Difference between revisions of "Xorg multiseat"

From ArchWiki
Jump to: navigation, search
(For LightDM (Light Display Manager) - Added sharing audio how-to)
m (For LightDM (Light Display Manager) - explanation)
(4 intermediate revisions by the same user not shown)
Line 335: Line 335:
 
}}
 
}}
  
If you wish to share audio equally among different users, add each user to the audio group:
+
But if you wish to share audio equally among different users, add each user to the audio group:
  
 
Example:
 
Example:
Line 343: Line 343:
 
}}
 
}}
  
Then put this in each user's respective ~/.asoundrc:
+
Then put this in each user's respective ~/.asoundrc rather than using /etc/asound.conf (this option also contains various tweaks to improve audio quality):
 
{{bc|1=
 
{{bc|1=
 
defaults.pcm.rate_converter "samplerate_best"
 
defaults.pcm.rate_converter "samplerate_best"
Line 359: Line 359:
 
         pcm "hw:0,0"      # you cannot use a "plug" device here, darn.
 
         pcm "hw:0,0"      # you cannot use a "plug" device here, darn.
 
         period_time 0
 
         period_time 0
         period_size 1024 # must be power of 2
+
         period_size 1024 # must be power of 2.
         buffer_size 8192  # dito. It
+
         buffer_size 8192  # ditto.
 +
        rate 44100
 
       #format "S32_LE"
 
       #format "S32_LE"
 
       #periods 128 # dito.
 
       #periods 128 # dito.
Line 405: Line 406:
 
In the previous case, each user has an equalizer they can configure separately.
 
In the previous case, each user has an equalizer they can configure separately.
  
Make sure to turn down and mute the audio channels that you do not use and turn off auto-mute microphone to avoid ALSA audio bugs.
+
Make sure to turn down and mute the audio channels that you do not use, turn off auto-mute microphone, and make sure no channel has a gain higher than 0 to avoid ALSA audio bugs. This can be done via alsamixer.
  
 
Finally you must set the {{ic|/etc/X11/xorg.conf}} file. You'll notice some options have been commented out which could be set according to your needs. Here is a sample, adjust to your own system configuration after determing hardware information:
 
Finally you must set the {{ic|/etc/X11/xorg.conf}} file. You'll notice some options have been commented out which could be set according to your needs. Here is a sample, adjust to your own system configuration after determing hardware information:
Line 536: Line 537:
 
}}
 
}}
  
Make sure to delete the {{ic|~/.Xauthority}} file in respective user directories before the initial reboot.
+
Additional Tips:
 +
 
 +
* Make sure to delete the {{ic|~/.Xauthority}} file in respective user directories before the initial reboot.
 +
 
 +
* To avoid tearing this seems to help on nearly all configurations - add this to /etc/environment:
 +
{{bc|1=
 +
CLUTTER_PAINT=disable-clipped-redraws:disable-culling
 +
CLUTTER_VBLANK=True
 +
}}
 +
 
 +
* To help avoid tearing on the web and maintain site compatibility it is advisable to install Pipelight for playing media online.
  
 
===For Auto Login multiseat (without Display Manager)===
 
===For Auto Login multiseat (without Display Manager)===

Revision as of 08:33, 15 February 2014

Tango-view-fullscreen.pngThis article or section needs expansion.Tango-view-fullscreen.png

Reason: Show how PulseAudio can be configured for multiple users without running PulseAudio system-wide. Explain how Multiseat be done using only one video card (and/or X Server) and without Xephyr. (Discuss in Talk:Xorg multiseat#)

Multiseat is a certain setup where multiple users work simultaneously on one computer. This is achieved by having two monitors, two keyboards and two mice. The advantages are quite obvious:

  • Less power consumption (only one computer)
  • Less hardware to purchase
  • All the cool kids do it

Requirements

Keyboards and mice

Any standard PS/2 or USB keyboards will suffice. Same thing for mice.

Graphics hardware

For the best possible result you'll need two graphics cards. I used an nVidia FX5500 AGP and an nVidia 6200 PCI. If you look around a bit you can certainly find new and decent PCI graphics card for a soft price.

It is possible to use only one videocard which has dual heads (like most nvidia cards will have), but this has some limitations: you have to use Xephyr on the second monitor which seems quite a messy solution from what I've read, and for optimal usage both screens need the same resolution.

If you have two pci-express slots, take advantage of them! That way you'll even be able to play two games at the same time. (PCI is too slow to play comfortably)

Processors and memory

If you really are working with two users on the same computer, I'd at least recommend a dual-core processor and plenty of RAM. A fast hard drive (10.000 RPM or higher) is also recommended for comfortable use.

Software

You'll need Xorg with the drivers for your graphics card (according to some sources, the closed source nvidia driver works better than the open source nv driver for this, I have t tested this myself) and the evdev (xf86-input-evdev) driver. That's all. All this can be found in the Arch Linux core and extra repositories.

Some X knowledge

If you know how X works this will be a lot easier. Before you start, I recommend generating a clean configuration with xorgconfig that works with a single screen. Read through this xorg configuration and make yourself familiar. And as usual the manpages will provide you with most of the answers. You may reference some man pages: xorg, xserver, startx, xdm, xinit. sudo X -configure, X -showopts may give you some hint.

Definitions

For this article to be clear, I'll be using the following definitions:

  • screen: A screen is something Xorg can display its stuff on. A screen has a monitor and a graphics card assigned to it.
  • monitor: A physical monitor like the one you're now sitting in front of.
  • server layout: a definition of which screen, keyboard and mouse to use.
  • seat: A workplace with a physical monitor, physical keyboard and physical mouse.

Tips and tricks

  • Set up ssh on your computer, so you can ssh to the machine from another computer (such as a laptop). This is very useful because you'll probably run into X not responding anymore or not giving you picture at all.
  • Finding out which keyboard and mouse is which: open a terminal and use cat to find out. For example, cat /dev/input/mouse1. If you then move your mouse and you see all weird things happening than that is the mouse you're moving. Same goes for keyboards, which are called eventN.
  • Try a basic configuration first. Don't start with the fancy stuff yet, get a very basic Xorg working first.
  • Leave your xorg.conf alone and create a new file, called xorg.conf.multiseat in /etc/X11 to store your new multiseat configuration. After this configuration is working you can overwrite the xorg.conf file with your new xorg.conf.multiseat.
  • Create a backup of all relevant configuration files. What do you mean you'll skip this one?
  • Take a look at the full configuration I used at the end of this article before you start.

About evdev

evdev is an Xorg driver which can make use of the kernel event devices, which you can find in /dev/input.

Setting up Xorg

The logic behind this is that you have two server layouts, each assigned with their own keyboard, mouse, video card and monitor.

The basics

First of all we'll set up the basics for xorg.

Section "ServerFlags"
        Option "AutoAddDevices"     "false"
        Option "AutoEnableDevices"  "false"
        Option "AllowMouseOpenFail" "on"
        Option "AllowEmptyInput" "on"
        Option "ZapWarning"         "on"
        Option "HandleSpecialKeys"  "off" # Zapping on
        Option "DRI2" "on"
        Option "Xinerama" "off"
EndSection

Defining available input devices

This part of the configuration tells Xorg which input devices it has available. Input devices are keyboards and mice, but can also be, for example, touchscreens and pens.

This section defines my first keyboard, called keyboard0. As you can seen it uses the evdev driver. /dev/input/event1 corresponds with the keyboard connected to the PS/2 port of my computer. Create a section like this for each keyboard you have. Don't forget to modify the identifier of course. Keep the identifier simple and match it with the other names. This keyboard0 will be used for screen0 together with mouse0.

Section "InputDevice"
        Identifier      "keyboard0"
        Driver          "evdev"
        Option          "Device"                "/dev/input/event1"
#     Option  "Device" "/dev/input/by-path/platform-i8042-serio-0-event-kbd"  
#     Option "Device" "/dev/input/by-id/usb-Tangtop_Generic_USBPS2-event-kbd"
        Option "xkb_rules" "evdev"
        Option "xkb_model" "evdev"
        Option "xkb_layout" "us"
        Option "GrabDevice" "on" # prevent send event to other X-servers
# If you are using a non en_US keyboard, set the layout here.
#       Option          "XkbLayout"             "be"
EndSection


This section defines my first mouse, called mouse0. This uses the regular mouse driver. /dev/input/mouse2 corresponds with the mouse connected to the PS/2 port of my computer. Create a section like this for each mouse you have.

Section "InputDevice"
        Identifier      "mouse0"
        Driver          "mouse"
        Option          "Protocol"              "IMPS/2"
        Option          "Device"                "/dev/input/mouse2"
EndSection
# or use evdev, that could assign by id
Section "InputDevice"
        Identifier "Mouse0"
        Driver "evdev"
        Option "Device" "/dev/input/by-id/usb-Tangtop_Generic_USBPS2-event-mouse"
        Option "GrabDevice" "on"
EndSection

Graphics card

Now we'll set up the graphics card for each screen.

Section "Device"
        Identifier      "nvidia0"
        Driver          "nvidia"
        Option          "NoLogo"                "1"  # Remove nvidia branding at startup
        BusId           "PCI:1:0:0"
        Option          "ProbeAllGpus"          "false"  # Only required for nvidia
EndSection

This section defines my first graphics card, called nvidia0. This uses the closed source nvidia driver. Take a close look at the BusID. This option specifies which hardware card to use. You can find out the BusId's with lspci. However, you'll soon find out this doesn't always match. That's because lspci displays the device address in hexadecimal form. Xorg however uses decimal form. So you'll need to convert your address from hexadecimal form to decimal. Thus a device address of 0:0a:0 in lspci would become 0:10:0 in xorg.conf.

Create a section like this for every graphics card you have.

Screens

This section defines my first screen, called screen0. Pay close attention to the "monitor" option. For easy recognition I called it the model of my monitor.

Section "Screen"
        Identifier              "screen0"
        Device                  "nvidia0"
        Monitor                 "l1730s"
        DefaultDepth    24
        Option                  "DPI"   "100x100"

        Subsection "Display"
                Depth   24
                Modes   "1280x1024"     "1024x768"
        EndSubsection

EndSection

Create a section like this for every screen you have.

Monitors

This section defines my first monitor, l1730s. Pay close attention to the identifier.

Section "Monitor"
        Identifier      "l1730s"
        HorizSync       30-93
        VertRefresh     60
        Option          "dpms"
EndSection

Create section like this for every monitor you have.

Serverlayout

Here's the fun stuff. This is how everything is added up. This is my first seat, called seat0. Here I tell Xorg for the server layout called "seat0" to use my screen0, which is attached to nvidia0, using keyboard0 and mouse0.

The AutoAddDevices option is now needed to keep HAL from automatically adding all your input devices to all the X servers.

Section "ServerLayout"
        Identifier      "seat0"
        Screen          "screen0"       0                   0
        InputDevice     "mouse0"        "CorePointer"
        InputDevice     "keyboard0"     "CoreKeyboard"
        Option "Clone" "off"
        Option "AutoAddDevices" "off"
        Option "DisableModInDev" "true"
        Option "SingleCard" "on"   # use this to simplfied isolatedevice option        
EndSection

Create a section like this for every seat you have with their respective keyboards, mice and screens.

Testing

Before we start modifying our login manager, we'll first start with testing out the individual seats. If these are working, then we're good to go.

I've used twm (tiny window manager) to test out if my seats work, but there's no reason you can't use KDE, gnome, or any other desktop environment or window manager. I've used this in my ~/.xinitrc:

exec twm

Use the following command to test out an individual seat:

startx -- -layout seat0 -config xorg.conf.multiseat

Do this for every seat you have. If they are all working correctly and the keyboard/mouse combination matches, then congratulations! You are almost finished! In case you are wondering why I didn't you use the full path to my new configuration file, that's because X doesn't allow that when running as non-root. It will search for xorg.conf.multiseat relative to /etc/X11.

Setting up the loginmanager

For KDM (KDE's Display Manager)

Open /usr/share/config/kdm/kdmrc and set the following variables:

StaticServers=:0,:1 #In the case of two seats. If you have three this would become :0,:1,:2 and so forth.
ReserveServers=:2,:3 #You can define here as many as you want, but these should always start at the highest seat + 1.

Next you'll need to add an [X-:n-Core] for each seat (where n = the seat)

[X-:0-Core]
ServerArgsLocal=-nolisten tcp -layout seat0

[X-:1-Core]
ServerArgsLocal=-nolisten tcp -layout seat1 -sharevts -novtswitch

Add section like this for every seat you have, and do not forget to change the :0 and the -layout seat0. Note that the "-sharevts" and "-novtswitch" options should be added for all seats except the first one. Otherwise, you can end with rectangles of virtual terminals "showing through" on your primary screen.

For GDM (Gnome's Display Manager)

Note: The following will work with GDM 2.20 but not with newer versions of GDM. GDM 2.20 is in AUR.

Open /etc/gdm/custom.conf and set the following variables (This sample demos two seats):

[servers]
0=Standard0
1=Standard1

[server-Standard0]
name=Standard server
command=/usr/bin/X -nolisten tcp -novtswitch -sharevts -r -config xorg.conf.multiseat
 -layout seat0
flexible=true

[server-Standard1]
name=Standard server
command=/usr/bin/X -nolisten tcp -novtswitch -sharevts -r -config xorg.conf.multiseat
 -layout seat1
flexible=true

For XDM (X Display Manager)

Open /etc/X11/xdm/Xservers and set the following variables (This sample demos two seats):

# NOTE: don't add -sharevts on seat0, otherwise it may reset in about 10~20 minutes automatically.
:0 local /usr/bin/X :0 vt07 -nolisten tcp  -novtswitch -layout seat0 -config xorg.conf.multiseat
:1 local /usr/bin/X :1 vt08 -nolisten tcp -sharevts -novtswitch -layout seat1 -config xorg.conf.multiseat

Also if you use the Archlinux theme edit /etc/X11/xdm/xdm-config for every screen:

DisplayManager._0.setup:        /etc/X11/xdm/arch-xdm/Xsetup
DisplayManager._0.startup:      /etc/X11/xdm/arch-xdm/Xstartup
DisplayManager._0.reset:        /etc/X11/xdm/arch-xdm/Xreset
DisplayManager._1.setup:        /etc/X11/xdm/arch-xdm/Xsetup
DisplayManager._1.startup:      /etc/X11/xdm/arch-xdm/Xstartup
DisplayManager._1.reset:        /etc/X11/xdm/arch-xdm/Xreset

For LightDM (Light Display Manager)

LightDM works well with ALSA only and PulseAudio removed if you wish to have shared audio, an alsamixer equalizer and software mixing.

In the example below LightDM and MATE with ALSA was installed with PulseAudio removed. PulseAudio could also be used but it requires a more complicated configuration to maintain high audio quality. The relevant hardware used is an ATI Radeon HD 5850 and an Intel Sandy Bridge (onboard) HD 3000. You configuration may vary.

Open /etc/lightdm/lightdm.conf and follow the sample. Autologin is optional. This works both as multi-user multiseat and single user multi-seat. In the first case only the last user to login will have audio control and access. Specific hardware could be addressed in /etc/asound.conf to allocate audio to both users simultaneously if required. Another option enables two different users to both access audio with their own equalizer (described further down). The sound card will be shared equally among the seats using ALSA with PulseAudio removed - libpulse itself should be kept for various software dependencies however:

[LightDM]
greeter-user=lightdm
log-directory=/var/log/lightdm
run-directory=/run/lightdm

[SeatDefaults]
xserver-command=/usr/bin/X
greeter-session=lightdm-gtk-greeter
greeter-show-manual-login=true
user-session=mate
session-wrapper=/etc/lightdm/Xsession
pam-service=lightdm-autologin
exit-on-failure=true

[Seat:0]
xserver-command=/usr/bin/X :0 -sharevts
xserver-layout=Layout0
#autologin-user=joeblow
#autologin-user-timeout=-1
#session-setup-script=/etc/lightdm/scripts/sound_start
#session-cleanup-script=/etc/lightdm/scripts/sound_stop
 
[Seat:1]
xserver-command=/usr/bin/X :1 -sharevts
xserver-layout=Layout1
#autologin-user=jillschmill
#autologin-user-timeout=-1

Next, remove respective ~/.asoundrc files (as well as related PulseAudio config files if you removed that) and follow this template with /etc/asound.conf for sound:

defaults.pcm.rate_converter "samplerate_best"

ctl.equal {
 type equal;
}

pcm.plugequal {
  type equal;
  # Modify the line below if you do not
  # want to use sound card 0.
  #slave.pcm "plughw:0,0";
  #by default we want to play from more sources at time:
  slave.pcm "plug:dmix";
}
#pcm.equal {
  # If you do not want the equalizer to be your
  # default soundcard comment the following
  # line and uncomment the above line. (You can
  # choose it as the output device by addressing
  # it with specific apps,eg mpg123 -a equal 06.Back_In_Black.mp3)
pcm.!default {
  type plug;
  slave.pcm plugequal;
}

But if you wish to share audio equally among different users, add each user to the audio group:

Example:

usermod -a -G ftp joeblow
usermod -a -G ftp jillschmill

Then put this in each user's respective ~/.asoundrc rather than using /etc/asound.conf (this option also contains various tweaks to improve audio quality):

defaults.pcm.rate_converter "samplerate_best"

ctl.equal {
 type equal;
}

pcm.ossmix {
    type dmix
    ipc_key 1024 # must be unique!
    ipc_key_add_uid false   # let multiple users share
    ipc_perm 0666           # IPC permissions for multi-user sharing (octal, default 0600)
    slave {
        pcm "hw:0,0"      # you cannot use a "plug" device here, darn.
        period_time 0
        period_size 1024 # must be power of 2.
        buffer_size 8192  # ditto.
        rate 44100
       #format "S32_LE"
       #periods 128 # dito.
       #rate 8000 # with rate 8000 you *will* hear,
       # if ossmix is used :)
    }
    # bindings are cool. This says, that only the first
    # two channels are to be used by dmix, which is
    # enough for (most) oss apps and also lets 
    # multichannel chips work much faster:
    bindings {
        0 0 # from 0 => to 0
        1 1 # from 1 => to 1
    }
}

pcm.plugequal {
  type equal;
  # Modify the line below if you do not
  # want to use sound card 0.
  #slave.pcm "plughw:0,0";
  #by default we want to play from more sources at time:
  slave.pcm "plug:ossmix";
}

#pcm.equal {
  # If you do not want the equalizer to be your
  # default soundcard comment the following
  # line and uncomment the above line. (You can
  # choose it as the output device by addressing
  # it with specific apps,eg mpg123 -a equal 06.Back_In_Black.mp3)
pcm.!default {
  type plug;
  slave.pcm plugequal;
}

Accessing the equalizer can be done with:

alsaequal -D equal

In the previous case, each user has an equalizer they can configure separately.

Make sure to turn down and mute the audio channels that you do not use, turn off auto-mute microphone, and make sure no channel has a gain higher than 0 to avoid ALSA audio bugs. This can be done via alsamixer.

Finally you must set the /etc/X11/xorg.conf file. You'll notice some options have been commented out which could be set according to your needs. Here is a sample, adjust to your own system configuration after determing hardware information:

Section "ServerFlags"
    Option         "DefaultServerLayout" "Layout1"
#    Option         "AllowMouseOpenFail"  "true"
    Option         "AutoAddDevices"      "false"
    Option         "AutoEnableDevices"   "false"
    Option         "DontZap"             "false"
    Option         "Xinerama" "0"
    Option         "AutoAddGPU" "FALSE"
EndSection

Section "ServerLayout"
    Identifier     "Layout0"
    Screen         0  "Screen0" 0 0
    InputDevice    "kbd_0" "CoreKeyboard"
    InputDevice    "mouse_0" "CorePointer"
    Option         "AllowEmptyInput"       "true"
    Option 	   "DontVTSwitch"          "true" 
EndSection

Section "ServerLayout"
    Identifier     "Layout1"
    Screen         0  "Screen1" 0 0
    InputDevice    "kbd_1" "CoreKeyboard"
    InputDevice    "mouse_1" "CorePointer"
    Option         "AllowEmptyInput"       "true"
    Option 	   "DontVTSwitch"          "true"
EndSection

Section "Module"
#    Load 	   "dri2"
#    Load 	   "glamoregl"
EndSection

Section "InputDevice"
    Identifier     "kbd_0"
    Driver 	   "evdev"
    Option         "Device"        "/dev/input/by-path/pci-0000:00:1a.0-usb-0:1.6:1.0-event-kbd"
    Option         "GrabDevice"    "on"
    Option 	   "XkbRules" "xorg"
    Option 	   "XkbModel" "105"
    Option 	   "XkbLayout" "us"
    Option  	   "Protocol"      "Standard"
EndSection

Section "InputDevice"
    Identifier     "kbd_1"
    Driver         "evdev"
    Option         "Device"        "/dev/input/by-path/pci-0000:04:00.0-usb-0:1:1.0-event-kbd"
    Option         "GrabDevice"    "on"
    Option 	   "XkbRules" "xorg"
    Option 	   "XkbModel" "105"
    Option 	   "XkbLayout" "us"
    Option  	   "Protocol"      "Standard"
EndSection

Section "InputDevice"
    Identifier     "mouse_0"
    Driver         "evdev"
    Option         "Device"        "/dev/input/by-path/pci-0000:00:1a.0-usb-0:1.5:1.0-event-mouse"
    Option         "GrabDevice"    "on"
EndSection

Section "InputDevice"
    Identifier     "mouse_1"
    Driver         "evdev"
    Option         "Device"        "/dev/input/by-path/pci-0000:00:1a.0-usb-0:1.3:1.0-event-mouse"
    Option         "GrabDevice"    "on"
EndSection

Section "Monitor"
    Identifier     "Monitor0"
    Option	   "VendorName" "Unknown"
    Option	   "ModelName" "Generic Autodetecting Monitor"
#    Option	   "DPMS" "true"
EndSection

Section "Monitor"
    Identifier     "Monitor1"
    Option	   "VendorName" "Unknown"
    Option	   "ModelName" "Generic Autodetecting Monitor"
EndSection

Section "Device"
    Identifier     "Device0"
    Driver         "radeon"
#    Option 	   "AccelMethod" "glamor"
    Option 	   "AccelMethod" "EXA"
    VendorName     ""
    BoardName      ""
    BusID          "PCI:1:0:0"
    Screen          0
#    Option         "EXAVSync"
EndSection

Section "Device"
    Identifier     "Device1"
    Driver         "intel"
    VendorName     ""
    BoardName      ""
    BusID          "PCI:0:2:0"
    Screen          0
#    Option         "AccelMethod" "UXA"
#    Option         "TearFree" "1"
EndSection

Section "Screen"
    Identifier "Screen0"
    Device     "Device0"
    Monitor    "Monitor0"
    DefaultDepth     24
    SubSection "Display"
    	Depth     24
    EndSubSection
EndSection

Section "Screen"
    Identifier     "Screen1"
    Device         "Device1"
    Monitor        "Monitor1"
    DefaultDepth    24
    SubSection     "Display"
        Depth       24
    EndSubSection
EndSection

Additional Tips:

  • Make sure to delete the ~/.Xauthority file in respective user directories before the initial reboot.
  • To avoid tearing this seems to help on nearly all configurations - add this to /etc/environment:
CLUTTER_PAINT=disable-clipped-redraws:disable-culling
CLUTTER_VBLANK=True
  • To help avoid tearing on the web and maintain site compatibility it is advisable to install Pipelight for playing media online.

For Auto Login multiseat (without Display Manager)

edit a script /boot/twin.sh

#!/bin/bash
cmd1="/bin/bash --login -c \"/usr/bin/xinit --"
cmd2="-nolisten tcp -keeptty -novtswitch -config xorg.multiseat.conf"
usr=(user1 user2)  # FIXME: assume user1, user2 is valid user id
declare -a pid
while true ; do
  for ((i=0; i<${#usr[*]}; i++)) ; do
    echo "usr[$i]=${usr[$i]} pid=${pid[$i]}"
    if [ -z "${pid[$i]}" ] || [ ! -d "/proc/${pid[$i]}" ] ; then
      # echo "pid ${pid[$i]} killed, execute again"  
      cmd3="-layout seat$i vt0"$((7+i))"\""
      if [ $i -gt 0 ] ; then
        cmd3="-sharevts $cmd3"
      fi
      #echo "cmd3=$cmd3"
      /bin/su ${usr[$i]} -l -c "$cmd1 :$i $cmd2 $cmd3" &
      pid[$i]=$!
      #echo "new pid=${pid[$i]}"
    fi
  done
  sleep 5  # check process exist per 5 second
done

Open /etc/inittab and setup as follows:

#id:3:initdefault:
id:5:initdefault:
...
x2:5:once:/root/twin.sh > /root/twin.log 2>&1

Troubleshooting

My Windows key doesn't work anymore

Put this in a startup file:

xmodmap -e "add Mod4 = Super_L Super_R"

Unreliable behaviour (black picture without cursor)

If everything seems to be set up correctly, but for some reason you always get a black picture without a cursor, try setting the first initialized card in the BIOS to be the PCI card one.

Little black boxes/dots on the desktop

This is actually portions of the virtual terminals being painted on top of X. It seems to be caused by the Linux kernel framebuffer. This can be fixed by disabling the framebuffer, or by removing the "-sharevts" option from the primary seat's X args.

Multimedia keys not working

If your keyboard(s) has extra "multimedia" keys, you may find that they stopped working in your multiseat setup. This is because such keyboards are often represented as more then one "event" device. As you did above, cat each /dev/input/event* device, this time pressing multimedia keys. Once you've found the right event device, add a separate keyboard InputDevice section for it, then add that InputDevice section to the corresponding ServerLayout section with the "SendCoreEvents" option, which indicates that input from this device should be handled, despite not being the core keyboard. In the end you should have sections something like the following:

Section "InputDevice"
    Identifier      "Keyboard0"
    Driver          "evdev"
    Option          "Device" "/dev/input/event6"
    Option          "XkbModel" "evdev"
EndSection

Section "InputDevice"
    Identifier      "Keyboard0Multimedia"
    Driver          "evdev"
    Option          "Device" "/dev/input/event7"
    Option          "XkbModel" "evdev"
EndSection

Section "ServerLayout"
    Identifier     "Layout0"
    Screen      0  "Screen0" 0 0
    InputDevice    "Keyboard0" "CoreKeyboard"
    InputDevice    "Keyboard0Multimedia" "SendCoreEvents"
    InputDevice    "Mouse0" "CorePointer"
    Option         "AutoAddDevices" "no"
EndSection

The Ctrl-Alt-Fx, Alt-Fx keys mess up with virtual terminals

(Oct 2010) I follows this guide and everything works, except for Atl-F1, Atl-F2,... mess things up. Then I follow this guide https://help.ubuntu.com/community/MultiseatX (read the part for Ubuntu 10.04):

# cd /usr/bin
# ln -s X X0
# ln -s X X1

Then fix in the /usr/share/config/kdm/kdmrc as follow

[General]
ConsoleTTYs=tty1,tty2,tty3,tty4,tty5,tty6
ServerVTs=7,8
StaticServers=:0,:1
ReserveServers=:2,:3
...

[X-:0-Core]
ServerVT=8
ServerCmd=/usr/bin/X1
ServerArgsLocal=-nolisten tcp -sharevts -novtswitch -keeptty -layout Seat1 -isolateDevice PCI:1:0:0

[X-:1-Core]
ServerVT=7
ServerCmd=/usr/bin/X0
ServerArgsLocal=-nolisten tcp -novtswitch -keeptty -layout Seat0 -isolateDevice PCI:0:2:0
...

It works for my computer: one on-board Intel card (xf86-video-intel driver), and one Nvidia card (xf86-video-nouveau driver). You can check if the parameters are passed correctly by:

$ ps aux | grep 'PCI' | grep -Ev 'grep'
root     16993  1.6  1.3  32900 26772 ?        S    08:09   0:19 /usr/bin/X0 :1 vt7 -nolisten tcp -novtswitch -keeptty -layout Seat0 -isolateDevice PCI:0:2:0 -auth /var/run/xauth/A:1-ES6CCb
root     17124  5.9  0.5  18996 11980 ?        S    08:09   1:09 /usr/bin/X1 :0 vt8 -nolisten tcp -sharevts -novtswitch -keeptty -layout Seat1 -isolateDevice PCI:1:0:0 -auth /var/run/xauth/A:0-Wgiyza

The ServerVT=7, ServerVT=8 would be pass to as vt7, vt8

Final configuration

/etc/X11/xorg.conf

This is my full xorg.conf with multiseat that works:

Section "Module"
	Load        "dbe"

	SubSection  "extmod"
		Option    "omit xfree86-dga"
	EndSubSection
	
	Load	"type1"
	Load	"speedo"
	Load	"freetype"
	Load	"glx"
EndSection


Section "Files"
	RgbPath	"/usr/share/X11/rgb"

	FontPath 	"/usr/share/fonts/misc"
	FontPath 	"/usr/share/fonts/75dpi"
	FontPath 	"/usr/share/fonts/100dpi"
	FontPath 	"/usr/share/fonts/TTF"
	FontPath 	"/usr/share/fonts/Type1"
	FontPath 	"/usr/share/fonts/msfonts"
	FontPath 	"/usr/share/fonts/misc2"
	FontPath 	"/usr/share/fonts/local"
	FontPath 	"/usr/local/share/fonts"
EndSection


Section "ServerFlags"
	# Option	"DontZap"
	Option	"AllowMouseOpenFail"	"true"
	# Option	"DefaultServerLayout"	"alltogether"
	Option	"Xinerama"	"0"
EndSection

Section "InputDevice"
	Identifier	"keyboard0"
	Driver		"evdev"
	Option		"Device"		"/dev/input/event1"
	Option		"XkbModel"		"evdev"
	Option		"XkbLayout"		"be"
EndSection

Section "InputDevice"
	Identifier	"keyboard1"
	Driver		"evdev"
	Option		"Device"		"/dev/input/event5"
	Option		"XkbModel"		"evdev"
	Option		"XkbLayout"		"be"
EndSection


Section "InputDevice"
	Identifier	"mouse0"
	Driver		"mouse"
	Option		"Protocol"		"IMPS/2"	# Auto detect
	Option		"Device"		"/dev/input/mouse2"
	Option		"ZAxisMapping"	"4 5"
EndSection

Section "InputDevice"
	Identifier	"mouse1"
	Driver		"mouse"
	Option		"Protocol"		"IMPS/2"
	Option		"Device"		"/dev/input/mouse1"
EndSection


Section "Device"
	Identifier	"nvidia0"
	Driver		"nvidia"
	Option		"RenderAccel"	"true"
	Option		"TripleBuffer"	"True"
	Option		"NoLogo"		"1"
	BusId		"PCI:1:0:0"
EndSection

Section "Device"
	Identifier	"nvidia1"
	Driver		"nvidia"
	Option		"RenderAccel"	"true"
	Option		"TripleBuffer"	"True"
	Option		"NoLogo"		"1"
	BusId		"PCI:0:10:0"
EndSection


Section "Screen"
	Identifier		"screen0"
	Device			"nvidia0"
	Monitor			"l1730s"
	DefaultDepth	24
	Option			"DPI"	"100x100"

	Subsection "Display"
		Depth	24
		Modes	"1280x1024"	"1024x768"
	EndSubsection
	
EndSection

Section "Screen"
 	Identifier		"screen1"
 	Device			"nvidia1"
 	Monitor			"cpdm151"
 	DefaultDepth	24
 	Option			"DPI"	"100x100"
 
 	Subsection "Display"
		Depth	24
		Modes	"1024x768"	"800x600"
 	EndSubsection
 	
EndSection

Section "ServerLayout"
	Identifier	"seat0"
	Screen		"screen0"	0				0
	InputDevice	"mouse0"	"CorePointer"
	InputDevice	"keyboard0"	"CoreKeyboard"
	Option          "AutoAddDevices"        "off"
EndSection

Section "ServerLayout"
 	Identifier	"seat1"
	Screen		"screen1"	0				0
	InputDevice	"mouse1"	"CorePointer"
	InputDevice	"keyboard1"	"CoreKeyboard"
	Option          "AutoAddDevices"        "off"
EndSection

Section "Extensions"
	Option	"Composite"	"Disable"
	Option	"RENDER"	"Enable"
EndSection

Section "Monitor"
	Identifier	"l1730s"
	HorizSync	30-93
	VertRefresh	60
	Option		"dpms"
EndSection

Section "Monitor"
	Identifier	"cpdm151"
	Option		"dpms"
	HorizSync	30-61
	VertRefresh	60
EndSection

/opt/kde/share/config/kdm/kdmrc

This is my kdmrc:

[General]
ConfigVersion=2.3
ConsoleTTYs=vc/1,vc/2,vc/3,vc/4,vc/5,vc/6
PidFile=/var/run/kdm.pid
ReserveServers=:2,:3
ServerVTs=-7
StaticServers=:0,:1

[Shutdown]
BootManager=Grub
HaltCmd=/sbin/halt
RebootCmd=/sbin/reboot

[X-*-Core]
AllowNullPasswd=false
AllowRootLogin=false
AllowShutdown=Root
Authorize=true
AutoReLogin=false
ClientLogFile=.xsession-errors-%s
Reset=/opt/kde/share/config/kdm/Xreset
Resources=/opt/kde/share/config/kdm/Xresources
Session=/opt/kde/share/config/kdm/Xsession
SessionsDirs=/etc/X11/sessions,/usr/share/xsessions,/opt/kde/share/apps/kdm/sessions
Setup=/opt/kde/share/config/kdm/Xsetup
Startup=/opt/kde/share/config/kdm/Xstartup

[X-*-Greeter]
AllowConsole=true
AntiAliasing=true
AuthComplain=true
BackgroundCfg=/opt/kde/share/config/kdm/backgroundrc
ColorScheme=
DefaultUser=
EchoMode=OneStar
FaceSource=PreferUser
FailFont=Tahoma,11,-1,5,75,0,0,0,0,0
FocusPasswd=false
ForgingSeed=1097313140
GUIStyle=
GreetFont=Tahoma,11,-1,5,75,0,0,0,0,0
GreetString=Arch Linux %r (%h)
GreeterPos=50,50
HiddenUsers=root
Language=en_US
LogoArea=None
LogoPixmap=
MaxShowUID=65000
MinShowUID=500
PreselectUser=None
SelectedUsers=
ShowUsers=NotHidden
SortUsers=true
StdFont=Tahoma,11,-1,5,50,0,0,0,0,0
UseBackground=false
UserCompletion=false
UserList=true

[X-:*-Core]
AllowNullPasswd=true
AllowRootLogin=true
AllowShutdown=All
NoPassEnable=false
NoPassUsers=

[X-:*-Greeter]
AllowClose=true
DefaultUser=glenn
FocusPasswd=true
LoginMode=DefaultLocal
PreselectUser=Previous

[X-:0-Core]
AutoLoginAgain=false
AutoLoginDelay=0
AutoLoginEnable=false
AutoLoginLocked=false
AutoLoginUser=glenn
ClientLogFile=.xsession-errors
ServerArgsLocal=-nolisten tcp -layout seat0 -sharevts -novtswitch 

[X-:1-Core]
ServerArgsLocal=-nolisten tcp -layout seat1 -sharevts -novtswitch 

[Xdmcp]
Enable=false
Willing=/opt/kde/share/config/kdm/Xwilling
Xaccess=/opt/kde/share/config/kdm/Xaccess

Related problems

PulseAudio

If two users want to use the sound card simultaneously, it is necessary to use a sound server, PulseAudio being most prevalent. Usually, the PulseAudio server runs only for active user and does not allow for multiple user instances. Solution to this problem is using the system-wide PulseAudio server. Although this approach is discouraged by its authors, it is probably most applicable setup.

Configuring for system-wide PulseAudio
  • Create user pulse and put him into group audio (PulseAudio drops root privileges and changes to user pulse. Group membership allows for device access.)
  • Create group pulse-access and put users, who will play sound locally into it (Group membership is used for access control for local access to PA daemon.)
  • In /etc/pulse/default.pa state explicitly the access rights
load-module module-native-protocol-unix auth-group=pulse-access auth-group-enable=1
Start PA as system-wide, under root:
pulseaudio --system

In /var/run/pulse should appear files for communication with daemon, namely pid and native.

User access

You can check communication with system daemon as non-root by e.g. pactl -s "unix:/var/run/pulse/native" list.

It is possible to enable automatic connection to local daemon in /etc/pulse/client.conf

auto-connect-localhost = yes

The users should be able to connect to PA server. All the cons for system-wide daemon become essentially pros, e.g. ability to control volume of other users streams in pavucontrol.

Troubleshooting

It is possible to enable the http interface to PA for debugging in /etc/pulse/default.pa load-module module-http-protocol-tcp and then connect to it at http://localhost:4714/

See also

  • The arckwiki page Multi-pointer X explains how to setup two separate pair of devices on the same session.