Is it true that in GCP, accounts that will be used to log in to linux machines can be provisioned in Google Cloud IAM? And if so, how is it achieved (i.e. using directory services or by amending etc files)?
OS Login simplifies SSH access management by connecting your Linux user account to your Google identity. Administrators can manage access to instances by setting IAM permissions.
Google-provided public images include utilities and components to manage VM access.
When you enable OS Login, a helper script activates these components and perform the configuration.