FWIW - I just tried to set a quick test project up and I recalled the discussion here so I thought I’d check it. Therefore I left both user and password at the default “postgres” and encountered the same issue/errors OP described in his first post. The solution in my case:
silverdr$ sudo -u postgres psql
psql (12.9 (Ubuntu 12.9-0ubuntu0.20.04.1))
Type "help" for help.
postgres=# \password postgres
Enter new password:
Enter it again:
postgres=# \q
silverdr$ mix ecto.create
Compiling 29 files (.ex)
Generated testapp app
The database for Testapp.Repo has been created
IOW - altering the ROLE “postgres” to have password “postgres” helped immediately. This is basically the same what @inko mentioned: if you want to use the “postgres” role, give it the password you have cofigured in the Elixir application config.
