***** How to get the Xserver up on a Dell Precision T5820 with Debian Stretch *****
*****                          Kees Lemmens, Nov 2018                         *****

On the Dell Precision T5820 the Xserver doesn't want to start up. It just crashes with a
segmentation fault.

I Tried this:

Nouveau from Stretch                          -> no success
Nvidia 390.87 and 410.78                      -> fails as well
Buster backports to install a new videodriver -> fails as well

backports was done using:

apt-get -t stretch-backports install -f -y --reinstall --allow-change-held-packages \
  xserver-xorg \
  xserver-xorg-core \
  xserver-xorg-video-intel \
  xserver-xorg-video-nouveau \
  libgl1-mesa-glx \
  libgl1-mesa-dri \
  libx11-6

However, when I booted the T5820 on a Ubuntu 18.04 live system the Xserver did work well! So,
I decided to use a virtual machine (KVM) to isolate the Xserver from the Ubuntu live system.

I created a directory Xserver_ubuntu and copied everything needed to run that Xserver to that
directory. This is the Ubuntu dynamic loader, the libc libraries, the Xserver itself in
usr/lib/xorg/ and of course the driver modules in /usr/lib/xorg/modules 

Then I made a wrapper script to start the Ubuntu Xserver from that directory on a Debian
system (using the nouveau driver from Ubuntu):

==============================================================================
#!/bin/bash

# This scripts makes it possible to use the Xserver from a Ubuntu
# 18.04 system - including its Ubuntu libraries and modules - on a Debian
# Stretch system with a completely different set of libraries.
#
# Kees Lemmens, Nov 2018

TOPDIR=/opt64/Xserver_ubuntu

$TOPDIR/lib/x86_64-linux-gnu/ld-2.27.so --library-path \
$TOPDIR/lib/x86_64-linux-gnu/:$TOPDIR/usr/lib/x86_64-linux-gnu:$TOPDIR/lib64 \
$TOPDIR/usr/lib/xorg/Xorg \
  -modulepath $TOPDIR/usr/lib/xorg/modules \
  -configdir $TOPDIR/etc/X11/ \
  -config $TOPDIR/etc/X11/xorg.conf $@
==============================================================================

And to my surprise it all works perfectly well!

Then I had to force KDM to use this new Xserver. Initially I tried from /etc/rc.local but
moved it later to /etc/kde4/kdm/kdmrc :

ServerCmd=/opt64/sbin/Xserver_ubuntu.sh
ServerArgsLocal=-br -nolisten tcp -query <hostname> 

One more thing: -query localhost didn't work for some reason, probably because the sockets
are in a different location on Ubuntu, but querying the real hostname (over tcp) works fine.

Kees Lemmens,
November 2018