Provided by: util-linux_2.36.1-8ubuntu1_amd64 bug


       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

       •      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 file.

       •      Optionally displays an alternative issue files or directories 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 /bin/login.

       •      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.


       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

              Baud  rates  should  be  specified  in descending order, so that the null character
              (Ctrl-@) can also be used for baud-rate switching.

              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 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.


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

       -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.

              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 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 path
              Specifies a ":" delimited list of files and directories to be displayed instead  of
              /etc/issue  (or other).  All specified files and directories are displayed, missing
              or empty files are silently ignored.   If the specified path is  a  directory  then
              display  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 option.

              Display  the  current  issue file (or other) on the current terminal and exit.  Use
              this option to review the current  setting,  it  is  not  designed  for  any  other
              purpose.  Note that output may use some default or incomplete information as proper
              output depends on terminal and agetty command line.

       -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 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 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 shells.

       -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.  If another baud rates specified  then  the
              original  baud  rate  is also saved to the end of the wanted baud rates list.  This
              can be used to return to the original baud rate after unexpected BREAKs.

       -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.


       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

       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 command line 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 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  can  be used to maintain 3rd-party
       messages independently on the primary system /etc/issue file.

       Since version 2.35 additional locations for issue file and directory are supported. If the
       default  /etc/issue  does  not  exist  than agetty checks for /run/issue and /run/issue.d,
       thereafter for /usr/lib/issue and /usr/lib/issue.d.  The directory /etc  is  expected  for
       host  specific configuration, /run is expected for generated stuff and /usr/lib for static
       distribution maintained configuration.

       The default path maybe overridden by --issue-file option. In this case specified path  has
       to  be  file  or  directory  and  all  the  default issue file and directory locations are

       The issue file feature is possible to completely disable by --noissue option.

       It is possible to review the current issue file by  agetty  --show-issue  on  the  current

       The issue files may contain certain escape codes to display the system name, date, time et
       cetera.  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, 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,  yellow  and  white.   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 can be
              used   to   keep  /etc/issue  distribution  and  release  independent.   Note  that
              \S{ANSI_COLOR} is converted to the real terminal escape sequence.

       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

       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 number 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, 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.


       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.


       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  from