289 lines
11 KiB
Markdown
289 lines
11 KiB
Markdown
---
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layout: "intro"
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page_title: "Build Infrastructure"
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sidebar_current: "gettingstarted-build"
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description: |-
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With Terraform installed, let's dive right into it and start creating some infrastructure.
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---
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# Build Infrastructure
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With Terraform installed, let's dive right into it and start creating
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some infrastructure.
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We'll build infrastructure on
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[AWS](https://aws.amazon.com) for the getting started guide
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since it is popular and generally understood, but Terraform
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can [manage many providers](/docs/providers/index.html),
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including multiple providers in a single configuration.
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Some examples of this are in the
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[use cases section](/intro/use-cases.html).
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If you don't have an AWS account,
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[create one now](https://aws.amazon.com/free/).
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For the getting started guide, we'll only be using resources
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which qualify under the AWS
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[free-tier](https://aws.amazon.com/free/),
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meaning it will be free.
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If you already have an AWS account, you may be charged some
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amount of money, but it shouldn't be more than a few dollars
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at most.
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~> **Warning!** If you're not using an account that qualifies under the AWS
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[free-tier](https://aws.amazon.com/free/), you may be charged to run these
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examples. The most you should be charged should only be a few dollars, but
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we're not responsible for any charges that may incur.
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## Configuration
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The set of files used to describe infrastructure in Terraform is simply
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known as a Terraform _configuration_. We're going to write our first
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configuration now to launch a single AWS EC2 instance.
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The format of the configuration files is
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[documented here](/docs/configuration/index.html).
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Configuration files can
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[also be JSON](/docs/configuration/syntax.html), but we recommend only using JSON when the
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configuration is generated by a machine.
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The entire configuration is shown below. We'll go over each part
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after. Save the contents to a file named `example.tf`. Verify that
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there are no other `*.tf` files in your directory, since Terraform
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loads all of them.
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```hcl
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provider "aws" {
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access_key = "ACCESS_KEY_HERE"
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secret_key = "SECRET_KEY_HERE"
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region = "us-east-1"
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}
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resource "aws_instance" "example" {
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ami = "ami-2757f631"
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instance_type = "t2.micro"
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}
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```
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~> **Note**: The above configuration is designed to work on most EC2 accounts,
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with access to a default VPC. For EC2 Classic users, please use `t1.micro` for
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`instance_type`, and `ami-408c7f28` for the `ami`. If you use a region other than
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`us-east-1` then you will need to choose an AMI in that region
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as AMI IDs are region specific.
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Replace the `ACCESS_KEY_HERE` and `SECRET_KEY_HERE` with your
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AWS access key and secret key, available from
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[this page](https://console.aws.amazon.com/iam/home?#security_credential).
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We're hardcoding them for now, but will extract these into
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variables later in the getting started guide.
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~> **Note**: If you simply leave out AWS credentials, Terraform will
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automatically search for saved API credentials (for example,
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in `~/.aws/credentials`) or IAM instance profile credentials.
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This option is much cleaner for situations where tf files are checked into
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source control or where there is more than one admin user.
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See details [here](https://aws.amazon.com/blogs/apn/terraform-beyond-the-basics-with-aws/).
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Leaving IAM credentials out of the Terraform configs allows you to leave those
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credentials out of source control, and also use different IAM credentials
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for each user without having to modify the configuration files.
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This is a complete configuration that Terraform is ready to apply.
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The general structure should be intuitive and straightforward.
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The `provider` block is used to configure the named provider, in
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our case "aws." A provider is responsible for creating and
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managing resources. Multiple provider blocks can exist if a
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Terraform configuration is composed of multiple providers,
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which is a common situation.
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The `resource` block defines a resource that exists within
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the infrastructure. A resource might be a physical component such
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as an EC2 instance, or it can be a logical resource such as
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a Heroku application.
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The resource block has two strings before opening the block:
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the resource type and the resource name. In our example, the
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resource type is "aws\_instance" and the name is "example."
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The prefix of the type maps to the provider. In our case
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"aws\_instance" automatically tells Terraform that it is
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managed by the "aws" provider.
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Within the resource block itself is configuration for that
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resource. This is dependent on each resource provider and
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is fully documented within our
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[providers reference](/docs/providers/index.html). For our EC2 instance, we specify
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an AMI for Ubuntu, and request a "t2.micro" instance so we
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qualify under the free tier.
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## Initialization
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The first command to run for a new configuration -- or after checking out
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an existing configuration from version control -- is `terraform init`, which
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initializes various local settings and data that will be used by subsequent
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commands.
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In particular, this command will install the plugins for the providers in
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use within the configuration, which in this case is just the `aws` provider:
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```
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$ terraform init
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Initializing the backend...
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Initializing provider plugins...
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- downloading plugin for provider "aws"...
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The following providers do not have any version constraints in configuration,
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so the latest version was installed.
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To prevent automatic upgrades to new major versions that may contain breaking
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changes, it is recommended to add version = "..." constraints to the
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corresponding provider blocks in configuration, with the constraint strings
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suggested below.
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* provider.aws: version = "~> 1.0"
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Terraform has been successfully initialized!
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You may now begin working with Terraform. Try running "terraform plan" to see
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any changes that are required for your infrastructure. All Terraform commands
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should now work.
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If you ever set or change modules or backend configuration for Terraform,
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rerun this command to reinitialize your environment. If you forget, other
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commands will detect it and remind you to do so if necessary.
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```
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The `aws` provider plugin is downloaded and installed in a subdirectory of
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the current working directory, along with various other book-keeping files.
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The output specifies which version of the plugin was installed, and suggests
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specifying that version in configuration to ensure that running
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`terraform init` in future will install a compatible version. This step
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is not necessary for following the getting started guide, since this
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configuration will be discarded at the end.
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## Execution Plan
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Next, let's see what Terraform would do if we asked it to
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apply this configuration. In the same directory as the
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`example.tf` file you created, run `terraform plan`. You
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should see output similar to what is copied below. We've
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truncated some of the output to save space.
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```
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$ terraform plan
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# ...
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+ aws_instance.example
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ami: "ami-2757f631"
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availability_zone: "<computed>"
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ebs_block_device.#: "<computed>"
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ephemeral_block_device.#: "<computed>"
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instance_state: "<computed>"
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instance_type: "t2.micro"
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key_name: "<computed>"
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placement_group: "<computed>"
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private_dns: "<computed>"
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private_ip: "<computed>"
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public_dns: "<computed>"
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public_ip: "<computed>"
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root_block_device.#: "<computed>"
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security_groups.#: "<computed>"
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source_dest_check: "true"
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subnet_id: "<computed>"
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tenancy: "<computed>"
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vpc_security_group_ids.#: "<computed>"
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```
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`terraform plan` shows what changes Terraform will apply to
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your infrastructure given the current state of your infrastructure
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as well as the current contents of your configuration.
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If `terraform plan` failed with an error, read the error message
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and fix the error that occurred. At this stage, it is probably a
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syntax error in the configuration.
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The output format is similar to the diff format generated by tools
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such as Git. The output has a "+" next to "aws\_instance.example",
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meaning that Terraform will create this resource. Beneath that,
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it shows the attributes that will be set. When the value displayed
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is `<computed>`, it means that the value won't be known
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until the resource is created.
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## Apply
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The plan looks good, our configuration appears valid, so it's time to
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create real resources. Run `terraform apply` in the same directory
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as your `example.tf`, and watch it go! It will take a few minutes
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since Terraform waits for the EC2 instance to become available.
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```
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$ terraform apply
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aws_instance.example: Creating...
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ami: "" => "ami-2757f631"
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instance_type: "" => "t2.micro"
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[...]
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aws_instance.example: Still creating... (10s elapsed)
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aws_instance.example: Creation complete
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Apply complete! Resources: 1 added, 0 changed, 0 destroyed.
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# ...
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```
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Done! You can go to the AWS console to prove to yourself that the
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EC2 instance has been created.
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Terraform also puts some state into the `terraform.tfstate` file
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by default. This state file is extremely important; it maps various
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resource metadata to actual resource IDs so that Terraform knows
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what it is managing. This file must be saved and distributed
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to anyone who might run Terraform. It is generally recommended to
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[setup remote state](https://www.terraform.io/docs/state/remote.html)
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when working with Terraform. This will mean that any potential secrets
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stored in the state file, will not be checked into version control
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You can inspect the state using `terraform show`:
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```
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$ terraform show
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aws_instance.example:
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id = i-32cf65a8
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ami = ami-2757f631
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availability_zone = us-east-1a
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instance_state = running
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instance_type = t2.micro
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private_ip = 172.31.30.244
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public_dns = ec2-52-90-212-55.compute-1.amazonaws.com
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public_ip = 52.90.212.55
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subnet_id = subnet-1497024d
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vpc_security_group_ids.# = 1
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vpc_security_group_ids.3348721628 = sg-67652003
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```
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You can see that by creating our resource, we've also gathered
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a lot more metadata about it. This metadata can actually be referenced
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for other resources or outputs, which will be covered later in
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the getting started guide.
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## Provisioning
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The EC2 instance we launched at this point is based on the AMI
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given, but has no additional software installed. If you're running
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an image-based infrastructure (perhaps creating images with
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[Packer](https://www.packer.io)), then this is all you need.
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However, many infrastructures still require some sort of initialization
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or software provisioning step. Terraform supports
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provisioners,
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which we'll cover a little bit later in the getting started guide,
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in order to do this.
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## Next
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Congratulations! You've built your first infrastructure with Terraform.
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You've seen the configuration syntax, an example of a basic execution
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plan, and understand the state file.
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Next, we're going to move on to [changing and destroying infrastructure](/intro/getting-started/change.html).
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