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Terraform Introduction

Links: 113 Terraform Index


  • Also known as IaC (Infrastructure as Code)
  • Ansible and Terraform have very different use cases.

IaC tools classification

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  • Configuration management:

    • Designed to Install and Manage Software
    • Maintains Standard Structure which means it is easy to update as compared to shell scripts.
    • Version Control
    • Idempotent: We can run the code multiple times and every time we run it will only make changes required to bring the environment in the defined state.
  • Server Templating:

    • Pre installed software and dependencies
    • Virtual machine and docker images
    • Immutable infrastructure: Once the VM or container is deployed it is designed to remain unchanged.
  • Provisioning Tools:

    • Deploy Immutable Infrastructure resources.
    • Servers, Databases, Network Components etc.
    • Multiple Providers
Terraform is vendor agnostic unlike CloudFormation which is only meant for AWS.

Why Terraform?

  • Free and open source tool developed by HashiCorp.
  • It installs as a single binary.
  • We can deploy infrastructure across multiple platforms including private and public cloud.

    • This is achieved using providers.
    • We can also manage network infrastructure using other providers.
    • Terraform supports 100's of providers because of this Terraform can work with any infrastructure platform.
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  • Terraform uses HashiCorp Configuration Language (HCL) (.tf) which is a simple declarative language to define the infrastructure resources as blocks of code.

  • Terraform works in 3 phases: init, plan and apply.

    • During the init phase terraform initialises the project and identifies the providers to be used for the current environment.
    • During the plan phase terraform drafts a plan to get to the target state.
    • During the apply phase terraform makes the necessary changes to the target environment to bring it to the desired state.
  • Every object that terraform manages is called a resource.

    • It can be a compute instance or a database server or any other component
  • Terraform records the state of the infrastructure as seen in the real world.

    • Based on this it can determine what actions to take for updating resources for a particular platform.
    • This ensures that the entire infrastructure is in the defined state at all times.
    • Terraform can read attributes of existing infrastructure components.
    • Terraform can manage resources created by other IaC tools.

Last updated: 2023-01-02