shadow/man/login.1

.\"$Id: login.1,v 1.17 2004/08/04 13:02:23 kloczek Exp $
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.TH LOGIN 1
.SH NAME
login \- begin session on the system
.SH SYNOPSIS
\fBlogin\fR [\fB-p\fR] [\fIusername\fR] [\fIENV=VAR\fR ...]
.br
\fBlogin\fR [\fB-p\fR] [\fB-h \fIhost\fR] [\fB-f \fIusername\fR]
.br
\fBlogin\fR [\fB-p\fR] \fB-r \fIhost\fR
.SH DESCRIPTION
\fBlogin\fR is used to establish a new session with the system. It is
normally invoked automatically by responding to the \fIlogin:\fR prompt on
the user\'s terminal. fBlogin\fR may be special to the shell and may not be
invoked as a sub-process. Typically, \fBlogin\fR is treated by the shell as
\fBexec login\fR which causes the user to exit from the current shell.
Attempting to execute \fBlogin\fR from any shell but the login shell will
produce an error message.
.PP

When invoked from the \fIlogin:\fR prompt, the user may enter environmental
variables after the username. These variables are entered in the form
\fBNAME=VALUE\fR. Not all variables may be set in the fashion, notably
\fBPATH\fR, \fBHOME\fR and \fBSHELL\fR. Additionally, \fBIFS\fR may be
inhibited if the user\'s login shell is \fB/bin/sh\fR.
.PP
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 \fBlogin\fR exits and the communications link
is severed.
.PP
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
\fBpasswd\fR(1) for more information.
.PP

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, \fI/etc/motd\fR, by creating a zero-length file \fI.hushlogin\fR in
your login directory. The mail message will be one of "\fBYou have new
mail.\fR", "\fBYou have mail.\fR", or "\fBNo Mail.\fR" according to the
condition of your mailbox.

.PP
Your user and group ID will be set according to their values in
the \fI/etc/passwd\fR file.
The value for \fB$HOME\fR, \fB$SHELL\fR, \fB$PATH\fR, \fB$LOGNAME\fR,
and \fB$MAIL\fR are set according to the appropriate fields in the
password entry.
Ulimit, umask and nice values may also be set according to
entries in the GECOS field.
.PP
On some installations, the environmental variable \fB$TERM\fR will be
initialized to the terminal type on your tty line, as specified in
\fI/etc/ttytype\fR.
.PP
An initialization script for your command interpreter may also be
executed.
Please see the appropriate manual section for more information on
this function.
.PP
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.
.SH OPTIONS
.IP "\fB-f\fR"
Do not perform authentication, user is preauthenticated.
.IP "\fB-h\fR"
Name of the remote host for this login.
.IP "\fB-p\fR"
Preserve environment.
.IP "\fB-r\fR"
Perform autologin protocol for rlogin.
.PP
The \fB-r\fP, \fB-h\fP and \fB-f\fP options are only used when \fBlogin\fP is
invoked by root.
.SH CAVEATS
This version of \fBlogin\fR has many compilation options, only some of which
may be in use at any particular site.
.PP
The location of files is subject to differences in system configuration.
.SH FILES
\fI/var/run/utmp\fR \- list of current login sessions
.br
\fI/var/log/wtmp\fR \- list of previous login sessions
.br
\fI/etc/passwd\fR \- user account information
.br
\fI/etc/shadow\fR \- encrypted passwords and age information
.br
\fI/etc/motd\fR \- system message file
.br
\fI/etc/nologin\fR \- prevent non-root users from logging in
.br
\fI/etc/ttytype\fR \- list of terminal types
.br
\fI$HOME/.hushlogin\fR \- suppress printing of system messages
.SH SEE ALSO
.BR mail (1),
.BR passwd (1),
.BR sh (1),
.BR su (1),
.BR login.defs (5),
.BR nologin (5),
.BR passwd (5),
.BR getty (8)
.SH AUTHOR
Julianne Frances Haugh <jockgrrl@ix.netcom.com>