login

LOGIN(1)                          User Commands                         LOGIN(1)



NAME
       login - begin session on the system

SYNOPSIS
       login [-p] [-h host] [-H] [-f username|username]

DESCRIPTION
       login is used when signing onto a system. If no argument is given, login
       prompts for the username.

       The user is then prompted for a password, where appropriate. Echoing is
       disabled to prevent revealing the password. Only a number of password
       failures are permitted before login exits and the communications link is
       severed. See LOGIN_RETRIES in CONFIG FILE ITEMS section.

       If password aging has been enabled for the account, the user may be
       prompted for a new password before proceeding. In such case old password
       must be provided and the new password entered before continuing. Please
       refer to passwd(1) for more information.

       The user and group ID will be set according to their values in the
       /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
       environment variable values for $HOME, $USER, $SHELL, $PATH, $LOGNAME,
       and $MAIL are set according to the appropriate fields in the password
       entry. $PATH defaults to /usr/local/bin:/bin:/usr/bin for normal users,
       and to /usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin for
       root, if not otherwise configured.

       The environment variable $TERM will be preserved, if it exists, else it
       will be initialized to the terminal type on your tty. Other environment
       variables are preserved if the -p option is given.

       Then the user’s shell is started. If no shell is specified for the user
       in /etc/passwd, then /bin/sh is used. If there is no home directory
       specified in /etc/passwd, then / is used, followed by .hushlogin check as
       described below.

       If the file .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 /var/log/lastlog exists, the last login
       time is printed, and the current login is recorded.

OPTIONS
       -p
           Used by getty(8) to tell login to preserve the environment.

       -f
           Used to skip a login authentication. This option is usually used by
           the getty(8) autologin feature.

       -h
           Used by other servers (such as telnetd(8) to pass the name of the
           remote host to login so that it can be placed in utmp and wtmp. Only
           the superuser is allowed use this option.

           Note that the -h option has an impact on the PAM service name. The
           standard service name is login, but with the -h option, the name is
           remote. It is necessary to create proper PAM config files (for
           example, /etc/pam.d/login and /etc/pam.d/remote).

       -H
           Used by other servers (for example, telnetd(8)) to tell login that
           printing the hostname should be suppressed in the login: prompt. See
           also LOGIN_PLAIN_PROMPT below.

       --help
           Display help text and exit.

       -V, --version
           Display version information and exit.

CONFIG FILE ITEMS
       login reads the /etc/login.defs configuration file (see login.defs(5)).
       Note that the configuration file could be distributed with another
       package (usually shadow-utils). The following configuration items are
       relevant for login:

       MOTD_FILE (string)
           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.

           The default value is /usr/share/misc/motd:/run/motd:/etc/motd. If the
           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 pam_motd(8) PAM module.

           The directories in the MOTD_FILE are supported since version 2.36.

           Note that login does not implement any filenames overriding behavior
           like pam_motd (see also MOTD_FIRSTONLY), but all content from all
           files is displayed. It is recommended to keep extra logic in content
           generators and use /run/motd.d rather than rely on overriding
           behavior hardcoded in system tools.

       MOTD_FIRSTONLY (boolean)
           Forces login to stop display content specified by MOTD_FILE after the
           first accessible item in the list. Note that a directory is one item
           in this case. This option allows login semantics to be configured to
           be more compatible with pam_motd. The default value is no.

       LOGIN_PLAIN_PROMPT (boolean)
           Tell login that printing the hostname should be suppressed in the
           login: prompt. This is an alternative to the -H command line option.
           The default value is no.

       LOGIN_TIMEOUT (number)
           Maximum time in seconds for login. The default value is 60.

       LOGIN_RETRIES (number)
           Maximum number of login retries in case of a bad password. The
           default value is 3.

       LOGIN_KEEP_USERNAME (boolean)
           Tell login to only re-prompt for the password if authentication
           failed, but the username is valid. The default value is no.

       FAIL_DELAY (number)
           Delay in seconds before being allowed another three tries after a
           login failure. The default value is 5.

       TTYPERM (string)
           The terminal permissions. The default value is 0600 or 0620 if tty
           group is used.

       TTYGROUP (string)
           The login tty will be owned by the TTYGROUP. The default value is
           tty. If the TTYGROUP does not exist, then the ownership of the
           terminal is set to the user’s primary group.

           The TTYGROUP can be either the name of a group or a numeric group
           identifier.

       HUSHLOGIN_FILE (string)
           If defined, this file can inhibit all the usual chatter during the
           login sequence. If a full pathname (for example, /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.

           If a full pathname is not specified, then hushed mode will be enabled
           if the file exists in the user’s home directory.

           The default is to check /etc/hushlogins and if it does not exist then
           ~/.hushlogin.

           If the HUSHLOGIN_FILE item is empty, then all the checks are
           disabled.

       DEFAULT_HOME (boolean)
           Indicate if login is allowed if we cannot change directory to the
           home directory. If set to yes, the user will login in the root (/)
           directory if it is not possible to change directory to their home.
           The default value is yes.

       LASTLOG_UID_MAX (unsigned number)
           Highest user ID number for which the 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 lastlog file for them. No LASTLOG_UID_MAX option present
           in the configuration means that there is no user ID limit for writing
           lastlog entries. The default value is ULONG_MAX.

       LOG_UNKFAIL_ENAB (boolean)
           Enable display of unknown usernames when login failures are recorded.
           The default value is no.

           Note that logging unknown usernames may be a security issue if a user
           enters their password instead of their login name.

       ENV_PATH (string)
           If set, it will be used to define the PATH environment variable when
           a regular user logs in. The default value is
           /usr/local/bin:/bin:/usr/bin.

       ENV_ROOTPATH (string), ENV_SUPATH (string)
           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
           /usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin.

FILES
       /var/run/utmp, /var/log/wtmp, /var/log/lastlog, /var/spool/mail/*,
       /etc/motd, /etc/passwd, /etc/nologin, /etc/pam.d/login,
       /etc/pam.d/remote, /etc/hushlogins, $HOME/.hushlogin

BUGS
       The undocumented BSD -r option is not supported. This may be required by
       some rlogind(8) programs.

       A recursive login, as used to be possible in the good old days, no longer
       works; for most purposes su(1) is a satisfactory substitute. Indeed, for
       security reasons, login does a vhangup(2) system call to remove any
       possible listening processes on the tty. This is to avoid password
       sniffing. If one uses the command login, then the surrounding shell gets
       killed by vhangup(2) because it’s no longer the true owner of the tty.
       This can be avoided by using exec login in a top-level shell or xterm.

AUTHORS
       Derived from BSD login 5.40 (5/9/89) by Michael Glad <glad@daimi.dk> for
       HP-UX. Ported to Linux 0.12: Peter Orbaek <poe@daimi.aau.dk>. Rewritten
       to a PAM-only version by Karel Zak <kzak@redhat.com>

SEE ALSO
       mail(1), passwd(1), passwd(5), utmp(5), environ(7), getty(8), init(8),
       lastlog(8), shutdown(8)

REPORTING BUGS
       For bug reports, use the issue tracker at
       https://github.com/karelzak/util-linux/issues.

AVAILABILITY
       The login command is part of the util-linux package which can be
       downloaded from Linux Kernel Archive
       <https://www.kernel.org/pub/linux/utils/util-linux/>.



util-linux {release-version}       2021-06-08                           LOGIN(1)