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authorDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-27 13:14:44 +0000
committerDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-27 13:14:44 +0000
commit30ff6afe596eddafacf22b1a5b2d1a3d6254ea15 (patch)
tree9b788335f92174baf7ee18f03ca8330b8c19ce2b /login-utils/login.1
parentInitial commit. (diff)
downloadutil-linux-30ff6afe596eddafacf22b1a5b2d1a3d6254ea15.tar.xz
util-linux-30ff6afe596eddafacf22b1a5b2d1a3d6254ea15.zip
Adding upstream version 2.36.1.upstream/2.36.1upstream
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
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+.\" Copyright 1993 Rickard E. Faith (faith@cs.unc.edu)
+.\" May be distributed under the GNU General Public License
+.TH LOGIN "1" "June 2012" "util-linux" "User Commands"
+.SH NAME
+login \- begin session on the system
+.SH SYNOPSIS
+.B login
+[
+.B \-p
+] [
+.B \-h
+.I host
+] [
+.B \-H
+] [
+.B \-f
+.I username
+|
+.I username
+]
+.SH DESCRIPTION
+.B login
+is used when signing onto a system. If no argument is given,
+.B login
+prompts for the username.
+.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
+.B login
+exits and the communications link is severed.
+.PP
+If password aging has been enabled for the account, the user may be
+prompted for a new password before proceeding. He will be forced to
+provide his old password and the new password before continuing.
+Please refer to
+.BR passwd (1)
+for more information.
+.PP
+The user and group ID will be set according to their values in the
+.I /etc/passwd
+file. There is one exception if the user ID is zero: in this case,
+only the primary group ID of the account is set. This should allow
+the system administrator to login even in case of network problems.
+The value for
+.BR $HOME ,
+.BR $USER ,
+.BR $SHELL ,
+.BR $PATH ,
+.BR $LOGNAME ,
+and
+.B $MAIL
+are set according to the appropriate fields in the password entry.
+.B $PATH
+defaults to
+.I /usr\:/local\:/bin:\:/bin:\:/usr\:/bin
+for normal users, and to
+.I /usr\:/local\:/sbin:\:/usr\:/local\:/bin:\:/sbin:\:/bin:\:/usr\:/sbin:\:/usr\:/bin
+for root, if not otherwise configured.
+.P
+The environment variable
+.B $TERM
+will be preserved, if it exists (other environment variables are
+preserved if the
+.B \-p
+option is given), else it will be initialized to the terminal type on your tty.
+.PP
+Then the user's shell is started. If no shell is specified for the
+user in
+.IR /etc\:/passwd ,
+then
+.I /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 below).
+.PP
+If the file
+.I .hushlogin
+exists, then a "quiet" login is performed (this disables the checking
+of mail and the printing of the last login time and message of the
+day). Otherwise, if
+.I /var\:/log\:/lastlog
+exists, the last login time is printed (and the current login is
+recorded).
+.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 login authentication. This option is usually
+used by the
+.BR getty (8)
+autologin feature.
+.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.
+.IP
+Note that the
+.B \-h
+option has an impact on the
+.B PAM service
+.BR name .
+The standard service name is
+.IR login ,
+but with the
+.B \-h
+option, the name is
+.IR remote .
+It is necessary to create proper PAM config files (e.g.,
+.I /etc\:/pam.d\:/login
+and
+.IR /etc\:/pam.d\:/remote ).
+.TP
+.B \-H
+Used by other servers (i.e.,
+.BR telnetd (8))
+to tell
+.B login
+that printing the hostname should be suppressed in the login: prompt.
+See also
+.B LOGIN_PLAIN_PROMPT
+below if your server does not allow the
+.B login
+command line to be configured.
+.TP
+\fB\-\-help\fR
+Display help text and exit.
+.TP
+\fB\-V\fR, \fB\-\-version\fR
+Display version information and exit.
+.SH CONFIG FILE ITEMS
+.B login
+reads the
+.IR /etc\:/login.defs (5)
+configuration file. Note that the configuration file could be
+distributed with another package (e.g., shadow-utils). The following
+configuration items are relevant for
+.BR login :
+.PP
+.B MOTD_FILE
+(string)
+.RS 4
+Specifies a ":" delimited list of "message of the day" files and directories
+to be displayed upon login. If the specified path is a directory then displays
+all files with .motd file extension in version-sort order from the directory.
+.PP
+The default value is
+.IR "/usr/share/misc/motd:/run/motd:/etc/motd" .
+If the
+.B MOTD_FILE
+item is empty or a quiet login is enabled, then the message of the day
+is not displayed. Note that the same functionality is also provided
+by the
+.BR pam_motd (8)
+PAM module.
+.PP
+The directories in the
+.B MOTD_FILE
+are supported since version 2.36.
+.PP
+Note that
+.B login
+does not implement any filenames overriding behavior like pam_motd
+(see also
+.BR MOTD_FIRSTONLY ),
+but all content from all files is displayed. It is
+recommended to keep extra logic in content generators and use
+.I /run/motd.d
+rather
+than rely on overriding behavior hardcoded in system tools.
+.RE
+.PP
+.B MOTD_FIRSTONLY
+(boolean)
+.RS 4
+Forces
+.B login
+to stop display content specified by
+.B MOTD_FILE
+after the first accessible item in the list.
+Note that a directory is one item in this case.
+This option allows
+.B login
+semantics to be configured to be more compatible with pam_motd.
+.RE
+.PP
+.B LOGIN_PLAIN_PROMPT
+(boolean)
+.RS 4
+Tell
+.B login
+that printing the hostname should be suppressed in the login:
+prompt.
+This is an alternative to the \fB\-H\fR command line option. The default
+value is
+.IR no .
+.RE
+.PP
+.B LOGIN_TIMEOUT
+(number)
+.RS 4
+Maximum time in seconds for login. The default value is
+.IR 60 .
+.RE
+.PP
+.B LOGIN_RETRIES
+(number)
+.RS 4
+Maximum number of login retries in case of a bad password. The default
+value is
+.IR 3 .
+.RE
+.PP
+.B FAIL_DELAY
+(number)
+.RS 4
+Delay in seconds before being allowed another three tries after a
+login failure. The default value is
+.IR 5 .
+.RE
+.PP
+.B TTYPERM
+(string)
+.RS 4
+The terminal permissions. The default value is
+.I 0600
+or
+.I 0620
+if tty group is used.
+.RE
+.PP
+.B TTYGROUP
+(string)
+.RS 4
+The login tty will be owned by the
+.BR TTYGROUP .
+The default value is
+.IR tty .
+If the
+.B TTYGROUP
+does not exist, then the ownership of the terminal is set to the
+user\'s primary group.
+.PP
+The
+.B TTYGROUP
+can be either the name of a group or a numeric group identifier.
+.RE
+.PP
+.B HUSHLOGIN_FILE
+(string)
+.RS 4
+If defined, this file can inhibit all the usual chatter during the
+login sequence. If a full pathname (e.g.,
+.IR /etc\:/hushlogins )
+is specified, then hushed mode will be enabled if the user\'s name or
+shell are found in the file. If this global hush login file is empty
+then the hushed mode will be enabled for all users.
+.PP
+If a full pathname is not specified, then hushed mode will be enabled
+if the file exists in the user\'s home directory.
+.PP
+The default is to check
+.I /etc\:/hushlogins
+and if it does not exist then
+.I ~/.hushlogin
+.PP
+If the
+.B HUSHLOGIN_FILE
+item is empty, then all the checks are disabled.
+.RE
+.PP
+.B DEFAULT_HOME
+(boolean)
+.RS 4
+Indicate if login is allowed if we cannot change directory to the
+home directory. If set to
+.IR yes ,
+the user will login in the root (/) directory if it is not possible
+to change directory to her home. The default value is
+.IR yes .
+.RE
+.PP
+.B LASTLOG_UID_MAX
+(unsigned number)
+.RS 4
+Highest user ID number for which the
+.I lastlog
+entries should be
+updated. As higher user IDs are usually tracked by remote user
+identity and authentication services there is no need to create
+a huge sparse
+.I lastlog
+file for them. No LASTLOG_UID_MAX option
+present in the configuration means that there is no user ID limit
+for writing
+.I lastlog
+entries.
+.RE
+.PP
+.B LOG_UNKFAIL_ENAB
+(boolean)
+.RS 4
+Enable display of unknown usernames when login failures are recorded.
+The default value is
+.IR no .
+.PP
+Note that logging unknown usernames may be a security issue if a
+user enters her password instead of her login name.
+.RE
+.PP
+.B ENV_PATH
+(string)
+.RS 4
+If set, it will be used to define the
+.B PATH
+environment variable when
+a regular user logs in. The default value is
+.I /usr\:/local\:/bin:\:/bin:\:/usr\:/bin
+.RE
+.PP
+.B ENV_ROOTPATH
+(string)
+.br
+.B ENV_SUPATH
+(string)
+.RS 4
+If set, it will be used to define the PATH environment variable when
+the superuser logs in. ENV_ROOTPATH takes precedence. The default value is
+.I /usr\:/local\:/sbin:\:/usr\:/local\:/bin:\:/sbin:\:/bin:\:/usr\:/sbin:\:/usr\:/bin
+.RE
+.SH FILES
+.nf
+.I /var/run/utmp
+.I /var/log/wtmp
+.I /var/log/lastlog
+.I /var/spool/mail/*
+.I /etc/motd
+.I /etc/passwd
+.I /etc/nologin
+.I /etc/pam.d/login
+.I /etc/pam.d/remote
+.I /etc/hushlogins
+.I .hushlogin
+.fi
+.SH BUGS
+The undocumented BSD
+.B \-r
+option is not supported. This may be required by some
+.BR rlogind (8)
+programs.
+.PP
+A recursive login, as used to be possible in the good old days, no
+longer works; for most purposes
+.BR su (1)
+is a satisfactory substitute. Indeed, for security reasons,
+.B login
+does a
+.BR vhangup (2)
+system call to remove any possible listening
+processes on the tty. This is to avoid password sniffing. If one
+uses the command
+.BR login ,
+then the surrounding shell gets killed by
+.BR vhangup (2)
+because it's no
+longer the true owner of the tty. This can be avoided by using
+.B exec login
+in a top-level shell or xterm.
+.SH AUTHORS
+Derived from BSD login 5.40 (5/9/89) by
+.MT glad@\:daimi.\:dk
+Michael Glad
+.ME
+for HP-UX
+.br
+Ported to Linux 0.12:
+.MT poe@\:daimi.\:aau.\:dk
+Peter Orbaek
+.ME
+.br
+Rewritten to a PAM-only version by
+.MT kzak@\:redhat.\:com
+Karel Zak
+.ME
+.SH SEE ALSO
+.BR mail (1),
+.BR passwd (1),
+.BR passwd (5),
+.BR utmp (5),
+.BR environ (7),
+.BR getty (8),
+.BR init (8),
+.BR lastlog (8)
+.BR shutdown (8)
+.SH AVAILABILITY
+The login command is part of the util-linux package and is
+available from
+.UR https://\:www.kernel.org\:/pub\:/linux\:/utils\:/util-linux/
+Linux Kernel Archive
+.UE .