[plug] No passwd for user

[Craig Ringer]

> That doesn't work does it? /etc/shadow stores te crypt (or MD5) 
> version of the password. And a blank entry wont be the crypt version 
> of ''. 

My bad. You need to leave the password entry in /etc/passwd blank even 
if you're using shadow passwords, and PAM handles that as a special case 
as far as I can tell - somewhat like "x" for "is in /etc/shadow". Maybe 
you have to blank the /etc/shadow entry too - anyway I delete both for 
the sake of neatness and it works perfectly on all my systems.