LOGIN(1)			 User Commands			      LOGIN(1)



NAME
       login - begin session on the system

SYNOPSIS
       login [-p] [username] [ENV=VAR...]

       login [-p] [-h host] [-f username]

       login [-p] -r host

DESCRIPTION
       login is used to establish a new session with the system. It is
       normally invoked automatically by responding to the login: prompt on
       the users terminal.  login may be special to the shell and may not be
       invoked as a sub-process. Typically, login is treated by the shell as
       exec login which causes the user to exit from the current shell.
       Attempting to execute login from any shell but the login shell will
       produce an error message.

       The user is then prompted for a password, where appropriate. Echoing is
       disabled to prevent revealing the password. Only a small number of
       password failures are permitted before login exits and the
       communications link is severed.

       If password aging has been enabled for your account, you may be
       prompted for a new password before proceeding. You will be forced to
       provide your old password and the new password before continuing.
       Please refer to passwd(1) for more information.

       After a successful login, you will be informed of any system messages
       and the presence of mail. You may turn off the printing of the system
       message file, /etc/motd, by creating a zero-length file .hushlogin in
       your login directory. The mail message will be one of "You have new
       mail.", "You have mail.", or "No Mail." according to the condition of
       your mailbox.

       Your user and group ID will be set according to their values in the
       /etc/passwd file. The value for $HOME, $SHELL, $PATH, $LOGNAME, and
       $MAIL are set according to the appropriate fields in the password
       entry. Ulimit, umask and nice values may also be set according to
       entries in the GECOS field.

       On some installations, the environmental variable $TERM will be
       initialized to the terminal type on your tty line, as specified in
       /etc/ttytype.

       An initialization script for your command interpreter may also be
       executed. Please see the appropriate manual section for more
       information on this function.

       A subsystem login is indicated by the presence of a "*" as the first
       character of the login shell. The given home directory will be used as
       the root of a new file system which the user is actually logged into.

       The login program is NOT responsible for removing users from the utmp
       file. It is the responsibility of getty(8) and init(8) to clean up
       apparent ownership of a terminal session. If you use login from the
       shell prompt without exec, the user you use will continue to appear to
       be logged in even after you log out of the "subsession".

OPTIONS
       -f
	  Do not perform authentication, user is preauthenticated.

       -h
	  Name of the remote host for this login.

       -p
	  Preserve environment.

       -r
	  Perform autologin protocol for rlogin.

       The -r, -h and -f options are only used when login is invoked by root.

CAVEATS
       This version of login has many compilation options, only some of which
       may be in use at any particular site.

       The location of files is subject to differences in system
       configuration.

       The login program is NOT responsible for removing users from the utmp
       file. It is the responsibility of getty(8) and init(8) to clean up
       apparent ownership of a terminal session. If you use login from the
       shell prompt without exec, the user you use will continue to appear to
       be logged in even after you log out of the "subsession".

       As any program, login appearance could be faked. If non-trusted users
       have a physical access to the machine, an attacker could use this to
       obtain the password of the next person sitting in front of the machine.
       Under Linux, the SAK mecanism can be used by users to initiate of a
       trusted path and prevent this kind of attack.

FILES
       /var/run/utmp
	  List of current login sessions.

       /var/log/wtmp
	  List of previous login sessions.

       /etc/passwd
	  User account information.

       /etc/shadow
	  Secure user account information.

       /etc/motd
	  System message of the day file.

       /etc/nologin
	  Prevent non-root users from logging in.

       /etc/ttytype
	  List of terminal types.

       $HOME/.hushlogin
	  Suppress printing of system messages.

SEE ALSO
       mail(1), passwd(1), sh(1), su(1), login.defs(5), nologin(5), passwd(5),
       securetty(5), getty(8).



User Commands			  02/25/2007			      LOGIN(1)