Terraform Wiki

Nov 5, 2022

• Software engineering
• Infrastructure as code

• Resource Dependencies
• Terraform Workspaces

# When to use Multiple Workspaces

Named workspaces allow conveniently switching between multiple instances of a single configuration within its single backend. They are convenient in a number of situations, but cannot solve all problems. A common use for multiple workspaces is to create a parallel, distinct copy of a set of infrastructure in order to test a set of changes before modifying the main production infrastructure. For example, a developer working on a complex set of infrastructure changes might create a new temporary workspace in order to freely experiment with changes without affecting the default workspace.

• Automating Terraform

# Pass terraform plan output to terraform apply in CI

When running in an orchestration tool, it can be difficult or impossible to ensure that the plan and apply subcommands are run on the same machine, in the same directory, with all of the same files present.

• terraform refresh is effectively an alias for terraform apply -refresh-only -auto-approve which is why it should NEVER be used. It is far too risky to run terraform refresh without first reviewing the proposed state changes.
• Instead, use terraform apply -refresh-only. This alternative command will present an interactive prompt for you to review and confirm the proposed state changes. After confirming, your Terraform remote state will be updated to match the settings of your managed remote objects. More info can be found about this in the Hashicorp documentation here.
• terraform init
  • The terraform init command is used to initialize a working directory containing Terraform configuration files. This is the first command that should be run after writing a new Terraform configuration or cloning an existing one from version control. It is safe to run this command multiple times.
• Terraform prints output values to the screen when a configuration is applied, but Terraform can also query all output values with the terraform output command, or selectively query certain output values using the below command template:

1

terraform output $RESOURCE_NAME

• You can use -target to plan/apply a specific Terraform resource within a module. Be careful, this is an advanced way to use Terraform and could break your infrastructure if done improperly.

1

terraform apply -target=aws_security_group.my_sg

• Turn on Verbose Logging by setting the TF_LOG environment variable to 1. 0 turns off logging.

1

export TF_LOG=1

• tfenv is a useful cli tool that can be used to easily switch between different versions of Terraform.

1
2
3
4

brew install tfenv
tfenv install 1.0.0
tfenv use 1.0.0
terraform version # verify you're using the right version

• If you place a .terraform-version hidden file at the root of your terraform directory, tfenv install (no argument) will install the version written in it.