Last updated 10-13-2021
Continuing from home page, this page discusses USB zeroclients. For network attached zeroclients see my https://raspiplayer.com/phisteck-ze7000/ Early multi-seat linux systems were configured in a system file named xorg.conf – this approach is now obsolete (derived from X windows which provided graphical desktop work stations for main frame computers). Linux now stores its dynamic hardware configuration information in a virtual file system built at each boot and updated as devices like USB flashdrives, network cable, and analog headphones are connected/disconnected.
The minimum hardware requirement for a USB zeroclient workstation attached to a named seat, is a USB to video display device with the DisplayLink dl-1×5 chip. To be useful for anything beyond digital signage, it also needs a USB keyboard/mouse which may be a USB wireless dongle. Normally a USB zeroclient contains an internal USB hub with USB video device, 2-4 USB ports (for keyboard/mouse, flashdrive or other DVD drive) and a USB analog audio device all built in . You establish a seat by a single line text system file giving the vendor and product id of this hub in the USB zero client. All such USB zero clients will be recognized and automatically named uniquely and will present a login screen on each zeroclient display.
A USB zeroclient has no cpu and its only memory is its display’s internal frame buffer. Upon logout, this frame buffer is overwritten with the login wallpaper and login form, eliminating any visual desktop data from the previous user session. The workstation can be in an attractive creative space, while its server is in a separate physically secure utility room or closet.
Plugable UD-160-A USB Docking Stations draw only 5.0-5.3 watts each with 1920 x 1080 resolution compared to providing a separate computer for each workstation. Mint Linux is already configured to use it as a USB zeroclient. When you connect the USB cable between it and the server, a new login screen will appear on the UD-`160-A connected display. No user configuration or extra software is required to use it. Unfortunately, Plugable has discontinued manufacture because it was competing with their newer USB 3.0 device marketed as a Docking Station for Windows. It uses a different USB video adapter that Linux does not have drivers for. Plugable still manufactures the USB 2.0 video adaptor as a standalone product as well as USB hubs and a USB audio adapter. It would be cheaper to purchase my one surplus UD-160-A if you live in Portland, OR or to search eBay for one.
Here they are connected to a 2012 vintage Dell Precision T1600 with Intel i3-2120 (@ 3.30 Ghz, 2 cores, each with hyperthreading) and 8 GB of DDR3. The left monitor user is watching the MJQ play “Bag’s Groove” full screen on Youtube while the middle user is watching Barbara Dennerlein playing Hammond B3 organ, “Jimmie’s Walk” full screen on Youtube. The third monitor on right is connected directly to the computer and is running task manager to report cpu and memory usage. Before the two users on the UD-160-A logged in, and the main computer was only running task manager, it was idling with cpu usage of 1% and memory usage of 11%. Once the two users on the UD-160-A logged in and were playing Youtube videos full screen, cpu usage ran 34-39% and memory usage 32% so additional UD-160-A based workstations could be supported.
All other USB zeroclients require a configuration file. I have two surplus HP T150 and one surplus HP T100. If you buy mine, I will supply the required configuration file I have written for them running on Mint Linux. HP only marketed these for Windows and Userful’s proprietary extensions to CentOS Linux. Other companies came to dominate this market with products using the same internal chips and HP discontinued manufacture of all its zeroclients.
Here you see two HP T150 directly connected to the USB 3.0 hub on the right which connects to the server with a single USB 3.0 cable. The HP T100 lacks USB ports for keyboard/mouse, so I have a silver Belkin USB hub above it where you can see a Logitech Unifying receiver for one of the Logitech keyboards. The Belkin USB 2.0 hub connects to the USB 3.0 hub so all three USB zero clients connect to the server with a single cable and require no power adapters themselves.
When all the hardware I bought new to research how multi-seat works, has sold, I will share the documentation I developed so others can connect any USB zero clients they already have or subsequently buy used from other sources. I can also provide documentation as a paid service before my surplus hardware has sold – please use my contact form for inquiries. Meanwhile I will be concentrating on solutions based on Raspberry Pi SBC and their piserver as most educational installations can not wait to buy discontinued products on eBay as home hobbyists may.