Set blank root password in linux

As like windows O.S. how to set blank password for a user ?


We have a command

# passwd -d (User name)

It will set blank Password for user but what about without password login?

ie There is no need of password prompt by linux

ya i am talking about MY fev. topic "PAM"

For that we have to change in "/etc/pam.d/login" file
.....................................................

auth optional system-auth

instead of :->

auth include system-auth
...........................................................

But on that condition users can login without password prompt in text mode only.