.TH NGETTY 8 "May 2010" . .SH NAME . .BR ngetty \- daemon for virtual console terminals . .SH SYNOPSIS .BR ngetty [ tty1 | vc/1 | 1 ] [ /dev/tty2 | vc/2 | 2 ] ... .br .BR ngetty-helper /dev/ttyX [ login ] .br .BR ngetty-argv :options:child:[name]:args [user [tty]] . .SH DESCRIPTION . .B ngetty is a daemon that starts login sessions on virtual console terminals, on demand. It opens the virtual console terminals specified by the .I tty... arguments, displays a .IR /etc/issue message, prints the login prompt on each terminal and waits for user name. On user action, .B ngetty executes .BR login (1) in a new process with the terminal the user is typing in as the controlling terminal. .PP .BR login (1) then prompts for a password to login with the system and finally, if the login succeeds, executes the user's login shell. .PP When the user logs out, .B ngetty restarts the corresponding virtual console terminal. .PP .PP Actually almost the whole work is done by a .B ngetty-helper program. It makes .IR /var/run/utmp , .IR /var/log/wtmp records, prints .IR /etc/issue , hostname, login prompt, waits for user name. .B ngetty invokes the .B ngetty-helper by need. . .SH HISTORY . The traditional way to enable logins on virtual console terminals is to start a bunch of .BR getty (8) programs, one for each virtual console terminal, from .BR init (8). As most users rarely login on virtual console terminals nowadays, preferring graphical logins instead, it seems wasteful to have all those .BR getty (8) processes doing nothing but wasting memory. Alternatively, .B ngetty manages logins on any number of virtual console terminals from a single, light, process. . .SH INVOCATION . .B ngetty does not use stdin, stdout or stderr and closes them. .PP When running .B 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.: .PP .RS 4 setsid ngetty tty... & .br ngetty-argv :-D:-S:-e:--:/sbin/ngetty::1:2:3:4 .RE .PP To start .B ngetty from .BR init (8), add something like this to .IR /etc/inittab : .PP .RS ng:2345:respawn:/sbin/ngetty tty1 tty2 ... tty6 .RE .PP If .B ngetty-argv is available use it to start ngetty from .IR /etc/inittab . See the example bellow. . .SH DIAGNOSTICS . If .B ngetty can not open one of the virtual console terminals specified in the .I tty... arguments, most likely because that .I tty device node does not exist, no greeting message will be displayed on that terminal, obviously, and .B ngetty will simply go on, ignoring the offending terminal. Create the missing .I tty device and send SIGCHLD to ngetty. Then it will reopen the new .IR tty . Instead of sending SIGCHLD you can login and logout on some working .IR tty . This also forces ngetty to reopen the new .IR tty . . .PP .B ngetty uses .B ngetty-helper program. It's path is hard-coded in .BR ngetty . Never remove .B ngetty-helper program nor move it to other location. .PP If, on user action, .B ngetty-helper can not execute .BR login (1), in all likelihood because the compiled-in .B LOGIN path does not match your system's .BR login (1) path, .B ngetty restarts the terminal and redisplays the greeting message. .PP In any case, .B ngetty does not output error messages. .PP .SH OPTIONS It's possible to set different options for .B ngetty\-helper program in file .IR /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: .PP .RS .B # options format: .br .B # [ttyX]=option[=value] .br .B #=debug .br =environ=,TERM=linux .br tty3=long-hostname .br tty1=clear=\e033c .br =newline= .br =timeout=180 .br tty1=timeout=60 .br tty1=delay=1 .RE .PP For security reasons .B ngetty-helper evaluate the file .IR /etc/ngetty/Conf only if it has mode: .PP .RS -rw------- root root /etc/ngetty/Conf .RE . .PP .B ngetty-helper recognizes the following options which might be embedded in the .I /etc/ngetty/Conf file: .TP .B # tty5=login-prog=/bin/login.test If a line starts with .BR # , .B space or .B tab it is a comment. .TP .B debug If debug is set .B ngetty-helper write on terminal all successfully applied options. Set this on the fist line of .IR /etc/ngetty/Conf file. .TP .B date-string Escape \fB\\d\fP (current day) in .IR /etc/issue as: .br \fBFri Jun 01 2007\fP. Default is: \fB2007-06-01\fP. .TP .B days=string Abbreviation for week days (21 bytes). Default is: .br .B =days=SunMonTueWedThuFriSat .TP .B months=string Abbreviation for months (36 bytes). Default is: .br .B =months=JanFebMarAprMayJunJulAugSepOctNovDec .TP .B 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 .IR /etc/localtime . Examples: .br \fB=tz=-18000\fP -0500 .br \fB=tz=7200\fP +0200 .br \fB=tz=/etc/localtime\fP .br \fB=tz=AUTO\fP .TP .B echo-off Turn the echo off just before starting /bin/login. It's similar to \fBstty -echo\fP. .TP .B newline=string Print this \fBstring\fP before writing out .IR /etc/issue . (default is \fB\e012\fP). Example: .br .B tty3=newline=\e012I am \el\e012 .TP .B clear=string Clear the screen before prompting for the login name with the \fBstring\fP (default is \fP\e033c\fP). Examples: .br .B tty1=clear= .br .B tty3=clear=\e033[H\e033[J .TP .B noclear-first=/etc/ngetty/.noclear Do not clear the screen before prompting for the login name the first time after reboot. Example: .br .B tty1=noclear-first=/etc/ngetty/.noclear.tty1 .TP .B nohangup Do not call vhangup() to disable writing to this tty by other applications. .TP .B long\-hostname By default the hostname is only printed until the first dot. With this option enabled, the full text from gethostname() is shown. . .TP .B nousername Do not ask for user name. Exec login(1) immediately. Example: .br .B =nousername .br \fB=login-prompt= Press ENTER to activate \el\bP . .TP .B deny=,black,list,users... Disable login process for some users. The first char after "deny=" is split char. Example: .br .B tty1=deny=,root,nobody,guest .TP .B allow=,white,list,users... Enable login process only for the users. The first char after "allow=" is split char. Example: .br .B =clear= .br .B =allow=,root,operator . .TP .B print=an:CM:PY:04:69 Accept only these chars in user name. Default is to accept only "\fB,-._ 0-9 a-z A-Z\fP". It's possible to insert here the output of .br .B printf 'tty3=print=az:AZ:\eABC\eXYZ:__' .br Here \fBABC\fP and \fBXYZ\fP are octal numbers. Examples: .br .B tty1=print=az:AZ .br .B tty2=print=az:AZ:__:,.:09 .TP .B issue-file=/etc/issue Change the issue file. Disable printing of the issue file with: .br .B =issue-file= .TP .B login-prog=/bin/login Change the login app. It's possible to use fgetty's .IR /bin/login1 application with: .br .B =echo-off .br .B =login-prog=/bin/login1 .TP .B login-buffer=string Read login name over the \fBstring\fP. Default string is 40 bytes long. Example: .br .B =login-buffer=12345678901234567 .TP .B login-prompt=\en login: Change the login prompt string. Example: .br \fB=login-prompt=\e033[1;33m\el\e033[0;39m \en login: \fP .TP .B nice=10 Change the priority by calling nice(). .TP .B delay=5 Sleep this many seconds before printing the file /etc/issue. .TP .B timeout=180 Wait at most this many seconds for user name. .TP .B chdir=/home Change into this directory before calling the login prog. .TP .B chroot=/chroot Call chroot() with this directory name. .TP .B autologin-name=username Log the specified user automatically in without asking for a login name and password. Check the \-f option from .B /bin/login for this. Example: .br .B tty1=autologin-name=maria .TP .B autologin-first=/etc/ngetty/.autologin Log in automatically only the first time after reboot without asking for a login name and password. Example: .br .B tty1=autologin-name=maria .br .B tty1=autologin-first=/etc/ngetty/.autologin .TP .B environ=,TERM=linux Replace the environ. The first char after "environ=" is split char. Examples: .br .B =environ=,TERM=vt100,PATH=/bin:/usr/bin,HOME=/ .br .B tty3=environ=,TERM=linux,TTY=/dev/tty3 .TP .B sh-A=line Exec this line before printing .IR /etc/issue . The line is executed using .B /bin/sh -c .IR line . It's good idea to use the full paths here. Example: .br .B tty4=sh-A=exec /bin/ps e -u root .br .B tty4=delay=8 .TP .B sh-B=line Similar to option .B sh-A. This is executed before asking for username. .TP .B login-argv=any_string Ngetty starts login application with options .br \fBlogin -- XYZ\fP # default .br \fBlogin -f XYZ\fP # if autologin-name=XYZ .br With this option it's possible to start login appl with \fBany_string\fP instead of \fB\--\fP or \fB-f\fP. Using the program \fBngetty-argv\fP(8) one can start arbitrary program with different arguments. Two very dangerous examples are (never try them): .br .B tty4=login-prog=/sbin/ngetty-argv .br .B tty5=login-prog=/sbin/ngetty-argv .br .B tty4=login-argv=,/bin/login,,-f,%U .br .B tty5=login-argv=:-C:/bin/bash:-bash . .PP .SH "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. .PP Do not edit the file .IR /etc/ngetty/Conf directly. Put the configurations in .IR /etc/ngetty/Conf.sed (the same syntax and permissions as .IR /etc/ngetty/Conf ) and after editing it, execute: .PP .RS .B cd /etc/ngetty && ./setup .RE .PP The script .I /etc/ngetty/setup removes comments, merges lines ending with a backslash and expands the string \fB=tz=AUTO\fP to numeric number. Then it updates .IR /etc/ngetty/Conf . .PP .SH "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. . .PP .SH "ISSUE ESCAPES" .B ngetty-helper recognizes the following escapes sequences which might be embedded after \fBlogin-prompt=\fP, \fBnewline=\fP, \fBclear=\fP or in the .I /etc/issue file: .IP \fB\ed\fP insert current day (localtime), .IP \fB\el\fP insert line on which .B ngetty is running, .IP \fB\em\fP inserts machine architecture (uname -m), .IP \fB\en\fP inserts machine's network node hostname (uname -n), .IP \fB\eo\fP inserts domain name, .IP \fB\er\fP inserts operating system release (uname -r), .IP \fB\et\fP insert current time (localtime), .IP \fB\es\fP inserts operating system name, .IP \fB\eu\fP insert the number of users which are currently logged in, .IP \fB\eU\fP insert the string "1 user" or " users", where is the number of users currently logged in, .IP \fB\ev\fP inserts operating system version (uname -v). .IP \fB\eXYZ\fP inserts a letter with octal code XYZ. .PP .SH EXAMPLE "\fBLinux\ eos\ i386\ #1\ Tue\ Mar\ 19\ 21:54:09\ MET\ 1996\fP" was produced by putting "\fB\\s\ \\n\ \\m\ \\v\fP" into .IR /etc/issue . . .PP .SH "NGETTY-ARGV" The program \fBngetty-argv\fP(8) splits argv[1] on strings, expands \fB%U\fP and \fB%T\fP 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 understand better how \fBngetty-argv\fP works try as non-root: .br .PP .B ngetty-argv ':/bin/echo:echo:%U: on %T' usr tty3 .br .B ngetty-argv ':/bin/sleep:-hacker:39:I am %U on %T' 123 X .PP .TP One can put also options for ngetty-argv at the beginning. .IP \fB--\fP last option .IP \fB-u503\fP setuid to 503 .IP \fB-g230\fP setgid to 230 .IP .br \fB-a120\fP exec alarm(120) before starting child .IP \fB-s10\fP sleep 10 secs before starting child .IP \fB-d/X/YZ\fP chdir(/X/YZ) before starting child .IP \fB-r/A/BC\fP chroot(/A/BC) before starting child .IP \fB-D\fP start the child in background and exit .IP \fB-N -C\fP NOTTY | SCTTY controlling tty .IP \fB-S\fP like \fBsetsid\fP(8) .IP \fB-e,HOME=/,TERM=linux\fP same as \fBenviron=\fP above .IP \fB-p/path/to/pid.file\fP write the child pid here . .PP One possible example for \fB/etc/ngetty/Conf\fP is: .RS 4 .br tty9=clear= .br tty9=issue-file= .br tty9=login-prompt=\en \ed \et qmail-qread: .br tty9=login-prog=/sbin/ngetty-argv .br tty9=login-argv=:-u106:-g503:-d/var/qmail:-- .br :./bin/qmail-qread:qread .RE .PP Another example is setting the TTY environ automatically: .RS 4 =login-prog=/sbin/ngetty-argv .br =login-argv=:-e,TTY=/dev/%T,TERM=linux:-- .br :/bin/login:login-%T:--:%U .RE . .PP I recommend using \fBngetty-argv \fP in .IR /etc/inittab also. Put as last argument runlevel string. Then ps will show \fBngetty-2345\fP instead of \fBngetty\fP. Next start tty1 ... tty6 on runlevels 2345. .RS 4 ng:\fB2345\fP:respawn:/sbin/ngetty-argv .br .-e.-S.-d/.-s1.--./sbin/%U.%U-%T.1.2.3.4.5.6 .br ngetty \fB2345\fP .RE . .PP On a terminal (in scripts) start ngetty with .RS 4 ngetty-argv .-N.-S.-e./sbin/%U.%U.8.9.10 ngetty .br ngetty-argv .-D.-S.-e./sbin/%U.%U.8.9.10 ngetty .RE .PP This program is a hack written for \fBngetty-helper\fP. 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 \fBargv0\fP(1) and \fBsetuidgid\fP(8). You can write own such programs and use them instead of ngetty-argv. . .SH FILES .TS tab (@); l l. /etc/ngetty/Conf@ \fBngetty-helper\fP configuration file /etc/ngetty/Conf.sed@ private setup file /etc/ngetty/setup@ updates \fBConf.sed -> Conf\fP /etc/issue@ printed before the login prompt /var/run/utmp@ the system status file /var/log/wtmp@ the system logging file /etc/inittab@ \fBinit\fP(8) configuration file .TE . .PP .SH SEE ALSO . .BR getty (8) .BR fgetty (8) .BR mingetty (8) .br .BR login (1) .BR nlogin (1) .BR argv0 (1) .BR setuidgid (8) .BR stty (1) .br http://sites.google.com/site/anbadeol/logind . .SH AUTHOR . Nikola Vladov .br http://riemann.fmi.uni-sofia.bg/ngetty/ . .SH COPYRIGHT . Copyright 2007,2008,2010 Nikola Vladov .PP 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. .PP This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.