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AGETTY(8)                                                            AGETTY(8)



NAME
       agetty - alternative Linux getty


SYNOPSIS
       agetty [-8ihLmnUw] [-f issue_file] [-l login_program] [-I init] [-t timeout] [-H login_host] port baud_rate,...
       [term]
       agetty [-8ihLmnw] [-f issue_file] [-l login_program] [-I init] [-t timeout] [-H login_host] baud_rate,...  port
       [term]


DESCRIPTION
       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 lines:

       o      Adapts the tty settings to parity bits and to erase, kill, end-of-line and uppercase characters when  it
              reads  a  login name.  The program can handle 7-bit characters 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).  See also --erase-
              chars and --kill-chars options.

       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.

ARGUMENTS
       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  estab-
              lished.

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

       baud_rate,...
              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.

OPTIONS
       -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 com-
              munications 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.

       -E     If -H fakehost option is given then -h fakehost options is added to the the /bin/login command line.

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

       -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 linefeed 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.

       -L [=mode]
              Control  CLOCAL line flag, the optional argument mode is 'auto', 'always' or 'never'.  If the mode argu-
              ment is omitted then the default is 'always'.  If the -L option is ommitted at all then the  default  is
              'auto'.

              The  mode 'always' forces 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 sig-
              nal.

              The  mode  'never'  explicitly  clears  CLOCAL  flags from line setting and the carrier detect signal is
              expected on the line.

              The mode 'auto' (agetty default) does not modify CLOCAL setting and follows the setting enabled by  ker-
              nel.

       -m     Try  to  extract the baud rate the CONNECT status message produced by Hayes(tm)-compatible 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 specified 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  process-
              ing  of  the  connection.  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 useful when you have a
              locally attached terminal where the serial line does not set the carrier detect signal.

       -U     Turn on support for detecting an uppercase only terminal.  This setting will detect a  login  name  con-
              taining only capitals as indicating an uppercase only terminal and turn on some upper to lower case con-
              versions.  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.

       --erase-chars string
              This  option specifies additional chars that should be interpreted as a backspace (ignore previous char)
              when user specifies login name. The default is ?#?, specify empty string to disable the default.

       --kill-chars string
              This option specifies additional chars that should be interpreted as a kill (ignore all previous  chars)
              when user specifies login name.  The default is ?@?, specify empty string to disable the default.


EXAMPLES
       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 details.

       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


ISSUE ESCAPES
       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 backslash (\) 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



FILES
       /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.

BUGS
       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.

DIAGNOSTICS
       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.

AUTHOR(S)
       W.Z. Venema <wietseATwzv.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 <poeATdaimi.dk>
       Linux port and more options. Still maintains the code.

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


AVAILABILITY
       The agetty command is part of the util-linux-ng package and is available from ftp://ftp.ker-
       nel.org/pub/linux/utils/util-linux-ng/.



                                                                     AGETTY(8)