NGETTY(8)						      System Manager's Manual							 NGETTY(8)

NAME

       ngetty - daemon for virtual console terminals

SYNOPSIS

       ngetty [ tty1 | vc/1 | 1 ] [ /dev/tty2 | vc/2 | 2 ] ...
       ngetty-helper /dev/ttyX [ login ]
       ngetty-argv :options:child:[name]:args [user [tty]]

DESCRIPTION

       ngetty is a daemon that starts login sessions on virtual console terminals, on demand.  It opens the virtual console terminals specified by
       the tty...  arguments, displays a /etc/issue message, prints the login prompt on each terminal and waits for user name.	 On  user  action,
       ngetty executes login(1) in a new process with the terminal the user is typing in as the controlling terminal.

       login(1) then prompts for a password to login with the system and finally, if the login succeeds, executes the user's login shell.

       When the user logs out, ngetty restarts the corresponding virtual console terminal.

       Actually almost the whole work is done by a ngetty-helper program.  It makes /var/run/utmp, /var/log/wtmp records, prints /etc/issue, host-
       name, login prompt, waits for user name.  ngetty invokes the ngetty-helper by need.

HISTORY

       The traditional way to enable logins on virtual console terminals is to start a bunch of getty(8) programs, one for  each  virtual  console
       terminal,  from	init(8).   As most users rarely login on virtual console terminals nowadays, preferring graphical logins instead, it seems
       wasteful to have all those getty(8) processes doing nothing but wasting memory.	Alternatively, ngetty manages logins on any number of vir-
       tual console terminals from a single, light, process.

INVOCATION

       ngetty does not use stdin, stdout or stderr and closes them.

       When  running  ngetty  in  the background, remember to disassociate it from the current controlling terminal by making it the process group
       leader of a new session, e.g.:

	   setsid ngetty tty...  &
	   ngetty-argv :-D:-S:-e:--:/sbin/ngetty::1:2:3:4

       To start ngetty from init(8), add something like this to /etc/inittab:

	      ng:2345:respawn:/sbin/ngetty tty1 tty2 ... tty6

       If ngetty-argv is available use it to start ngetty from /etc/inittab.  See the example bellow.

DIAGNOSTICS

       If ngetty can not open one of the virtual console terminals specified in the tty...  arguments, most likely because that  tty  device  node
       does  not  exist,  no  greeting message will be displayed on that terminal, obviously, and ngetty will simply go on, ignoring the offending
       terminal.  Create the missing tty device and send SIGCHLD to ngetty.  Then it will reopen the new tty.  Instead of sending SIGCHLD you  can
       login and logout on some working tty.  This also forces ngetty to reopen the new tty.

       ngetty uses ngetty-helper program.  It's path is hard-coded in ngetty.  Never remove ngetty-helper program nor move it to other location.

       If,  on	user action, ngetty-helper can not execute login(1), in all likelihood because the compiled-in LOGIN path does not match your sys-
       tem's login(1) path, ngetty restarts the terminal and redisplays the greeting message.

       In any case, ngetty does not output error messages.

OPTIONS

       It's possible to set different options for ngetty-helper program in file /etc/ngetty/Conf.  If the option begin with "=" it's  applied  for
       all tty.  If it start with a tty name it's applied only on current tty.	Examples:

	      # options format:
	      # [ttyX]=option[=value]
	      #=debug
	      =environ=,TERM=linux
	      tty3=long-hostname
	      tty1=clear=33c
	      =newline=
	      =timeout=180
	      tty1=timeout=60
	      tty1=delay=1

       For security reasons ngetty-helper evaluate the file /etc/ngetty/Conf only if it has mode:

	      -rw-------    root   root   /etc/ngetty/Conf

       ngetty-helper recognizes the following options which might be embedded in the /etc/ngetty/Conf file:

       # tty5=login-prog=/bin/login.test
	      If a line starts with #, space or tab it is a comment.

       debug  If  debug  is  set  ngetty-helper write on terminal all successfully applied options.  Set this on the fist line of /etc/ngetty/Conf
	      file.

       date-string
	      Escape d (current day) in /etc/issue as:
	      Fri Jun 01 2007.	Default is: 2007-06-01.

       days=string
	      Abbreviation for week days (21 bytes).  Default is:
	      =days=SunMonTueWedThuFriSat

       months=string
	      Abbreviation for months (36 bytes).  Default is:
	      =months=JanFebMarAprMayJunJulAugSepOctNovDec

       tz=string
	      Change the timezone offset.  If the string starts with slash it's the name of tzfile.  The string is positive number  if	the  local
	      time zone is east of the Prime Meridian and negative if it is west.  Default is /etc/localtime.  Examples:
	      =tz=-18000	-0500
	      =tz=7200		+0200
	      =tz=/etc/localtime
	      =tz=AUTO

       echo-off
	      Turn the echo off just before starting /bin/login.  It's similar to stty -echo.

       newline=string
	      Print this string before writing out /etc/issue.	(default is 12).  Example:
	      tty3=newline=12I am l12

       clear=string
	      Clear the screen before prompting for the login name with the string (default is 33c).	Examples:
	      tty1=clear=
	      tty3=clear=33[H33[J

       noclear-first=/etc/ngetty/.noclear
	      Do not clear the screen before prompting for the login name the first time after reboot.	Example:
	      tty1=noclear-first=/etc/ngetty/.noclear.tty1

       nohangup
	      Do not call vhangup() to disable writing to this tty by other applications.

       long-hostname
	      By default the hostname is only printed until the first dot.  With this option enabled, the full text from gethostname() is shown.

       nousername
	      Do not ask for user name.  Exec login(1) immediately.  Example:
	      =nousername
	      =login-prompt= Press ENTER to activate l

       deny=,black,list,users...
	      Disable login process for some users.  The first char after "deny=" is split char.  Example:
	      tty1=deny=,root,nobody,guest

       allow=,white,list,users...
	      Enable login process only for the users.	The first char after "allow=" is split char.  Example:
	      =clear=
	      =allow=,root,operator

       print=an:CM:PY:04:69
	      Accept only these chars in user name.  Default is to accept only ",-._ 0-9 a-z A-Z".  It's possible to insert here the output of
	      printf 'tty3=print=az:AZ:ABCXYZ:__'
	      Here ABC and XYZ are octal numbers.  Examples:
	      tty1=print=az:AZ
	      tty2=print=az:AZ:__:,.:09

       issue-file=/etc/issue
	      Change the issue file.  Disable printing of the issue file with:
	      =issue-file=

       login-prog=/bin/login
	      Change the login app.  It's possible to use fgetty's /bin/login1 application with:
	      =echo-off
	      =login-prog=/bin/login1

       login-buffer=string
	      Read login name over the string.	Default string is 40 bytes long.  Example:
	      =login-buffer=12345678901234567

       login-prompt=
 login:
	      Change the login prompt string.  Example:
	      =login-prompt=33[1;33ml33[0;39m  
 login:

       nice=10
	      Change the priority by calling nice().

       delay=5
	      Sleep this many seconds before printing the file /etc/issue.

       timeout=180
	      Wait at most this many seconds for user name.

       chdir=/home
	      Change into this directory before calling the login prog.

       chroot=/chroot
	      Call chroot() with this directory name.

       autologin-name=username
	      Log the specified user automatically in without asking for a login name and password.  Check the -f option from /bin/login for this.
	      Example:
	      tty1=autologin-name=maria

       autologin-first=/etc/ngetty/.autologin
	      Log in automatically only the first time after reboot without asking for a login name and password.  Example:
	      tty1=autologin-name=maria
	      tty1=autologin-first=/etc/ngetty/.autologin

       environ=,TERM=linux
	      Replace the environ.  The first char after "environ=" is split char.  Examples:
	      =environ=,TERM=vt100,PATH=/bin:/usr/bin,HOME=/
	      tty3=environ=,TERM=linux,TTY=/dev/tty3

       sh-A=line
	      Exec this line before printing /etc/issue.  The line is executed using /bin/sh -c line.  It's good idea to use the full paths  here.
	      Example:
	      tty4=sh-A=exec /bin/ps e -u root
	      tty4=delay=8

       sh-B=line
	      Similar to option sh-A.  This is executed before asking for username.

       login-argv=any_string
	      Ngetty starts login application with options
	      login -- XYZ	# default
	      login -f XYZ	# if autologin-name=XYZ
	      With  this  option  it's possible to start login appl with any_string instead of -- or -f.  Using the program ngetty-argv(8) one can
	      start arbitrary program with different arguments.  Two very dangerous examples are (never try them):
	      tty4=login-prog=/sbin/ngetty-argv
	      tty5=login-prog=/sbin/ngetty-argv
	      tty4=login-argv=,/bin/login,,-f,%U
	      tty5=login-argv=:-C:/bin/bash:-bash

WARNING

       If ngetty-helper finds stdout or stderr open it exits immediately with error 100.  Ngetty invokes it correctly.	See also the program test-
       helper.c in source package.

       Do  not	edit  the  file  /etc/ngetty/Conf  directly.   Put  the configurations in /etc/ngetty/Conf.sed (the same syntax and permissions as
       /etc/ngetty/Conf) and after editing it, execute:

	      cd /etc/ngetty && ./setup

       The script /etc/ngetty/setup removes comments, merges lines ending with a backslash and expands the  string  =tz=AUTO  to  numeric  number.
       Then It updates /etc/ngetty/Conf.

SIGNALS

       If  ngetty  receives  SIGTERM  it kill all child's PID (first with SIGTERM and then with SIGKILL) and exit immediately.	It does not change
       UID, GID and mode of the controlling tty devices.  It does not catch the other signals.	Sending SIGCHLD to ngetty forces it to reread  his
       internal cache tables and to restart failed tty devices.

ISSUE ESCAPES

       ngetty-helper  recognizes  the  following  escapes  sequences  which  might  be	embedded  after  login-prompt=, newline=, clear= or in the
       /etc/issue file:

       d     insert current day (localtime),

       l     insert line on which ngetty is running,

       m     inserts machine architecture (uname -m),

       
     inserts machine's network node hostname (uname -n),

       o     inserts domain name,

       
     inserts operating system release (uname -r),

       	     insert current time (localtime),

       s     inserts operating system name,

       u     insert the number of users which are currently logged in,

       U     insert the  string  "1 user" or "<n> users", where <n> is the number of users currently logged  in,

       v     inserts operating system version (uname -v).

       XYZ   inserts a letter with octal code XYZ.

EXAMPLE

       "Linux eos i386 #1 Tue Mar 19 21:54:09 MET 1996" was produced by putting "s 
 m v" into /etc/issue.

NGETTY-ARGV
       The program ngetty-argv(8) splits argv[1] on strings, expands %U and %T to username and tty and then start the the application.	The  first
       char after "login-argv=" is split char.	In the examples above every user logs on tty4 without password and tty5 is always root.  To under-
       stand better how ngetty-argv works try as non-root:

       ngetty-argv ':/bin/echo:echo:%U: on %T' usr tty3
       ngetty-argv ':/bin/sleep:-hacker:39:I am %U on %T' 123 X

       One can put also options for ngetty-argv at the beginning.

	      --	 last option

	      -u503	 setuid to 503

	      -g230	 setgid to 230

	      -a120	 exec alarm(120) before starting child

	      -s10	 sleep 10 secs before starting child

	      -d/X/YZ	 chdir(/X/YZ)  before starting child

	      -r/A/BC	 chroot(/A/BC) before starting child

	      -D	 start the child in background and exit

	      -N -C	 NOTTY | SCTTY controlling tty

	      -S	 like setsid(8)

	      -e,HOME=/,TERM=linux     same as environ= above

	      -p/path/to/pid.file      write the child pid here

       One possible example for /etc/ngetty/Conf is:
	   tty9=clear=
	   tty9=issue-file=
	   tty9=login-prompt=
  d 		qmail-qread:
	   tty9=login-prog=/sbin/ngetty-argv
	   tty9=login-argv=:-u106:-g503:-d/var/qmail:--
	     :./bin/qmail-qread:qread

       Another example is setting the TTY environ automatically:
	   =login-prog=/sbin/ngetty-argv
	   =login-argv=:-e,TTY=/dev/%T,TERM=linux:--
	     :/bin/login:login-%T:--:%U

       I recommend using ngetty-argv  in /etc/inittab also.  Put as last argument runlevel string.  Then  ps  will  show  ngetty-2345  instead	of
       ngetty.	Next start tty1 ... tty6 on runlevels 2345.
	   ng:2345:respawn:/sbin/ngetty-argv
	     .-e.-S.-d/.-s1.--./sbin/%U.%U-%T.1.2.3.4.5.6
	     ngetty 2345

       On a terminal (in scripts) start ngetty with
	   ngetty-argv .-N.-S.-e./sbin/%U.%U.8.9.10 ngetty
	   ngetty-argv .-D.-S.-e./sbin/%U.%U.8.9.10 ngetty

       This  program  is a hack written for ngetty-helper.  There is no additional code in ngetty-helper and it's possible to start a program with
       any args.  It is like a filter between ngetty-helper and login application.  One can easy modify it without touching  ngetty-helper.   It's
       similar to DJB well known argv0(1) and setuidgid(8).  You can write own such programs and use them instead of ngetty-argv.

FILES

       /etc/ngetty/Conf        ngetty-helper configuration file
       /etc/ngetty/Conf.sed    private setup file
       /etc/ngetty/setup       updates Conf.sed -> Conf
       /etc/issue	       printed before the login prompt
       /var/run/utmp	       the system status file
       /var/log/wtmp	       the system logging file
       /etc/inittab	       init(8) configuration file

SEE ALSO

       getty(8) fgetty(8) mingetty(8)
       login(1) nlogin(1) argv0(1) setuidgid(8) stty(1)
       http://anbadeol.googlepages.com/logind.html

AUTHOR

       Nikola Vladov
       http://riemann.fmi.uni-sofia.bg/ngetty/

COPYRIGHT

       Copyright 2007,2008 Nikola Vladov

       This  program  is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by
       the Free Software Foundation; either version 2 of the License, or (at your option) any later version.

       This program is distributed in the hope that it will be useful, but WITHOUT ANY	WARRANTY;  without  even  the  implied	warranty  of  MER-
       CHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for more details.

								     June 2008								 NGETTY(8)