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    Command:

    getty

    
    
    
    

    SYNOPSIS

           agetty  [-8chiLmnsUw]  [-a  user]  [-f  issue_file] [-H login_host] [-I
           init] [-l login_program] [-t timeout] port baud_rate,...  [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).
    
           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 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/get-
           tytab (SunOS 4) files.
    
    
    

    ARGUMENTS

           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
    
    
    

    OPTIONS

           -8, --8bits
                  Assume  that the tty is 8-bit clean, hence disable parity detec-
                  tion.
    
           -a, --autologin username
                  Log the specified user automatically in  without  asking  for  a
                  login  name and password. The -f username option is added to the
                  /bin/login command line by default. The  --login-options  option
                  changes  this  default behaviour and then only \u is replaced by
                  the username and no other option is added to the  login  command
                  line.
    
           -c, --noreset
                  Don't  reset terminal cflags (control modes). See termios(3) for
                  more details.
    
           -f, --issue-file 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.
    
           -h, --flow-control
                  Enable hardware (RTS/CTS) flow control. It is  left  up  to  the
                  application  to  disable software (XON/XOFF) flow protocol where
                  appropriate.
    
           -H, --host 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.
    
           -i, --noissue
                  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.
    
           -I, --init-string 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 login_program
                  Invoke  the specified login_program instead of /bin/login.  This
                  allows the use of a non-standard login program (for example, one
                  (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, --skip-login
                  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
                  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.
    
           -o, --login-options "login_options"
                  Options  that  are passed to the login program.  \u is  replaced
                  by  the  login  name.  The  default  /bin/login  command line is
                  "/bin/login -- <username>".
    
                  Please read the SECURITY NOTICE below if you want to use this.
    
           -p, --login-pause
                  Wait for any key before dropping to the login  prompt.   Can  be
                  combined  with  --autologin  to  save  memory by lazily spawning
                  shells.
    
           -R, --hangup
                  Do call vhangup() for a virtually hangup of the specified termi-
                  nal.
    
           -s, --keep-baud
                  Try to keep the existing baud rate. The baud rates from the com-
                  mand line are used when agetty receives a BREAK character.
    
           -t, --timeout timeout
                  Terminate if no user name could be read within timeout  seconds.
                  This option should probably not be used with hard-wired lines.
    
           -U, --detect-case
                  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-cr
                  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.
                  With  this  option enabled, the full qualified hostname by geth-
                  ostname() or if not found by gethostbyname() is shown.
    
           --version
                  Output version information and exit.
    
           --help Output help screen and exit.
    
    
    

    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
    
    
    

    SECURITY NOTICE

           If  you  use  the --login-program and --login-options options, be aware
           that a malicious user may try to enter lognames with embedded  options,
           which  then get passed to the used login program. Agetty does check for
           a leading "-" and makes sure the logname gets passed as  one  parameter
           (so embedded spaces will not create yet another parameter), but depend-
           ing on how the login binary parses the command line that might  not  be
           sufficient.   Check  that the used login program can not be abused this
           way.
    
           Some  programs use "--" to indicate that the rest  of  the  commandline
           should  not be interpreted as options. Use this feature if available by
           passing "--" before the username gets passed by \u.
    
    
    

    ISSUE ESCAPES

           The issue-file (/etc/issue or the file set with the -f option) may con-
           tain  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.
           n      Insert  the nodename of the machine, also known as the hostname.
                  Same as 'uname -n'.
    
           o      Insert the NIS domainname of the machine. Same as 'hostname -d'.
    
           O      Insert the DNS domainname of the machine.
    
           r      Insert the release number of the OS. Same as 'uname -r'.
    
           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 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 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  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
    
    
    

    AVAILABILITY

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

    util-linux May 2011 AGETTY(8)

    
    
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