[LightDM] how is start-default-seat supposed to work?

[Greg Klanderman]

>>>>> On April 28, 2020 Adam Nielsen <a.nielsen at shikadi.net> wrote:

>> I would like to have lightdm only run on seat-1, and not seat0.
>> I am running debian testing, with lightdm 1.26.0-7.

> Why do you want to do this?

I am logging in on the console VT1 and starting X via xinit manually
on seat0, and my son is using lightdm to log in on seat-1.  I don't
need lightdm on seat0, and it occasionally causes a VT switch to VT7
where it's running.

> The solution will be different depending
> on whether you only want one seat forever, or whether you want to
> retain the ability to start the other seat as needed.

I am using both seats, just not lightdm on seat0.

> I guess start-default-seat is to handle the default configuration where
> no specific seat is configured, but you still want to bring up seat0.

Did you look at the code?  All the code that starts seats is guarded
by an if statement (two cases actually, covering logind and no logind,
see src/lightdm.c, around lines 873 and 888) checking that this option
is true.

There is some code just above that adds a hook when the dbus-service
option is on, service_add_xlocal_seat_cb, so lightdm might still start
on an added seat even with start-default-seat=false.

But it will not start any seats by default, even specific seats
configured under a [Seat:seat-1] block rather than [Seat:*], as the
doc seems to imply:

# start-default-seat = True to always start one seat if none are defined in the configuration

>> So generic [Seat:*] configs would not be considered
>> for purposes of whether to start a specific seat; to start on seat0,
>> you would need some config lines under [Seat:seat0], and likewise in
>> order to start on seat-1, you would need some config lines under
>> [Seat:seat-1].
>> 
>> However, that did not work

> Did you fix the problem from your other thread that was preventing X
> from starting as seat-1 due to the lack of a suitable display device?
> Possibly that is why it did not work.

I just replied on that thread.. happy to work thru that one first.

many thanks,
Greg


> Cheers,
> Adam.