Section 1: login
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LOGIN(1) LOGIN(1)
NAME
login - Begin session on the system
SYNOPSIS
login [-f] [-h] [-p] [-r] [username] [ENV=VAR ...]
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 user's terminal. login may be spe-
cial 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.
When invoked from the login: prompt, the user may enter
environmental variables after the username. These vari-
ables are entered in the form NAME=VALUE. Not all vari-
ables may be set in the fashion, notably PATH, HOME and
SHELL. Additionally, IFS may be inhibited if the user's
login shell is /bin/sh.
The user is then prompted for a password, where appropri-
ate. Echoing is disabled to prevent revealing the pass-
word. Only a small number of password failures are per-
mitted 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 sys-
tem 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 val-
ues in the /etc/passwd file. The value for $HOME, $SHELL,
$PATH, $LOGNAME, and $MAIL are set according to the appro-
priate 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 initialize to the terminal type on your tty line,
as specified in /etc/ttytype.
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LOGIN(1) LOGIN(1)
An initialization script for your command interpreter may
also be executed. Please see the appropriate manual sec-
tion for more information on this function.
A subsystem login is indicated by the presense of a "*" as
the first character of the login shell. The given home
directory will be used as the root of a new filesystem
which the user is actually logged into.
OPTIONS
-p Preserve environment.
-f Do not perform authentication, user is preauthenti-
cated.
-h Name of the remote host for this login.
-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.
FILES
/etc/utmp - list of current login sessions
/etc/wtmp - list of previous login sessions
/etc/passwd - user account information
/etc/shadow - encrypted passwords and age information
/etc/motd - system message file
/etc/nologin - prevent non-root users from logging in
/etc/ttytype - list of terminal types
$HOME/.profile - initialization script for default shell
$HOME/.hushlogin - suppress printing of system messages
SEE ALSO
getty(8), mail(1), passwd(1), sh(1), su(1), login.defs(5),
passwd(5), nologin(5)
AUTHOR
Julianne Frances Haugh (jfh@bga.com)
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