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An experience full-stack engineer well versed with Core Java, Spring/Springboot, MVC, Security, AOP, Frontend (Angular & React), and cloud technologies (such as AWS, GCP, Jenkins, Docker, K8).

Terraform Apply Command

Hello. In this tutorial, we will explain the basics of the Terraform apply command, that engineers use on daily basis.

1. Introduction

Terraform is an open-source tool developed by HashiCorp for building, changing, and versioning the infrastructure safely and efficiently. It is used to manage the infrastructure of the popular cloud service providers and custom in-house solutions. It helps manage both low-level (Compute, Storage, Networking, etc.) and high-level components (such as SaaS, DNS, etc.) Terraform deployment automation is divided into different sections i.e. –

  • IaaC – IaaC is popularly known as the Infrastructure as a Code wherein the infrastructure is described using a high-level configuration syntax. This allows a blueprint of the infrastructure which can be deployed, versioned, and shared for re-use
  • Execution Plans – Terraform has a planning step where it generates an execution plan. The execution plan tells the administrator what Terraform will do once applied and helps to avoid any surprises when it creates the infrastructure
  • Resource Graph – Terraform builds a graph of all the resources and parallelizes the creation and modification of non-dependent resources. This offers insights into learning the dependencies in their infrastructure
  • Change Automation – Terraform allows to apply of complex changesets to the infrastructure with minimal human intervention

1.1 Configuration language

Terraform has its configuration language designed to meet the infrastructure automation requirements. The main purpose of this language is to declare resources and a group of resources (gathered into a module) represents a larger unit of configuration. Language syntax consists of a few elements i.e. – Blocks, Arguments, and Expressions.

  • Blocks – Containers for other contents and represents the object configuration
  • Arguments – Assign a value to the name and appear within the blocks
  • Expressions – Represents a single value, referenced value, or combination of other values

1.2 Steps

To create the infrastructure via the Terraform scripts following commands need to be executed in a sequence. However, details and actions may differ between workflows.

  • terraform init – Initializing the new or existing terraform configuration
  • terraform plan – Generate the execution plan from the resources specified in the file
  • terraform apply – Create the infrastructure from the resources specified in the file
  • terraform destroy – Destroy the created infrastructure
terraform apply - workflow
Fig. 1: Terraform workflow

2. Terraform Apply Command

Terraform apply command is used to perform changes to the real infrastructure environment. This command scans the current work directory for the configuration and applies the changes to the environment. This command looks for the plan file on the instruction and if one does not exist then the command will create a replacement plan automatically and prompt approval for its use. If the created plan does not include any changes to resource or output values then the command will exit immediately.

terraform apply command
Fig. 2: Terraform apply command

That is all for this tutorial and I hope the article served you with whatever you were looking for. Happy Learning and do not forget to share!

3. Summary

In this tutorial, we learned an introduction to Terraform and the apply command which is used to create the infrastructure in the real environment. Terraform apply is the final command in the following responsible for deploying your resources listed in the terraform file in the cloud environment.

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