Note: You are currently viewing documentation for Moodle 3.2. Up-to-date documentation for the latest stable version of Moodle is probably available here: Upload users.
Upload user authentication method gotcha
Not sure how to word this or where to highlight it, but there should be a banner warning admins that if they upload a CSV in the upload users area without an authentication column (auth) populated with the correct auth method for the users they want to update, Moodle will change the updated users to having the manual authentication type tagged to their profiles. In other words, missing column = default to manual authentication interpretation by Moodle.
This then means that any integrations using that auth method to update users will not work until the auth method is put back to the correct method. (We see this most often with LDAP auth users.)
Upshot: always include the auth column if this user uploads area is not your main way of creating/updating users on the site. --Lesli Smith 1/12/2016