AGETTY(8)                    System Administration                   AGETTY(8)

       agetty - alternative Linux getty

       agetty [options] 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  hardwired
       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: Control-U (kill); DEL and
              backspace (erase); carriage return and line feed (end of  line).
              See also the --erase-chars and --kill-chars options.

       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 or directory in-
              stead of /etc/issue or /etc/issue.d.

       o      Optionally does not ask for a login name.

       o      Optionally invokes  a  non-standard  login  program  instead  of

       o      Optionally turns on hardware 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-

              This argument is optional and unnecessary for virtual terminals.

              The  default  for serial terminals is keep the current baud rate
              (see --keep-baud) and if unsuccessful then default to '9600'.

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

              The default is 'vt100', or 'linux' for Linux on a virtual termi-
              nal, or 'hurd' for GNU Hurd on a virtual terminal.

       -8, --8bits
              Assume  that the tty is 8-bit clean, hence disable parity detec-

       -a, --autologin username
              Automatically log in the specified user  without  asking  for  a
              username  or  password.  Using this option causes an -f username
              option and argument to be added to the /bin/login command  line.
              See  --login-options,  which can be used to modify this option's

              Note that --autologin may affect the way how agetty  initializes
              the serial line, because on auto-login agetty does not read from
              the line and it has no opportunity optimize the line setting.

       -c, --noreset
              Do not reset terminal cflags (control  modes).   See  termios(3)
              for more details.

       -E, --remote
              Typically  the  login(1) command is given a remote hostname when
              called by something such  as  telnetd(8).   This  option  allows
              agetty  to  pass what it is using for a hostname to login(1) for
              use in utmp(5).  See --host, login(1), and utmp(5).

              If the --host fakehost option is given, then an -h fakehost  op-
              tion and argument are added to the /bin/login command line.

              If  the --nohostname option is given, then an -H option is added
              to the /bin/login command line.

              See --login-options.

       -f, --issue-file file|directory
              Display the contents of file  instead  of  /etc/issue.   If  the
              specified  path is a directory then displays all files with .is-
              sue file extension in version-sort  order  from  the  directory.
              This  allows custom messages to be displayed on different termi-
              nals.  The --noissue 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

       -H, --host fakehost
              Write the specified fakehost 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.

       -J, --noclear
              Do not clear the screen before prompting for the login name.  By
              default the screen is cleared.

       -l, --login-program login_program
              Invoke the specified login_program instead of /bin/login.   This
              allows  the use of a non-standard login program.  Such a program
              could, for example, ask for a dial-up password or use a  differ-
              ent password file. See --login-options.

       -L, --local-line[=mode]
              Control  the  CLOCAL  line  flag.  The optional mode argument is
              'auto', 'always' or 'never'.  If the mode argument  is  omitted,
              then the default is 'always'.  If the --local-line option is not
              given at all, then the default is 'auto'.

              always Forces the line to be a local line with no need for  car-
                     rier  detect.  This can be useful when you have a locally
                     attached terminal where the serial line does not set  the
                     carrier-detect signal.

              never  Explicitly  clears  the CLOCAL flag from the line setting
                     and the carrier-detect signal is expected on the line.

              auto   The agetty default.  Does not modify the  CLOCAL  setting
                     and follows the setting enabled by the kernel.

       -m, --extract-baud
              Try  to  extract  the  baud rate from 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 --extract-baud feature may fail on heavily-loaded sys-
              tems, you still should enable BREAK  processing  by  enumerating
              all expected baud rates on the command line.

              Display  supported baud rates.  These are determined at compila-
              tion time.

       -n, --skip-login
              Do not prompt the user for a login name.  This can  be  used  in
              connection with the --login-program option to invoke a non-stan-
              dard login process such as a BBS system.   Note  that  with  the
              --skip-login option, agetty gets no input from the user who logs
              in and therefore will not be able to figure out parity,  charac-
              ter 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.

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

       -o, --login-options "login_options"
              Options  and arguments that  are passed to login(1). Where \u is
              replaced by the login name. For example:

                  --login-options '-h darkstar -- \u'

              See --autologin, --login-program and --remote.

              Please read the SECURITY NOTICE below before using this option.

       -p, --login-pause
              Wait  for  any  key before dropping to the login prompt.  Can be
              combined with --autologin to  save  memory  by  lazily  spawning

       -r, --chroot directory
              Change root to the specified directory.

       -R, --hangup
              Call vhangup() to do a virtual hangup of the specified terminal.

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

       -t, --timeout timeout
              Terminate if no user name could be read within timeout  seconds.
              Use  of  this option with hardwired terminal lines is not recom-

       -U, --detect-case
              Turn on support for detecting an uppercase-only terminal.   This
              setting will detect a login name containing only capitals as in-
              dicating 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 file (or oth-
              ers)  and  the  login  prompt.   This   is   useful   with   the
              --init-string option.

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

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

              By default the hostname is only printed  until  the  first  dot.
              With  this option enabled, the fully qualified hostname by geth-
              ostname(3P) or (if not found) by getaddrinfo(3) is shown.

       --erase-chars string
              This option specifies additional characters that should  be  in-
              terpreted  as a backspace ("ignore the previous character") when
              the user types the login name.  The default  additional  'erase'
              has  been  '#',  but  since  util-linux 2.23 no additional erase
              characters are enabled by default.

       --kill-chars string
              This option specifies additional characters that should  be  in-
              terpreted  as a kill ("ignore all previous characters") when the
              user types the login name.  The default  additional  'kill'  has
              been  '@',  but since util-linux 2.23 no additional kill charac-
              ters are enabled by default.

       --chdir directory
              Change directory before the login.

       --delay number
              Sleep seconds before open tty.

       --nice number
              Run login with this priority.

              Ask all running agetty instances to reload and update their dis-
              played  prompts,  if  the user has not yet commenced logging in.
              After doing so the command will exit.  This feature might be un-
              supported on systems without Linux inotify(7).

              Display version information and exit.

       --help Display help text and exit.

       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 hardwired line or a console tty:

              /sbin/agetty 9600 ttyS1

       For  a directly connected terminal without proper carrier-detect wiring
       (try this if your terminal just sleeps instead of giving  you  a  pass-
       word: prompt):

              /sbin/agetty --local-line 9600 ttyS1 vt100

       For an old-style dial-in line with a 9600/2400/1200 baud modem:

              /sbin/agetty --extract-baud --timeout 60 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  mo-
       dem/computer  DCD  track modem/modem DCD, makes a DTR drop cause a dis-
       connection, and turns on auto-answer after 1 ring):

       /sbin/agetty --wait-cr --init-string 'ATE0Q1&D2&C1S0=1 15' 115200 ttyS1

       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 cannot  be  abused  this

       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.

       The  default  issue  file is /etc/issue. If the file exists then agetty
       also checks for /etc/issue.d directory. The directory is  optional  ex-
       tension  to  the  default  issue  file  and content of the directory is
       printed after /etc/issue content. If the /etc/issue does not exist than
       the  directory is ignored. All files with .issue extension from the di-
       rectory are printed in version-sort order. The directory allow to main-
       tain  3rd-party messages independently on the primary system /etc/issue

       The default path maybe overridden by --issue-file option. In this  case
       specified  path  has to be file or directory and the default /etc/issue
       as well as /etc/issue.d are ignored.

       The issue files may contain certain escape codes to display the  system
       name, date, time etcetera.  All escape codes consist of a backslash (\)
       immediately followed by one of the characters listed below.

       4 or 4{interface}
              Insert the IPv4 address of the specified network interface  (for
              example: \4{eth0}).  If the interface argument is not specified,
              then select the first fully configured (UP, non-LOCALBACK,  RUN-
              NING) interface.  If not any configured interface is found, fall
              back to the IP address of the machine's hostname.

       6 or 6{interface}
              The same as \4 but for IPv6.

       b      Insert the baudrate of the current line.

       d      Insert the current date.

       e or e{name}
              Translate the human-readable name to an escape sequence and  in-
              sert it (for example: \e{red}Alert text.\e{reset}).  If the name
              argument is not specified, then insert \033.  The currently sup-
              ported  names  are: black, blink, blue, bold, brown, cyan, dark-
              gray, gray, green, halfbright, lightblue, lightcyan,  lightgray,
              lightgreen,  lightmagenta,  lightred,  magenta,  red, reset, re-
              verse, and yellow.  All unknown names are silently ignored.

       s      Insert the system name (the name of the operating system).  Same
              as 'uname -s'.  See also the \S escape code.

       S or S{VARIABLE}
              Insert  the  VARIABLE  data  from /etc/os-release.  If this file
              does not exist then fall back to  /usr/lib/os-release.   If  the
              VARIABLE  argument  is  not specified, then use PRETTY_NAME from
              the file or the system name (see \s).  This escape  code  allows
              to  keep  /etc/issue distribution and release independent.  Note
              that \S{ANSI_COLOR} is converted to the real terminal escape se-

       l      Insert the name of the current tty line.

       m      Insert the architecture identifier of the machine.  Same as 'un-
              ame -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

       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, that is, the build-date and such.

       An 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

              the system status file.

              printed before the login prompt.

       /etc/os-release /usr/lib/os-release
              operating system identification data.

              problem reports (if syslog(3) is not used).

              init(8) configuration file for SysV-style init daemon.

       The  baud-rate  detection  feature (the --extract-baud 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, al-
       ways use the --extract-baud 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 al-
       ways output with 7-bit characters and space parity.

       The baud-rate detection feature (the  --extract-baud  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.   Er-
       ror  messages are produced if the port argument does not specify a ter-
       minal device; if there is no utmp entry for the current process (System
       V only); and so on.

       Werner Fink <>
       Karel Zak <>

       The  original  agetty  for  serial terminals was written by W.Z. Venema
       <>  and  ported   to   Linux   by   Peter   Orbaek

       The  agetty  command is part of the util-linux package and is available

util-linux                       February 2016                       AGETTY(8)
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