LTSP and x11vnc

A few years back, I wrote a system that ended up replacing about 200 terminals in 5 different offices with LTSP running on VMs. 2 and bit years latter, the last bunch of users were moved from terminals to LTSP. This time, they got FIT-PC2s as opposed to diskless PCs. Lucky them; less noise. But they are complaining that they find the mouse to unwieldy. And because they have locked down desktops, they don't have a config app to tweak the mouse acceleration and threshold. So I poked around and found that the settings are in :

/home/$USER/.config/xfce4/mcs_settings/mouse.xml

Now, that is hardly exciting.

What is exciting: I then wanted to set up x11vnc so that I could see what the users were experiencing. I've used x11vnc often on the same desktop, but my first attempt at doing it with LTSP failed. So I go on #LTSP to complainlook for a solution, which turned out to be -noshm.

They first complained that LTSP-4 (which I'm using) is far to archaic (which it is). They then got me on track for the next little bit of bash:

#!/bin/bash



USER=$1



error () { echo "$*" >&2; exit 5 }



if [[ ! $USER ]] ; then

    error "Usage: $0 user"

fi



userpid="$(pgrep -u $USER xfwm4)"

if [[ ! $userpid ]] ; then

    error "User $USER isn't logged in"

elif [[ $userpid =~ ' ' ]] ; then

    error "User $USER is probably logged on several times: $userpid"

fi



userenv="$(tr '\0' '\n' < /proc/$userpid/environ | egrep '^DISPLAY=|^XAUTHORITY=')"



eval "$userenv"

if [[ ! $XAUTHORITY ]] ; then

    XAUTHORITY=/home/$USER/.Xauthority

fi

export DISPLAY XAUTHORITY



echo DISPLAY=$DISPLAY

echo XAUTHORITY=$XAUTHORITY



exec x11vnc -noshm -nopw

All the error checking might be hiding the really interesting bit: I'm pulling DISPLAY and XAUTHORITY from the user's environment, via /proc. Something I'd never thought of doing before.