We first look for the"default_user" in slim.conf. Then we look for the"autologin-user" in lightdm. conf. Then we look for the user with UID 1000, and if all else fails, we use the user named"demo". If all of this fails then we issue a warning"No default user <name> found on the system". This should also show up on the screen and in the live-init.log file.

Fri Jun 19 11:41:38 EDT 2015 /live/etc/init.d/live-init
live-init : Localizing/configuring X-Windows
Automount disabled
Enabling fstab hotplugging
Localizing source repos using Antarctica/South_Pole
Assuming hwclock is set to local time
Scanning for hardware specific video modules ...
Found video module(s) nvidia
No default user demo found on the system.
No default user demo found on the system.

skidoo wrote:Yes, a pair of logged lines"no default user demo found" is logged during each boot.
Just know that I haven't touched/managed any user accounts during testing. Autologin was the default; I haven't changed that (nor any session config stuff).

sed -r -n 's/^\s*default_user\s+//p' /etc/slim.conf | cat -A

What's the output of this command?
Quote:
sed -r -n 's/^\s*default_user\s+//p' /etc/slim.conf | cat -A

demo$
demo$

# shutdown / reboot messages
shutdown_msg The system is shutting down...
reboot_msg The system is rebooting...

default_user demo
# Set to"yes" to enable this feature
#focus_password no

# current theme, use comma separated list to specify a set to
# randomly choose from
current_theme antiX

# Lock file
#lockfile /var/run/slim.lock

# Log file
#logfile /var/log/slim.log

# Automatically login the default user (without entering
# the password. Set to"yes" to enable this feature
auto_login yes

# default user, leave blank or remove this line
# to avoid pre-loading the username.
default_user demo
auto_login yes
lockfile /var/run/slim.lock
logfile /var/log/slim.log