terraform command reference

3 min read | by Jordi Prats

The terraform's command line interface tool accepts a variety of subcommands and flags to modify how it will handle it's operations. This reference guide provides a quick overview of the available options.

Plan

• terraform graph: Using terraform graph we can generate a visual representation of a terraform code or plan
• terraform validate: terraform validate can help us to validate terraform code we are writing
• terraform: plan in json format: Writing terraform modules it is usefull to be able to conditionally include a resource

Init

• terraform init -upgrade: Using the upgrade flag we can retrieve it's changes instead of downloading all over again

Debugging

• terraform console: Using terraform console we can manually test terraform code
• Enable debug on terraform: By using the TF_LOG variable we can enable different levels of debug information on terraform

State operations

• Terraform 1.1: Using the moved block: The moved block allows to perform resource renaming as code
• merging terraform states from several projects: Using tfstate-merge we can copy the resources into a new project without altering it's state or having to import them
• terraform state pull / terraform state push: Using terraform state pull and terraform state push we can merge resources from different terraform states
• terraform state list: Listing resources on the terraform state can help us to understand what's going on under the hood
• terraform import: Using terraform import we can smooth the transition to manually created resources to IaC
• terraform state rm: Remove resources from the terraform state: Using terraform state rm we can instruct terraform to no longer manage some of it's objects
• Managing terraform state: rename resources: A refactor can cause terraform to try to recreate all the infrastructure. This can be avoided by renaming the resources on the terraform state
• terraform state show: inspect a resource's state: Using terraform state show we can dig into the managed resource's state

Apply

• Terraform apply refresh false: Using terraform with the option refresh set to false we can prevent terraform from undoing changes
• terraform taint: Using terraform taint of the replace option we can tell terraform to replace a managed resource
• Apply changes using terraform to a specific resource: Infrastructure drift can happen at the worst time, we can work around it telling terraform to target a specific resource

Format code

• terraform fmt: terraform ftm helps maintain the style of terraform code consistent

Output

• terraform output values: We can use terraform output for retrieving values from the terraform state

Installation

• tfenv: Terraform version manager: tfenv allows you to switch between terraform versions easily