login manpage

Search topic Section

LOGIN(1)			 User Commands			      LOGIN(1)

       login - begin session on the system

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

       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  prevent  revealing	 the password.	Only a small number of
       password failures are permitted before login exits and  the  communica-
       tions 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  variables  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 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).

       -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

       -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.
	      See  also LOGIN_PLAIN_PROMPT below if your server does not allow
	      to configure login command line.

       -V     Print version and exit.

       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

       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  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 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 ter-
	   minal is set to the user's primary group.

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

       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

	   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 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 login.  The default value is /usr/local/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:


       init(8), getty(8), mail(1),  passwd(1),	passwd(5),  environ(7),	 shut-

       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.

       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 PAM-only version by Karel Zak <kzak@redhat.com>

       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-

util-linux			   June 2012			      LOGIN(1)