Public lab with fresh desktop on each boot/login

I wonder if anyone could kindly help me with my LTSP public lab. It's all
running fine, but I'd really like to implement the approach taken in this
post:
https://ubuntuforums.org/showthread.php?t=2177959
Whereby whenever anyone logs in they get a fresh clean version of the
desktop taken from a template.

It's all working to the extent that my 12 (fat-client) PCs now autologin,
per mac address, each to their own account. However I can't get the
/opt/ltsp/ltsp-session.sh script for overwriting the individual users
desktop, from the template one upon each boot, to work:


#!/bin/bash

if groups | grep &>/dev/null '\blab\b'; then
# For users in the 'lab' group, copy from 'template' user
shopt -s dotglob
find /home/$USER/* ! -path /home/$USER/.Xauthority -exec rm -rf {} \;
rsync --archive --exclude .Xauthority /home/template/* /home/$USER/
shopt -u dotglob
chmod -R go-wrx /home/$USER
fi

/usr/bin/xfce4-session

if [ $USER == template ]; then
# Make 'template' user copyable
shopt -s dotglob
chmod -R a+r /home/template/*
find /home/template/* -type d -exec chmod a+x {} \;
shopt -u dotglob
fi


The script is implemented by

[Default]
LDM_XSESSION = /opt/ltsp/ltsp-session.sh

in /var/lib/tftpboot/ltsp/fat_amd64/lts.conf

When I turn that option on the boot of the client gets so far then hangs.

I'm using ubuntu server 16.04 and have created a fat amd64 client image.
All the basics work fine.

Anyone else got an LTSP setup working with a clean/refreshed desktop upon
boot (copied from a template?) working?

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