login - Begin session on the system
login [-p] [username] [ENV=VAR ...]
login [-p] [-h host] [-f username]
login [-p] -r host
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 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.
When invoked from the login: prompt, the user may enter environmental
variables after the username. These variables are entered in the form
NAME=VALUE. Not all variables 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 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 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 initialize
to the terminal type on your tty line, as specified in
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 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.
-p Preserve environment.
-f Do not perform authentication, user is preauthenticated.
-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.
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.
/var/run/utmp - list of current login sessions
/var/log/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
getty(8), mail(1), passwd(1), sh(1), su(1), login.defs(5), passwd(5),
Julianne Frances Haugh (email@example.com)
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