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Old 11-02-07, 01:59 PM   #1
RedShift1
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Default Building a multi-seat Xorg configuration with a dual head card

Hello,

I've been attempting to build a multi-seat (meaning, two or more monitors with each their own keyboard and mouse, allowing multiple users to work on the same computer simultaneously) computer on a dual-head geforce FX 5500 video card. The first monitor (l1730s) is connected to the VGA output, the second monitor (cpdm151) is connected to the DVI output (with a DVI-to-VGA piece).

However, everytime I want to start the second seat (seat1), I get the following errors in the X log:
Code:
(EE) Screen 0 deleted because of no matching config section.
(EE) Device(s) detected, but none match those in the config file.
Here is my xorg configuration: http://users.opengate.be/~glenn/xorg.conf.multiseat

Is it even possible to create a multiseat configuration with only a dual-head videocard? Usually people just take two seperate videocards.

PS: Don't mind missing mouses or keyboards in the configuration.
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Old 11-02-07, 03:24 PM   #2
AaronP
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Default Re: Building a multi-seat Xorg configuration with a dual head card

No, multiseat is not supported on a single card.
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Old 11-02-07, 05:04 PM   #3
RedShift1
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Default Re: Building a multi-seat Xorg configuration with a dual head card

Well that's a bummer. This is a driver limitation?
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Old 11-03-07, 02:34 AM   #4
AaronP
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Default Re: Building a multi-seat Xorg configuration with a dual head card

It's a limitation in both the X driver and the X server. Theoretically, an X server could support multiseat in a single process with the existing driver architecture. The problem is that the current multiseat implementation essentially runs two completely separate X servers. This works mostly okay with two separate graphics devices, but when both X servers are trying to drive the same hardware, stuff breaks.
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Old 12-14-08, 05:14 PM   #5
joh417
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Default Re: Building a multi-seat Xorg configuration with a dual head card

Hello,

Since AaronP post is very old, I would like to know if that limitation (with single dual-head cards) still exist...

Anybody has a multi-seat system in ubuntu 8.10 with a dual-head card?

Thanks and sorry for my english.
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Old 12-16-08, 11:54 AM   #6
mehukatti
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Default Re: Building a multi-seat Xorg configuration with a dual head card

I'm using a dual head setup with single X server. I have a projector connected with VGA and a monitor with DVI. The screens are :0.1 and :0.0
I also have a mini keyboard with built-in mouse (Scorpius P20) and a "normal" keyboard and mouse for the other "seat". However, even though I have two keyboards and mice, they do not work "separately". For example, there is only one mouse cursor that can be moved with either mouse, even between the screens (although windows can't be dragged between them). This really doesn't bother me as there are no other users. But it would still be nice to know, if it would be possible to have the keyboads and mice work completely separately in each screen in a real multi seat fashion. This would be nice eg. when hosting a party where two guys/gals could be using the computer at the same time. I really haven't tried to configure my setup this way, but I would imagine one would just need to say to X server to associate one keyboard/mouse only with screen :0.0 and the other one with :0.1. So essentially there is nothing limiting in Nvidia drivers considering this, but perhaps in the X server itself?

This is my configuration:
http://mtbnews.net/people/mehukatti/xorg.conf
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Old 12-16-08, 10:27 PM   #7
JaXXoN
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Default Re: Building a multi-seat Xorg configuration with a dual head card

Hi!

There are plenty of success reports with solutions built on xephyr,
even including (accelerated?) OpenGL, i.e.:
http://dodji.blogspot.com/2007/10/xe...as-landed.html

Unfortunately, there is no good single resource on that topic. Most
documentation seems to be pretty outdated and things seem to
be distribution specific.


Here's how i got at least something working on my machine using Fedora 8:

The following procedure allows to open a xephyr window while a user
session is already in progress. This is very handy, i.e. if your girl friend
walks in while your are working on all available displays and she likes to
do something on your computer. So you can "evacuate" one display and
place xeyphr into it instead, so she has her own work space with separate
mouse and keyboard :-)


1. Download the Xephyr package for Debian Lenny, unpack it and install Xephyr:

Code:
     wget http://ftp.de.debian.org/debian/pool/main/x/xorg-server/xserver-xephyr_1.4.2-9_i386.deb
     ar -x xserver-xephyr_1.4.2-9_i386.deb
     tar -xzf data.tar.gz
     cp ./usr/bin/Xephyr /usr/local/bin/Xephyr
     chmod u+s /usr/local/bin/Xephyr
2. Make sure that your currently running (main) X-Server is not using the mouse and
keyboard that are intended to be used with Xephyr. I did this by specifying the
keyboard and mouse to be used with the "main/real" X-Server with the following
entries in my xorg.conf:

Code:
Section "InputDevice"
    Identifier     "Keyboard0"
    Driver         "evdev"
    Option         "Phys"         "usb-0000:00:0b.0-4.3/input0"
    Option         "XkbRules"     "xorg"
    Option         "XkbModel"     "evdev"
    Option         "XkbLayout"    "de"
    Option         "XkbVariant"   "nodeadkeys"
EndSection

Section "InputDevice"
    Identifier     "Mouse0"
    Driver         "mouse"
    Option         "Protocol"        "IMPS/2"
    Option         "Device"          "/dev/input/by-path/pci-0000:00:0b.0-usb-0:4.2:1.0-mouse"
    Option         "ZAxisMapping"    "4 5"
    Option         "Emulate3Buttons" "no"
EndSection

Section "ServerLayout"
    Identifier     "Layout0"
    InputDevice    "Keyboard0" "CoreKeyboard"
    InputDevice    "Mouse0"    "CorePointer"
    Screen 0       "Screen0" 0 0
EndSection
Where the the available keyboards and mice can be detected with

Code:
cat /proc/bus/input/devices | grep -B 5 kbd
cat /proc/bus/input/devices | grep -B 5 mouse

3. Run Xephyr from a console

Code:
xauth add :1 . e35a4dd7ad107110869f6972fa8326ad
xinit /usr/local/bin/fvwm95 -- /usr/local/bin/Xephyr :1 -screen 1280x1024 \
-fp /usr/share/X11/fonts/misc,/usr/share/X11/fonts/100dpi,/usr/share/X11/fonts/75dpi,/usr/share/X11/fonts/TTF,/usr/share/X11/fonts/Type1 \
-mouse evdev,,device=/dev/input/by-path/pci-0000:00:0b.0-usb-0:8:1.0-event-mouse,5 \
-keybd evdev,,device=/dev/input/by-path/pci-0000:00:0b.0-usb-0:3.1:1.0-event-kbd,xkbrules=xorg,xkbmodel=evdev,xkblayout=us \
+extension GLX
(where "/usr/local/bin/fvwm95" is my preferred window manager - YMMV)


However, it's not yet working perfectly for me:

* The mouse wheel is not yet working inside xephyr
* some fonts are missing (font path missing?)
* 3D is not working (i guess it is necessary to re-compile xephyr)
* It would be nice to start as different user


If you like to have a "static" multi-seat setup, where a display is always
bound to a different user session, i guess you need to setup gdm accordingly,
like it is described, here (didn't yet tried it out myself, yet):
http://netpatia.blogspot.com/2006/09...th-ubuntu.html

regards

Bernhard
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Old 12-22-08, 01:22 PM   #8
joh417
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Default Re: Building a multi-seat Xorg configuration with a dual head card

thanks for the answers, I think I will try xephyr but I think that it would be cool having a multiseat only modifying xorg.conf. I am not sure if that's possible though...
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Old 10-01-09, 10:34 AM   #9
Fiable.biz
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Default Re: Building a multi-seat Xorg configuration with a dual head card

And what if I want to work usually in dualseat?
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Old 10-02-09, 05:34 PM   #10
JaXXoN
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Default Re: Building a multi-seat Xorg configuration with a dual head card

Quote:
Originally Posted by Fiable.biz View Post
And what if I want to work usually in dualseat?
You mean there should a login prompt show up for each display after system boot?
In this case you need to configure the login manager (i.e. gdm) to first start the real
X-server (input-less) and then the two Xephyrs on top of that.

Here's a description for debian to get an idea on how to do that:
http://en.wikibooks.org/wiki/Multiterminal_with_Xephyr

However, I don't know the current state of Xephyr - I guess 3D is still
experimental and not compiled-in by default. Even then I'd expect
quite some performance drop compared to the "real" driver.
So unless you just do some simple 2D office type of stuff, I'd recommend
purchasing another PCI/PCIe card.

regards

Bernhard
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Old 10-03-09, 03:11 AM   #11
Fiable.biz
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Default Re: Building a multi-seat Xorg configuration with a dual head card

In fact, when I posted, I hadn't noticed the link
http://netpatia.blogspot.com/2006/09...th-ubuntu.html
you gave. But after I saw it I still couldn't manage to make it work on my Mandriva 2009 Spring. The link you just gave for a Wikibook requires 1 card per monitor.
I've several problems.
1) I tried to modify my xorg.conf file, but when I logout-login, I get 2 blank screens, with not even a cursor.
2) Another problem is about kdm. On my computer, gdm is not installed, kdm is active, xdm is installed but doesn't appear if I type "ps -eal | grep dm" , so I suppose it's not active. Except from /etc/X11/xorg.org , I don't know what configuration file(s) kdm reads. I have a /etc/X11/gdm/custom.conf file, with only one, "daemon" section.
I get no error no warning message in /var/log/kdm.log . In /var/log/Xorg.0.log , I get no error message but these warning messages:
Code:
(WW) AllowEmptyInput is on, devices using drivers 'kbd', 'mouse' or 'vmmouse' will be disabled.
(WW) Disabling Keyboard1
(WW) Disabling Mouse1
(WW) "dri" will not be loaded unless you've specified it to be loaded elsewhere.
(WW) Falling back to old probe method for v4l
(WW) NVIDIA(0): No TwinView "MetaModes" specified; will fall back to Display
(WW) NVIDIA(0):     SubSection modes.
(WW) NVIDIA(0): No valid modes for "1366x768"; removing.
(WW) NVIDIA(0): No valid modes for "1360x765"; removing.
(WW) NVIDIA(0): Cannot find size of first mode for KTC K-500 (CRT-0); cannot
(WW) NVIDIA(0):     compute DPI from KTC K-500 (CRT-0)'s EDID.
(WW) NVIDIA(0): Option "PreferredMode" is not used
The full Xorg.0.log is here: http://ca.pastebin.com/m3bb2c2af
and my xorg.conf file is there
http://ca.pastebin.com/m32aef079

Last edited by Fiable.biz; 10-03-09 at 03:17 AM. Reason: Added a link
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Old 02-01-10, 07:57 PM   #12
jess
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Default Re: Building a multi-seat Xorg configuration with a dual head card

If this last post is still active, I have been successful with two servers having one with several displays.

Further details are available on Wikipedia, Chris Taylor's Blog (Seneca University), Universidade Federale do Parana (C3SL lab) and many Ubuntu forums.

Search terms that should generate good sources are:

multiseat x mdm multihead

It seems that your best bet is to look at the login manager configuration help. It's an easy step to forget, but essential to having the separate interfaces.

Jess
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