Xorg multiseat

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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#)

Tango-edit-clear.pngThis article or section needs language, wiki syntax or style improvements.Tango-edit-clear.png

Reason: Written in first person, more like a blog post. (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


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.


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 nvidia driver for this, I haven'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.


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.
  • Create a backup of all relevant configuration files. What do you mean you'll skip this one?

About evdev

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

Attaching devices to a seat

Systemd's loginctl lets you assign devices to seats by creating udev rules.

Identify devices

Look at the default seat (seat0) status, here is an example:

# loginctl seat-status seat0
        Sessions: *11
                  ├ /sys/devices/pci0000:00/0000:00:02.0/0000:03:00.0/drm/card0
                  │ (drm:card0)
                  ├ /sys/devices/pci0000:00/0000:00:02.0/0000:03:00.0/graphics/fb0
                  │ (graphics:fb0) "radeondrmfb"
                  ├ /sys/devices/pci0000:00/0000:00:02.0/0000:03:00.1/sound/card1
                  │ (sound:card1) "Generic"
                  │ └ /sys/devices/pci0000:00/0000:00:02.0/0000:03:00.1/sound/card1/input15
                  │   (input:input15) "HD-Audio Generic HDMI/DP,pcm=3"
                  ├ /sys/devices/pci0000:00/0000:00:12.0/usb3
                  │ (usb:usb3)
                  │ ├ /sys/devices/pci0000:00/0000:00:12.0/usb3/3-1/3-1:1.2/0003:046D:C52B.0006/input/input5
                  │ │ (input:input5) "Logitech Unifying Device. Wireless PID:101b"
                  │ └ /sys/devices/pci0000:00/0000:00:12.0/usb3/3-1/3-1:1.2/0003:046D:C52B.0006/input/input6
                  │   (input:input6) "Logitech Unifying Device. Wireless PID:200a"
                  ├ /sys/devices/pci0000:00/0000:00:14.2/sound/card0
                  │ (sound:card0) "SB"
                  │ ├ /sys/devices/pci0000:00/0000:00:14.2/sound/card0/input7
                  │ │ (input:input7) "HDA ATI SB Line"
                  │ └ /sys/devices/pci0000:00/0000:00:14.2/sound/card0/input9
                  │   (input:input9) "HDA ATI SB Rear Mic"
                  ├ /sys/devices/pci0000:00/0000:00:04.0/0000:02:00.0/drm/card1
                  │ (drm:card1)
                  ├ /sys/devices/pci0000:00/0000:00:04.0/0000:02:00.0/graphics/fb1
                  │ (graphics:fb1) "radeondrmfb"
                  ├ /sys/devices/pci0000:00/0000:00:04.0/0000:02:00.1/sound/card2
                  │ (sound:card2) "HDMI"
                  │ └ /sys/devices/pci0000:00/0000:00:04.0/0000:02:00.1/sound/card2/input16
                  │   (input:input16) "HDA ATI HDMI HDMI/DP,pcm=3"
                  ├ /sys/devices/pci0000:00/0000:00:12.1/usb4/4-1/4-1:1.0/input/input2
                  │ (input:input2) "CHESEN PS2 to USB Converter"
                  ├ /sys/devices/pci0000:00/0000:00:12.1/usb4/4-1/4-1:1.1/input/input3
                  │ (input:input3) "CHESEN PS2 to USB Converter"
                  └ /sys/devices/pci0000:00/0000:00:12.1/usb4/4-2/4-2:1.0/input/input4
                    (input:input4) "Microsoft Microsoft 3-Button Mouse with IntelliEye(TM)"

If you are unsure, try comparing with lspcior lsusb to identify devices.

Assign devices

Seats are created based on graphics cards. Hence we will start by assigning a graphics card:

# loginctl attach seat-1 /sys/devices/pci0000:00/0000:00:04.0/0000:02:00.0/drm/card1
# loginctl attach seat-1 /sys/devices/pci0000:00/0000:00:04.0/0000:02:00.0/graphics/fb1

Then add input devices:

# loginctl attach seat-1 /sys/devices/pci0000:00/0000:00:12.1/usb4/4-1/4-1:1.0/input/input2
# loginctl attach seat-1 /sys/devices/pci0000:00/0000:00:12.1/usb4/4-1/4-1:1.1/input/input3
# loginctl attach seat-1 /sys/devices/pci0000:00/0000:00:12.1/usb4/4-2/4-2:1.0/input/input4

With multiple sound cards you can assign one per seat that will run out of the box with per user session pulseaudio:

# loginctl attach seat-1 /sys/devices/pci0000:00/0000:00:04.0/0000:02:00.1/sound/card2/input16
# loginctl attach seat-1 /sys/devices/pci0000:00/0000:00:04.0/0000:02:00.1/sound/card2

You should be able to see that the hardware has been partitioned into two seats:

# loginctl seat-status seat0
# loginctl seat-status seat-1

Setting up Xorg

Since you can attach devices to seats with loginctl there is no need to have an specific Xorg configuration. Anyway you can create parts of or the entire configuration set for two server layouts, each assigned with their own keyboard, mouse, video card and monitor.

xorg.conf.d tree example:
├── 00-keyboard.conf   #created by localectl
├── 31-monitor-seat0.conf
├── 32-monitor-seat1.conf
├── 40-serverflags.conf
├── 41-graphic-seat0.conf
├── 42-graphic-seat1.conf
├── 51-screen-seat0.conf
├── 52-screen-seat1.conf
├── 61-layout-seat0.conf
└── 62-layout-seat1.conf

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.

Configure your devices as read in Xorg#Input devices. The "Identifier" will let you assign to a ServerLayout and "Device" defines which physical device are you configuring.

Section "InputDevice"
        Identifier      "keyboard0"
        Option          "Device"                "/dev/input/event1"
        #Option          "Device"                "/dev/input/by-path/pci-0000:00:1a.0-usb-0:1.6:1.0-event-kbd"  # or by path
        Option "GrabDevice" "on" # prevent send event to other X-servers

Same for other input devices.


Configure your monitors as seen on Xorg#Monitor settings. Pay close attention to the identifier.

Section "Monitor"
    Identifier             "monitor0"


Section "ServerFlags"
        Option "AutoAddGPU" "off"

Graphics card

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.

Section "Device"
        Identifier      "graphic0"
        Driver          "nvidia"
        Option          "NoLogo"                "1"  # Remove nvidia branding at startup
        BusId           "PCI:1:0:0"
        MatchSeat       "seat-1"                     # Needed when only configuring part of Xorg for non-seat0.
        Option          "Monitor-DVI-1"         "monitor1"  #assigns monitor configuration to graphic output port


Pay close attention to the "monitor" option.

Section "Screen"
        Identifier              "screen0"
        Device                  "graphic0"
        Monitor                 "monitor0"
        DefaultDepth    24
        Subsection "Display"
                Depth   24
                Modes   "1280x1024"     "1024x768"


Create a section for every seat (pay attention to Identifier) you have with their respective keyboards, mice and screens.

Section "ServerLayout"
        Identifier      "seat-1"
        Screen          "screen1"       0                   0
        InputDevice     "mouse1"        "CorePointer"
        InputDevice     "keyboard1"     "CoreKeyboard"
        Option          "Seat"  "seat-1"
        Option          "SingleCard" "on"   # use this to simplfied isolatedevice option

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:
  • To help avoid tearing on the web and maintain site compatibility it is advisable to install Pipelight for playing media online.


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


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)

ServerArgsLocal=-nolisten tcp -layout seat0 -seat seat0

ServerArgsLocal=-nolisten tcp -layout seat-1 -seat seat-1 -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 "-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.


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 -seat seat0
:1 local /usr/bin/X :1 vt08 -nolisten tcp -novtswitch -layout seat-1 -seat seat-1
Note: If seat numbers are not correctly assigned to sessions (loginctl will show a session without seat) by XDM, then your attached devices could have strange behavoir like lack of permissions, sound card undetected by pulseaudio... LightDM should be fine.

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

LightDM has automatic multiseat detection, but if you need you can configure it on /etc/lightdm/lightdm.conf


greeter-hide-users=false # Bug: lightdm-gtk-greeter doesn't load user saved session when greeter-hide-users=true[1]

xserver-command=/usr/bin/X :0
xserver-command=/usr/bin/X :1
Note: Since version 1.16 Xorg server no longer handles VTs if it was started as a non-seat0. So there's no need to pass option -sharevts [2].

For Auto Login multiseat (without Display Manager)

edit a script /boot/twin.sh

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 $cmd3"
      #echo "cmd3=$cmd3"
      /bin/su ${usr[$i]} -l -c "$cmd1 :$i $cmd2 $cmd3" &
      #echo "new pid=${pid[$i]}"
  sleep 5  # check process exist per 5 second

Open /etc/inittab and setup as follows:

x2:5:once:/root/twin.sh > /root/twin.log 2>&1


One sound card for each seat

As soon as you attach the sound card to the seat, Pulseaudio will detect and use it.

Multiple users on single sound card: 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.


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/

Multiple users on single sound card: ALSA

Setup with PulseAudio removed, shared audio through an alsamixer equalizer and software mixing. The relevant hardware used is an ATI Radeon HD 5850 and an Intel Sandy Bridge (onboard) HD 3000. Configuration steps may vary.

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.

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;

Only the last user to login will have audio control and access but if you wish to share audio equally among different users, add each user to the audio group:


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

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.


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"

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

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

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


ServerArgsLocal=-nolisten tcp -sharevts -novtswitch -keeptty -layout Seat1 -isolateDevice PCI:1:0:0

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:

$ pgrep -af PCI
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

See also

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