LightDM - Apr 2020 - lightdm goes into tight loop trying to create greeter sessions and fills up logs

> I am seeing lightdm run fine for a couple days, then while there is
> still an active user session on seat-1, it decides it needs to create
> a greeter session on seat-1.  That fails repeatedly, with it
> attempting to create the greeter session 30-50 times per second.  This
> quickly fills up the log file to many Gb, and uses significant CPU.
This isn't a LightDM problem.  What is happening is that your machine
is configured to start a second seat (seat-1), which causes LightDM to
load as the login handler for that seat.  In order to provide this it
launches another X instance, which then complaints that it hasn't been
set up with a display device - perhaps you only have one and it's in
use by the existing seat.

To fix the problem, either configure your system to only have one seat,
or configure X11 with appropriate devices so that it can bring up the
second seat without error.

Cheers,
Adam.

>>>>> On April 28, 2020 Adam Nielsen <a.nielsen at
shikadi.net> wrote:
>> I am seeing lightdm run fine for a couple days, then while there is
>> still an active user session on seat-1, it decides it needs to create
>> a greeter session on seat-1.  That fails repeatedly, with it
>> attempting to create the greeter session 30-50 times per second.  This
>> quickly fills up the log file to many Gb, and uses significant CPU.
> This isn't a LightDM problem.  What is happening is that your machine
> is configured to start a second seat (seat-1), which causes LightDM to
> load as the login handler for that seat.  In order to provide this it
> launches another X instance, which then complaints that it hasn't been
> set up with a display device - perhaps you only have one and it's in
> use by the existing seat.
Hi Adam, thanks for your reply.  Did you look at the logs I posted on
the debian bug report?  After being started, lightdm runs fine on both
seat0 (VT7) and seat-1.  The greeter remains running on seat0 (I am
logged in directly from the VT1 console terminal, where I started X
the old fashioned way) and my son has an active session on seat-1
where he logged in via lightdm/greeter.  About 2-3 *days* later, it
decided that it needed to start a greeter on seat-1, and went into a
tight loop failing repeatedly.  I included the complete lightdm log up
until it starts looping.  Have been through several cycles of this,
and it seems to reliably happen a few days after restarting lightdm.

thanks,
Greg

> To fix the problem, either configure your system to only have one seat,
> or configure X11 with appropriate devices so that it can bring up the
> second seat without error.
> Cheers,
> Adam.