ... Output truncated ...

Plan: 1 to add, 0 to change, 0 to destroy.

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.

This output shows the execution plan, describing which actions Terraform will take in order to change real infrastructure to match the configuration.

The output format is similar to the diff format generated by tools such as Git. The output has a + next to aws_instance.example, meaning that Terraform will create this resource. Beneath that, it shows the attributes that will be set. When the value displayed is (known after apply), it means that the value won't be known until the resource is created.

Terraform will now pause and wait for your approval before proceeding. If anything in the plan seems incorrect or dangerous, it is safe to abort here with no changes made to your infrastructure.

In this case the plan is acceptable, so type yes at the confirmation prompt to proceed. Executing the plan will take a few minutes since Terraform waits for the EC2 instance to become available.

## ... Output truncated ...

Do you want to perform these actions?
  Terraform will perform the actions described above.
  Only 'yes' will be accepted to approve.

  Enter a value: yes

aws_instance.example: Creating...
aws_instance.example: Still creating... [10s elapsed]
aws_instance.example: Creation complete after 1m50s [id=i-0bbf06244e44211d1]

Apply complete! Resources: 1 added, 0 changed, 0 destroyed.

You've now created infrastructure using Terraform! Visit the EC2 console to see the created EC2 instance. Make sure you're looking at the same region that was configured in the provider configuration!

»Inspect state

When you applied your configuration, Terraform wrote data into a file called terraform.tfstate. This file now contains the IDs and properties of the resources Terraform created so that it can manage or destroy those resources going forward.

You must save your state file securely and distribute it only to trusted team members who need to manage your infrastructure. In production, we recommend storing your state remotely. Remote stage storage enables collaboration using Terraform but is beyond the scope of this tutorial.

Inspect the current state using terraform show.

$ terraform show
# aws_instance.example:
resource "aws_instance" "example" {
    ami                          = "ami-830c94e3"
    arn                          = "arn:aws:ec2:us-east-1:130490850807:instance/i-0bbf06244e44211d1"
    associate_public_ip_address  = true
    availability_zone            = "us-west-2"
    cpu_core_count               = 1
    cpu_threads_per_core         = 1
    disable_api_termination      = false
    ebs_optimized                = false
    get_password_data            = false
    id                           = "i-0bbf06244e44211d1"
    instance_state               = "running"
    instance_type                = "t2.micro"
    ipv6_address_count           = 0
    ipv6_addresses               = []
    monitoring                   = false
    primary_network_interface_id = "eni-0f1ce5bdae258b015"
    private_dns                  = "ip-172-31-61-141.ec2.internal"
    private_ip                   = "172.31.61.141"
    public_dns                   = "ec2-54-166-19-244.compute-1.amazonaws.com"
    public_ip                    = "54.166.19.244"
    security_groups              = [
        "default",
    ]
    source_dest_check            = true
    subnet_id                    = "subnet-1facdf35"
    tenancy                      = "default"
    volume_tags                  = {}
    vpc_security_group_ids       = [
        "sg-5255f429",
    ]

    credit_specification {
        cpu_credits = "standard"
    }

    root_block_device {
        delete_on_termination = true
        iops                  = 100
        volume_id             = "vol-0079e485d9e28a8e5"
        volume_size           = 8
        volume_type           = "gp2"
    }
}

When Terraform created this EC2 instance, it also gathered a lot of information about it. These values can be referenced to configure other resources or outputs, which we discuss more later on in these tutorials.

»Manually Managing State

Terraform has a built in command called terraform state for advanced state management. For example, if you have a long state file, you may want a list of the resources in state, which you can get by using the list subcommand.

$ terraform state list
aws_instance.example

»Troubleshooting

If terraform validate was successful and your apply still failed, you may be encountering a common error.

If you use a region other than us-east-1, you will also need to change your ami, since AMI IDs are region specific. Choose an AMI ID specific to your region by following these instructions, and modify example.tf with this ID. Then re-run terraform apply.
If you do not have a default VPC in your AWS account in the correct region, navigate to the AWS VPC Dashboard in the web UI, create a new VPC in your region, and associate a subnet and security group to that VPC. Then add the security group ID (vpc_security_group_ids) and subnet ID (subnet_id) into your aws_instance resource, and replace the values with the ones from your new security group and subnet.
```
resource "aws_instance" "example" {
  ami                    = "ami-830c94e3"
  instance_type          = "t2.micro"
+ vpc_security_group_ids = ["sg-0077..."]
+ subnet_id              = "subnet-923a..."
}
```
Save the changes to example.tf, and re-run terraform apply.
Remember to add these lines to your configuration for the rest of the get started track. For more information, review this document from AWS on working with VPCs.

»Next Steps

Now that you have created your first infrastructure using Terraform, continue to the next tutorial to modify your infrastructure.

For more detail on the concepts we used in this tutorial:

Read about the format of the configuration files in the terraform documentation.
Learn more about Terraform providers.
Find examples of Terraform configurations using multiple providers in the documentation use cases section.
Read this blog post and these docs to learn more about AWS authentication.
For more information about the terraform state command and subcommands for moving or removing resources from state, see the CLI state command documentation.

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