Imported from util-linux-2.2 tarball.

[thirdparty/util-linux.git] / login-utils / login.1

.\" Copyright 1993 Rickard E. Faith (faith@cs.unc.edu)
.\" May be distributed under the GNU General Public License
.TH LOGIN 1 "1 February 1993" "Linux 0.99" "Linux Programmer's Manual"
.SH NAME
login \- sign on
.SH SYNOPSIS
.BR "login [ " name " ]"
.br
.B "login \-p"
.br
.BR "login \-h " hostname
.br
.BR "login \-f " name
.SH DESCRIPTION
.B login
is used when signing onto a system.  It can also be used to switch from one
user to another at any time (most modern shells have support for this
feature built into them, however).

If an argument is not given,
.B login
prompts for the username.

If the user is
.I not
root, and if
.I /etc/nologin
exists, the contents of of this file are printed to the screen, and the
login is terminated.  This is typically used to prevent logins when the
system is being taken down.

If the user is root, then the login must be occuring on a tty listed in
.IR /etc/securetty .
Failures will be logged with the
.B syslog
facility.

After these conditions are checked, the password will be requested and
checks (if a password is required for this username).  Ten attempts are
allowed before
.B login
dies, but after the first three, the response starts to get very slow.
Login failures are reported via the
.B syslog
facility.  This facility is also used to report any successful root logins.

If the file
.I .hushlogin
exists, then a "quiet" login is performed (this disables the checking of
the checking of mail and the printing of the last login time and message of
the day).  Otherwise, if
.I /var/adm/lastlog
exists, the last login time is printed (and the current login is recorded).

Random administrative things, such as setting the UID and GID of the tty
are performed.  The TERM environment variable is preserved, if it exists
(other environment variables are preserved if the
.B \-p
option is used).  Then the HOME, PATH, SHELL, TERM, MAIL, and LOGNAME
environment variables are set.  PATH defaults to
.I /usr/local/bin:/bin:/usr/bin:.
for normal users, and to
.I /sbin:/bin:/usr/sbin:/usr/bin
for root.  Last, if this is not a "quiet" login, the message of the day is
printed and the file with the user's name in
.I /usr/spool/mail
will be checked, and a message printed if it has non-zero length.

The user's shell is then started.  If no shell is specified for the user in
.BR /etc/passwd ,
then
.B /bin/sh
is used.  If there is no directory specified in
.IR /etc/passwd ,
then
.I /
is used (the home directory is checked for the
.I .hushlogin
file described above).
.SH OPTIONS
.TP
.B \-p
Used by
.BR getty (8)
to tell
.B login
not to destroy the environment
.TP
.B \-f
Used to skip a second login authentication.  This specifically does
.B not
work for root, and does not appear to work well under Linux.
.TP
.B \-h
Used by other servers (i.e.,
.BR telnetd (8))
to pass the name of the remote host to
.B login
so that it may be placed in utmp and wtmp.  Only the superuser may use this
option.
.SH FILES
.nf
.I /etc/utmp
.I /etc/wtmp
.I /usr/spool/mail/*
.I /etc/motd
.I /etc/passwd
.I /etc/nologin
.I .hushlogin
.fi
.SH "SEE ALSO"
.BR init (8),
.BR getty (8),
.BR mail (1),
.BR passwd (1),
.BR passwd (5),
.BR environ (7),
.BR shutdown (8)
.SH BUGS
Linux, unlike other draconian operating systems, does not check quotas.

The undocumented BSD
.B \-r
option is not supported.  This may be required by some
.BR rlogind (8)
programs.
.SH AUTHOR
Derived from BSD login 5.40 (5/9/89) by Michael Glad (glad@daimi.dk) for HP-UX
.br
Ported to Linux 0.12: Peter Orbaek (poe@daimi.aau.dk)