Zenity in Thin Clients using LTSP
 

Hi, guys!
I have a problem with zenity --warning.
I have a "Fat server" and Thin Clients(TCs) linked to it. Students does log in on TCs when I apply time for them.
I have one box(zenity --warning) with a message:"3 minutes to shutdown.\nPlease, save your documents." and I don't get it to appear at Thin Client.
This message must appear in students's displays when there is 3 minutes to finish their time. Actually, this is a piece of the script.
if [ $tempo2 -eq 3 ]
then
disp=$(who | grep -iw $aluno | awk '{print $2}')
OLDISPLAY=$DISPLAY
OLDXAUT=$XAUTHORITY
export DISPLAY=0.0
export XAUTHORITY=/cic/$aluno/.Xauthority
su $aluno -c 'zenity --warning --title="CIC" --text="Faltam 3 minutos para acabar seu tempo!\nSalve seus arquivos"'&
XAUTHORITY=$OLDXAUT
DISPLAY=$OLDISPLAY

Thanks!

by the way, it is not shutdown, I only want throw down the user whose time is ended. The TC keeps on waiting a new user... I've already developed it...
elif [ $tempo2 -eq 0 ]
then
pkill -9 -u $aluno
usermod -L $aluno
/usr/local/bin/cic-skel $aluno
fi

Who can help, I'll thank.