AdvancedTerraformUsage.md

Advanced Terraform Usage

Terraform - Plan

Once Terraform project is initialized, terraform plan command can be run multiple times to generate a plan to review prior to running terraform apply that actually creating cloud resources. This is helpful to:

1. verify that the Terraform script runs with no errors
2. review the cloud resources and dependencies before creating them
3. when run after infrastructure has been created with 'terraform apply' it diffs between the local definitions and the actual infrastructure

Terraform accepts inputs when prompted or you can conveniently pass them into the command line with -var or -var-file options. This overrides any default values in variables.tf

# to generate a terraform plan
terraform plan -var-file=sample-input.tfvars -out ./my-viya4-iac.plan

Terraform - Show

Run terraform show command to display the plan again

# to review the plan
terraform show my-viya4-iac.plan

Terraform - Apply

After any errors are resolved and satisfied with the plan, run the terraform apply command to create resources on the cloud provider. When a plan file is not provided, Terraform generates a plan at that time that may differ from previous plan runs.

# run apply to create resources based on the plan
terraform apply ./my-viya4-iac.plan

Terraform - State

After the resources are created use terraform state list to list all the resources and terraform state show to get details of a resource.

terraform state list
# to get more details on a particular resource
terraform state show <resource-name-from-state-list>

Terraform - Output

To display the outputs captured by terraform you can use the terraform output command to show all or a specific output variable.

terraform output
# to get the value of a specific output variable
terraform output <output-variable>