https://stackoverflow.com/questions/45177941/terraform-conditional-provisioning
Hi Sparrowform is lightweight provisioner for Terraform based infrastructure. The benefits against other provison tools, it's decouple stage of terraform apply which does infrastructure bootstrap from provision stage, so you may do this:
$ terraform apply # does infra bootstrap, it's implied no provisioner inside
$ sparrowform --ssh_user=my-user --ssh_private_key=/path/to/key # do provision
Obviously you are free not to run sparrowform in subsequent runs. It does it's job (install ansible related dependencies, that is it). Then you drop your initial ssh_private_key and goes with new private key ( ansible related I guess ?)