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Re: Two computers in one: two users each with their own accounts, monitor, and keyboard?

2010/1/6 Boyd Stephen Smith Jr. <bss@iguanasuicide.net>:
> On Wednesday 06 January 2010 02:58:48 Dotan Cohen wrote:
>> I have a desktop computer with onboard VGA and option to add a
>> discrete video card. It has plenty of spare USB ports for mice and
>> keyboards.
>> Does Debian support using this computer for _two_ workstations, each
>> with their own user accounts, monitor, and keyboard?
> From what I understand about Linux in general, no.  At the very least, doing
> so your be overly complicated.
> The first problem to solve is getting two separate X sessions to run at the
> same time, but using separate hardware.  It should be possible, but I've never
> tried it.  You'd have to write two fairly complex xorg.conf files to make sure
> the inputs and outputs are explicit and that X completely ignores the other
> hardware -- neither session can (e.g.) try to "turn off" the unused
> inputs/outputs.  Then you'd want to start them on the same "virtual terminal",
> something which will only work if your xorg.conf files are correct AND Xorg
> and the kernel don't actively try and prevent this.
> If you can get that working, you should be able to run a login manager on each
> session.  Then two different (or the same) user could login to each session.
> I guess the login manager is actually responsible to starting the X session,
> but once you could get two sessions running at the same time on the same vt,
> it should be relatively easy to start two login managers -- one for set of
> hardware / xorg.conf.
> If you even got that far, you'd still have some interference issues.  Things
> like Ctrl+Alt+Fx or Alt+SysRq+x would still affect all of the hardware by
> switching to another virtual terminal.  Modern login managers probably even
> have some facility for using and switching to other virtual terminals, which
> would switch both sets of hardware.  I'd wager that all of these could be
> disabled, for either all keyboards or all but one, but I don't know how off
> the top of my head.
> I think it would be easier simply scale the second computer down to a "thin
> client".  It would need it's own CPU, RAM, and I/O but it should be able to
> mount most file-systems via ro-nfs with a few filesystems mounted with rw-nfs
> (or nbd/iscsi/eata) after netbooting.  It would run its own Xorg instance, but
> use XDMCP to (graphically) login to the primary computer, such that all the X
> programs would run on the primary computer, and all the user settings/data
> would be on the primary computer -- users wouldn't even need a login to the
> thin client.
> Without hard disks, and needing only enough CPU power to run X, the second
> system could be *very* small.  Since it could share (at least) /usr with the
> main system, it wouldn't need to be separately updated much.
> This post turned out a lot longer and a lot less informative than I had hoped.
> TLDR: No; look into something like LTSP, but small-scale.

Thanks, Boyd, that was actually ver informative. As there is no room
for a second tower, I will see about modding the existing tower for
two motherboards. There actually is room, only the CPU cooling tubes
might be problematic.

Oh, and I'm going to have to see if a single 500W power supply with
another pigtail soldered will power both! That should probably be the
weak point in the system!

Dotan Cohen


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