Getting the Most Out of Your Userful System

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Copyright © 2016 Userful Corporation. All rights reserved.
(Updated 2016.03.03)


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Userful provides a powerful and versatile multiseat solution; like all complex software systems, there are some limitations, cautions and tips that system administrators should be familiar with.

This document is essential reading for any Userful system administrators.

Getting Started

Multimedia - Adobe Reader, Flash and DVDs


Adobe Reader and Flash Plugin are installed by default. However, other audio and video codecs required for multimedia playback are not installed by default on a Userful Multiplatform system due to licensing issues.
Userful has provided a convenient one-step method to install these packages with "Third-Party Add-ons". Open Control Center >System Operations > System Updates and click "Check for Updates". Several packages will be listed; click "OK" to install packages. System will be rebooted automatically for changes to take effect.

DVD Playback

  • For DVD playback, supported packages must be installed.
  • Users must be in the cdrom user group to access the optical drive through the Userful System Tray.

System Performance is Enhanced by Availability of DNS Services

While it is possible to run a Userful Multiplatform system without DNS services (e.g., without a connection to the internet), testing has shown that several system processes are slower in the absence of DNS.

Userful software engineers are investigating solutions to allow optimal performance in non-internet connected Userful Multiplatform deployments.

Intitial Mouse Assignment Issue

When Userful Multiplatform is first enabled (i.e. immediately after installation, or after a configuration reset), the mouse pointer is (often) invisible on the onboard station. The workaround is to hit “Ctrl-Alt-Backspace” once. This resets X and should return full mouse functionality.

Recovery From Sudden Power Loss

As with any computer system, it is strongly recommended to use an "uninterruptible power supply" (UPS) with Userful Multiplatform deployments. In the event of a power outage, the UPS can provide power to the system long enough to allow for a graceful shutdown.

In the event of a sudden power loss to a Userful Multiplatform system, it is extremely important to wait at least one minute before attempting to restart the system. Failure to do so may result in a frozen system requiring an additional power off/power on cycle to recover.


With Userful Multiplatform, zero client stations are hotpluggable, meaning that USB connections can plugged and unplugged on a running system without requiring a system reboot.

  • Note: In rare cases, repeated hot-plugging may cause problems and system instability. Repeated, rapid hotplugging is therefore not recommended.

Hotplugging Input Devices

A USB keyboard or mouse (Note: PS/2 input devices are not hotpluggable) must be unplugged from the zero client device (or USB hub) for more than 1.5 seconds to reset device assignment. With zero client devices, input devices will be automatically reassigned; otherwise.

Please note that hotplugging input devices with network zero client stations should be avoided on systems under heavy load, as it may cause system instability and freezing; if this should occur a reboot is necessary to fix the issue.

Hotplugging USB Zero Client Stations

If a USB zero client device is disconnected from the computer and reconnected within 10 seconds, the session on that station will be resumed after input devices are reassigned. If the disconnection is more than 10 seconds, the session will be killed, and the login screen will be shown once the device is reconnected.

Hotplugging Network Zero Client Stations

The term "hotplugging" is not technically accurate for these stations, as the term refers to USB connections, not network connections. However, it is possible to disconnect the network cable from a device, then reconnect the station successfully without requiring a full system reboot. Please note that all session data will be lost, and the station will come up on the log-in screen.

Running 3D Applications

Userful offers 3D software rendering and therefore can run applications that do not require hardware acceleration, such as Google Earth, K3DSurf and KSudoko. Please note that 3D graphics performance improves with more powerful CPUs. For optimal performance, avoid simultaneously running more 3D applications than the number of CPU cores in the host machine (i.e. a quad core CPU is best suited to run a maximum of 4 simultaneous 3D applications).

Multiseat Audio

With Userful Multiplatform, each user can enjoy independent audio -- including volume and source control. Most zero client devices have integrated audio jacks that are assigned to each station automatically; if using video cards for multiseat, Userful recommends using USB hubs with integrated audio to connect input devices for each station.

Per Station Settings

For the most part, listening to audio on a Userful system is no different from using sound on a Windows® or Mac® OS. Typically, all users will need to worry about is adjusting volume using the volume applet that is typically found in the panel at the upper-right hand corner of the screen (see image at right). This applet is a graphical front end to one of the higher-level Linux sound applications called PulseAudio.

To open the volume applet, simply left click on the "horn" icon in the panel.


Users can also click on "Sound Preferences" (see images at right) to control input/output sources and volume individually. With a Userful system, both input and output sound devices are usually identified as a "USB Sound Device".

System-wide Settings


Some lower-level sound processes are controlled by a kernel module/device driver called ALSA (Advanced Linux Sound Architecture); if having a problem with audio that cannot be resolved with the desktop panel Volume applet, it may be necessary to adjust ALSA settings.

The simplest way to manage ALSA is through a semi-graphical interface that can be started by typing sudo alsamixer in the command line. (Normal users may not be able to start alsamixer; sudo or admin privileges may be required, depending on system configuration.) To adjust input and output levels for a specific sound device (i.e./ the onboard sound card, a USB zero client device, or a USB audio hub):

  1. Open a terminal and type sudo alsamixer
  2. Press F6 key to open a list of available sound devices -- see image at right.
    • Note that it may be impossible to tell which particular USB zero client or audio device in the list corresponds with a given physical device. Thus changes to ALSAMixer settings should be made with caution.
  3. Use the up and down arrow keys to select a device, and press Enter to select the device.
  4. Use the left and right arrow keys to select ouput (speaker) or input (mic) levels, and then use the up and down arrows to adjust those levels.
  5. Press Esc to exit ALSAMixer.

Userful maintains documentation on How to Set Audio Input Levels with ALSAMixer, but for more detailed information please see the ALSAMixer documentation.

Audio Limitations

Userful Multiplatform can provide each user with an enjoyable audio experience, but there are some limitations that should be taken in consideration.

  1. If an application is playing audio when a USB zero client device station is unplugged and replugged ("hotplugged"), the audio stream will stop -- even though, if watching a movie, video may resume playing. To get audio playback to restart, the application must be closed and restarted.
  2. For a given user session, only one application can play sound at a time. This means that if already listening to .mp3's using Rhythymbox, a user cannot simultaneously listen to the audio stream from a movie playing in Totem.
  3. Default volume levels can be affected by sound cards, playback devices (including those on USB hubs or USB zero client devices), speaker/headphone quality, application settings and user settings. Audio levels from the onboard (host) PC may be different from those experienced by users on stations. Individual users are responsible for setting audio output and input volumes to their preferred levels. Once a user has adjusted these settings, the audio settings should be retained after logout.

Playing Video Files

Video files can be played simply by double-clicking on the file icon. In CentOS, the default media player is called "Movie Player", but other media players are available. The VLC player is required to play DVDs using the Userful System Tray.

Using the CD/DVD Drive

Optical drives (either in the system tower or USB-connected) are managed through the Userful System Tray. Please see the Multimedia and Storage guide for more details.

Using Flash Drives

NOTE: Avoid using USB keys in the host computer (system box) that have the same volume label as keys in use on the stations.

For instructions on how to change storage volume labels for external USB-connected drives such as USB keys, please refer to

Flash drives and other USB-connected storage devices are managed through the Userful System Tray. Please see the Multimedia and Storage guide for more details.

Using Digital Cameras

Today's digital cameras use either a mass storage protocol (like USB flash drives) or the newer Picture Transfer Protocol (PTP); many cameras can use both. Check your camera's documentation to learn which protocol it uses.

To access pictures using a mass storage protocol, simply treat the camera as a flash drive (refer to the Multimedia and Storage guide for more information).

To access pictures using the PTP protocol, it is easiest to use picture management software.

gThumb is an image viewer and photo management application for the GNOME desktop environment. It is installed by default on Userful systems; other applications are available through Add/Remove Programs

Using gThumb

  1. Connect the camera to the zero client device or USB hub at a user station.
  2. Turn on the camera.
  3. Open gThumb Image Viewer via Desktop Menu Icon > Graphics > gThumb Image Viewer

  1. Import photos via File > Import Photos
    Importing photo.png

    Using Webcams

    Webcams can be accessed through applications like | Cheese or Skype as described below.

    1. A single usb-connected webcam can be used on the onboard (host PC) station.
      • Any user logged into the onboard station will be able to access the webcam.
      • The webcam should be plugged directly into ports on the host PC.
    2. A single usb-webcam can be used plugged into any USB zero client station.
      • For best results, a webcam should be used on only one station attached to a host system.
        • With some hardware, it may be possible to use more than one webcam per host (i.e., to have a webcam on more than one USB-zero-client-device-connected station), but each webcam must be plugged into a different system USB bus. Please review the documentation for your system hardware for details about how many system USB buses exist and where the ports are located on the computer box.
      • Any user logged into the onboard station will be able to access the webcam.
      • The webcam should be plugged directly into ports on the USB zero client device.
      • The USB zero client device must have an independent power supply (power-over-USB may not be enough to power the webcam).
    3. Webcams CANNOT be connected to network zero client devices.
    4. The LAME Mp3 codecs must be installed for webcams to work.

    Please Note: Due to the sheer number and variety of webcams and webcam applications available, Userful cannot guarantee that any particular webcam will work "out of the box" with any particular application.

    Userful recommends testing your webcam with the "Cheese" application; if the webcam is supported by CentOS linux, it should "just work" with Cheese.

    A list of webcams that should work with Ubuntu linux can be found at the linux webcam driver developers site.