You have a Linux VM that must connect to Cloud SQL.

[Reference: https://cloud.google.com/compute/docs/access/create-enable-service-accounts-for-instances, , https://cloud.google.com/compute/docs/access/create-enable-service-accounts-for-instances, Changing the service account and access scopes for an instance If you want to run the VM as a different identity, or you determine that the instance needs a different set of scopes to call the required APIs, you can change the service account and the access scopes of an existing instance. For example, you can change access scopes to grant access to a newAPI, or change an instance so that it runs as a service account that you created, instead of the Compute Engine default service account. However, Google recommends that you use the fine-grained IAM policies instead of relying on access scopes to control resource access for the service account. To change an instance's service account and access scopes, the instance must be temporarily stopped. To stop your instance, read the documentation for Stopping an instance. After changing the service account or access scopes, remember to restart the instance. Use one of the following methods to the change service account or access scopes of the stopped instance., , ]