AGETTY(8)                   System Administration                  AGETTY(8)

NAME         top

       agetty - alternative Linux getty

SYNOPSIS         top

       agetty [options] port [baud_rate...] [term]

DESCRIPTION         top

       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:

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

       ·      Optionally deduces the baud rate  from  the  CONNECT  messages
              produced by Hayes(tm)-compatible modems.

       ·      Optionally does not hang up when it is given an already opened
              line (useful for call-back applications).

       ·      Optionally does not display the  contents  of  the  /etc/issue

       ·      Optionally  displays  an  alternative  issue file or directory
              instead of /etc/issue or /etc/issue.d.

       ·      Optionally does not ask for a login name.

       ·      Optionally invokes a non-standard  login  program  instead  of

       ·      Optionally turns on hardware flow control.

       ·      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         top

       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 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

              This   argument   is  optional  and  unnecessary  for  virtual

              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
              login and the shell.

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

OPTIONS         top

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

       -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 behavior.

       -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
              option 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
              .issue   file   extension   in  version-sort  order  from  the
              directory.  This allows custom messages  to  be  displayed  on
              different  terminals.  The --noissue option will override this

       -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 preceded 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 different 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
                     carrier  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
              systems,   you   still   should  enable  BREAK  processing  by
              enumerating all expected baud rates on the command line.

              Display  supported  baud  rates.   These  are  determined   at
              compilation 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-
              standard  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,  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

       -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

       -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

       -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 recommended.

       -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 file (or
              others) 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
              enabled, 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
              gethostname(3P) or (if not found) by getaddrinfo(3) is shown.

       --erase-chars string
              This option specifies additional  characters  that  should  be
              interpreted  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
              interpreted  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
              characters 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
              displayed  prompts,  if the user has not yet commenced logging
              in.  After doing so the command will exit.  This feature might
              be unsupported on systems without Linux inotify(7).

              Display version information and exit.

       --help Display help text and exit.

EXAMPLES         top

       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
       password: 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
       modem/computer DCD track modem/modem DCD, makes a DTR drop cause a
       disconnection, 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 depending on how the login binary parses the command
       line that might not be sufficient.  Check that the used login program
       cannot 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 FILES         top

       The default issue file is /etc/issue. If the file exists then agetty
       also checks for /etc/issue.d directory. The directory is optional
       extension 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 directory are printed in version-sort order. The directory allow
       to maintain 3rd-party messages independently on the primary system
       /etc/issue file.

       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

       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, RUNNING) 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
              insert it (for example: \e{red}Alert text.\e{reset}).  If the
              name argument is not specified, then insert \033.  The
              currently supported names are: black, blink, blue, bold,
              brown, cyan, darkgray, gray, green, halfbright, lightblue,
              lightcyan, lightgray, lightgreen, lightmagenta, lightred,
              magenta, red, reset, reverse, 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

       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

       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
              number of current users logged in.

       v      Insert the version of the OS, that is, the build-date and

       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

FILES         top

              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.

BUGS         top

       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,  always 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
       always 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.

DIAGNOSTICS         top

       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.

AUTHORS         top

       Werner Fink ⟨⟩
       Karel Zak ⟨⟩

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

AVAILABILITY         top

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

COLOPHON         top

       This page is part of the util-linux (a random collection of Linux
       utilities) project.  Information about the project can be found at 
       ⟨⟩.  If you have a
       bug report for this manual page, send it to  This page was obtained from the
       project's upstream Git repository
       ⟨git://⟩ on
       2018-04-30.  (At that time, the date of the most recent commit that
       was found in the repository was 2018-04-30.)  If you discover any
       rendering problems in this HTML version of the page, or you believe
       there is a better or more up-to-date source for the page, or you have
       corrections or improvements to the information in this COLOPHON
       (which is not part of the original manual page), send a mail to

util-linux                      February 2016                      AGETTY(8)

Pages that refer to this page: tty(4)ttyS(4)issue(5)systemd.exec(5)ttytype(5)utmp(5)systemd-getty-generator(8)