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user:jr018429:portfolio:hpc_0_eoce_0x2_preparation [2011/05/18 13:16] – [Procedure] jr018429user:jr018429:portfolio:hpc_0_eoce_0x2_preparation [2011/05/18 13:42] (current) – [Background] jr018429
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 +<WRAP centeralign round graybg box 96%>
 +<WRAP muchbigger>PREPARATION FOR MULTI-SEAT LINUX</WRAP>
 +<WRAP bigger>John T. Rine</WRAP>
 +</WRAP>
 +======Objective======
 +The object of this project is to set up and verify a multi-seat Linux configuration (one machine, many users).\\
 +======Materials/Reading/Prerequisites======
 +To do this project, you will need to have successfully completed:
  
 +  * Linux/*BSD Desktop Install
 +The materials required for this project are:\\
 +
 +^Description^Quantity^
 +|PC to be multiseat host|1|
 +|LCDs|multiple|
 +|keyboards|multiple|
 +|mice|multiple|
 +|Linux Desktop install CD|1|
 +|USB docking stations|multiple|
 +
 +======Background======
 +Lately, computing has concerned itself with the idea of a single computing resource allocated to a single user. However, with this approach, computing resources are usually wasted. There are exceptions to the one resource per user rule, a multi-tasking system for example, allows for multiple logins, there can still only be one physical user at the computer's main console, however. Multi-seat Linux allows many users to simultaneously share any single Linux PC.\\
 +According to the Web page from which the pictures and instructions were taken, a multi-seat configuration "is great for education, libraries, internet cafes, etc — anywhere where you have clusters of client machines with light 3D/video app demands, and want the simplicity and savings of just one server machine with many terminals connected."\\
 +======Requirements/Functionality/Analysis======
 +**Requirements**\\
 +The instructor's requirements for this project are:\\
 +Configure and document the process of setting up a Linux machine to serve as the host machine to support multiple physical users.\\
 +\\
 +**Functionality**\\
 +Regarding this project, once the setup and installation are complete, the instructor asks the student to explore the following functionality:\\
 +  * graphical login on each head
 +  * no interference between seats
 +  * administration
 +    * adding new software
 +    * configuring settings for all users
 +    * screen capture by administrator
 +    * screen broadcasting
 +  * individual USB flash drive access
 +  * per-seat audio
 +\\
 +**Analysis**\\
 +Regarding this project, the instructor asks the student to lookout for the following things:\\
 +  * How is overall CPU load with respect to the number of heads?
 +    * idle
 +    * active
 +  * Is there a sweet spot with regards to number of seats and host hardware?
 +\\
 +If possible, the instructor wants the student to try the configuration with both a 32-bit machine and a 64-bit machine (how well can the older 32-bit machine handle the load, how much more work can the newer 64-bit machine adequately handle?).\\
 +\\
 +======Procedure======
 +{{:user:jr018429:portfolio:2009-09-22-195134-fourseats.jpg|}}\\
 +The photos both above and below and the instructions below were taken from http://plugable.com/2009/11/16/setting-up-usb-multiseat-with-displaylink-on-linux-gdm-up-to-2-20/. Please see the reference section. \\
 +\\
 +**1. DisplayLink framebuffer driver**\\
 +udlfb is in the staging tree of Linux kernels 2.6.32 and later. We'll install the latest version here. First, make sure you have git installed with "sudo apt-get install git-core", and create a directory which will host all the source code you download with git (e.g. ~/git/).
 +<code>
 +sudo apt-get install module-assistant
 +sudo module-assistant prepare
 +git clone http://git.plugable.com/webdav/udlfb/
 +cd udlfb
 +make
 +sudo make install
 +sudo depmod -a
 +</code>
 +Now, when you plug in a DisplayLink device, you should see a "green screen" as the driver successfully loads and sets the graphics mode to match your monitor.\\
 +\\
 +**2. DisplayLink X server**\\
 +This will get the X server installed, ready for use by later scripts.\\
 +<code>
 +sudo apt-get install pkg-config xorg-dev
 +cd ~git
 +git clone http://git.plugable.com/webdav/xf-video-udlfb/
 +cd xf-video-udlfb
 +./configure
 +make
 +sudo make install
 +</code>
 +\\
 +We now need to create or modify a few scripts and configuration files. You'll need to use sudo to edit files in these system directories. You can cut/paste the text below, or download the files with "git clone http://git.plugable.com/webdav/misc-udlfb/" and copy each to the right location, and fix up ownership and permissions on the files.\\
 +\\
 +**3. udev script**\\
 +Create a file called /lib/udev/rules.d/50-usbseat.rules owned by user root, with the following contents.\\
 +<code>
 +# set all DisplayLink devices to configuration 1
 +# see http://libdlo.freedesktop.org/wiki/DeviceQuirks for more info
 +ATTR{idVendor}=="17e9", ATTR{bConfigurationValue}=="2", RUN="/bin/echo 1 > /sys%p/bConfigurationValue"
 + 
 +# aliases for display, kbd, mouse attached to specific hubs
 + 
 +KERNEL=="fb*",SUBSYSTEMS=="usb",PROGRAM="/bin/cat /sys/%p/../../../devnum",SYMLINK+="usbseat/%c/display",RUN+="usbseat.sh %c"
 +KERNEL=="mouse*", SUBSYSTEMS=="usb", ATTRS{bInterfaceClass}=="03", ATTRS{bInterfaceProtocol}=="02", PROGRAM="/bin/cat /sys/%p/../../../../../devnum",SYMLINK+="usbseat/%c/mouse",RUN+="usbseat.sh %c"
 +KERNEL=="event*", SUBSYSTEM=="input", ATTRS{bInterfaceClass}=="03", ATTRS{bInterfaceProtocol}=="01",PROGRAM="/bin/cat /sys/%p/../../../../../devnum",SYMLINK+="usbseat/%c/keyboard",RUN+="usbseat.sh %c"
 +KERNEL=="control*", SUBSYSTEM=="sound", SUBSYSTEMS=="usb", PROGRAM="/bin/cat /sys/%p/../../../../../devnum", SYMLINK+="usbseat/%c/sound"
 + 
 +# Handle when keyboard and mouse are one more hub downstream. Relying on pnp order to have already set up mouse, keyboard on upstream hub if we're daisy-chaining
 +KERNEL=="event*", SUBSYSTEM=="input", ATTRS{bInterfaceClass}=="03", ATTRS{bInterfaceProtocol}=="01",PROGRAM="/bin/cat /sys/%p/../../../../../../devnum",SYMLINK+="usbseat/%c/keyboard",RUN+="usbseat.sh %c"
 +KERNEL=="mouse*", SUBSYSTEMS=="usb", ATTRS{bInterfaceClass}=="03", ATTRS{bInterfaceProtocol}=="02", PROGRAM="/bin/cat /sys/%p/../../../../../../devnum",SYMLINK+="usbseat/%c/mouse",RUN+="usbseat.sh %c"
 +</code>
 +\\
 +The udev subsystem will run this script automatically each time a USB device is attached.\\
 +\\
 +**4. usbseat.sh script**\\
 +Create a file /lib/udev/usbseat.sh owned by user root with the following contents. Make sure to "sudo chmod a+x" to make the file executable.\\
 +<code>
 +#!/bin/bash
 +# takes the "seat number" as parameter $1
 +# the seat number is the kernel device id of the hub the seat's devices are sitting off of
 +# called once for every usb device that MIGHT be part of a seat, when they arrive or remove 
 + 
 +if [[ !(-n `/bin/pidof gdm`) ]]; then
 +    exit 0
 +fi
 + 
 +seat_running=`/usr/bin/gdmdynamic -l | /bin/sed -n -e "/:$1,/p"`
 + 
 +# $ACTION environment variable is set by udev subsystem
 +case "$ACTION" in
 + 'remove')
 + if [[ -n "{$seat_running}" ]]; then
 + /usr/bin/gdmdynamic -v -d $1
 + fi
 + ;;
 + *)
 +                # A device which might be part of a seat has been added
 + 
 + # if we already have a running seat for this #, exit
 + if [[ -n "${seat_running}" ]]; then
 + exit 0
 + fi
 + 
 + if [[ -e /dev/usbseat/$1/keyboard && -e /dev/usbseat/$1/mouse && -e /dev/usbseat/$1/display ]]; then
 + 
 + # We have a newly complete seat. Start it.
 + TMPFILE=`/bin/mktemp` || exit 1
 + /bin/sed "s/%ID_SEAT%/$1/g" < /lib/udev/usbseat-xf86.conf.sed > $TMPFILE
 + /usr/bin/gdmdynamic -v -t 2 -s 1 -a "$1=/usr/X11R6/bin/X -br :$1 -audit 0 -nolisten tcp vt07 -config $TMPFILE"
 + /usr/bin/gdmdynamic -v -r $1
 + fi
 + ;;
 +esac
 + 
 +exit 0
 +</code>
 +\\
 +**5. X config file**\\
 +Create file /lib/udev/usbseat-xf86.conf.sed with contents\\
 +<code> 
 +Section "ServerFlags"
 + Option "AutoEnableDevices" "false"
 + Option "AutoAddDevices" "false"
 + Option  "DefaultLayout" "seat"
 + Option "DontZoom" "true"
 + Option "DontZap" "true"
 + Option "AllowMouseOpenFail" "yes"
 +EndSection
 + 
 +Section "Module"
 + Load "ddc"
 +EndSection
 + 
 +Section "Files"                                                                                                              
 +    ModulePath      "/usr/lib/xorg/modules"
 +    ModulePath      "/usr/local/lib/xorg/modules"
 +EndSection
 + 
 +Section "Device"
 + Identifier "dl"
 + driver    "displaylink"
 + Option "fbdev" "/dev/usbseat/%ID_SEAT%/display"
 +EndSection
 + 
 +Section "InputDevice"
 + Identifier "keyboard"
 + Driver "evdev"
 + Option "CoreKeyboard"
 + Option "Device" "/dev/usbseat/%ID_SEAT%/keyboard"
 + Option "XkbModel" "evdev"
 + Option "XkbLayout" "us"
 +EndSection
 + 
 +Section "InputDevice"
 + Identifier "mouse"
 + Driver "mouse"
 + Option "CorePointer"
 + Option "Protocol" "ImPS/2"
 + Option "Device" "/dev/usbseat/%ID_SEAT%/mouse"
 +        Option  "Buttons" "5"
 + Option "ZAxisMapping" "4 5"
 +EndSection
 + 
 +Section "Monitor"
 + Identifier "monitor"
 +EndSection
 + 
 +Section "Screen"
 + Identifier "screen"
 + Device "dl"
 + Monitor "monitor"
 +EndSection
 + 
 +Section "ServerLayout"
 + Identifier "seat"
 + Screen 0 "screen" 0 0 
 + InputDevice "keyboard" "CoreKeyboard"
 + InputDevice "mouse" "CorePointer"
 +EndSection
 +</code>
 +\\
 +**6. fbcon workaround**\\
 +[update: this step is no longer needed with the latest udlfb from git or in kernels 2.6.37+]\\
 +\\
 +fbcon is a standard Linux kernel module, which aggressively assumes it can open any framebuffer device and take it over for use as a text terminal. Unfortunately, that's not what we want if we're going to be using that framebuffer to run its own X server. So we need to add a file /etc/modprobe.d/fbcon.conf to disable fbcon and leave our framebuffers free for other uses.\\
 +<code>
 +blacklist font
 +blacklist tileblit
 +blacklist bitblit
 +blacklist fbcon
 +</code>
 +This file will not take effect until you run\\
 +<code>
 +sudo update-initramfs -u
 +</code>
 +\\
 +Now, when you reboot and run "lsmod" you should not see fbcon in the loaded modules. And in /sys/class/graphics you should see fb0, instead of fbcon.\\
 +\\
 +**7. xrandr workaround**\\
 +[update: this workaround is not needed when running xf86-video-fbdev or with recent displaylink X servers with this patch]\\
 +\\
 +The DisplayLink X server currently has limited RANDR support, but later versions of GDM assume better. So for the time being, a workaround is required to get GDM applications (including gdmlogin) to display properly within the actual screen area -- otherwise they tend to think the screen has a strange rotation, and display themselves completely off it.\\
 +\\
 +Add these lines into /etc/gdm/Init/Default, right after the definition of gdmwhich()\\
 +<code>
 +XRANDR=`gdmwhich xrandr`
 +if [ "x$XRANDR" != "x" ]; then
 +  $XRANDR -o 0
 +fi
 +</code>
 +\\
 +**8. /etc/rc.local script**\\
 +Add the following lines to your /etc/rc.local script to check for attached usb terminals that were attached (at boot), and udev found them before GDM was running.\\
 +<code>
 +oldIFS=$IFS
 +IFS=/
 +for seat in /dev/usbseat/*; do
 + set $seat
 + /lib/udev/usbseat.sh $4
 +done
 +IFS=$oldIFS
 +</code>
 +\\
 +**9. /etc/init.d/gdm patch**\\
 +In recent versions of X, the system largely assumes that you'll only run one X server, and it will own all devices. So to support multiseat with multiple X servers easily, we need to have two configurations: normal (using only your primary graphics), and multiseat (where your primary graphics isn't used). We do this by detecting whether you have a USB terminal attached and configured, and if so coming up with a different gdm configuration.\\
 +\\
 +Add these lines to your /etc/init.d/gdm script, just after the section to "Allow cdd to override the config" (around line 35).\\
 +<code>
 +# Allow usbseat to override the config
 +if [ -f /etc/gdm/gdm-usbseat.conf ]; then
 + for usbseat in /dev/usbseat/*; do
 + seatid=${usbseat##*/}
 + if [ -e "/dev/usbseat/$seatid/keyboard" -a -e "/dev/usbseat/$seatid/mouse" -a -e "/dev/usbseat/$seatid/display" ]; then
 + CONFIG_FILE="--config=/etc/gdm/gdm-usbseat.conf"
 + fi
 + done
 +fi
 +</code>
 +\\
 +**10. Create /etc/gdm/gdm-usbseat.conf**\\
 +This is the alternative gdm.conf that will be used when a USB terminal is present at boot:\\
 +<code>
 +[daemon]
 +DynamicXServers=true
 +FlexibleXServers=0
 +Greeter=/usr/lib/gdm/gdmgreeter
 + 
 +[security]
 + 
 +[xdmcp]
 + 
 +[gui]
 + 
 +[greeter]
 + 
 +[chooser]
 + 
 +[debug]
 + 
 +[servers]
 +0=inactive
 +</code>
 +\\
 +{{:user:jr018429:portfolio:2009-09-22-200342-edubuntu.jpg|{{:user:jr018429:portfolio:2009-09-22-200342-edubuntu.jpg|}}\\
 +Now, when you boot with USB terminal(s) attached, graphical logins will come up on all of those, while your primary display will remain a text console.\\
 +
 +======References======
 +  * http://lab46.corning-cc.edu/haas/spring2011/hpc0/projects/multiseat
 +  * http://plugable.com/2009/11/16/setting-up-usb-multiseat-with-displaylink-on-linux-gdm-up-to-2-20/
 +  * http://linuxgazette.net/124/smith.html
 +  * http://en.wikipedia.org/wiki/Multiseat_configuration
 +  * http://linuxagora.com/vbforum/showthread.php?p=3710
 +  * http://www2.userful.com/
 +    * http://www.userful.com/products/userful-multiseat-linux
 +  * http://www.oreillynet.com/onlamp/blog/2005/12/multiseat_x_under_linux.html
 +  * http://blog.chris.tylers.info/index.php?/archives/14-Multiseat-X-Under-X11R6.97.0.html
 +  * http://www.linuxtoday.com/it_management/2009010800335OSBZDP
 +  * http://www.x.org/wiki/Development/Documentation/Multiseat

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