There could be scenarios where you want to import the already existing resources from cloud providers into terraform.

Terraform has an import modude which does this job and using the module is a tedious process

https://www.terraform.io/docs/cli/import/index.html

There is tool called Terraformer which does the job of reverese terraforming

https://github.com/GoogleCloudPlatform/terraformer

Google cloud

https://gist.github.com/kiranchavala/54a930c8da148cc2b637c053dc1ba8ba

AWS

https://gist.github.com/kiranchavala/c2a01a7a43ea15cb8921a710d6cf22ea

Azure

https://gist.github.com/kiranchavala/18a1c555c198eb0944cbad3791602dc7

Openstack

https://gist.github.com/kiranchavala/c63243b0b76adcdafc7d06d87a304370

Cloudstack

https://gist.github.com/kiranchavala/c1b81f1d629b0567e08e219891d4ed48