/lib/live/config/1170-xfce4-panel is in live-config 5.20170112+deb9u1.
This file is owned by root:root, with mode 0o755.
The actual contents of the file can be viewed below.
| 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 | #!/bin/sh
## live-config(7) - System Configuration Components
## Copyright (C) 2006-2015 Daniel Baumann <mail@daniel-baumann.ch>
##
## This program comes with ABSOLUTELY NO WARRANTY; for details see COPYING.
## This is free software, and you are welcome to redistribute it
## under certain conditions; see COPYING for details.
#set -e
Cmdline ()
{
	# Reading kernel command line
	for _PARAMETER in ${LIVE_CONFIG_CMDLINE}
	do
		case "${_PARAMETER}" in
			live-config.username=*|username=*)
				LIVE_USERNAME="${_PARAMETER#*username=}"
				;;
		esac
	done
}
Init ()
{
	# Checking if package is installed or already configured
	if [ ! -e /var/lib/dpkg/info/xfce4-panel.list ] || \
	   [ -e /var/lib/live/config/xfce4-panel ]
	then
		exit 0
	fi
	echo -n " xfce4-panel"
}
Config ()
{
	if [ ! -e /home/"${LIVE_USERNAME}"/.config/xfce4/xfconf/xfce-perchannel-xml/xfce4-panel.xml ]
	then
		sudo -u "${LIVE_USERNAME}" mkdir -p /home/"${LIVE_USERNAME}"/.config/xfce4/xfconf/xfce-perchannel-xml
		sudo -u "${LIVE_USERNAME}" cp /etc/xdg/xfce4/panel/default.xml /home/"${LIVE_USERNAME}"/.config/xfce4/xfconf/xfce-perchannel-xml/xfce4-panel.xml
	fi
	# Creating state file
	touch /var/lib/live/config/xfce4-panel
}
Cmdline
Init
Config
 |