How Do You Troubleshoot The Terraform Error “Authentication using either SSH …must be enabled in Linux profile”?

Problem scenario
You try to run terraform apply to create an Azure VM but you receive a message like this:

Error: Error applying plan:

1 error(s) occurred:

* azurerm_virtual_machine.myterraformvm: 1 error(s) occurred:

* azurerm_virtual_machine.myterraformvm: compute.VirtualMachinesClient#CreateOrUpdate: Failure sending request: StatusCo" Message="Authentication using either SSH or by user name and password must be enabled in Linux profile." Target="linux"

What should you do?

Solution
1. Back up your .tf file. Look at your .tf file. Find a stanza like this:

key_data = "ssh-rsa AAAAC5Mx{snip}ikjmI3w"

2. Replace "ssh-rsa AAAAC5Mx{snip}ikjmI3w" with the content of the .pub file of your choice. If you do not have one, create one by running this: ssh-keygen -t rsa -P ""
Press enter to the prompt. You should know have an id_rsa.pub file. Use the content of this file (despite it being very long) as the key_data value.

3. Run terraform init again. Run terraform apply again. Now the username as specified with admin_username in the .tf file will allow you to log into the Azure VM from the server you created the id_rsa.pub file when you use ssh. From other Windows workstations, you will probably not be allowed to log in the new Azure VM with that admin_username; so you will probably want to create some new users on the new Azure VM.