multiseat with multiple X servers (or “the right way”)

So last week I posted on lkml an old patch that we were carrying for a long time in the Linux community. It basically brings the multiple (old) video cards functionally again on Linux and X server (and this time doing on the right and beauty way). For the people that was following multiseat implementations, this is a HUGE step: we will finally be able to discard the old and ugly hack (a mix of Xorg, several Xephyr servers + evdev) and and go to a clean way, starting multiple X servers in parallel. Cool! Well, not that much, because it might take some time to be in your beloved distribution :)

It’s too early and I don’t know if it’s recommended to say this, but if you want to give a try basically you have to get all X components, this X server patches, my libpciaccess and Dave’s kernel patchset. Again: it’s a very unstable work!

If you’re concerned with the technical explanations then you can follow the nice memo that Dave wrote about this.

10 thoughts on “multiseat with multiple X servers (or “the right way”)

  1. @ avilella:
    lets say that this work is just minor part of the hybrid graphics implementation on Linux. Unfortunately we’re far from this yet.

    @ Potatoes:
    this work touches a very low-level part of multiseat. Nothing related with plug and play.

  2. Userful’s multi-seat approach is different from and better than X’s approach. And as a result it “just works” and supports all video cards supported by X, and can be configured quickly and easily. Userful virtualizes a single instance of X to support multiple users. Other multi-seat approaches start separate instances of X (one for each user). The separate instance approach has the following limitations:
    1. They don’t support using both heads on consumer dual head cards. The hardware cost savings alone of using dual-head single chip cards instead of single chip single head cards or very expensive dual chip dual head cards can easily exceed a hundred dollars per head, in addition to enabling you to fit more users on the limited number of PCI slots in your motherboard. 2. They are very finicky about the graphics cards and chipsets supported. 3. They are less resource efficient (each instance of X imposes a RAM and CPU overhead).
    Userful’s approach also offers easy configuration, and a bunch of other benefits.
    Userful has been deploying multi-station Linux since early 2002 and developed some GPL’d kernel patches to help make multi-station work. Eventually they switched approaches because of the difficulties listed above.
    Userful’s Desktop Multiplier package also includes some graphical install and configuration tools, cross distro testing and quality assurance, and builds RPM/DEB packages to make installation and removal on supported distros comparatively effortless.
    Userful also builds some other layers on top like easy graphical configuration.

    1. @ z12:
      hahaueha I’m attempted to delete your post because sounds like a commercial/advertising but I’d prefer to let it here. The reason that I’ll let here is because it’s hilarious and ridiculous, so it makes my blog more funny…. but seriously, 90% of the things you said that is crap. Grow up and work collaborative to understand where you’re stepping!

  3. Tiago, when you said “old” what exactly you mean ? I have 2 GeForce 6600gt working in a multi-seat configuration running 2 XServers at same time (using FC5 + X Window System Version 7.0.0 + nvidia 9755 – yes VERY old – proprietary driver version ). I´m trying (without success :-/) to upgrade my system to an updated distro since FC9, then FC10, and now FC11, but all tries lead to same result: as soon as the second X server starts, the first head/monitor turns off . Can you tellm me if VgaArbiter will help me ? Or it´s targeted for older cards (not PCIe ones ?) ? PS: The only way to get video signal in both heads at same time is to start both X servers with same user at same time. If I try to start the X, and, after it starts, I fired the second X, the first X´s monitor turns off. The same configuration (using older versions of X server/kernel ( and NVIDIA drivers works perfectly (I´m using it for 3 years – even with OpenGL) :-). TIA ! Cuqui

  4. I forgot to say: when I start both X ant same time with the same user, booth screens show the same (so, it´s not a solution). Regards !

  5. > and go to a clean way, starting multiple X servers
    > in parallel.
    Sounds cool.
    How did it pan out?
    Do we now have easy setup of multiseat X on all major distributions?

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