Video Card Zero Client Stations

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Copyright © 2016 Userful Corporation. All rights reserved.
(Updated 2016.04.29)


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Userful Multiplatform™ is extends Linux to support several fully independent and concurrent workstations using a single computer box. This is accomplished by adding video devices (either video cards, USB zero client devices or network zero client devices), keyboards and mice to a single PC system and installing Userful's software.

This document provides guidelines and instructions for configuring host PC with video card zero client stations.

How Many Video Card Zero Client Stations Can Be Supported?

Even with single-user computer systems (i.e./ a stand-alone desktop computer or personal laptop), user experience depends on several factors:

  1. The speed and power of the CPU
  2. The available system memory (RAM)
  3. The demands made upon the system by the operating system and applications
  4. The speed and capacity of network connections and hardware

With multi-station computing, these factors influence the maximum user capacity of a given system configuration.

Some limitations are imposed by the hardware used to multiply the system:

  • With multiple video cards, deployments are typically limited to 8 additional stations + 1 onboard station (8 + 1) because of a limit on the number of PCI expansion slots available on standard (i.e. not custom or very high-end) motherboards.

Minimum PC Specifications

The following are the minimum system requirements that can be expected to give a satisfactory user experience under most normal use cases, with Userful and USB zero client devices.

For up to 6 stations:

  • Dual Core Processor
  • 8 GB RAM
  • 1 high-speed USB controller interface

For up to 10 stations

  • Quad Core Processor
  • 16 GB RAM
  • 2 high-speed USB controller interfaces

Choosing Video Cards

Userful requires that only one video card driver be in use in the system. Therefore, some care must be taken choosing host system motherboards (and integrated graphics processing units, or GPUs) and extra video cards for stations.

Please contact Userful for advice regarding which video cards may be appropriate for your deployment.

Theoretically, any nVIDIA cards supported by CentOS can be used to create a multiseat system (up to a configuration of 4 dual-head cards for 8 additional stations) with Userful provided that:

  • All video cards used for multiseat are using the same nVIDIA driver version, AND
    • If the onboard/integrated GPU is nVIDIA, that it uses the same driver version as the extra nVIDIA cards; or,
    • If the integrated GPU is NOT nVIDIA (i.e., Intel or ATI), that the onboard video be disabled in the BIOS. Please check system BIOS documentation for information on how to disable onboard graphics.

Please Note: The open-source nVIDIA driver, nouveau, is incompatible with Userful Multiplatform, so the appropriate proprietary driver must be installed. To find the correct driver for the video cards, go to the NVIDIA download center.

Getting Started

Prior to installing Userful Multiplatform™, you will need to add enough video cards to provide a video head for each station.

In addition to adding video cards and monitors, it is important to have enough available USB ports for connecting USB input devices and peripherals. Userful recommends using a dedicated USB hub with audio output/input capability for each station.

Setting up Stations

  • Position one monitor and USB hub (with attached keyboard and mouse) for each workstation.
    • (Note: the system PS/2 keyboard and mouse connections can be used to connect one station, ideally the "onboard" station)
  • Connect all cables to the back of the computer, including Ethernet, monitors, USB keyboards and mice, printers, etc.
  • Power on all monitors and then turn on the computer.

Input Devices

Each station in a multiseat configuration must have dedicated input devices (keyboard and mouse, or equivalent).

Manual Device Assignment

Only with onboard station having multiple video cards and input devices(e.g. 2 keyboards/ mice); input devices are assigned manually.

When first starting up a station, Userful's "Press F-key" utility is launched; this allows the user to link keyboards and mice to a specific monitor with a single key press and/or mouse click.

For each workstation that requires input device assignment, the display will prompt you to press a function key (F-1 through F-10) on the keyboard in front of the monitor in order to link the correct keyboard to the specific monitor.

Both a keyboard and a mouse are required in order to create a station. If you have the mouse plugged into the same USB hub (through a PS/2 or USB connection) as the keyboard, the mouse will be automatically assigned along with the keyboard when you press the correct function key.

If the mouse is plugged into a separate USB port or PS/2 connection, you will be prompted to press a button on the mouse in order to link it with the correct monitor and keyboard combination.

Resetting Assignment

You may reassign keyboards and mice at any point by simply pressing the Ctrl-Alt-Break key combination or re-connecting the input device by unplugging for at least 1.5 seconds and re-connecting it to the USB port while the system is running. The assignment screen will automatically appear on top of your current desktop. No work will be lost, simply press the correct F-key and return to your desktop.

Station Reset

Occasionally, it may be necessary to restart or reset a video card zero client station. The method used depends on the reason a reset is needed as well as the desired result.

NOTE: Resetting or restarting a station will log out the user.

  • If the display on an individual station is corrupted or frozen, you can reset the X window manager by hitting "CTRL-ALT-BACKSPACE".
  • If resetting the X window manager does not resolve the issue, OR if several stations are frozen or otherwise require a reset, a system reboot is necessary.


This section presents solutions to the most commonly encountered troubleshooting tasks. For a comprehensive list of troubleshooting tips, please visit

Keyboard does not work

Press the “Caps Lock” or “Num Lock” key. Do the corresponding LEDs illuminate or turn off?

  • If not, re-connect (disconnect and reconnect the keyboard). If this still does not resolve the problem there is possibly a problem with the keyboard or the USB port. Try a different keyboard, or try the problem keyboard at a different Station.
  • If the "Caps Lock" light illuminates in response to your key presses but the keyboard does not work:
    • Restart the station (Ctrl+Alt+Del)
    • Unlink and re-assign the keyboard (Ctrl+Alt+Break) then press the correct F-key to re-link (this is in case this keyboard has been mis-assigned)
    • Unlink and re-assign all keyboards connected to the machine (in case another keyboard has been mis-assigned)
    • Use Remote Monitoring and Control from another station or computer and perform a Hard Reset.
    • Reboot the computer (or schedule a reboot from Admin Mode using another station)

Single station frozen

If the display is frozen in an abnormal state or part way through an operation, press Ctrl+Alt+Del to restart that station. However if the station appears to be in a normal state (e.g., either the welcome screen, desktop or web browser or screensaver appears to be displaying normally) but the keyboard/mouse does not respond, it is most likely that the keyboard has disconnected. See “Keyboard does not work”, above.

If the above methods do not reset the station, press Ctrl+Alt+Backspace to forcefully stop and restart the station.

All stations frozen

Shut down the system by pressing and holding the power button for four seconds. Press and release the power button to restart the system.

Mouse does not work

Is the laser (red light on the bottom of the optical mouse) illuminated? If not, try disconnecting and re-connecting the mouse. If this fails follow the instructions for troubleshooting keyboards.

The station is working (the cursor moves) but Ctrl+Alt+Del/A/R/F/T do not work

An active menu (created by a right-click or pull down) steals the key-press. Close the menu and try again.

OnBoard will not turn on

Turn off the switch on the computer (at the back of the computer; the I/O (power) switch has a circle on one side and a line on the other. Pressing the side with the circle turns the power OFF.), or unplug and reconnect the power cord. Then retry the power button to turn on the Userful Desktop again. If the computer still shows no sign of life but the wall plug is working the problem may be a faulty PC power supply. Contact Userful for support.

Power button does not turn off the computer

Press and hold the power button (typically on the front or top of the computer) for at least ten seconds. If this does not work, turn off the power switch on the computer (at the back of the computer; the I/O (power) switch has a circle on one side and a line on the other. Pressing the side with the circle turns the power OFF.) and unplug the power cord from the back of the computer. Wait 10 seconds, then reconnect the power.

One monitor receives no signal

Check that the monitor cable is firmly connected to the correct VGA port on the back of the computer and any extension cables. Also ensure that thumb screws have been tightened.

Frequent unexpected reboot or freezing

These may be symptoms of hardware failure. Please contact Customer Support.