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Old 01-06-2010, 09:59 AM
"Boyd Stephen Smith Jr."
 
Default Two computers in one: two users each with their own accounts, monitor, and keyboard?

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.
--
Boyd Stephen Smith Jr. ,= ,-_-. =.
bss@iguanasuicide.net ((_/)o o(\_))
ICQ: 514984 YM/AIM: DaTwinkDaddy `-'(. .)`-'
http://iguanasuicide.net/ \_/
 
Old 01-06-2010, 01:24 PM
Avi Greenbury
 
Default Two computers in one: two users each with their own accounts, monitor, and keyboard?

Dotan Cohen wrote:
> 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

Thin clients do come in very physically thin sizes - I've seen several
that are about the size of a domestic router. The only manufacturer who
supports Linux that I can think of at the minute is Wyse, but I know
there are several more.

Though this would be decidedly less fun than making X do what you
want


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http://aviswebsite.co.uk/asking-questions


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Old 01-06-2010, 01:35 PM
Stephen Powell
 
Default Two computers in one: two users each with their own accounts, monitor, and keyboard?

On 2010-01-06 at 03:58:48 -0500, 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? The goal is to
> save space, electricity, and maintenance in a cramped desk in which
> now two people must each have their own computer (home environment). I
> prefer to stick with Lenny but am willing to experiment with Squeeze
> or even a Debian derivative if need be. Thanks in advance.

I honestly don't know if what you want to do is possible, or if so
how. It wouldn't surprise me if Debian can support two monitors
on the same workstation. It would surprise me if Debian can support
two different keyboards on the same workstation. But I really don't
know. But here's something that I know is possible. If you have
a real ASCII terminal, such as a VT100, a serial port on your CPU
case, and a "crossover" serial cable (or a "straight" serial cable
and a null modem), it is possible to connect the ASCII terminal
to the serial port and use it to login to your system. Of course,
this won't provide you with a graphical user interface, only a
full-screen ASCII terminal.

I actually have a couple of ASCII terminals, and I've always
wanted to hook one up to one of my Debian boxes, but I've never
gotten around to it; so I won't be of much practical, step-by-step
help. If you decide to go that route, and you get it working,
please let me know what you did and how you did it.


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Old 01-06-2010, 02:20 PM
"Boyd Stephen Smith Jr."
 
Default Two computers in one: two users each with their own accounts, monitor, and keyboard?

On Wednesday 06 January 2010 09:06:06 green wrote:
> Boyd Stephen Smith Jr. wrote at 2010-01-06 04:59 -0600:
> > 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.
>
> Actually, it would NOT need to be separately updated at all.
>
> > TLDR: No; look into something like LTSP, but small-scale.
>
> I set up LTSP once for 2 workstations, with one running Fedora (before I
> discovered Debian) and the other network-booting from it. The setup was
> simple (I was new to Linux then) and the only significant issue I remember
> was that 3D applications did not work over the network and maybe there was
> some trouble with removable media.

Yes. I meant to mention that any sort of DRI and the 3D acceleration that
goes with it generally fails when using a local X server and remote X clients.
The composite extension also doesn't work well, IIRC -- but perhaps it will if
your local X server and the applications you are using are happy with using
colors/images that contain an alpha channel.

Technically, OpenGL was designed with network transparency in mind, but it
doesn't always work well when large textures and/or changing textures or
geometries are involved.
--
Boyd Stephen Smith Jr. ,= ,-_-. =.
bss@iguanasuicide.net ((_/)o o(\_))
ICQ: 514984 YM/AIM: DaTwinkDaddy `-'(. .)`-'
http://iguanasuicide.net/ \_/
 
Old 01-06-2010, 02:39 PM
John Hasler
 
Default Two computers in one: two users each with their own accounts, monitor, and keyboard?

<http://wiki.debian.org/Multi_Seat_Debian_HOWTO>
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Old 01-06-2010, 02:54 PM
Andrew Sackville-West
 
Default Two computers in one: two users each with their own accounts, monitor, and keyboard?

On Wed, Jan 06, 2010 at 10:58:48AM +0200, 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?

At least one debian user that I know of do this, Hugo VanWoerkom:
http://lists.debian.org/debian-user/2007/03/msg00511.html

or at least did it at some point.

Also, I thought Kent West was doing this as well, but I could be
wrong. Google is not yielding other results for me at the moment. The
point is it has been done, and probably still can be done. It just
requires a little fiddly stuff.

hth

A
 
Old 01-06-2010, 02:55 PM
Stan Hoeppner
 
Default Two computers in one: two users each with their own accounts, monitor, and keyboard?

Boyd Stephen Smith Jr. put forth on 1/6/2010 9:20 AM:

> Technically, OpenGL was designed with network transparency in mind, but it
> doesn't always work well when large textures and/or changing textures or
> geometries are involved.

Waaay back in the day this was true, when an SGI, SUN, HP, Intergraph, or IBM
workstation cost $20-$40K USD, and before 3D chips were common. Companies would
have four engineers with X terminals sharing one workstation.

In the mid-late 90's the model started to change with the introduction of the
Pentium Pro, the Glint chip, and Windows NT4. At that point companies could
afford to put a $10K USD workstation with better 3D graphics performance on each
engineer's desk for about the same capital outlay.

This trend was accelerated by the proliferation of ultra high performance,
inexpensive, volume 3D graphics chips (3Dlabs, nVidia) going into the consumer
space. Due to the average PC cost, OpenGL architecture shifted from a multiuser
to a singe user focus. I actually recall reading a Linux announcement some
years ago that mutiuser 3D OpenGL would no longer be supported, period. I think
this was back in '02 or '03. To make OpenGL really scream on single user 3D
chips, they had to eliminate over the network OpenGL completely, as keeping that
capability would have totally hosed the rendering pipeline performance for 3D chips.

--
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Old 01-06-2010, 03:01 PM
Stan Hoeppner
 
Default Two computers in one: two users each with their own accounts, monitor, and keyboard?

John Hasler put forth on 1/6/2010 9:39 AM:
> <http://wiki.debian.org/Multi_Seat_Debian_HOWTO>

What about sound? Is the 2nd user not assumed to visit youtube?

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Old 01-06-2010, 03:21 PM
John Hasler
 
Default Two computers in one: two users each with their own accounts, monitor, and keyboard?

Stan writes:
> What about sound?

Two sound cards. Sound is handled entirely seperately from video.
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Old 01-06-2010, 04:03 PM
Stan Hoeppner
 
Default Two computers in one: two users each with their own accounts, monitor, and keyboard?

John Hasler put forth on 1/6/2010 10:21 AM:
> Stan writes:
>> What about sound?
>
> Two sound cards. Sound is handled entirely seperately from video.

No kidding? (sarcasm)

The question is how do you configure the 2nd user session to use a secondary
sound device? That is what the original OP needs to know.

--
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