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Re: [LUG] Multihead X (was debian code names)

 

On Sat, 17 Jul 2010 14:37:50 +0100
Rob Beard wrote:

>   On 17/07/2010 12:11, Grant Sewell wrote:
> 
> <snip>
> >>> What I would like to do something is investigate multi-seat X,
> >>> that is having two monitors, two keyboards and two mice (and
> >>> maybe two soundcards) attached to one machine and creating two
> >>> 'independent' desktops which can be used (kind of in a way like
> >>> LTSP but with only one machine and no server).
> >>>
> >>> I've been looking into it but I've had so much on my plate and a
> >>> lack of space and hardware that I haven't really done much about
> >>> it.  I did try and get it working a couple of years back but had
> >>> no joy.  However maybe if a few of us got together one day with
> >>> some hardware we could possibly get something up and running.
> >>> Something like this could possibly be a great way of using
> >>> resources, such as when a reasonable spec (say Athlon XP, Athlon
> >>> 64, Pentium 4) PC is donated to somewhere we could turn the one
> >>> machine into two machines.
> >> It ought to be possible.
> > It is.  Last time I looked into it it worked but wasn't especially
> > stable... ie if user B logged out, then user A's X session was also
> > killed while the login manager restarted.  Not clever.
> >
> I've read that on Ubuntu at least they're working on getting X to run
> as a user rather than root, maybe that might resolve the issues.
> Saying that I don't know when it's going to be integrated into a
> distro.

That sounds interesting.  What's their reasoning behind this?

> >> You'll need a seconds keyboard and mouse (USB or old serial?) and a
> >> system with 2 graphics cards.
> > 2 x USB mice, 2 x USB keyboards, 2 x PCI(e) GFX cards.
> > USB because they can each be identified individually, likewise for
> > the GFX cards.  Once the devices can be uniquely identified, you
> > can set up X to have specific keyboard, mouse and GFX card as a
> > single X session, and the other keyboard/mouse/GFX card as a
> > different X session.
> >
> Last time I tried it I was using a single dual head graphics card, I 
> think that didn't help.  I guess a PCIe and PCI card in a box might
> do the job.

Haven't tried with a single card... I don't think it'd be particularly
easy as you'd have to try and specify head-1 as session 1 and head-2 as
session 2, and I'm not sure how you'd do that.

The 'guide' I was looking at (about 3 years ago, IIRC) indicated that
using separate PCI or PCIe cards would be better as they'll all have
different PCI-IDs which can be specified in the X conf file.  It also
suggested that mixing cards with different chips was easier but tended
to be slower than using cards with the same chips.

> >> You might make it work by using some sort of virtualisation and
> >> giving each host access to it's own graphics/keboard/mouse. If that
> >> works, you could probably have as many desktops as you've got slots
> >> to plug graphics cards into... (Assuming you can share the USB bus
> >> somehow).
> > Sounds like overkill. :D
> >> Can't say it's a project that enthuses me though :)
> > I tried it a few years back with my BTEC students.  It was fun, but
> > a bit over their heads I think.  Might try it again soon. :)
> 
> I'd be interested to know how you get on, as I say it's something
> I've wanted to try.  It is possible at the moment with a proprietary
> package which I believe is called Userful, it's available for
> personal use giving 2 machines although the paid for version can
> support up to 10 machines (presumably using a load of dual head
> graphics cards).

Cool!  I'll have a look at that.  Thanks.

Grant.

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