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 small number of
       password failures are permitted before login exits and the
       communications link is severed.

       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 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 value 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 (other
       environment variables are preserved if the -p option is given), else it
       will be initialized to the terminal type on your tty.

       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 directory
       specified in /etc/passwd, then / is used (the home directory is checked
       for the .hushlogin file 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 not to destroy the environment.

       -f     Used to skip a second login authentication.  This specifically
              does not work for root, and does not appear to work well under
              Linux.

       -h     Used by other servers (i.e., telnetd(8)) to pass the name of the
              remote host to login so that it may be placed in utmp and wtmp.
              Only the superuser may use this option.

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

       -H     Used by other servers (i.e., telnetd(8)) to tell login that
              printing the hostname should be suppressed in the login: prompt.
              See also LOGIN_PLAIN_PROMPT below if your server does not allow
              to configure login command line.

       --help Display help text and exit.

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

CONFIG FILE ITEMS
       login reads the /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
       login(1):

       MOTD_FILE (string)
           If defined, a ":" delimited list of "message of the day" files to
           be displayed upon login.  The default value is /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 pam_motd(8) PAM module.

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

       LOGIN_TIMEOUT (number)
           Max 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.

       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 (e.g.  /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 her 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.

       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 her password instead of her 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
       .hushlogin

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

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() 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() 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.

AUTHOR
       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⟩

AVAILABILITY
       The login command is part of the util-linux package and is available
       from Linux Kernel Archive ⟨https://www.kernel.org/pub/linux/utils/util-
       linux/⟩.



util-linux                         June 2012                          LOGIN(1)