login - sign on
login [ name ]
login -h hostname
login -f name
login is used when signing onto a system. If an argument is not given, login prompts for the username. If the user is not root, and if /etc/nologin exists, the contents of this file are printed to thescreen, and the login is terminated. This is typically used to prevent logins when the system is being taken down. If special access restrictions are specified for the user in /etc/usertty, these must be met, or the log in attempt will be denied.
-p Used by getty(8) to tell login not to destroy the environment
-f Used to skip a second login authentication. This specifically does not work for root, and does not appear to work well under Linux.
-h Used by other servers (i.e., telnetd(8)) to pass the name of the remote host to login so that it may be placed in utmp and wtmp. Only the superuser may use this option. Note that the -h option has impact on the PAM service name. The standard service name is "login", with the -h option the name is "remote". It’s necessary to create a proper PAM config files (e.g. /etc/pam.d/login and /etc/pam.d/remote ).