I forgot my password. What can I do?
If the admin didn't disable any necessary functions, you can go to the login page and click on “Send new password” (see How to login for more information). If this doesn't work, ask the admin to give you a new password in the UserManager.
But sending a new password doesn't work and I am the admin and cannot access the User Manager. How can I retrieve my password and get back my admin permissions?
You can
conf/local.php$conf['superuser'] = 'foo';
$conf['superuser'] = '@admin';
just remember its name
conf/users.auth.php...:user,admin