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Linux 2.6 - man page for agetty (linux section 8)

AGETTY(8)										AGETTY(8)

       agetty - alternative Linux getty

       agetty  [-c8ihLmnsUw]  [-f  issue_file]	[-l  login_program]  [-I  init]  [-t timeout] [-H
       login_host] port baud_rate,...  [term]

       agetty opens a tty port, prompts for a login name and invokes the /bin/login  command.  It
       is normally invoked by init(8).

       agetty  has  several  non-standard features that are useful for hard-wired and for dial-in

       o      Adapts the tty settings to parity bits and to erase, kill, end-of-line  and  upper-
	      case  characters	when it reads a login name.  The program can handle 7-bit charac-
	      ters with even, odd, none or space parity, and 8-bit characters with no parity. The
	      following  special  characters  are  recognized: @ and Control-U (kill); #, DEL and
	      back space (erase); carriage return and line feed (end of line).

       o      Optionally  deduces  the	baud  rate  from  the  CONNECT	 messages   produced   by
	      Hayes(tm)-compatible modems.

       o      Optionally  does	not  hang  up when it is given an already opened line (useful for
	      call-back applications).

       o      Optionally does not display the contents of the /etc/issue file.

       o      Optionally displays an alternative issue file instead of /etc/issue.

       o      Optionally does not ask for a login name.

       o      Optionally invokes a non-standard login program instead of /bin/login.

       o      Optionally turns on hard-ware flow control

       o      Optionally forces the line to be local with no need for carrier detect.

       This program does not use the /etc/gettydefs (System V) or /etc/gettytab (SunOS 4) files.

       port   A path name relative to the /dev directory. If a "-" is specified,  agetty  assumes
	      that its standard input is already connected to a tty port and that a connection to
	      a remote user has already been established.

	      Under System V, a "-" port argument should be preceded by a "--".

	      A comma-separated list of one or more baud rates. Each time agetty receives a BREAK
	      character it advances through the list, which is treated as if it were circular.

	      Baud  rates  should  be  specified  in descending order, so that the null character
	      (Ctrl-@) can also be used for baud rate switching.

       term   The value to be used for the TERM environment  variable.	This  overrides  whatever
	      init(8) may have set, and is inherited by login and the shell.

       -c     Don't reset terminal cflags (control modes). See termios(3) for more details.

       -8     Assume that the tty is 8-bit clean, hence disable parity detection.

       -h     Enable hardware (RTS/CTS) flow control. It is left up to the application to disable
	      software (XON/XOFF) flow protocol where appropriate.

       -i     Do not display the contents of /etc/issue  (or  other)  before  writing  the  login
	      prompt.  Terminals  or  communications  hardware may become confused when receiving
	      lots of text at the wrong baud rate; dial-up scripts may fail if the  login  prompt
	      is preceded by too much text.

       -f issue_file
	      Display  the contents of issue_file instead of /etc/issue.  This allows custom mes-
	      sages to be displayed on different terminals.  The -i  option  will  override  this

       -I initstring
	      Set  an initial string to be sent to the tty or modem before sending anything else.
	      This may be used to initialize a modem.  Non printable characters may  be  sent  by
	      writing  their  octal code preceded by a backslash (\). For example to send a line-
	      feed character (ASCII 10, octal 012) write \012.

       -l login_program
	      Invoke the specified login_program instead of /bin/login.  This allows the use of a
	      non-standard  login  program  (for example, one that asks for a dial-up password or
	      that uses a different password file).

       -H login_host
	      Write the specified login_host into the utmp file.  (Normally,  no  login  host  is
	      given,  since agetty is used for local hardwired connections and consoles. However,
	      this option can be useful for identifying terminal concentrators and the like.

       -m     Try to extract the baud rate the CONNECT status message produced by  Hayes(tm)-com-
	      patible  modems.	These  status  messages  are  of the form: "<junk><speed><junk>".
	      agetty assumes that the modem emits its status message at the same speed as  speci-
	      fied with (the first) baud_rate value on the command line.

	      Since  the  -m  feature may fail on heavily-loaded systems, you still should enable
	      BREAK processing by enumerating all expected baud rates on the command line.

       -n     Do not prompt the user for a login name. This can be used  in  connection  with  -l
	      option  to invoke a non-standard login process such as a BBS system. Note that with
	      the -n option, agetty gets no input from user who logs in and  therefore	won't  be
	      able  to	figure	out parity, character size, and newline processing of the connec-
	      tion. It defaults to space parity, 7 bit characters, and ASCII CR (13)  end-of-line
	      character.   Beware that the program that agetty starts (usually /bin/login) is run
	      as root.

       -t timeout
	      Terminate if no user name could be read within timeout seconds. This option  should
	      probably not be used with hard-wired lines.

       -L     Force the line to be a local line with no need for carrier detect. This can be use-
	      ful when you have a locally attached terminal where the serial line  does  not  set
	      the carrier detect signal.

       -s     Try  to  keep the existing baud rate. The baud rates from the command line are used
	      when agetty receives a BREAK character.

       -U     Turn on support for detecting an uppercase only terminal.  This setting will detect
	      a  login name containing only capitals as indicating an uppercase only terminal and
	      turn on some upper to lower case conversions.  Note that this has  no  support  for
	      any unicode characters.

       -w     Wait  for  the  user or the modem to send a carriage-return or a linefeed character
	      before sending the /etc/issue (or other) file and the login prompt. Very useful  in
	      connection with the -I option.

       This  section  shows  examples for the process field of an entry in the /etc/inittab file.
       You'll have to prepend appropriate values for the other fields.	See inittab(5)	for  more

       For a hard-wired line or a console tty:
	    /sbin/agetty 9600 ttyS1

       For a directly connected terminal without proper carriage detect wiring: (try this if your
       terminal just sleeps instead of giving you a password: prompt.)
	    /sbin/agetty -L 9600 ttyS1 vt100

       For a old style dial-in line with a 9600/2400/1200 baud modem:
	    /sbin/agetty -mt60 ttyS1 9600,2400,1200

       For a Hayes modem with a fixed 115200 bps interface to  the  machine:  (the  example  init
       string  turns  off modem echo and result codes, makes modem/computer DCD track modem/modem
       DCD, makes a DTR drop cause a dis-connection and turn on auto-answer after 1 ring.)
	    /sbin/agetty -w -I 'ATE0Q1&D2&C1S0=1\015' 115200 ttyS1

       The issue-file (/etc/issue or the file set with the -f option) may contain certain  escape
       codes  to  display the system name, date and time etc. All escape codes consist of a back-
       slash (\) immediately followed by one of the letters explained below.

       b      Insert the baudrate of the current line.

       d      Insert the current date.

       s      Insert the system name, the name of the operating system.

       l      Insert the name of the current tty line.

       m      Insert the architecture identifier of the machine, eg. i486

       n      Insert the nodename of the machine, also known as the hostname.

       o      Insert the NIS domainname of the machine.

       O      Insert the DNS domainname of the machine.

       r      Insert the release number of the OS, eg. 1.1.9.

       t      Insert the current time.

       u      Insert the number of current users logged in.

       U      Insert the string "1 user" or "<n> users" where <n> is the number of current  users
	      logged in.

       v      Insert the version of the OS, eg. the build-date etc.

       Example: On my system, the following /etc/issue file:

	      This is \n.\o (\s \m \r) \t

       displays as

	      This is thingol.orcan.dk (Linux i386 1.1.9) 18:29:30

       /var/run/utmp, the system status file.
       /etc/issue, printed before the login prompt.
       /dev/console, problem reports (if syslog(3) is not used).
       /etc/inittab, init(8) configuration file.

       The  baud-rate  detection  feature  (the -m option) requires that agetty be scheduled soon
       enough after completion of a dial-in call (within 30 ms with  modems  that  talk  at  2400
       baud).  For  robustness, always use the -m option in combination with a multiple baud rate
       command-line argument, so that BREAK processing is enabled.

       The text in the /etc/issue file (or other) and the login prompt	are  always  output  with
       7-bit characters and space parity.

       The  baud-rate  detection feature (the -m option) requires that the modem emits its status
       message after raising the DCD line.

       Depending on how the program was configured, all diagnostics are written  to  the  console
       device  or  reported  via the syslog(3) facility.  Error messages are produced if the port
       argument does not specify a terminal device; if there is no utmp  entry	for  the  current
       process (System V only); and so on.

       W.Z. Venema <wietse@wzv.win.tue.nl>
       Eindhoven University of Technology
       Department of Mathematics and Computer Science
       Den Dolech 2, P.O. Box 513, 5600 MB Eindhoven, The Netherlands

       Peter Orbaek <poe@daimi.aau.dk>
       Linux port and more options. Still maintains the code.

       Eric Rasmussen <ear@usfirst.org>
       Added -f option to display custom login messages on different terminals.

       The agetty command is part of the util-linux package and is available from ftp://ftp.ker-


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