.\"	$NetBSD: login.1,v 1.12 1998/04/10 09:31:55 fair Exp $
.\"
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.\"    must display the following acknowledgement:
.\"	This product includes software developed by the University of
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.\"	@(#)login.1	8.2 (Berkeley) 5/5/94
.\"
.Dd May 5, 1994
.Dt LOGIN 1
.Os BSD 4
.Sh NAME
.Nm login
.Nd log into the computer
.Sh SYNOPSIS
.Nm
.Op Fl fps
.Op Fl h Ar hostname
.Op Ar user
.Sh DESCRIPTION
The
.Nm
utility logs users (and pseudo-users) into the computer system.
.Pp
If no user is specified, or if a user is specified and authentication
of the user fails,
.Nm
prompts for a user name.
Authentication of users is done via passwords.
If the user can be authenticated via S/Key, then the S/Key challenge is
incorporated in the password prompt.  The user then has the option of
entering their normal password or the S/Key response.  Neither will be
echoed. 
.Pp
The options are as follows:
.Bl -tag -width Ds
.It Fl f
The
.Fl f
option is used when a user name is specified to indicate that proper
authentication has already been done and that no password need be
requested.
This option may only be used by the super-user or when an already
logged in user is logging in as themselves.
.It Fl h
The
.Fl h
option specifies the host from which the connection was received.
It is used by various daemons such as
.Xr telnetd  8 .
This option may only be used by the super-user.
.It Fl p
By default,
.Nm
discards any previous environment.
The
.Fl p
option disables this behavior.
.It Fl s
Require a secure authentication mechanism like Kerberos or S/Key to be used.
.El
.Pp
If the file
.Pa /etc/nologin
exists,
.Nm
displays its contents to the user and exits.
This is used by
.Xr shutdown  8
to prevent users from logging in when the system is about to go down.
.Pp
Immediately after logging a user in,
.Nm
displays the system copyright notice, the date and time the user last
logged in, the message of the day as well as other information.
If the file
.Dq Pa .hushlogin
exists in the user's home directory, all of these messages are suppressed.
This is to simplify logins for non-human users, such as
.Xr uucp 1 .
.Nm
then records an entry in the
.Xr wtmp 5
and
.Xr utmp 5
files and executes the user's command interpreter.
.Pp
Login enters information into the environment (see
.Xr environ 7 )
specifying the user's home directory (HOME), command interpreter (SHELL),
search path (PATH), terminal type (TERM) and user name (both LOGNAME and
USER).
.Pp
The standard shells,
.Xr csh 1
and
.Xr sh 1 ,
do not fork before executing the
.Nm
utility.
.Sh FILES
.Bl -tag -width /var/mail/userXXX -compact
.It Pa /etc/motd
message-of-the-day
.It Pa /etc/nologin
disallows logins
.It Pa /var/run/utmp
current logins
.It Pa /var/log/lastlog
last login account records
.It Pa /var/log/wtmp
login account records
.It Pa /var/mail/user
system mailboxes
.It Pa \&.hushlogin
makes login quieter
.El
.Sh SEE ALSO
.Xr chpass 1 ,
.Xr passwd 1 ,
.Xr rlogin 1 ,
.Xr skey 1 ,
.Xr getpass 3 ,
.Xr ttyaction 3 ,
.Xr utmp 5 ,
.Xr environ 7
.Sh HISTORY
A
.Nm
appeared in
.At v6 .
.Sh TRADEMARKS AND PATENTS
S/Key is a Trademark of Bellcore.