2.1. Known Limitations

XFree do not support DRI acceleration on multiple graphic cards, the only way to use accelrated XFree is to use Nvidia's closed source driver and GLlibrary or a single card using DRI and multiple cards useing Nvidia's closed source drivers. XFree extensions not dependand on DRI should work.

Most of the multiheaded graphic cards can be used only for a single user/display. In order to start independant X servers the heads have to be explicit addressable (which can not be done with most of the cards). It should be possible to use cards with explicit addressable heads for independent displays, but this is not yet tested.

In the following cases it might be possible to use a single multiheaded card for mupliple independant displays :

Using/configuring independent devices for the independent screens/users is pretty hard or not explored, exceptions are the input devices, graphic cards and sound thanks artsd. Some examples of such unexplored areas:

In case you succeed in configuring such devices for independent usage by multiple users, please share with us how you did it.

Note

This doesn't mean that the devices wont work, but that every user will have access to all devices.

Currently under Backstreet Ruby you can have a maximum of 8 Virtual Terminals (16 for Ruby-2.6). This means that without hotplug configured if you are using USB keyboards with fancy keys you are limited to maximum of 4 independent users ( for Ruby-2.6 - 8 users). So do use hotplug if you are going to setup a system for more then 4 users ( even systems with 2 attached USB keyboards benefit from using hotplug).

If you are using hotplug the maximal number of independent users is 8 for Backstreet Ruby and 16 for Ruby-2.6.

The problem is being reviewed by the developers and hopefully soon the limitation will be lifted to bigger numbers. (Theoreticaly it should be possible to lift it up to 20, 30 independent users.)

Caution

This also means : DO NOT start your system with dumbcon=8 or higher number, it will lead to upredictable results (actually the kernel will reboot your system !!!). For Ruby-2.6 the maximal allowable number is 15.