254 lines
7.2 KiB
Groff
254 lines
7.2 KiB
Groff
.TH AGETTY 8
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.ad
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.fi
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.SH NAME
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agetty \- alternative Linux getty
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.SH SYNOPSIS
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.na
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.nf
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agetty [-ihLmw] [-l login_program] [-I init] [-t timeout] port baud_rate,... [term]
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agetty [-ihLmw] [-l login_program] [-I init] [-t timeout] baud_rate,... port [term]
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.SH DESCRIPTION
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.ad
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.fi
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\fIagetty\fP opens a tty port, prompts for a login name and invokes
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the /bin/login command. It is normally invoked by \fIinit(8)\fP.
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\fIagetty\fP has several \fInon-standard\fP features that are useful
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for hard-wired and for dial-in lines:
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.IP o
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Adapts the tty settings to parity bits and to erase, kill,
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end-of-line and uppercase characters when it reads a login name.
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The program can handle 7-bit characters with even, odd, none or space
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parity, and 8-bit characters with no parity. The following special
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characters are recognized: @ and Control-U (kill); #, DEL and
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back space (erase); carriage return and line feed (end of line).
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.IP o
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Optionally deduces the baud rate from the CONNECT messages produced by
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Hayes(tm)-compatible modems.
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.IP o
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Optionally does not hang up when it is given an already opened line
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(useful for call-back applications).
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.IP o
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Optionally does not display the contents of the \fI/etc/issue\fP file
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(System V only).
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.IP o
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Optionally invokes a non-standard login program instead of
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\fI/bin/login\fP.
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.IP o
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Optionally turns on hard-ware flow control
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.IP o
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Optionally forces the line to be local with no need for carrier detect.
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.PP
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This program does not use the \fI/etc/gettydefs\fP (System V) or
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\fI/etc/gettytab\fP (SunOS 4) files.
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.SH ARGUMENTS
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.na
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.nf
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.fi
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.ad
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.TP
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port
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A path name relative to the \fI/dev\fP directory. If a "-" is
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specified, \fIagetty\fP assumes that its standard input is
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already connected to a tty port and that a connection to a
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remote user has already been established.
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.sp
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Under System V, a "-" \fIport\fP argument should be preceded
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by a "--".
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.TP
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baud_rate,...
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A comma-separated list of one or more baud rates. Each time
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\fIagetty\fP receives a BREAK character it advances through
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the list, which is treated as if it were circular.
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.sp
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Baud rates should be specified in descending order, so that the
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null character (Ctrl-@) can also be used for baud rate switching.
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.TP
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term
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The value to be used for the TERM environment variable. This overrides
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whatever init(8) may have set, and is inherited by login and the shell.
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.SH OPTIONS
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.na
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.nf
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.fi
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.ad
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.TP
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-h
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Enable hardware (RTS/CTS) flow control. It is left up to the
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application to disable software (XON/XOFF) flow protocol where
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appropriate.
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.TP
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-i
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Do not display the contents of \fI/etc/issue\fP before writing the
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login prompt. Terminals or communications hardware may become confused
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when receiving lots of text at the wrong baud rate; dial-up scripts
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may fail if the login prompt is preceded by too much text.
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.TP
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-I initstring
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Set an initial string to be sent to the tty or modem before sending
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anything else. This may be used to initialize a modem. Non printable
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characters may be sent by writing their octal code preceded by a
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backslash (\\). For example to send a linefeed character (ASCII 10,
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octal 012) write \\012.
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.PP
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.TP
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-l login_program
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Invoke the specified \fIlogin_program\fP instead of /bin/login.
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This allows the use of a non-standard login program (for example,
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one that asks for a dial-up password or that uses a different
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password file).
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.TP
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-m
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Try to extract the baud rate the \fIconnect\fP status message
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produced by some Hayes(tm)-compatible modems. These status
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messages are of the form: "<junk><speed><junk>".
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\fIagetty\fP assumes that the modem emits its status message at
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the same speed as specified with (the first) \fIbaud_rate\fP value
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on the command line.
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.sp
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Since the \fI-m\fP feature may fail on heavily-loaded systems,
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you still should enable BREAK processing by enumerating all
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expected baud rates on the command line.
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.TP
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-t timeout
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Terminate if no user name could be read within \fItimeout\fP
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seconds. This option should probably not be used with hard-wired
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lines.
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.TP
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-L
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Force the line to be local line with no need for carrier detect. This can
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be useful when you have locally attached terminal where the serial line
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does not set the carrier detect signal.
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.TP
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-w
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Wait for the user or the modem to send a carriage-return or a linefeed
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character before sending the /etc/issue file and the login prompt.
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.PP
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.SH EXAMPLES
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.na
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.nf
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This section shows sample entries for the \fI/etc/inittab\fP file.
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For a hard-wired line:
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.ti +5
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tty1:con80x60:/sbin/agetty 9600 tty1
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For a dial-in line with a 9600/2400/1200 baud modem:
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.ti +5
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ttyS1:dumb:/sbin/agetty -mt60 ttyS1 9600,2400,1200
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These examples assume you use the simpleinit(8) init program for Linux.
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If you use a SysV like init (does /etc/inittab mention "respawn"?), refer
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to the appropriate manual page.
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.SH ISSUE ESCAPES
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The \fI/etc/issue\fP file may contain certain escape codes to display the
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system name, date and time etc. All escape codes consist of a backslash
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(\\) immediately followed by one of the letters explained below.
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.TP
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b
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Insert the baudrate of the current line.
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.TP
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d
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Insert the current date.
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.TP
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s
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Insert the system name, the name of the operating system.
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.TP
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l
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Insert the name of the current tty line.
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.TP
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m
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Insert the architecture identifier of the machine, eg. i486
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.TP
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n
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Insert the nodename of the machine, also known as the hostname.
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.TP
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o
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Insert the domainname of the machine.
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.TP
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r
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Insert the release number of the OS, eg. 1.1.9.
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.TP
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t
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Insert the current time.
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.TP
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u
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Insert the number of current users logged in.
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.TP
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U
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Insert the string "1 user" or "<n> users" where <n> is the number of current
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users logged in.
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.TP
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v
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Insert the version of the OS, eg. the build-date etc.
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.TP
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Example: On my system, the following \fI/etc/issue\fP file:
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.na
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.nf
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.ti +.5
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This is \\n.\\o (\\s \\m \\r) \\t
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.TP
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displays as
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.ti +.5
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This is thingol.orcan.dk (Linux i386 1.1.9) 18:29:30
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.fi
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.SH FILES
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.na
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.nf
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/var/run/utmp, the system status file.
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/etc/issue, printed before the login prompt (System V only).
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/dev/console, problem reports (if syslog(3) is not used).
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/etc/inittab (Linux simpleinit(8) configuration file).
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.SH BUGS
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.ad
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.fi
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The baud-rate detection feature (the \fI-m\fP option) requires that
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\fIagetty\fP be scheduled soon enough after completion of a dial-in
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call (within 30 ms with modems that talk at 2400 baud). For robustness,
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always use the \fI-m\fP option in combination with a multiple baud
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rate command-line argument, so that BREAK processing is enabled.
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The text in the /etc/issue file and the login prompt
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are always output with 7-bit characters and space parity.
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The baud-rate detection feature (the \fI-m\fP option) requires that
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the modem emits its status message \fIafter\fP raising the DCD line.
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.SH DIAGNOSTICS
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.ad
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.fi
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Depending on how the program was configured, all diagnostics are
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written to the console device or reported via the syslog(3) facility.
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Error messages are produced if the \fIport\fP argument does not
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specify a terminal device; if there is no utmp entry for the
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current process (System V only); and so on.
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.SH AUTHOR(S)
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.na
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.nf
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W.Z. Venema <wietse@wzv.win.tue.nl>
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Eindhoven University of Technology
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Department of Mathematics and Computer Science
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Den Dolech 2, P.O. Box 513, 5600 MB Eindhoven, The Netherlands
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Peter Orbaek <poe@daimi.aau.dk>
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Linux port.
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.SH CREATION DATE
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.na
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.nf
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Sat Nov 25 22:51:05 MET 1989
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.SH LAST MODIFICATION
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.na
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.nf
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91/09/01 23:22:00
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.SH VERSION/RELEASE
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.na
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.nf
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1.29
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