alternative Linux getty
[-8chiLmnsUw] [-a user] [-f
issue_file] [-H login_host] [-I
init] [-l login_program] [-t
timeout] port baud_rate,... [term]
add an example, a script, a trick and tips
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
/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
/sbin/agetty -w -I ’ATE0Q1&D2&C1S0=1\015’
ttyS0:vt100:/bin/agetty -l /bin/login ttyS0 57600
opens a tty port, prompts for a login name and invokes the
/bin/login command. It is normally invoked by
has several non-standard features that are useful for
hard-wired 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:
@ and Control-U (kill); #, DEL and back space (erase);
carriage return and line feed (end of line).
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
Optionally displays an alternative issue file instead of
Optionally does not ask for a login name.
Optionally invokes a non-standard login program instead
Optionally turns on hard-ware flow control
Optionally forces the line to be local with no need for
does not use the /etc/gettydefs (System V) or
/etc/gettytab (SunOS 4) files.
Assume that the tty is 8-bit
clean, hence disable parity detection.
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
Don’t reset terminal
cflags (control modes). See termios(3) for more
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.
Enable hardware (RTS/CTS) flow
control. It is left up to the application to disable
software (XON/XOFF) flow protocol where appropriate.
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
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.
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.
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
Force 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.
Try to extract the baud rate
the CONNECT status message produced by
Hayes(tm)-compatible modems. These status messages are
of the form:
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.
-m feature may fail on heavily-loaded systems,
you still should enable BREAK processing by enumerating all
expected baud rates on the command line.
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
Options that are passed to the
login program. \u is replaced by the login name. The default
/bin/login command line is "/bin/login --
Please read the
SECURITY NOTICE below if you want to use this.
Wait for any key before
dropping to the login prompt. Can be combined with
--autologin to save memory by lazily
Do call vhangup() for a
virtually hangup of the specified terminal.
Try to keep the existing baud
rate. The baud rates from the command line are used when
agetty receives a BREAK character.
Terminate if no user name could
be read within timeout seconds. This option should
probably not be used with hard-wired lines.
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
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
Do not clear the screen before
prompting for the login name (the screen is normally
Do not print a newline before
writing out /etc/issue.
By default the hostname will be
printed. With this option enabled, no hostname at all will
By default the hostname is only
printed until the first dot. With this option enabled, the
full qualified hostname by gethostname() or if not found by
gethostbyname() is shown.
Output version information and
Output help screen and exit.
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 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.
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.
W.Z. Venema <wietse[:at:]wzv.win.tue[:dot:]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[:at:]daimi.aau[:dot:]dk>
Linux port and more options. Still maintains the code.
Eric Rasmussen <ear[:at:]usfirst[:dot:]org>
Added -f option to display custom login messages on different
The agetty command is part of the util-linux package and is
available from ftp://ftp.kernel.org/pub/linux/utils/util-linux/.
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.
/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.
The issue-file (/etc/issue or the file set with the -f
option) may contain 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.
Insert the baudrate of the current line.
Insert the current date.
Insert the system name, the name of the operating system. Same as
Insert the name of the current tty line.
Insert the architecture identifier of the machine. Same as
Insert the nodename of the machine, also known as the hostname.
Same as ’uname -n’.
Insert the NIS domainname of the machine. Same as ’hostname
Insert the DNS domainname of the machine.
Insert the release number of the OS. Same as ’uname
Insert the current time.
Insert the number of current users logged in.
Insert the string "1 user" or "<n> users" where <n>
is the number of current users logged in.
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
This is thingol.orcan.dk (Linux i386 1.1.9) 18:29:30
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 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.
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.
detection feature (the -m option) requires that
the modem emits its status message after raising the