How can I have a user without a password?

In addition to removing the password from /etc/shadow, you need
to take one of the following steps:

Edit /etc/default/login and comment out PASSREQ=YES or change it
to PASSREQ=NO. This allows all users to remove their password!

The second way is to give a particular user no password with the
following entry in /etc/shadow:



user::9092:9999:9999::::