Porteus

according to cheatcodes.txt

login=user_name
... Lets you specify the name of user (could be also 'root')
which will be autologged into GUI session.
If username is not provided then booting stops on the lxdm/kdm login screen.

In Porteus-XFCE-v3.2.2-x86_64.iso, specify login= will still login into guest account, if specify login='', Porteus will display login screen and pre-filled username textbox with ''

How to boot Porteus into login screen with nothing inside username textbox?

LABEL copy2ram
MENU LABEL Copy To RAM
KERNEL vmlinuz
APPEND initrd=initrd.xz copy2ram login=
TEXT HELP
...
ENDTEXT

copy /etc/slim.conf to /mnt/sda1/porteus/rootcopy/etc/

changing auto_login values to no or default_user values to blank seems to solve my issue, thanks

default_user values will be pre-filled in username textbox, which is excellent if you put it root, enter and fill in password