[bug#56690] [PATCH] gnu: seatd-service-type: Should use seat group.

[Liliana Marie Prikler <liliana.prikler@ist.tugraz.at>]

Am Dienstag, dem 09.08.2022 um 22:47 +0300 schrieb muradm:
> There is no such specification as login manager or what ever. User 
> is any one/thing acquiring resources via seat management. It is 
> perfectly fine to run mingetty, login into bash and from command line
> start sway that will use libseat to acquire video for instance. Who is
> user here?
> 
> There is also no display manager as it was before. Please see my
> explanation to unmatched-paren: 
> https://debbugs.gnu.org/cgi/bugreport.cgi?msg=46;bug=56690
> What is sway in this usecase, it is not a user (like you or me),
> it is not a display manager (as gdm, sddm etc.). It is just
> application requiring video card (not only) resource, which
> it instead of having exclusive root access, uses libseat to
> acquire it in "seat managy" way. And greetd does/should not
> care about seatd/libseat until it is not required to acquire
> resources in "seat managy" way. Instead it is a greeter which
> is totatly customizable, could be even a bash script or small
> suckless-like application or else.
> 
> This is the point of seatd I suppose, to do one thing only
> without enforcing on who should do what.
> 
> Thus, none of your proposals are suitable, and I can't come up
> with something better than "seat management user" or "libseat
> user". However in my opinion, the one who commits into such
> setup, should be aware of what is seatd libseat and how, why to
> interact with it.
I think you're mixing user and application here, which makes explaining
this to others difficult.  For instance, GDM is both an application
(display manager) and a user launching this application.  Likewise for
most other display managers.  Thus, there is a 1:1 mapping between
users and applications.

With seatd, from what I understand, there is no such mapping.  However,
given your description, the following is unclear: Does alice need to be
in the seat group to run bash?  To run sway?  To run sway *only if not
having talked to greetd first*?

> > > > > +  (group seatd-group (default "seat"))
> > > > > +  (existing-group? seatd-existing-group? (default #f))
> > > > AFAIK this is not necessary.  accounts-service-type can 
> > > > handle
> > > > multiple eq? groups, so as long as you're careful with what 
> > > > you put
> > > > into group, you shouldn't get an error.
> > > ok field removed
> > Note ‘eq?’ groups here.  In other words, you should be able to 
> > take a
> > group (not just a group name) for the group field, sanitize the 
> > field
> > so that it will always be a group, and then use that group in 
> > seatd-
> > accounts (see the second option mentioned in
> > <79341a82bf9cd5fc6c2227255095f3fe2927dcbe.camel@ist.tugraz.at>). 
> > If
> > for instance instead of seat, you wanted the video group, you 
> > would
> > have to take the one from %base-groups, rather than creating a 
> > new one.
> Sorry, but I'm not so proficient in english as you. I can only
> speculate on what is written here. And that reference does not
> say anything to me, even duck duck go gives single result, it is
> your message. Could you please be more specific here, and/or
> provide more useful hyperlink style references. Thanks in advance.
I'll explain it in terms of lisp:

(define seat1 (user-group (name "seat") (system #t))
(define seat2 (user-group (name "seat") (system #t))
(operating-system (groups (list seat1 seat1))) ; works, eq?
(operating-system (groups (list seat2 seat2))) ; works, eq?
(operating-system (groups (list seat1 seat2))) ; doesn't work

For field sanitizers, see define-record-type*.

Cheers