How to detach postgres without deleting db user?

@Elder It’s typically a bad practice to use the same PG user across multiple applications.

In any case, this is a bug in the Stolon setup’s detach command, you can workaround the issue by doing the following:

Why can’t I have more than one pg attached?

You can attach more than one app to a database, they just “shouldn’t” have the same user. You can look at the attach options if you need additional customization. fly pg attach --help.