Known Issues

From Multiseat

This page contains known issues with mdm or the components used by mdm. If a fix or work around is known it will be displayed. Be sure to read this page before e-mailing anyone.

Mouse wheel does not work

There is a bug in the version of Xephyr present in Ubuntu 8.04 and 8.10, where an incorrect number of buttons are monitored (the mouse wheel is treated as an up and down button) and stops the mouse wheel from working. A small patch is available in the repository to fix the problem.

To patch Xephyr in Ubuntu follow these instructions:-

1. Install the required tools

sudo apt-get install build-essential fakeroot dpkg-dev

2. Create your working directory and download the source

mkdir xephyr
cd xephyr
apt-get source xserver-xephyr

3. Get the build dependencies

sudo apt-get build-dep xserver-xephyr

4. Download the Xephyr patch

wget -O 151_xephyrmousewheel.patch http://git.c3sl.ufpr.br/gitweb?p=multiseat/mdm.git;a=blob_plain;f=dependencies/fix-mouse-wheel.patch;hb=HEAD

5. Edit the patch

nano xephyrmousewheel.patch

6. Make sure it looks like below

diff -u xorg-server-1.5.2/hw/kdrive/src/kinput.c xorg-server-1.5.2/hw/kdrive/src/kinput.c
--- xorg-server-1.5.2/hw/kdrive/src/kinput.c    2008-10-14 11:36:39.000000000 -0200
+++ xorg-server-1.5.2/hw/kdrive/src/kinput.c        2008-10-14 11:36:08.000000000 -0200
@@ -1283,7 +1283,7 @@
        return NULL;
    pi->emulateMiddleButton = kdEmulateMiddleButton;
    pi->transformCoordinates = !kdRawPointerCoordinates;
-    pi->nButtons = 3;
+    pi->nButtons = 5;
    pi->inputClass = KD_MOUSE;

    if (!arg)

7. Copy the patch into the Debian patches folder

cp 151_xephyrmousewheel.patch xorg-server-1.5.2/debian/patches

8. Append the patch list

echo 151_xephyrmousewheel.patch >> xorg-server-1.5.2/debian/patches/series

9. Edit the Debian changelog and add a new version

nano xorg-server-1.5.2/debian/changelog

xorg-server (2:1.5.2-2ubuntu4) intrepid; urgency=low

 * Fixed mouse wheel in Xephyr sessions

-- Joe Blogs <Joe@Blogs.com>  Wed, 18 Feb 2009 17:53:42 -0700

10. Build the package

dpkg-buildpackage -rfakeroot -b

11. And finally install the package

dpkg -i xserver-xephyr_1.5.2-2ubuntu4_i386.deb

This bug has been fixed in the version of Xephyr in Ubuntu Jaunty, however the current release of mdm will not work out of the box with Jaunty without some tweaking.

Keyboard LED's are linked between keyboards

The 3 keyboard LED's (Caps Lock, Num Lock and Scroll Lock) all appear to be linked. Turning caps lock on in one seat will illuminate the LED on all the seats, but only the first seat will actually type in caps. This bug is confirmed to happen in Ubuntu Hardy and Intrepid.

There is no known fix for this bug, but it appears to be fixed in Ubuntu Jaunty.

mdm uses open source nv driver instead of Nvidia binary driver

The mdm discover-devices script does not support the detection and configuration of the closed source Nvidia driver. Whilst it is prefered to use the open source driver, there are cases where Nvidia cards may not function properly. There is a wiki page regarding using mdm with the Nvidia binary driver.