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1 .\" $NetBSD: login.1,v 1.29 2008/11/18 15:52:57 wiz Exp $
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30 .\" @(#)login.1 8.2 (Berkeley) 5/5/94
31 .\"
32 .Dd November 19, 2008
33 .Dt LOGIN 1
34 .Os
35 .Sh NAME
36 .Nm login
37 .Nd authenticate users and set up their session environment
38 .Sh SYNOPSIS
39 .Nm
40 .Op Fl Ffps
41 .Op Fl a Ar address
42 .Op Fl h Ar hostname
43 .Op Ar user
44 .Sh DESCRIPTION
45 The
46 .Nm
47 utility logs users (and pseudo-users) into the computer system.
48 .Pp
49 If no user is specified, or if a user is specified and authentication
50 of the user fails,
51 .Nm
52 prompts for a user name.
53 Authentication of users is done via passwords.
54 If the user can be authenticated via
55 .Tn S/Key ,
56 then the
57 .Tn S/Key
58 challenge is incorporated in the password prompt.
59 The user then has the option of entering their Kerberos or normal
60 password or the
61 .Tn S/Key
62 response.
63 Neither will be echoed.
64 .Pp
65 The options are as follows:
66 .Bl -tag -width Ds
67 .It Fl a
68 The
69 .Fl a
70 option specifies the address of the host from which the connection was received.
71 It is used by various daemons such as
72 .Xr telnetd 8 .
73 This option may only be used by the super-user.
74 .It Fl F
75 The
76 .Fl F
77 option acts like the
78 .Fl f
79 option, but also indicates to
80 .Nm
81 that it should attempt to rewrite an existing Kerberos 5 credentials cache
82 (specified by the KRB5CCNAME environment variable) after dropping
83 permissions to the user logging in.
84 This flag is not supported under
85 .Xr pam 8 .
86 .It Fl f
87 The
88 .Fl f
89 option is used when a user name is specified to indicate that proper
90 authentication has already been done and that no password need be
91 requested.
92 This option may only be used by the super-user or when an already
93 logged in user is logging in as themselves.
94 .It Fl h
95 The
96 .Fl h
97 option specifies the host from which the connection was received.
98 It is used by various daemons such as
99 .Xr telnetd 8 .
100 This option may only be used by the super-user.
101 .It Fl p
102 By default,
103 .Nm
104 discards any previous environment.
105 The
106 .Fl p
107 option disables this behavior.
108 .It Fl s
109 Require a secure authentication mechanism like
110 .Tn Kerberos
111 or
112 .Tn S/Key
113 to be used.
114 This flag is not supported under
115 .Xr pam 8 .
116 .El
117 .Pp
118 If a user other than the superuser attempts to login while the file
119 .Pa /etc/nologin
120 exists,
121 .Nm
122 displays its contents to the user and exits.
123 This is used by
124 .Xr shutdown 8
125 to prevent normal users from logging in when the system is about to go down.
126 .Pp
127 Immediately after logging a user in,
128 .Nm
129 displays the system copyright notice, the date and time the user last
130 logged in, the message of the day as well as other information.
131 If the file
132 .Dq Pa .hushlogin
133 exists in the user's home directory, all of these messages are suppressed.
134 This is to simplify logins for non-human users.
135 .Nm
136 then records an entry in the
137 .Xr wtmp 5
138 and
139 .Xr utmp 5
140 files, executes site-specific login commands via the
141 .Xr ttyaction 3
142 facility with an action of "login", and executes the user's command
143 interpreter.
144 .Pp
145 .Nm
146 enters information into the environment (see
147 .Xr environ 7 )
148 specifying the user's home directory (HOME), command interpreter (SHELL),
149 search path (PATH), terminal type (TERM) and user name (both LOGNAME and
150 USER).
151 .Pp
152 The user's login experience can be customized using
153 login class capabilities as configured in
154 .Pa /etc/login.conf
155 and documented in
156 .Xr login.conf 5 .
157 .Pp
158 The standard shells,
159 .Xr csh 1
160 and
161 .Xr sh 1 ,
162 do not fork before executing the
163 .Nm
164 utility.
165 .Sh FILES
166 .Bl -tag -width /var/mail/userXXX -compact
167 .It Pa /etc/login.conf
168 login class capability database
169 .It Pa /etc/motd
170 message-of-the-day
171 .It Pa /etc/nologin
172 disallows non-superuser logins
173 .It Pa /var/run/utmp
174 list of current logins
175 .It Pa /var/log/lastlog
176 last login account records
177 .It Pa /var/log/wtmp
178 login account records
179 .It Pa /var/mail/user
180 system mailboxes
181 .It Pa \&.hushlogin
182 makes login quieter
183 .El
184 .Sh SEE ALSO
185 .Xr chpass 1 ,
186 .Xr newgrp 1 ,
187 .Xr passwd 1 ,
188 .Xr rlogin 1 ,
189 .Xr skey 1 ,
190 .Xr getpass 3 ,
191 .Xr ttyaction 3 ,
192 .Xr login.conf 5 ,
193 .Xr passwd.conf 5 ,
194 .Xr utmp 5 ,
195 .Xr environ 7 ,
196 .Xr kerberos 8 ,
197 .Xr pam 8
198 .Sh HISTORY
199 A
200 .Nm
201 appeared in
202 .At v6 .
203 .Sh TRADEMARKS AND PATENTS
204 .Tn S/Key
205 is a trademark of
206 .Tn Bellcore .