login(1) - phpMan

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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 approprate.  Echoing is disabled  to  pre-
       vent  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 adminitrator 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 other configured.

       The environment variable $TERM will be preserved, if it exists  (other  environment  vari-
       ables  are  preserved  if the -p option is given) or be initialize 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 check-
       ing  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 a
              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.

       -V     Print version 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  configura-
       tion items are relevant for login(1):

       MOTD_FILE (string)
           If  defined,  ":"  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 quiet login
           is enabled then the message of the day is not displayed.  Note that the same function-
           ality is also provided by pam_motd(8) PAM module.

       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 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 TTY-
           GROUP 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 not a full pathname is 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 does not exist then ~/.hushlogin

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

       DEFAULT_HOME (boolean)
           Indicate if login is allowed if we can not 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.

       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 an user enter her pass-
           word instead of her login name.

       ENV_PATH (string)
           If  set,  it  will be used to define the PATH environment variable when a regular user
           login.  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
           login.   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
       init(8), getty(8), mail(1), passwd(1), passwd(5), environ(7), 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 AT daimi.dk> for HP-UX
       Ported to Linux 0.12: Peter Orbaek <poe AT daimi.dk>
       Rewritten to PAM-only version by Karel Zak <kzak AT redhat.com>

AVAILABILITY
       The login command is part of the util-linux package and is  available  from  Linux  Kernel
       Archive <ftp://ftp.kernel.org/pub/linux/utils/util-linux/>.



util-linux                                  June 2012                                    LOGIN(1)

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