1LOGIN(1) User Commands LOGIN(1)
2
6 login - begin session on the system
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9 login [-p] [-h host] [-H] [-f username|username]
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12 login is used when signing onto a system. If no argument is given,
13 login prompts for the username.
14 The user is then prompted for a password, where appropriate. Echoing is
16 disabled to prevent revealing the password. Only a number of password
17 failures are permitted before login exits and the communications link
18 is severed. See LOGIN_RETRIES in CONFIG FILE ITEMS section.
19 If password aging has been enabled for the account, the user may be
21 prompted for a new password before proceeding. In such case old
22 password must be provided and the new password entered before
23 continuing. Please refer to passwd(1) for more information.
24 The user and group ID will be set according to their values in the
26 /etc/passwd file. There is one exception if the user ID is zero. In
27 this case, only the primary group ID of the account is set. This should
28 allow the system administrator to login even in case of network
29 problems. The environment variable values for $HOME, $USER, $SHELL,
30 $PATH, $LOGNAME, and $MAIL are set according to the appropriate fields
31 in the password entry. $PATH defaults to /usr/local/bin:/bin:/usr/bin
32 for normal users, and to
33 /usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin for root,
34 if not otherwise configured.
35 The environment variable $TERM will be preserved, if it exists, else it
37 will be initialized to the terminal type on your tty. Other environment
38 variables are preserved if the -p option is given.
39 Then the user’s shell is started. If no shell is specified for the user
41 in /etc/passwd, then /bin/sh is used. If there is no home directory
42 specified in /etc/passwd, then / is used, followed by .hushlogin check
43 as described below.
44 If the file .hushlogin exists, then a "quiet" login is performed. This
46 disables the checking of mail and the printing of the last login time
47 and message of the day. Otherwise, if /var/log/lastlog exists, the last
48 login time is printed, and the current login is recorded.
49
51 -p
52 Used by getty(8) to tell login to preserve the environment.
53 -f
55 Used to skip a login authentication. This option is usually used by
56 the getty(8) autologin feature.
57 -h
59 Used by other servers (such as telnetd(8) to pass the name of the
60 remote host to login so that it can be placed in utmp and wtmp.
61 Only the superuser is allowed use this option.
62 Note that the -h option has an impact on the PAM service name. The
64 standard service name is login, but with the -h option, the name is
65 remote. It is necessary to create proper PAM config files (for
66 example, /etc/pam.d/login and /etc/pam.d/remote).
67 -H
69 Used by other servers (for example, telnetd(8)) to tell login that
70 printing the hostname should be suppressed in the login: prompt.
71 See also LOGIN_PLAIN_PROMPT below.
72 --help
74 Display help text and exit.
75 -V, --version
77 Display version information and exit.
78
80 login reads the /etc/login.defs configuration file (see login.defs(5)).
81 Note that the configuration file could be distributed with another
82 package (usually shadow-utils). The following configuration items are
83 relevant for login:
84 MOTD_FILE (string)
86 Specifies a ":" delimited list of "message of the day" files and
87 directories to be displayed upon login. If the specified path is a
88 directory then displays all files with .motd file extension in
89 version-sort order from the directory.
90 The default value is /usr/share/misc/motd:/run/motd:/etc/motd. If
92 the MOTD_FILE item is empty or a quiet login is enabled, then the
93 message of the day is not displayed. Note that the same
94 functionality is also provided by the pam_motd(8) PAM module.
95 The directories in the MOTD_FILE are supported since version 2.36.
97 Note that login does not implement any filenames overriding
99 behavior like pam_motd (see also MOTD_FIRSTONLY), but all content
100 from all files is displayed. It is recommended to keep extra logic
101 in content generators and use /run/motd.d rather than rely on
102 overriding behavior hardcoded in system tools.
103 MOTD_FIRSTONLY (boolean)
105 Forces login to stop display content specified by MOTD_FILE after
106 the first accessible item in the list. Note that a directory is one
107 item in this case. This option allows login semantics to be
108 configured to be more compatible with pam_motd. The default value
109 is no.
110 LOGIN_PLAIN_PROMPT (boolean)
112 Tell login that printing the hostname should be suppressed in the
113 login: prompt. This is an alternative to the -H command line
114 option. The default value is no.
115 LOGIN_TIMEOUT (number)
117 Maximum time in seconds for login. The default value is 60.
118 LOGIN_RETRIES (number)
120 Maximum number of login retries in case of a bad password. The
121 default value is 3.
122 LOGIN_KEEP_USERNAME (boolean)
124 Tell login to only re-prompt for the password if authentication
125 failed, but the username is valid. The default value is no.
126 FAIL_DELAY (number)
128 Delay in seconds before being allowed another three tries after a
129 login failure. The default value is 5.
130 TTYPERM (string)
132 The terminal permissions. The default value is 0600 or 0620 if tty
133 group is used.
134 TTYGROUP (string)
136 The login tty will be owned by the TTYGROUP. The default value is
137 tty. If the TTYGROUP does not exist, then the ownership of the
138 terminal is set to the user’s primary group.
139 The TTYGROUP can be either the name of a group or a numeric group
141 identifier.
142 HUSHLOGIN_FILE (string)
144 If defined, this file can inhibit all the usual chatter during the
145 login sequence. If a full pathname (for example, /etc/hushlogins)
146 is specified, then hushed mode will be enabled if the user’s name
147 or shell are found in the file. If this global hush login file is
148 empty then the hushed mode will be enabled for all users.
149 If a full pathname is not specified, then hushed mode will be
151 enabled if the file exists in the user’s home directory.
152 The default is to check /etc/hushlogins and if it does not exist
154 then ~/.hushlogin.
155 If the HUSHLOGIN_FILE item is empty, then all the checks are
157 disabled.
158 DEFAULT_HOME (boolean)
160 Indicate if login is allowed if we cannot change directory to the
161 home directory. If set to yes, the user will login in the root (/)
162 directory if it is not possible to change directory to their home.
163 The default value is yes.
164 LASTLOG_UID_MAX (unsigned number)
166 Highest user ID number for which the lastlog entries should be
167 updated. As higher user IDs are usually tracked by remote user
168 identity and authentication services there is no need to create a
169 huge sparse lastlog file for them. No LASTLOG_UID_MAX option
170 present in the configuration means that there is no user ID limit
171 for writing lastlog entries. The default value is ULONG_MAX.
172 LOG_UNKFAIL_ENAB (boolean)
174 Enable display of unknown usernames when login failures are
175 recorded. The default value is no.
176 Note that logging unknown usernames may be a security issue if a
178 user enters their password instead of their login name.
179 ENV_PATH (string)
181 If set, it will be used to define the PATH environment variable
182 when a regular user logs in. The default value is
183 /usr/local/bin:/bin:/usr/bin.
184 ENV_ROOTPATH (string), ENV_SUPATH (string)
186 If set, it will be used to define the PATH environment variable
187 when the superuser logs in. ENV_ROOTPATH takes precedence. The
188 default value is
189 /usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin.
190
192 /var/run/utmp, /var/log/wtmp, /var/log/lastlog, /var/spool/mail/*,
193 /etc/motd, /etc/passwd, /etc/nologin, /etc/pam.d/login,
194 /etc/pam.d/remote, /etc/hushlogins, $HOME/.hushlogin
195
197 The undocumented BSD -r option is not supported. This may be required
198 by some rlogind(8) programs.
199 A recursive login, as used to be possible in the good old days, no
201 longer works; for most purposes su(1) is a satisfactory substitute.
202 Indeed, for security reasons, login does a vhangup(2) system call to
203 remove any possible listening processes on the tty. This is to avoid
204 password sniffing. If one uses the command login, then the surrounding
205 shell gets killed by vhangup(2) because it’s no longer the true owner
206 of the tty. This can be avoided by using exec login in a top-level
207 shell or xterm.
208
210 Derived from BSD login 5.40 (5/9/89) by Michael Glad <glad@daimi.dk>
211 for HP-UX. Ported to Linux 0.12: Peter Orbaek <poe@daimi.aau.dk>.
212 Rewritten to a PAM-only version by Karel Zak <kzak@redhat.com>
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215 mail(1), passwd(1), passwd(5), utmp(5), environ(7), getty(8), init(8),
216 lastlog(8), shutdown(8)
217
219 For bug reports, use the issue tracker at
220 https://github.com/karelzak/util-linux/issues.
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223 The login command is part of the util-linux package which can be
224 downloaded from Linux Kernel Archive
225 <https://www.kernel.org/pub/linux/utils/util-linux/>.
226util-linux 2.37.2 2021-06-02 LOGIN(1)