How to add extra user to group

So the current patches mostly revolve around adding an option to switch the utility from dealing with databases in /etc to databases in /var/lib/extrausers. That works reasonably well for creating new users, or new groups to act as a primary for a new user.

Having the usermod command work on the extrausers group database would probably handle your case for adding an extrausers user to an extrausers group. That still leaves a bunch of other problems though:

  1. adding /etc/passwd users to an extrausers group.
  2. refusing to add a user to extrausers whose name is taken by an /etc/passwd user.
  3. as above but for groups.

Ideally you want all the commands to act on the two sets of databases as one, rather than being able to switch between them.