Provided by: util-linux_2.32-0.1ubuntu2_amd64 bug

NAME

       agetty - alternative Linux getty

SYNOPSIS

       agetty [options] 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  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 file.

       ·      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 /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.

ARGUMENTS

       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 "--".

       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 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.

OPTIONS

       -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.

       -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 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 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.

       --list-speeds
              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.

       -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.

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

       --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  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.

       --reload
              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).

       --version
              Display version information and exit.

       --help Display help text 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 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

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 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

       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 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, 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 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
              -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 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 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.

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

       /dev/console
              problem reports (if syslog(3) is not used).

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

BUGS

       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

       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

       Werner Fink ⟨werner@suse.de⟩
       Karel Zak ⟨kzak@redhat.com⟩

       The    original    agetty    for   serial   terminals   was   written   by   W.Z.   Venema
       <wietse@wzv.win.tue.nl> and ported to Linux by Peter Orbaek <poe@daimi.aau.dk>.

AVAILABILITY

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