ubuntu root login unblocking

in ed/k/x/ubuntu there is no root password by default so you'll first need to set a root password with

$ sudo -i
# passwd

on xubuntu you can now login to the gui as root but on kubuntu you still can't since KDE is preventing root logins so you'll also need to edit

/etc/kde4/kdm/kdmrc

and comment out the line with a #

# AllowRootLogin=false

see also