So I have an active Moodle environment and I've been using Moodle to handle credentials and logins. I want to move to using Google for single sign on purposes.
If I make this change what will happen to all the student credentials and profiles on Moodle? Will they transfer to the new Google? I'm worried about student data and class history.
The authentication type is part of the user record. If they are Moodle manual accounts now... they will stay Moodle manual accounts. This is how different users can have different authentication mechanisms (if they are set up) on the same Moodle site.
If you enable a different authentication and want to use that for all/some of your users, you would need to change the authentication type of every account (and possibly the username if they are not the same).
Do NOT change your primary admin to something other than a manual account. You will regret that eventually
Are you saying that it is possible for me to set the authentication type as a partial thing? So if I want to make all incoming freshmen use Google but leave the Sophomores - Seniors, I can do that?
Because that would be great. Then I just leave the admin as local manual and all students go over gradually.
You can indeed.
Just set up the new auth type. If new users don't have a manual profile they will automatically be tried with the external type. If that succeeds they will have that authentication from now on.