How to configure an user (in debian) to login without password ? An user without password needs to login in physical terminals (ttys - not pty) either using su - user from another user, without being asked for password.(secure isn't a requirement in this environment)
Passwordless login (from physical console and from others users)
users;login;password
Ensuring that the file /etc/pam.d/commom-auth has only module args nullok instead of nullok_secure, allows users to login without password when the user has not password.