Section 6. Terraform CLI.md

Section 6. Terraform CLI

Terraform CLI

Terraform fmt

• Formats code for readability
• Helps code consistent easy to maintain
• Use for:
  • Before pushing code on your version control
  • After upgrade Terraform or modules
  • If you made any changes on code

Example

terraform fmt

Terraform taint

• Recreate a resource (destroyed and created) in the next terraform apply execution
• Modify the state file (because recreate the resource)
• Maybe can force to recreate other resources (if they're referenced)
• Use for:
  • Run provisioners
  • Replace misbehaving resources
  • Check recreate doesn't affect or change any attributes

Example

terraform taint <resource>

Terraform import

• Maps existing resources to Terraform using a resource id
• id depends of provider. AWS, GCP, Azure, etc.
• Don't import the same resources to multiple Terraform code because create conflicts in the future
• Use for:
  • You need to work with existing rsources
  • Not allowed create new resources
  • You don't have any control of creation procress of infrastructure

Example

terraform import <resource>.<id>

Terraform Configuration Block

• Config for controlling Terraform behavior
• Block only allows constant values. Don't allow named resources or variables
• Use for:
  • Configure vendor backend for store state files
  • Terraform version
  • Terraform providers
  • Experimental Terraform features
  • Passing metadata to providers

Example

provider "aws" {
  region = var.region
}

provider "kubernetes" {
  host                   = data.aws_eks_cluster.cluster.endpoint
  cluster_ca_certificate = base64decode(data.aws_eks_cluster.cluster.certificate_authority.0.data)
  token                  = data.aws_eks_cluster_auth.cluster.token
}

terraform {
  required_providers {
    aws = {
      source  = "hashicorp/aws"
      version = "~> 3.30.0"
    }
    kubernetes = {
      source  = "hashicorp/kubernetes"
      version = "2.0.2"
    }
  }

  required_version = ">= 0.15"

  backend "s3" {
    bucket = "CHANGE-ME"
    key    = "CHANGE-ME"
    region = "CHANGE-ME"
  }
}

Terraform Workspaces (CLI)

• Workspaces are alternate state files within the same working directory
• By default, starts with a single workspace: default. Cannot be deleted
• Are meant to share resources and to help enable collaboration

Examples

# create workspace
terraform workspace new <name>

# select workspace
terraform workspace select <name>

# access workspace name
${terraform.workspace}

• Cases of use:
  • Test changes using parallel, distinct copy of infra
  • Modeled againsts brances in version control
  • Use logic to deploy some code. For example, if the workspace is "developer" you can make some tests and if it's "default" you can deploy directly

Examples

# create resources based of workspace name
resource "aws_instance" "test" {
  count = terraform.workspace == "default" ? 2 : 1
  ...
}
  
# create resources based of workspace name
resource "aws_s3_bucket" "test" {
  bucket = terraform.workspace
  ...
}

Debugging Terraform

• Use TF_LOG env var for enable verbose in Terraform. By default, send logs to stderr
• Allows: TRACE, DEBUG, INFO, WARN, ERROR
• Send logs to path: TF_LOG_PATH
• Set logging env vars:
  • export TF_LOG=XXXX
  • export TF_LOG_PATH=XXXX