Amlan is an AWS technical architect and an active Tech blogger. He is 2X AWS certified and Terraform certified associate.

All posts by Amlan Chakladar - DevOps & Cloud Expert

Amlan Chakladar

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Terraform

Terraform is not just another open source tool to manage infrastructure. One can define whole infrastructure components and implement the same using a specific coding language called Hashicorp Code Language (HCL). It has a full coding structure within itself, along with its own syntax and terminologies. 
For this post, I will focus on a specific, important part of the language. All coding languages have a fundamental concept of ‘variables’ and ‘scopes’. Terraform also has its own version of this called Terraform Locals. There is also a concept of variables on Terraform which can be used to assign dynamic values, but we won&#8217;t be covering that in this post. I will instead explain locals and why (and how) they should be used in your Terraform scripts.

Terraform Locals are <a href="https://learn.hashicorp.com/tutorials/terraform/locals?in=terraform/configuration-language" target="_blank" rel="nofollow noopener">named values</a> which can be assigned and used in your code. It mainly serves the purpose of reducing duplication within the Terraform code. When you use Locals in the code, since you are reducing duplication of the same value, you also increase the readability of the code. But how does it differ from a Terraform variable, you may ask. There are a few differences which can be pointed out.  
The first difference can be pointed towards the scope. A Local is only accessible within the local module vs a Terraform variable which can be scoped globally. Another thing to note is that a local in Terraform doesn&#8217;t change its value once assigned. A variable value can be manipulated via expressions. This makes it easier to assign expression outputs to locals and use that throughout the code instead of using the expression itself at multiple places. 
If you want to compare Terraform Local to a general programming language construct, it will be equivalent to a local temporary variable declared within a function. Here is an example of local declaration in a Terraform script:

Now, let&#8217;s move on to see how to use a Terraform local. When you use a Terraform local in the code, there are two parts to it:  
<ul>
<li style="font-weight: 400;" aria-level="1">First, declare the local along and assign a value</li>
<li style="font-weight: 400;" aria-level="1">Then, use the local name anywhere in the code where that value is needed</li>
</ul>
Let’s look at an example for assigning a local:

Here we are assigning two local values. There can be many locals defined within the locals section. These locals are assigned the values to the right. Now, the locals’ name can be used across the code.   
The values assigned to the locals are not limited to just strings or constants. Expression outputs can also be assigned:

Locals can be assigned maps as values. Maps are nothing but a list of key value pairs. Here is an example of assigning a map to the local:

One thing to note here is that the local name defined has to be unique across the code, because this is the name with which it will be referenced in various places.
Now that we have seen how to declare a local, let&#8217;s see how to use one. Since the local has been defined with a specific name, the local can be referenced anywhere with the expression 
<code>local.&lt;declared_name&gt;</code>
Make sure to take into account the fact that the declare block for local is “locals”, and the reference usage is “local”. I have seen this mistake happen many times, so this is something to be careful of. 
Now let&#8217;s see an example of the usage. I will use the same local defined above for <a href="https://spacelift.io/blog/terraform-aws-s3-bucket" target="_blank" rel="noopener">the s3 bucket</a> name, to deploy an s3 bucket:

Here it can be seen that the bucket name has been built using the local name which was defined earlier in an example. When deploying, the local expression will be replaced with the actual value from the declaration block.  
Instead of being used as a static value block as above, it can also be used as an expression to replace a part of a longer text. Here is an example where a local is being used to specify a part of the bucket name:

Terraform local is very similar to a variable in a coding language. The difference being that the local is just scoped to the present script which it is a part of. But a local can also be combined with a Terraform variable and used overall in a Terraform script.  
The way it is combined is that the variable which is declared in the script, like in the variables.tf file, can be used to assign a value to the local. Let’s look at an example.
Here a variable is declared in the variables.tf file in a <a href="https://spacelift.io/blog/what-are-terraform-modules-and-how-do-they-work" target="_blank" rel="noopener">Terraform module</a>:

This variable can be used as a default value to the local in the Terraform script:

As you can see, a local can be easily combined with a Terraform variable to create complicated default value expressions for the Terraform local. This is very useful for scenarios where the local is needed to be made more dynamic based on input variable values.

Here are some examples of using Terraform locals in multiple scenarios.  
The following script declares a Terraform local to define default tag values for Terraform resources. This value is used throughout the script. Here, an IAM role is being created with the tag local used:

If you want to know more about destroying resources from Terraform, see: <a href="https://spacelift.io/blog/how-to-destroy-terraform-resources" target="_blank" rel="noopener">How to Destroy Resources from Terraform: Tutorial and Examples</a>
In this below example, the local value is being merged with a <a href="https://spacelift.io/blog/how-to-use-terraform-variables" target="_blank" rel="noopener">Terraform variable value</a>. The merged value is used in the script. The output value is also defined to output the tag values:

This post should give you a good perspective of using Locals in Terraform. It is recommended to use Locals generously in the code to avoid repetitions in the code. Additionally, the locals will help make the code more readable. All the best with your Terraform explorations!

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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Terraform locals

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How to download and install Terraform - tutorial

When I started learning Terraform, the first thing I struggled with was getting proper instructions on how to install Terraform on my system or any cloud server which I was using. There are many resources available online that guide you through the installation steps, and of course Terraform docs also have a very good installation guide.
In this guide you will find all the necessary steps in one place regardless of whether you are installing Terraform on Windows, Linux or macOS.

Before you start the installation process, there are some prerequisites which you will need to fulfill:
<ul>
<li style="font-weight: 400;" aria-level="1">A Windows PC if you are installing on Windows</li>
<li style="font-weight: 400;" aria-level="1">A Linux system (virtual or local) if you are installing on Linux (in this post, I am using Ubuntu 20.04 to demonstrate the steps)</li>
<li style="font-weight: 400;" aria-level="1">Some basic CLI knowledge</li>
</ul>
In this post, I will be covering the installation steps for Terraform on three different operating systems. You can follow the steps based on the system you are using. These are the high level topics I will be covering in this post: 
<ul>
<li style="font-weight: 400;" aria-level="1">Installing Terraform on Windows</li>
<li style="font-weight: 400;" aria-level="1">Installing Terraform on Linux (Ubuntu) using Package repository</li>
<li style="font-weight: 400;" aria-level="1">Installing Terraform on Linux using Zip archive file</li>
<li style="font-weight: 400;" aria-level="1">Installing Terraform on macOS</li>
</ul>

Let’s start with the basics.
<h3>Download the installation file</h3>
1. Navigate to the Terraform download page (<a href="https://www.terraform.io/downloads.html" target="_blank" rel="nofollow noopener">https://www.terraform.io/downloads.html</a>). It should list out Terraform downloads for various platforms. Navigate to the Windows section and download the respective version. For this example I am downloading V1.1.0.

image17-2

Downloading Terraform on Windows

2. It will download a zip file. Create a folder on the C drive as C:/terraform. Download the zip file in this folder. Unzip the file to extract the .exe file.

image21

Download the installation file on Windows

<h3>Update Path Environment Variable</h3>
1. Next open the Start menu and search for <a href="https://docs.microsoft.com/en-us/azure/developer/terraform/get-started-windows-bash?tabs=bash" target="_blank" rel="nofollow noopener">Environment variables</a>. Open the Environment variables settings page.

image13-3

Update Path Environment Variable

2. On the Environment variables edit page, open the Path variable as shown below:

image10-1-1

Edit environment variables

3. On the opened Path pop up, click New and add the Terraform download folder. This is the folder where the zip file was downloaded and unzipped (C:/terraform).

image4-2-2

add the Terraform download folder

4. Click OK on the above window to save the Path variable addition. If needed, restart your system to apply the variable changes.
5. Open a Command prompt and run this command to verify Terraform is installed successfully:

image20

verify if Terraform is installed successfully

<h3>Verify if the Correct Version of Terraform Is Installed</h3>
Just like below:

image5-5

correct version of Terraform

Here I am taking an example of installing on Ubuntu 20.04 to demonstrate the Linux installation. There are two paths to install on Linux. We’ll go through each path below. 
<h3>Installation Using Package Repositories on Linux (Ubuntu)</h3>
First, I will go through the steps to install Terraform using the Linux package repository. Follow these steps for Ubuntu. For other Linux versions steps are similar and will depend on the specific package repositories. Log in to the system and run these steps as root for sudo access:
1. Make sure the system is up-to-date and install these packages which are needed for further steps:

2. Next add the Hashicorp GPG key needed by the repository:

3. Then, add the official repository for HashiCorp for Linux:

4. Now that we have added the repo to the list, let&#8217;s update to add the relevant repository content:

5. Once update, run this command to install Terraform:

That should complete the installation. To verify the installation, run this and verify the output:

image12-2

verify the installation on Linux

To verify the version installed, run: <code>terraform –version</code>

<h3>Install Using Package repositories on Linux</h3>
Next, we will see the method for installing Terraform using the downloaded zip file. Log in to the system and run these commands as root:  
1. Before starting the installation, get the download link from the Terraform website. Navigate to <a href="https://www.terraform.io/downloads.html" target="_blank" rel="nofollow noopener">https://www.terraform.io/downloads.html</a> and move to the specific OS version. Here we are looking for Linux:

image3-7

download link for Linux from the Terraform site

2. Copy the link for the respective download:

image16

Copy the link for the Linux download

3. Now, log in to the Ubuntu system. Make sure Wget and Unzip are installed. If not, install the same:

4. Download the Terraform zip file by running the following command. Put the URL copied earlier in the command for download:

image8-4

wget

5. The zip file should download:

image19

The downloaded zip file

6. Unzip the zip file in the current folder:

image10-2

unzip terraform_1.1.0_linux_amd64.zip

7. The Terraform executable should get unzipped in the current folder:

image13-2

terraform executable

8. Move the Terraform executable file to /usr/bin folder:

9. That should complete the Terraform installation. Verify the installation by verifying the version:

image11-3

Verify the installation on Linux

Next, we will go through the steps to install Terraform on macOS. 
1. Log in to the system and create a folder for the Terraform executable:

2. Navigate to the new folder:

3. From the Terraform downloads website, copy the macOS Terraform zip file download link:

image5-7

copy the Mac OS terraform zip file download link

4. Download the zip file in the previously created folder:

5. Unzip the Terraform files in the current folder:

The unzipped files will be in the current folder.
6. Add Terraform to the PATH. Navigate to the home folder and execute this command to open and edit the bash profile:

Add these two lines on the opened file:

7. Execute the file for the path changes to get into effect:

8. Now that Terraform is installed, verify the Terraform version by running

This should show the Terraform version which is installed in the system.
That completes your installation of Terraform on Mac OS.
Next step? Import existing infrastructure into Terraform. See more here: <a href="https://spacelift.io/blog/importing-exisiting-infrastructure-into-terraform" target="_blank" rel="noopener">How to Import Existing Infrastructure into Terraform (Tutorial with Examples)</a>

Terraform allows you to <a href="https://events19.linuxfoundation.org/wp-content/uploads/2017/12/Hashicorp-Terraform-Deep-Dive-with-no-Fear-Victor-Turbinsky-Texuna.pdf" target="_blank" rel="noopener">convert a whole cloud infrastructure</a> to config or code files. These files can be used to spin up the entire infrastructure quickly and easily. It is an open source tool by Hashicorp. Anyone can use it to manage a cloud infrastructure on any of the cloud providers. 
In this post, we went through the steps to install Terraform on Windows, Linux, as well as macOS. I hope this helps you with your installations. And if you’re interested in how to upgrade Terraform to the latest version, see: <a href="https://spacelift.io/blog/terraform-version-upgrade" target="_blank" rel="noopener">Upgrading Terraform to the Latest Version</a>

What is Terraform? What is it Used For, How it Works (Examples)

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Learn how to download and install Terraform on Windows, Linux, and macOS. Terraform installation made easy! See a full tutorial.

Amlan Chakladar

Terraform Locals: What Are They, How to Use Them [Examples]

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