AGETTY linux command manual

AGETTY(8)                                                      AGETTY(8)

       agetty - alternative Linux getty

       agetty  [-ihLmnw]  [-f  issue_file]  [-l  login_program] [-I init] [-t
       timeout] [-H login_host] port baud_rate,...  [term]
       agetty [-ihLmnw] [-f issue_file]  [-l  login_program]  [-I  init]  [-t
       timeout] [-H login_host] baud_rate,...  port [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 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  follow-
              ing  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 pro-
              duced 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

       o      Optionally  displays  an  alternative  issue  file  instead  of

       o      Optionally does not ask for a login name.

       o      Optionally  invokes  a  non-standard  login  program instead of

       o      Optionally turns on hard-ware flow control

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

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

       port   A path name relative to the /dev directory. If a "-" is  speci-
              fied,  agetty  assumes  that its standard input is already con-
              nected 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 switch-

       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.

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

       -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 pre-
              ceded by too much text.

       -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 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  hard-
              wired  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  pro-
              duced by Hayes(tm)-compatible modems. These status messages are
              of the form: "".  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 pro-
              cess 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  connection. It defaults to space parity, 7 bit characters,
              and ASCII CR (13) end-of-line character.  Beware that the  pro-
              gram 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

       -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 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

       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 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 " users" where  is the num-
              ber 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 (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  argu-
       ment, 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 writ-
       ten 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 
       Eindhoven University of Technology
       Department of Mathematics and Computer Science
       Den Dolech 2, P.O. Box 513, 5600 MB Eindhoven, The Netherlands

       Peter Orbaek 
       Linux port and more options. Still maintains the code.

       Eric Rasmussen 
       Added -f option to display custom login messages on different terminals.

       Sat Nov 25 22:51:05 MET 1989