LOGIN(1)

NAME
login - Begin session on the system

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

DESCRIPTION
login is used when signing onto a system. If no argument is given, login prompts for the username. The user is then prompted for a password, where approprate. 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 the account, the user may be prompted for a new password before proceeding. He will be forced to provide his old password and the new password before continuing. Please refer to passwd(1) for more information. The user and group ID will be set according to their values in the file. There is one exception if the user ID is zero: in this case, only the primary group ID of the account is set. This should prevent that the system adminitrator cannot login in case of network problems. The value for $HOME, $SHELL, $PATH, $LOGNAME, and $MAIL are set according to the appropriate fields in the password entry. $PATH defaults to /usr/local/bin:/bin:/usr/bin:. for normal users, and to /sbin:/bin:/usr/sbin:/usr/bin for root if not other configured. Ulimit, umask and nice values may also be set according to entries in the GECOS field. The environment variable $TERM will be preserved, if it exists (other environment variables are preserved if the -p option is given) or be initialize to the terminal type on your tty line, as specified in /etc/ttytype. Then the user's shell is started. If no shell is specified for the user in /etc/passwd, then /bin/sh is used. If there is no directory specified in /etc/passwd, then / is used (the home directory is checked for the .hushlogin file described above). This login implementation does ignore /etc/nologin and /etc/securetty. You need to configure this in the PAM configuration file for login in /etc/pam.d/login. login reads the /etc/login.defs(5) configuration file. Please refer to this documenation for options which could be set.

OPTIONS

-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.

SPECIAL ACCESS RESTRICTIONS
The file /etc/securetty lists the names of the ttys where root is allowed to log in. One name of a tty device without the /dev/ prefix must be specified on each line. If the file does not exist, root is allowed to log in on any tty. You need to add the /lib/security/pam_securetty.so module in /etc/pam.d/login for activating.

FILES
/var/run/utmp - list of current login sessins
/var/log/wtmp - list of previous login sessions
/var/log/lastlog - list of times of previous user logins
/etc/passwd - user account information
/etc/shadow - encrypted passwords and age information
/etc/motd - system message file
/etc/ttytype - list of terminal types (/etc/login.defs)

SEE ALSO
init(8), getty(8), mail(1), passwd(1), passwd(5), environ(7), shutdown(8), login.defs(5)

BUGS
A recursive login, as used to be possible in the good old days, no longer works; for most purposes su(1) is a satisfactory substitute. Indeed, for security reasons, login does a vhangup() system call to remove any possible listening processes on the tty. This is to avoid password sniffing. If one uses the command "login", then the surrounding shell gets killed by vhangup() because it's no longer the true owner of the tty. This can be avoided by using "exec login" in a top-level shell or xterm.

AUTHOR
Derived from BSD login 5.40 (5/9/89) by Michael Glad (glad@daimi.dk) for HP-UX
Ported to Linux 0.12: Peter Orbaek (poe@daimi.aau.dk)
Added new features: Thorsten Kukuk (kukuk@suse.de)