LM 18.3: New user created by GUI is not assigend to standard groups.

[Anton7]

Hello,
if I add a new user by GUI (Preferences - Users and Groups) in LM 18.3 this ("Standard") user is not assigned to the usually necessary users groups for a standard user.
Only a new user group is created which has the name of the new user.
Is this a bug or normal or a misconfiguration of my system?
I found no description that user groups have to be assigend after adding new user by GUI.

I then added gnome-user-tools to LM. Now a new user is assigned to some groups. But in gnome-system-tools "users and groups" GUI there is no overview to which groups one user belongs, so I have to go trough all the groups or use the terminal or check the etc/groups.

Is there any description of "all" user groups? Is there any description, which groups a new user has to be assigned to for which functionality? Obviously many software adds its own group. But also obviously the user must not be assigned to all this groups to use the functionality of this software.

Thanks for any related links or descriptions. I think I did reasonable searches but found nothing about that, only tons of decriptions "how to add new user". I also know how to add / edit user by terminal, but this is not the topic here.
Anton

[rene]

Is there any description of "all" user groups?

No, because mostly no such thing exists. I recently looked at that issue in the context of another thread here and I'm afraid this is a bit of a mess...

The installer places the initial administrator user in its usergroup and "sudo, adm, cdrom, dip, plugdev, lpadmin, sambashare". The first two of these are as standard for administrator users, the rest as determined by the on a new install existing groups from among

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sed -n '/^Template: passwd\/user-default-groups/,/^Template:/ { /^Default:/p }' /var/lib/dpkg/info/user-setup.templates

As you have noticed, creating a new user through Cinnamon's "User and Groups" does not in fact add a new user to any group other than its usergroup, "sudo" if an Administrator and "nopasswdlogin" if set to login without a password.

The MATE and Xfce editions (of Mint 18 and 19) use users-admin from the gnome-system-tools package as their GUI user admin tool and by default create a Custom user, by default added to its usergroup only. It however uses the command-line tool adduser as its backend which may by setting ADD_EXTRA_GROUPS=1 in /etc/adduser.conf be configured to add additional groups EXTRA_GROUPS, by default set to "dialout cdrom floppy audio video plugdev users".

If you tell users-admin to create an "Administrator" or "Desktop user" instead, the user is other than to that/those added to "cdrom, floppy, dialout, tape, dip, adm, plugdev, fax, audio, scanner, fuse, video" in either case and additionally to "sudo, sambashare, lpadmin" in the former, as determined by

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sed -n '/^Groups=/p' /etc/gnome-system-tools/user-profiles.conf

Given this between editions of Mint and/or potentially between GUI versus command line (adduser) differing behaviour the really only candidate for "the standard Linux Mint user groups" is either the mentioned initial-user installer groups, or no groups other than the usergroup and "sudo" for Administrators.

What it in the end comes down to is that UNIX groups are diminishing in importance as an authentication mechanism. "We" are only perhaps 10% of the way there at the moment but authentication is switching to things like polkit which although it is currently for the most part itself based on UNIX groups (specifically, a polkit Administrator is on Ubuntu/Mint root or a member of groups "sudo" or "admin") does not need UNIX groups, can/could authenticate strictly on per-user basis.

And what it then also comes down to is that you probably shouldn't deeply care about any of it. UNIX groups seem to have entered the first stage of obsolescence, with most of their remaining uses more or less historical...