I upgraded from 11 to 12 like one year ago and from 12 to 13 some days ago (upgrade to 14 seems that will be straightforward) but in my case what I did:
- Don't upgrade directly from 12 to 14, go to 13 first
- If you have warnings after moving from 11, fix them first
- Run the 0.13upgrade command in your code that will generate the required_providers
- Run terraform-v13 init
- Change to correct workspace if using some
- Run terraform-v13 plan which will probably fail due to the new explicit required-providers rule, if that happens you need to modify the state with the correct providers https://www.terraform.io/upgrade-guides/0-13.html#why-do-i-see-provider-during-init- . In my case I have a lot of modules so I created an script that automated that process
- Execute again terraform-v13 plan and verify that it will not make uncommon changes
- Then run terraform-v13 apply.
