HOWTO:Multi-Seat with current xorg / udev /systemd

dambacher · Last edited by dambacher on Wed Nov 06, 2013 7:15 am; edited 1 time in total

Hi everybody
It took me some hours to figure out how to correctly set up the udev rules to tag my docking station inputs to have a multiseat setup with the current xorg servers 1.14.3

So for your convenient use:
/etc/udev/rules/99-seat-rules

John R. Graham · Posted: Tue Nov 05, 2013 7:09 pm Post subject:

Moved from Desktop Environments to Documentation, Tips & Tricks.

- John
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steveL · Posted: Wed Nov 06, 2013 5:24 am Post subject:

Lovely post dambacher.

You might want to split the files in xorg.conf.d so you have a small code section for each; and perhaps add a note that we should of course adjust parameters to our particular devices (especially identifiers.)

Also, I don't see anything specific to systemd: it appears only to need udev tags applied to devices, which xorg picks up on (does that require evdev?) If it's non-specific, then you might want to edit the post title, so openrc users don't get put off reading it.

Again, nice post, thanks,
steveL.

dambacher · Posted: Wed Nov 06, 2013 7:08 am Post subject:

Hi steveL

My xorg.conf.d is modular, but for ease of reading I merged it here.

The TAG and ID_SEAT flags will be evaluated by systemd / logind to set up the seat.
TAG and ID_SEAT are queried by xf86-input-evdev if you use the -seat option to set udev matches.
And if I read the code correctly ID_INPUT.tags is also queried by xf86-input-evdev with and without -seat option.

The xorg support for multiseat is claimed to be not completely ready because graphics card selection is not implemented .
therefore I use the --serverlayout to change card and monitor accordingly (no need for wrapper functions like in fedora) and InputClass with Matches and Option "Ignore"
This way it works without the -seat option and in non systemd setups, too (I had that before).

bye
dambacher

More reading:
http://wiki.gentoo.org/wiki/Multiseat
http://www.freedesktop.org/wiki/Software/systemd/multiseat/
http://www.x.org/wiki/Development/Documentation/Multiseat/
http://cgit.freedesktop.org/xorg/xserver/tree/config/udev.c?h=server-1.14-branch

dambacher · Posted: Thu Nov 07, 2013 9:36 am Post subject:

I just found out that multi-seat handling with sytemd/logind , x and gnome3/gdm3 is not fully elaborated yet. I will update on this.

lightdm, kdm and gdm users (gdm up to version 2.20) can find a solution, e.g. https://help.ubuntu.com/community/MultiseatX

dambacher · Posted: Sun Nov 23, 2014 3:45 pm Post subject:

as with systemd-217 and xorg-server-1.16.1 you can use multiseat without patching.

you basically configure two server layouts in a single xorg.conf
but leaving the input devices to be autoattached.
and then use MatchSeat to select the server layout for the seat.

steveL · Posted: Wed Nov 26, 2014 8:15 pm Post subject:

Thanks dambacher, that was a load of info ;) Have to admit I don't find multi-seat half as interesting as multi-head; I'd rather have LTSP or something for an internet cafe or classroom, and keep the separation.

You mentioned that you had this running before without systemd; is it effectively the same setup? ie tag the devices with udev and then assign them in xorg .conf. Seems to be from the ubuntu page, but it'd be nice to have an illustrated setup under openrc.

ISTR we just used to have different server layouts or something, though as I said I'm not a multi-seat user, and in fact see it as out of scope for the "average desktop or laptop" use-case. (Not knocking what anyone else chooses to do, ofc.) Seems like main difference is tagging USB devices according to hub.

dambacher · Posted: Wed Nov 26, 2014 8:44 pm Post subject:

Hi steveL
Yes I had a setup running openrc and xfce before switching to gnome3
I used to login on console and then startx -layout $altlayout
And i used udev tagging with these MatchTag entries in xorg.conf .
Bye

steveL · Posted: Thu Nov 27, 2014 6:34 pm Post subject:

Nice one, thanks.