Introduction

This post covers various methods to configure terraform with Google Cloud Platform credentials. It assumes the terraform project structure of provider.tf, variables.tf, terraform.tfvars, etc. Terraform provider.tf, variables.tf, and instance.tf files are provided in the repository. The only file needed is the terraform.tfvars file which examples are given below on how to create.

Prerequisits

A Vagrantfile is provided in the http://github.com/justsomedevnotes/terraform-gcp-credentials repository with required binaries.

• Google Cloud Platform account
• gcloud command line
• terraform

Describing the Approaches

There are two approaches that I know of to give your terraform configurations permission to access your GCP account. The first is using GCP service accounts. The second is using the gcloud default login credentials. The first involves creating a service account key, downloading it, and giving it to terraform (demonstrated in the first section below). The second is logging in using the gcloud command line and not providing any credentials to terraform configuration allowing it to default to your gcloud credentials (demonstrated in the second section below).

Using GCP Service Accounts

There are two ways to set the service account key in the terraform configuration; 1) referencing the json file, 2) copying the actual content in the terraform configuration. Both ways require a key, so lets go ahead and get the key.

In the Google Cloud console select the below (make sure to select adequate permissions such as project --> owner)

  API & Services --> Credentials --> Create Credentials --> Service Account Key --> New Service Account 

Save this key in a location that your shell and terraform will have access.

Referencing the JSON

In your terraform.tfvars file, just add a reference to the JSON file in the service account key variable entry.

terraform.tfvars

 project = "your project"
 region = "us-central1"# or whatever region you want
 zone = "us-central1-a" # or whatever zone you want 
service_account_key = "my_service_account_key.json" # or whatever your file is named 

Referencing the actual Service Account Key Value

Rather than referencing the JSON file, the actual key value can be inserted directly into the terraform configuration files. The below approach inserts the value into the tfvars file and is referenced by the provider.tf file.

project = "your project"
 region = "us-central1"# or whatever region you want
 zone = "us-central1-a" # or whatever zone you want 
sservice_account_key = <<SERVICE_ACCOUNT_KEY
# insert the key value here
SERVICE_ACCOUNT_KEY

Once the key value or the json is set, give the Testing the Credentials section a try.

Using Default gcloud Credentials

The second approach is to not provide any credentials to the terraform configuration files. Terraform will look for the gcloud configuration and use those credentials if found. This would probably be more of a testing some development type use-case.

gcloud auth application-default login 

It should prompt you for a verification code. Just follow the link to retrieve the verification code and update the local gcloud credentials. Once the gcloud credentials are set, terraform can execute using the default credentials and the provider.tf credentials entry can be removed or commented out. Give the Testing the Credentials section a try.

Testing the Credentials

Using the instance.tf file provided in the repository execute the below commands.
Initialize terraform...

terraform init

create the plan...

terraform plan -out=plan

apply the plan...

terraform apply plan

If everything executes successfully you will have a new compute instance created. Congratulations! Don't forget to destroy when you are finished.

terraform destroy