How to recover a lost Rails master key

You know that sinking feeling when you accidentally delete your master.key file and need to rebuild your local set of credentials… well that was going to be my morning.

Fortunately Rails apps only reload configuration when the server is restarted. That means the key should be somewhere in memory.

One puts Rails.application.credentials.key and I was back in business.

PS Keep a copy of your key, especially for production, in your password manager. Future you will greatly appreciate it.