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
- 1 Requirements
- 2 Definitions
- 3 Tips and tricks
- 4 About evdev
- 5 Setting up Xorg
- 6 Testing
- 7 Setting up the loginmanager
- 8 Troubleshooting
- 9 Final configuration
- 10 Related problems
Keyboards and mice
Any standard PS/2 or USB keyboards will suffice. Same thing for mice.
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 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.
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.confalone and create a new file, called
/etc/X11to store your new multiseat configuration. After this configuration is working you can overwrite the
xorg.conffile with your new
- 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.
evdev is an Xorg driver which can make use of the kernel event devices, which you can find in
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.
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 "HandleSepcialKeys" "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
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
Create a section like this for every graphics card you have.
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.
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.
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.
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
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
Setting up the loginmanager
For KDM (KDE's Display Manager)
/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)
/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)
/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 Auto Login multiseat (without Display Manager)
edit a script /boot/twin.sh
/etc/inittab and setup as follows:
#id:3:initdefault: id:5:initdefault: ... x2:5:once:/root/twin.sh > /root/twin.log 2>&1
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
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
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
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=1Start PA as system-wide, under root:
/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/