Multiple X Sessions on one Box

Zoltan Boszormenyi zboszor at
Sun May 16 07:47:31 UTC 2004

Tom 'Needs A Hat' Mitchell írta:
> Note that more than two can be started but do not get carried away.
> Linux starts logins on a list of virtual terminals.  Each can be
> accessed CTL+ALT+Fn where n is a number 1 through about 8.  By default
> the X server is started at vt7, and if you make the above change an X
> server will be started at vt7 and vt8.  CTL+ALT+F7 will get the first,
> and CTL+ALT+F8 will get the second.  See the lines in /etc/inittab
>     1:2345:respawn:/sbin/mingetty tty1
>     ...
>     6:2345:respawn:/sbin/mingetty tty6
> which I suspect set the stage that puts the first X server on vt7.
> Some things are well not shared ... sound is one.

Except if you play with /etc/security/console.perms and the
/dev/... permissions.

Look at , they separated consoles nicely.
I use it on my home machine with two Radeons (9200SE/AGP and 7000/PCI),
two PS2 keyboards and two USB mice. I use it on FC1 and the
2.6.6-rc3-mm1 kernel. I used dumbcon=1 boot option (new in changes) and I get these messages during boot:

Console: Colour VGA+ 80x25 vc:1-16
Console: mono dummy device 80x25 vc:17-17
serio: i8042 AUX port at 0x60,0x64 irq 12
keyboard.c: [AT Raw Set 2 keyboard] vc:1-16
input: AT Raw Set 2 keyboard on isa0060/serio1
serio: i8042 KBD port at 0x60,0x64 irq 1
keyboard.c: [AT Translated Set 2 keyboard] vc:17-17
input: AT Translated Set 2 keyboard on isa0060/serio0

So multiple keyboard inputs go into separated VCs.
The X servers must be started with "vt7" and "vt17"
options so they use their own keyboards.

> I do not know how all the display drivers in the universe work with
> multiple X servers.  I would not leave a stress test running on one
> and attempt to do remote virtualized brain surgery on a real person in
> the other.

I can't comment about virtual lobotomy. :-) Here are my observations
on the technical side:

The only real problem with the radeon driver in FC1's
XFree86-4.3.0 is that when I logout on :0 then the CRT on
:1 goes blank. The gdm login screen comes back on :0 and
I have to  and Ctrl-Alt-NumpadMinus to get back my picture
and resolution.

With the latest DRI changes in -mm, both cards can have accelerated
3D. E.g. we can use two tuxracers at once. Seriously! I had to use
a trick however, the radeon DRI driver in the kernel initializes
cards in (bus number;card number) increasing order:

[drm] Initialized radeon 1.10.0 20020828 on minor 0: ATI Technologies 
Inc Radeon RV100 QY [Radeon 7000/VE]
[drm] Initialized radeon 1.10.0 20020828 on minor 1: ATI Technologies 
Inc RV280 [Radeon 9200 SE]

I have to enumerate the X servers in the same order in gdm.conf
otherwise neither one finds its dri device.

BTW I have an MSI K8T Neo with Athlon64 3200+ and 512MB memory
so it's not really stressed by two tuxracers. :-)

I would like to see this functionality in the mainline kernel
and really supported by Fedora Core (say 3...) including the
possibility of setting it up with system-config-display.

Best regards,
Zoltán Böszörményi

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