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provision an AWS EKS Kubernetes cluster with Terraform

Want to level up your Kubernetes knowledge? Explore our tutorials and step-by-step guides written by Kubernetes experts. Learn Kubernetes best practices and solutions to the most difficult problems.

Kubernetes Guides and Tutorials | Spacelift Blog

Kubernetes

Terraform

Jacob Martin

AWS EKS provides managed <a href="https://spacelift.io/blog/kubernetes-cluster" target="_blank" rel="noopener">Kubernetes clusters</a> as a service. You’re on AWS and want to avoid getting into the details of setting up a Kubernetes cluster from scratch? EKS is the way to go!
In this guide, you will learn how to provision an AWS EKS Kubernetes cluster with Terraform. Let&#8217;s start with the basics.

First, locally install Terraform:

as well as the AWS CLI:

and kubectl:

If you’re on a different operating system, please find the respective installation instructions here:
<ul>
<li style="font-weight: 400;" aria-level="1">Terraform: <a href="https://learn.hashicorp.com/tutorials/terraform/install-cli" target="_blank" rel="nofollow noopener">https://learn.hashicorp.com/tutorials/terraform/install-cli</a></li>
<li style="font-weight: 400;" aria-level="1">awscli: <a href="https://docs.aws.amazon.com/cli/latest/userguide/install-cliv2.html" target="_blank" rel="nofollow noopener">https://docs.aws.amazon.com/cli/latest/userguide/install-cliv2.html</a></li>
<li style="font-weight: 400;" aria-level="1">kubectl: <a href="https://kubernetes.io/docs/tasks/tools/" target="_blank" rel="nofollow noopener">https://kubernetes.io/docs/tasks/tools/</a></li>
</ul>

Now, you’ll need to configure your AWS CLI with access credentials to your AWS account. You can do this by running

and providing your Access Key ID and Secret Access Key. You will also need to add the region. For the purposes of this guide, we will use us-east-2. Terraform will later use these credentials to provision your AWS resources.

You can now clone a repository which contains everything you need to set up EKS:

Inside you’ll see a few files, the main one being eks-cluster.tf:

It uses the EKS Terraform module to set up an EKS cluster with 2 worker groups (the actual nodes running your workloads): one with a single medium machine, and one with two small machines.

You can now create all of those resources using Terraform. First, run

to initialize the Terraform workspace and download any <a href="https://spacelift.io/blog/what-are-terraform-modules-and-how-do-they-work" target="_blank" rel="noopener">modules</a> and providers which are used.
In order to do a dry run of the changes to be made, run

This will show you that 51 resources will be added, as well as their relevant details. You can then run terraform apply with the resulting plan, in order to actually provision the resources:

This may take a few minutes to finish. You might get a “timed out” error, in which case just repeat both the terraform plan and terraform apply steps.
In the end you will get a list of outputs with their respective values printed out. Make note of your cluster_name.

In order to use kubectl, which is the main tool to interact with a Kubernetes cluster, you have to give it credentials to your EKS Kubernetes cluster. You can do this by running

Make sure to replace &lt;output.cluster_name&gt; with the relevant value from your Terraform apply outputs.

<ul>
<li><a href="https://spacelift.io/blog/terraform-environments" target="_blank" rel="noopener"><span data-sheets-value="{&quot;1&quot;:2,&quot;2&quot;:&quot;Managing Multiple Terraform Environments Efficiently&quot;}" data-sheets-userformat="{&quot;2&quot;:513,&quot;3&quot;:{&quot;1&quot;:0},&quot;12&quot;:0}">Managing Multiple Terraform Environments Efficiently</a></li>
<li><a href="https://spacelift.io/blog/terraform-automation" target="_blank" rel="noopener">How to Automate Terraform Deployments and Infrastructure Provisioning</a></li>
<li><a href="https://spacelift.io/blog/5-ways-to-manage-terraform-at-scale" target="_blank" rel="noopener">5 Ways to Manage Terraform at Scale</a></li>
</ul>

You can now view the nodes of your cluster by running

This command is so long because it displays custom columns, thanks to which we can indeed see that there are 2 smaller nodes, and 1 bigger node.
Let’s deploy an Nginx instance to see if the cluster is working correctly.

You can see the status of it by running:

And finally set up a tunnel from your computer to this pod:

If you open <a href="http://localhost:3000" target="_blank" rel="nofollow noopener">http://localhost:3000</a> in your browser, you should see the web server greet you:

welcome to ngix

In order to destroy the resources we’ve created in this session, run

This may again take up to a few minutes. You can read more about it here: <a href="https://spacelift.io/blog/how-to-destroy-terraform-resources" target="_blank" rel="noopener">How to Delete Resources from Terraform Using the Destroy Command.</a>

I hope this guide helped you on your Kubernetes journey on AWS! If you want more help managing your Terraform state file, building more complex workflows based on Terraform, and managing AWS credentials per run, instead of using a static pair on your local machine, check out <a href="https://spacelift.io" target="_blank" rel="noopener">Spacelift</a>. We’d love to have you!

Spacelift helps manage Terraform state, build more complex workflows, supports policy as code, programmatic configuration, context sharing, drift detection, resource visualization and many more.

Initialize/ plan/ apply your IaC, manage modules, state, and more. 

frame-8479

Frame 8479

Importing Existing Infrastructure into Terraform - Step by Step

5 Ways to Manage Terraform at Scale - Best Practices

How Spacelift Can Improve Your Infrastructure as Code

Learn how to provision an AWS EKS Kubernetes cluster with Terraform. See a full step-by-step tutorial.

10-provision-kubernetes-cluster

Provisioning AWS EKS Cluster with Terraform - Tutorial

Importing existing infrastructure into terraform

Sumeet Ninawe

In this tutorial, you will learn ways to import pre-existing cloud resources before you continue to develop the IaC in Terraform. This guide will provide you with an IaC import scenario which is often faced by teams starting to adopt Terraform for their operations.

Terraform is a relatively new technology and adopting it to manage an organisation’s cloud resources might take some time and effort. The lack of human resources and the steep learning curve involved in using Terraform effectively causes teams to start using cloud infrastructure directly via their respective web consoles.
For that matter, any kind of IaC method (CloudFormation, Azure ARM templates, Pulumi, etc.) requires some training and real-time scenario handling experience. Things get especially complicated when dealing with concepts like states and remote backends. In a worst case scenario, you can lose the <a href="https://spacelift.io/blog/terraform-state" target="_blank" rel="noopener"><code>terraform.tfstate</code> file</a>. Luckily, you can use the import functionality to rebuild it.
Getting the pre-existing cloud resources under the Terraform management is facilitated by Terraform import. <code>import</code> is a Terraform CLI command which is used to read real-world infrastructure and update the state, so that future updates to the same set of infrastructure can be applied via IaC.
The import functionality helps update the state locally and it does not create the corresponding configuration automatically. However, the Terraform team is working hard to improve this function in upcoming releases.

With an understanding of why we need to import cloud resources, let us begin by importing a simple resource &#8211; EC2 instance in AWS. I am assuming the Terraform installation and configuration of AWS credentials in AWS CLI is already done locally. We will not go into the details of that in this tutorial. To import a simple resource into Terraform, follow the below step-by-step guide.

<h3>1. Prepare the EC2 Instance</h3>
Assuming the Terraform installation and configuration of AWS credentials in AWS CLI is already done locally, begin by importing a simple resource—EC2 instance in AWS. For the sake of this tutorial, we will create an EC2 resource manually to be imported. This could be an optional step if you already have a target resource to be imported.
<h4>Terraform: Create EC2 Instance in Existing VPC</h4>
Go ahead and provision an EC2 instance in your AWS account. Here are the example details of the EC2 instance thus created:
Name: MyVM 
Instance ID: i-0b9be609418aa0609 
Type: t2.micro 
VPC ID: vpc-1827ff72 
&#8230;

<h3>2. Create main.tf and Set Provider Configuration</h3>
The aim of this step is to import this EC2 instance into our Terraform configuration. In your desired path, create `main.tf` and configure the <a href="https://spacelift.io/blog/terraform-aws-provider" target="_blank" rel="noopener">AWS provider</a>. The file should look like the one below.
<h4>Importing EC2 Instance into Terraform Configuration: Example</h4>

Run <code>terraform init</code> to initialize the <a href="https://spacelift.io/blog/what-are-terraform-modules-and-how-do-they-work" target="_blank" rel="noopener">Terraform modules</a>. Below is the output of a successful initialization.

<h3>3. Write Config for Resource To Be Imported</h3>
As discussed earlier, Terraform import does not generate the configuration files by itself. Thus, you need to create the corresponding configuration for the EC2 instance manually. This doesn’t need many arguments as we will have to add or modify them when we import the EC2 instance into our state file.
However, if you don’t mind not seeing colorful output on CLI, you can begin adding all the arguments you know. But this is not a foolproof approach, because normally the infrastructure you may have to import will not have been created by you. So it is best to skip a few arguments anyway.
In a moment we will take a look at how to adjust our configuration to reflect the exact resource. For now, append the <code>main.tf</code> file with EC2 config. For example, I have used the below config. The only reason I have included <code>ami</code> and <code>instance_type</code> attribute, is that they are the required arguments for <code>aws_instance</code> resource block.

<h3>4. Import</h3>
Think of it as if the cloud resource (EC2 instance) and its corresponding configuration were available in our files. All that’s left to do is to map the two into our state file. We do that by running the import command as follows.

A successful output should look like this:

The above command maps the <code>aws_instance.myvm</code> configuration to the EC2 instance using the ID. By mapping I mean that the state file now “knows” the existence of the EC2 instance with the given ID. The state file also contains information about each attribute of this EC2 instance, as it has fetched the same using the import command.

<h3>5. Observe State Files and Plan Output</h3>
Please notice that the directory now also contains <code>terraform.tfstate</code> file. This file was generated after the import command was successfully run. Take a moment to go through the contents of this file.
Right now our configuration does not reflect all the attributes. Any attempt to <code>plan</code>/<code>apply</code> this configuration will fail because we have not adjusted the values of its attributes. To close the gap in configuration files and state files, run <code>terraform plan</code> and observe the output.

The plan indicates that it would attempt to replace the EC2 instance. But this goes completely against our purpose. We could do it anyway by simply not caring about the existing resources, and creating new resources using configuration.
The good news is that Terraform has taken note of the existence of an EC2 instance that is associated with its state.

<h3>6. Improve Config To Avoid Replacement</h3>
At this point, it is important to understand that the <code>terraform.tfstate</code> file is a vital piece of reference for Terraform. All of its future operations are performed with consideration for this state file. You need to investigate the state file and update your configuration accordingly so that there is a minimum difference between them.
The use of the word “minimum” is intentional here. Right now, you need to focus on not replacing the given EC2 instance, but rather aligning the configuration so that the replacement can be avoided. Eventually, you would achieve a state of 0 difference.
Observe the plan output, and find all those attributes which cause the replacement. The plan output will highlight the same. In our example, the only attribute that causes replacement is the AMI ID. Closing this gap should avoid the replacement of the EC2 instance.
Change the value of <code>ami</code> from “unknown” to what is highlighted in the plan output, and run <code>terraform plan</code> again. Notice the output.

This time the plan does not indicate the replacement of the EC2 instance. If you get the same output, you are successful in partially importing our cloud resource. You are currently in a state of lowered risk—if we apply the configuration now, the resource will not be replaced, but a few attributes would change.

<ul>
<li><a href="https://spacelift.io/blog/5-ways-to-manage-terraform-at-scale" target="_blank" rel="noopener">5 Ways to Manage Terraform at Scale</a></li>
<li><a href="https://spacelift.io/blog/terraform-automation" target="_blank" rel="noopener">How to Automate Terraform Deployments and Infrastructure Provisioning</a></li>
<li><a href="https://spacelift.io/blog/why-devops-engineers-recommend-spacelift" target="_blank" rel="noopener">Why DevOps Engineers Recommend Spacelift</a></li>
</ul>

<h3>7. Improve Config To Avoid Changes</h3>
If we want to achieve a state of 0 difference, you need to align your resource block even more. The plan output highlights the attribute changes using <code>~</code> sign. It also indicates the difference in the values. For example, it highlights the change in the instance_type value from “t2.micro” to “unknown”.
In other words, if the value of <code>instance_type</code> had been “t2.micro”, Terraform would NOT have asked for a change. Similarly, you can see there are changes to the tags highlighted as well. Let’s change the configuration accordingly so that we close these gaps. The final <code>aws_instance</code> resource block should look as follows:

Run <code>terraform plan</code> again, and observe the output.

If you have the same output, congratulations, as you have successfully imported a cloud resource into your Terraform config. It is now possible to manage this configuration via Terraform directly, without any surprises.

In this section, you will learn how to import resources into the modules. For reference, we use the AWS VPC module (version 3.2.0) that creates 29 resources. Move the <code>terraform.tfstate</code> file to another location, so that Terraform becomes unaware of the existing resources.
This poses a challenge of importing the AWS VPC module into your configuration. Modules wrap multiple AWS resources into a single package that can be reused in various projects. You should expect a large codebase and many resources to be part of the module.
The process of importing resources created using a module is very similar to what we have discussed thus far, with a little difference in running the command. Go through the <code>.tf</code> files included in the module’s source, and identify the resources to be imported.
For example, the AWS VPC module creates a VPC resource. To import this resource, run the command as below.
<h3>Terraform Import Module Example</h3>

This command imports the target VPC resource in AWS, to our module’s configuration. Running the `plan` command indicates how many resources will be created. In other words, how many resources are yet to be imported.

The above output indicates 28 more resources to be imported to (re)build a perfectly consistent <code>terraform.tfstate</code> file. One less as we have successfully imported the VPC resource. Referring to the plan output, identify the resources in AWS and repeat the process for import.

As you have seen, the process of importing simple resources is pretty straightforward. The key here is to understand how Terraform state works. However, things can get quite tedious when importing complex deployments.
In the case of complex deployments, the team should have a clear identification of resources they want to manage using Terraform. A diagram representing the entire landscape helps to plan and to get the parts of deployment under Terraform’s management.
Planning output is key. If it is well-formatted, you will build a perfectly consistent state file. Prioritize and mitigate configurations that cause replacement of target resources followed by configurations that cause changes. Import the resources as they are to satisfy the state file until there are no gaps. Any enhancement or code restructuring can be focused on and implemented once you achieve 0 gaps.
<h3>Difference Between Terraform Import and Terraform State Mv</h3>
With <code>terraform import</code> you are importing existing infrastructure resources inside of your state to manage them with Terraform. However, if you want to keep an object created with Terraform and manage it as a different resource (having a different name or moving it under a different module inside your configuration), you will need to use <code>terraform state mv</code>.

Although this article provides a comprehensive overview of possible approaches towards importing resources into Terraform, there is always room for some particular and unusual scenarios. If you have any questions or would like to share your common practices, feel free to tell us by leaving a comment below!
We encourage you also to explore <a href="https://docs.spacelift.io/" target="_blank" rel="noopener">how Spacelift makes it easy to work with Terraform</a>. If you need any help managing your Terraform infrastructure, building more complex workflows based on Terraform, and managing AWS credentials per run, instead of using a static pair on your local machine, Spacelift is a fantastic tool for this. It supports Git workflows, policy as code, programmatic configuration, context sharing, drift detection, and many more great <a href="https://spacelift.io/blog/how-specialized-solution-can-improve-your-iac" target="_blank" rel="noopener">features right out of the box</a>. You can check it for free, by <a href="https://spacelift.io" target="_blank" rel="noopener">creating a trial account</a>.

Build more complex workflows based on Terraform using policy as code, programmatic configuration, context sharing, drift detection, resource visualization and many more.

How to Deploy your Infrastructure in CI/CD using Terraform

How to Automate Terraform Deployments and Infrastructure Provisioning

See a step-by-step guide on importing existing infrastructure into Terraform. Check examples and learn how to import instances into a Terraform configuration.

9-terraform-import

Occasionally you might want to rename an AWS S3 bucket you are managing with Terraform. However, names of S3 buckets are immutable, which means you can’t change them directly. If you tried, Terraform would destroy the old one and then create a new one, resulting in data loss.
To avoid this, you need to create a new bucket with the desired name, move the data over to it, make the relevant Terraform state replacements, and finally delete the old bucket.
In this post you will learn how to rename an AWS S3 bucket in <a href="https://spacelift.io/blog/what-is-terraform" target="_blank" rel="noopener">Terraform</a>. First things first &#8211; let’s say you have a bucket definition in your Terraform code:

and you want to change the name of the bucket to <code>new-name</code>.

Firstly, we’ll need to <a href="https://spacelift.io/blog/terraform-aws-s3-bucket" target="_blank" rel="noopener">create a new bucket</a>. You can do this using the AWS CLI or the <a href="https://docs.aws.amazon.com/awsconsolehelpdocs/latest/gsg/console-help-gsg.pdf" target="_blank" rel="nofollow noopener">AWS console</a>. Just make sure to properly replicate the old settings, especially the ACL (so that your data doesn’t accidentally become public).
Now, we can copy all the files from the old to the new bucket:

Now that we have our new bucket, we need to remove the old one from our Terraform state and <a href="https://spacelift.io/blog/importing-exisiting-infrastructure-into-terraform" target="_blank" rel="noopener">import</a> the new one in its place:

If you tried to run Terraform now, it would show you that there’s drift—and yes, there would be! We’ve just imported a bucket into a resource which still has <code>old-name</code> in the config.

That’s why we now have to finally change the name of the bucket in our Terraform config:

If you run Terraform now, you’ll see that there are no changes to be made.

<ul>
<li><a href="https://spacelift.io/blog/terraform-best-practices" target="_blank" rel="noopener">12 Best Practices for Using Terraform</a></li>
<li><a href="https://spacelift.io/blog/terraform-automation" target="_blank" rel="noopener">How to Automate Terraform Deployments and Infrastructure Provisioning</a></li>
<li><a href="https://spacelift.io/blog/how-specialized-solution-can-improve-your-iac" target="_blank" rel="noopener">How to Improve Your Infrastructure as Code using Terraform</a></li>
</ul>

If you want to, you can now delete your old bucket using:

Make sure all the data has successfully been copied over to the new bucket.

If you’re using Spacelift then you can use <a href="https://docs.spacelift.io/concepts/run/task" target="_blank" rel="noopener">tasks</a> to run the above arbitrary AWS CLI commands. The default runner image already contains the AWS CLI, so no changes are necessary there.
One additional thing you can do is <a href="https://docs.spacelift.io/concepts/stack/stack-locking" target="_blank" rel="noopener">lock the Stack</a> while you’re running the migration, this way nobody will accidentally run Terraform or make any other changes while you’re moving the data.
And that’s it! If you have any questions about how to rename an AWS S3 bucket, drop me a line in the comments and I’ll get back to you straight away.

If you are struggling with Terraform automation and management, check out Spacelift. It helps you manage Terraform state, build more complex workflows, and adds several must-have capabilities for end-to-end infrastructure management.

Terraform Taint, Untaint, Replace - How to Use It (Examples)

Learn how to rename an AWS S3 bucket in Terraform. See renaming process of Amazon s3 bucket in a few simple steps.

8-rename-aws-s3-bucket

How to rename aws s3 bucket

How to Rename an AWS S3 Bucket in Terraform - Step by Step

Mudassar Shafique

If you have heard of Terraform but are not exactly sure what it is or when to use it, you have landed at the right place. This post will cover it all starting off with defining Terraform.
<dfn>Terraform</dfn> is a powerful open-source Infrastructure as Code (IaC) software tool offered by HashiCorp. It facilitates provisioning and managing your infrastructure on-prem and in the cloud. As an open-source tool it can be easily extended with the help of its plugin-based architecture.

Terraform can be connected with different infrastructure hosts and achieve complex management scenarios and compliance across multiple clouds. Its configuration can be easily packaged, shared, and reused in the form of <a href="https://spacelift.io/blog/what-are-terraform-modules-and-how-do-they-work" target="_blank" rel="noopener">Terraform modules</a>.
In this post we will go over some basic elements and features of Terraform that can help you get started. Before we move forward, however, let’s discuss Infrastructure as Code (IaC) a bit more to develop a good understanding of Terraform.

Traditionally, the process of preparing a Windows or Linux server for your lab or data center consisted of several steps involving mouse clicks, running scripts, and manually configuring different aspects such as storage and networking. Doing this at scale for hundreds or thousands of servers becomes increasingly complex and error-prone.
<a href="https://www.redhat.com/cms/managed-files/pa-terraform-and-ansible-overview-f14774wg-201811-en.pdf" target="_blank" rel="noopener">IaC</a> makes this process much easier by allowing you to define and provision your infrastructure with the help of a declarative language. With this approach, you can gain consistency, repeatability, and enhanced reliability. 
In addition to day one infrastructure setup, this approach also helps with the management of any changes that happen to your infrastructure along the way, commonly referred to as drift management. (If you’re interested in how to manage Terraform workflows at scale, see: <a href="https://spacelift.io/blog/5-ways-to-manage-terraform-at-scale" target="_blank" rel="noopener">How to Manage Terraform at Scale</a>)
Other common IaC tools include Cloud Formation Templates (CFT) for AWS, Azure Resource Manager (ARM) templates for Microsoft Azure, and Deployment Manager for Google cloud.

At a high level, Terraform can be thought of as consisting of two main parts: Terraform Core and Plugins. Core is responsible for life cycle management of infrastructure. It is the open-source binary that you download and use from the command line. 
Terraform Core takes into consideration the current state and evaluates it against your desired configuration. It then proposes a plan to add or remove infrastructure components as needed. Next, it takes care of provisioning or decommissioning any resources if you choose to apply the plan.
Terraform Plugins provide a mechanism for Terraform Core to communicate with your infrastructure host or SaaS providers. Terraform Providers and Provisioners are examples of plugins as mentioned above. Terraform Core communicates with the plugins via Remote Procedure Call (RPC).

terraform-definition

terraform definition

A typical Terraform workflow will consist of the following steps:
<h3>Step 1. Write </h3>
Declare your infrastructure resources as code in Hashicorp Configuration Language (HCL). 
<h3>Step 2. Review the Plan</h3>
Terraform will display a plan to add or remove resources based on the comparison of your declared infrastructure and the current state of any existing resources.
<h3>Step 3. Apply</h3>
Accept the planned changes to add or remove any infrastructure resources. This workflow works well for a single author as Terraform State is stored locally. As more contributors join the team, it becomes important to ensure everyone has a correct view of the current infrastructure state and changes are applied sequentially without overlaps. 
Terraform offers Enterprise and Cloud versions for teams to work together. These store the state remotely so everyone can have a consistent view. Terraform Cloud is available as a hosted service, whereas Terraform Enterprise enables you to deploy and self-host the Terraform Cloud in your private instance. Authors contribute their code to a central version control system (e.g. Github) and Terraform Cloud uses the latest code versions from the central repository.

<h3>Terraform CLI</h3>
Terraform is an <a href="https://github.com/hashicorp/terraform" target="_blank" rel="nofollow noopener">open-source</a> tool that compiles to a single binary file that can be downloaded on your system and used interactively from the command prompt. The latest version of Terraform can be downloaded <a href="https://www.terraform.io/downloads.html" target="_blank" rel="nofollow noopener">here</a>. A list of available Terraform commands can be retrieved from the command line

<ul>
<li><a href="https://spacelift.io/blog/5-ways-to-manage-terraform-at-scale" target="_blank" rel="noopener"><span data-sheets-value="{&quot;1&quot;:2,&quot;2&quot;:&quot;5 Ways to Manage Terraform at Scale – Best Practices&quot;}" data-sheets-userformat="{&quot;2&quot;:513,&quot;3&quot;:{&quot;1&quot;:0},&quot;12&quot;:0}">5 Ways to Manage Terraform at Scale – Best Practices</a></li>
<li><a href="https://spacelift.io/blog/how-specialized-solution-can-improve-your-iac" target="_blank" rel="noopener"><span data-sheets-value="{&quot;1&quot;:2,&quot;2&quot;:&quot;How to Improve Your Infrastructure as Code using Terraform&quot;}" data-sheets-userformat="{&quot;2&quot;:513,&quot;3&quot;:{&quot;1&quot;:0},&quot;12&quot;:0}">How to Improve Your Infrastructure as Code using Terraform</a></li>
<li><a href="https://spacelift.io/blog/terraform-in-ci-cd" target="_blank" rel="noopener"><span data-sheets-value="{&quot;1&quot;:2,&quot;2&quot;:&quot;How to Deploy your Infrastructure in CI/CD using Terraform&quot;}" data-sheets-userformat="{&quot;2&quot;:513,&quot;3&quot;:{&quot;1&quot;:0},&quot;12&quot;:0}">How to Deploy your Infrastructure in CI/CD using Terraform</a></li>
</ul>

<h3>Terraform Language</h3>
Infrastructure is defined in the <a href="https://www.vmware.com/content/dam/digitalmarketing/vmware/en/pdf/products/nsx/vmware-nsx-t-data-center-and-terraform.pdf" target="_blank" rel="noopener">Hashicorp Configuration Language (HCL)</a> when working with Terraform. HCL is a declarative language targeted towards DevOps tools and servers. It provides a nice balance between machine-readable formats such as JSON and configuration formats included in high-level languages such as Ruby. 
Infrastructure components managed by Terraform are called Resources. Examples of resources include virtual machines, database tables, AWS S3 buckets, VPCs, and more. Each resource block in HCL helps define the resource and configure its properties. An example VPC resource looks like this:

<h3>Terraform Providers</h3>
Terraform needs to connect to your infrastructure host to effectively manage your infrastructure. Infrastructure hosts generally have a published API that facilitates operations to create, update and delete infrastructure elements. <a href="https://spacelift.io/blog/terraform-providers" target="_blank" rel="noopener">Terraform Providers</a> supply an abstraction to these APIs. 
Terraform configuration must include providers for it to connect with required cloud or SaaS services. Providers are published by infrastructure hosts and made available to Terraform as plugins. The plugin-based architecture allows publishers to independently publish and maintain their providers. The <a href="https://registry.terraform.io/browse/providers" target="_blank" rel="nofollow noopener">Terraform registry</a> is the main directory of publicly available providers (you can also find the <a href="https://registry.terraform.io/providers/spacelift-io/spacelift/latest/docs" target="_blank" rel="nofollow noopener">Spacelift Terraform Provider</a> in this registry).
Here is an example of configuring AWS Terraform Provider in HCL:

<h3>Terraform Provisioners</h3>
<a href="https://spacelift.io/blog/terraform-provisioners" target="_blank" rel="noopener">Provisioners</a> are another type of plugin available to use with Terraform as a means of configuring the infrastructure and making it ready for service. For example, you might need to copy certain files to your virtual machine necessary for your application to function, or you might need to run configuration management software (e.g. Chef or Puppet, etc.) that you normally use to configure your environment. 
Provisioners add complexity to overall usage of Terraform. Their behavior cannot be easily modeled with Terraform for planning as they can take a wide range of actions and might access your critical infrastructure services with high privileges. Hashicorp recommends using Provisioners as a last resort for your needs, only after searching for options available with other Terraform constructs.

<h3>Terraform Modules</h3>
Modules provide a way to package resources that provide relevant functionality together as a group. Each Terraform configuration has at least one module called the root module and can call other modules referred to as child modules. 
It is easy to write modules and share them with your team or others. The <a href="https://registry.terraform.io/browse/modules" target="_blank" rel="nofollow noopener">Terraform registry</a> hosts a large collection of Terraform modules for commonly used configuration scenarios. Terraform can automatically download these modules if you include them in your configuration.

<h3>Terraform State</h3>
Terraform stores a representation of your infrastructure objects, their interdependencies and bindings in a configuration file named terraform.tfstate. Storing the state information helps Terraform immensely in making planning and execution decisions. State can be stored locally as well as remotely in a team environment.
<span data-sheets-value="{&quot;1&quot;:2,&quot;2&quot;:&quot;Read more about the elements of Terraform architecture.&quot;}" data-sheets-userformat="{&quot;2&quot;:513,&quot;3&quot;:{&quot;1&quot;:0},&quot;12&quot;:0}">Read more about the <a href="https://spacelift.io/blog/terraform-architecture" target="_blank" rel="noopener">elements of Terraform architecture</a>.

Let’s take a look at some common scenarios where Terraform can be used:
<h3>Example 1. Rapidly Build and Dispose Environments</h3>
It is common practice to have multiple environments in a typical IT organization such as Development, Testing, Staging, and Production. Terraform allows us to save all the infrastructure resources and their interdependencies specific to an environment as code in Hashicorp Configuration Language (HCL). We can use this code to quickly create a new environment as needed. 
For example, when we need to test a new feature and want to make sure our Testing environment is an exact copy of Production, we can quickly create a Test environment with the help of code that is used to create the Production, ensuring our changes will run smoothly when moved to Production after testing. 
Similarly, when developing a new feature we might need to create a new development environment for a short period of time. We can easily create and tear down one with the help of Terraform automation. The same concept applies to building recovery environments in case a disaster strikes and makes the Production unavailable.
<h3>Example 2. Use Multiple Clouds</h3>
Using more than one public cloud provider can be very beneficial if we want to have some fault tolerance for our application. In case cloud services for a particular region fail for a cloud provider, the application can continue to work if it is configured to use multiple cloud providers. It is also common to keep some resources on-prem and use a hybrid environment, combining private and public cloud resources. 
Terraform is cloud-agnostic. It can deploy applications across multiple clouds quickly and consistently. With Terraform, we don’t have to worry about using deployment tools specific to cloud providers. Instead, we can have a uniform experience working with different clouds.
<h3>Example 3. Deploy N-Tier Applications</h3>
N-Tier applications provide separation of concerns by having different tiers targeted to specific purposes. For example, a typical web application will have a tier dedicated to databases, and another tier for web servers. The web servers will depend on databases to function properly and will be behind a load balancer that will distribute requests among these web servers. 
Terraform can help ensure dependencies in this environment are implemented correctly, as databases will have to be deployed and be available before web servers. It is also easy to scale multi-tiered applications by adding more resources to a specific tier. 
For example, if you feel your application can be more robust with the help of an additional database server, it can be a matter of a simple configuration change and deployment with Terraform to add another server to the database tier.
<h3>Example 4. Work with Popular PaaS tools</h3>
Infrastructure provisioning is an important part of application deployment. However, it is not the only one required for successful deployment of applications. Modern applications use several tools to accomplish critical functions such as scheduling of resources, caching and routing, etc. Kubernetes is a popular orchestration platform used to productively deploy containers across multiple hardware resources. 
Terraform Providers not only work as abstractions for infrastructure hosts, but they can essentially interact with any API based platform such as Kubernetes. This allows us to use Terraform as a single tool to deploy infrastructure and then configure any required platforms like Kubernetes.
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Terraform solves several important infrastructure problems and naturally has some overlapping features with other infrastructure tools. Let’s take a look at some frequently asked questions about other tools in relation to Terraform
<ul>
<li style="font-weight: 400;" aria-level="1">
<h3>Should I use Terraform or other popular configuration management tools like Chef or Puppet?</h3>
There is a basic difference between Terraform and configuration management tools. Terraform focuses on making it easy to provision and manage your infrastructure, whereas configuration management software is used to prepare the VMs and Servers to fit your application and environment needs after provisioning. Furthermore, Terraform can be used in conjunction with configuration management tools as they address separate concerns.</li>
<li style="font-weight: 400;" aria-level="1">
<h3>What about cloud specific tools like Cloud Formation and ARM Templates?</h3>
While cloud specific tools can be excellent at managing resources for a particular cloud provider, Terraform strives to be cloud agnostic. It allows you to use the same language to define your resources across different clouds and makes it easy to work with multi-cloud and hybrid cloud scenarios. 
</li>
<li style="font-weight: 400;" aria-level="1">
<h3>What about common orchestration tools such as Kubernetes?</h3>
</li>
</ul>
Similarly to configuration management tools, container orchestration platforms focus on a separate concern and can be easily used in collaboration with Terraform. They usually have a robust API that helps develop Terraform Providers that in turn can be used effectively with Terraform Core, for example. <a href="https://registry.terraform.io/providers/hashicorp/kubernetes/latest" target="_blank" rel="nofollow noopener">Kubernetes Terraform Provider</a> can be found in the Terraform Provider registry. 
<ul>
<li>
<h3>Why use Terraform instead of our home grown scripts?</h3>
There are several reasons for moving away from custom ad-hoc scripts. A common issue encountered is their limitation to scale and adapt to new infrastructure needs. A custom script typically addresses a specific environment and needs updating and refactoring as new applications and infrastructure are added to the IT organization. This creates an overhead in terms of time, effort, and budget to achieving business-critical goals.</li>
</ul>

In this post, we have briefly discussed the main features and use cases of Terraform that will help you get started. We encourage you also to explore <a href="https://docs.spacelift.io/" target="_blank" rel="noopener">how Spacelift makes it easy to work with Terraform</a>. Have questions? Drop us a line in the comments below.

Spacelift effectively manages Terraform state, more complex workflows, supports policy as code, programmatic configuration, context sharing, drift detection, resource visualization and includes many more features.

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