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AGETTY(8)		     System Administration		     AGETTY(8)

NAME
       agetty - alternative Linux 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
	      "--".

       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 switch‐
	      ing.

       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, --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.

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

       -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
	      that  asks for a dial-up password or that uses a different pass‐
	      word file).

       -L, --local-line
	      Force the line to be a local  line  with	no  need  for  carrier
	      detect. This can be useful when you have a locally attached ter‐
	      minal where the serial line does not set the carrier detect sig‐
	      nal.

       -m, --extract-baud
	      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, --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.

       --noclear
	      Do not clear the screen before prompting for the login name (the
	      screen is normally cleared).

       --nohints
	      Do not print hints about Num, Caps and Scroll Locks.

       --nonewline
	      Do not print a newline before writing out /etc/issue.

       --nohostname
	      By  default  the	hostname  will	be  printed.  With this option
	      enabled, no hostname at all will be shown.

       --long-hostname
	      By default the hostname is only printed  until  the  first  dot.
	      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.

       b      Insert the baudrate of the current line.

       d      Insert the current date.

       s      Insert  the  system name, the name of the operating system. Same
	      as `uname -s'.

       l      Insert the name of the current tty line.

       m      Insert the architecture  identifier  of  the  machine.  Same  as
	      `uname -m'.

       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
       (System V only); and so on.

AUTHOR(S)
       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.

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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