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docs: improve agetty.8 manual page 

Reviewed-by: J William Piggott <elseifthen@gmx.com>
Signed-off-by: Sami Kerola <kerolasa@iki.fi>
This commit is contained in:
Sami Kerola 2017-04-03 22:17:52 +01:00
parent 343cc27559
commit c9151874b6
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GPG Key ID: A9553245FDE9B739
1 changed files with 68 additions and 61 deletions
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129
term-utils/agetty.8
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@ -89,18 +89,17 @@ or 'hurd' for GNU Hurd on a virtual terminal.
Assume that the tty is 8-bit clean, hence disable parity detection.
.TP
\-a, \-\-autologin \fIusername\fP
Log the specified user automatically in without asking for a login name and
password. The \-f \fIusername\fP option is added to the \fB/bin/login\fP
command line by default. The \-\-login\-options option changes this default
behavior and then only \\u is replaced by the \fIusername\fP and no other
option is added to the login command line.
Automatically log in the specified user without asking username or password.
Use of this option causes \fB\-f \fIusername\fR option and argument to be
added to the \fB/bin/login\fP command line. This option can combined with
\fB\-\-login\-options\fR, and then \\u is replaced by the \fIusername\fR.
.TP
\-c, \-\-noreset
Don't reset terminal cflags (control modes). See \fBtermios\fP(3) for more
Do not reset terminal cflags (control modes). See \fBtermios\fP(3) for more
details.
.TP
\-E, \-\-remote
If an \fB\-\-host\fP \fIfakehost\fP option is given, then an \fB\-h\fP
If the \fB\-\-host\fP \fIfakehost\fP option is given, then an \fB\-h\fP
\fIfakehost\fP option and argument are added to the \fB/bin/login\fP
command line.
.IP
@ -110,7 +109,7 @@ is added to the \fB/bin/login\fP command line.
\-f, \-\-issue\-file \fIissue_file\fP
Display the contents of \fIissue_file\fP instead of \fI/etc/issue\fP.
This allows custom messages to be displayed on different terminals.
The \-i option will override this option.
The \-\-noissue option will override this option.
.TP
\-h, \-\-flow\-control
Enable hardware (RTS/CTS) flow control. It is left up to the
@ -118,10 +117,10 @@ application to disable software (XON/XOFF) flow protocol where
appropriate.
.TP
\-H, \-\-host \fIlogin_host\fP
Write the specified \fIlogin_host\fP into the utmp file. (Normally,
Write the specified \fIlogin_host\fP into the utmp file. Normally,
no login host is given, since \fBagetty\fP is used for local hardwired
connections and consoles. However, this option can be useful for
identifying terminal concentrators and the like.)
identifying terminal concentrators and the like.
.TP
\-i, \-\-noissue
Do not display the contents of \fI/etc/issue\fP (or other) before writing the
@ -137,29 +136,36 @@ backslash (\\). For example, to send a linefeed character (ASCII 10,
octal 012), write \\012.
.TP
\-J, \-\-noclear
Do not clear the screen before prompting for the login name
(the screen is normally cleared).
Do not clear the screen before prompting for the login name.
By default screen is cleared.
.TP
\-l, \-\-login\-program \fIlogin_program\fP
Invoke the specified \fIlogin_program\fP 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
password file).
Invoke the specified \fIlogin_program\fP instead of /bin/login. This allows
the use of a non-standard login program. Such program could for example
ask for a dial-up password or use a different password file.
.TP
\-L, \-\-local\-line[=\fImode\fP]
Control the CLOCAL line flag. The optional \fImode\fP argument is 'auto', 'always' or 'never'.
If the \fImode\fP argument is omitted, then the default is 'always'. If the
\-\-local\-line option is not given at all, then the default is 'auto'.
The \fImode\fP '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.
The \fImode\fP 'never' explicitly clears the CLOCAL flag from the line setting and
the carrier-detect signal is expected on the line.
The \fImode\fP 'auto' (agetty default) does not modify the CLOCAL setting
and follows the setting enabled by the kernel.
.PP
.RS
.PD 1
.TP
\fIalways\fR
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.
.TP
\fInever\fR
Explicitly clears the CLOCAL flag from the line setting and the
carrier-detect signal is expected on the line.
.TP
\fIauto\fR
The \fBagetty\fR default. Does not modify the CLOCAL setting and follows
the setting enabled by the kernel.
.PD
.RE
.TP
\-m, \-\-extract\-baud
Try to extract the baud rate from the CONNECT status message
@ -169,29 +175,30 @@ messages are of the form: "<junk><speed><junk>".
the same speed as specified with (the first) \fIbaud_rate\fP value
on the command line.
.sp
Since the \fB\-m\fP feature may fail on heavily-loaded systems,
you still should enable BREAK processing by enumerating all
Since the \fB\-\-extract\-baud\fP feature may fail on heavily-loaded
systems, you still should enable BREAK processing by enumerating all
expected baud rates on the command line.
.TP
\-n, \-\-skip\-login
Do not prompt the user for a login name. This can be used in
connection with the \fB\-l\fP option to invoke a non-standard login process such
as a BBS system. Note that with the \-n option, \fBagetty\fR gets no input from
the 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 \fBagetty\fR starts (usually /bin/login)
is run as root.
Do not prompt the user for a login name. This can be used in connection
with the \fB\-\-login\-program\fP option to invoke a non-standard login
process such as a BBS system. Note that with the \fB\-\-skip\-login\fR
option, \fBagetty\fR 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 \fBagetty\fR starts (usually /bin/login) is run as root.
.TP
\-N, \-\-nonewline
Do not print a newline before writing out /etc/issue.
.TP
\-o, \-\-login\-options "\fIlogin_options\fP"
\-o, \-\-login\-options "\fI/path/command --option argument -- \\u\fP"
Options that are passed to the login program. \\u is replaced
by the login name. The default \fB/bin/login\fP command line
is "/bin/login -- <username>".
Please read the SECURITY NOTICE below if you want to use this.
by the login name. The default is "/bin/login -- \\u".
.IP
Also see the \fB\-\-autologin\fR and \fB\-\-remote\fR options.
.IP
Please read the SECURITY NOTICE below before using this option.
.TP
\-p, \-\-login\-pause
Wait for any key before dropping to the login prompt. Can be combined
@ -208,9 +215,8 @@ Try to keep the existing baud rate. The baud rates from
the command line are used when agetty receives a BREAK character.
.TP
\-t, \-\-timeout \fItimeout\fP
Terminate if no user name could be read within \fItimeout\fP
seconds. This option should probably not be used with hardwired
lines.
Terminate if no user name could be read within \fItimeout\fP seconds.
Use of this option with hardwired terminal lines is not recommended.
.TP
\-U, \-\-detect\-case
Turn on support for detecting an uppercase-only terminal. This setting
@ -221,7 +227,8 @@ 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 \fI/etc/issue\fP (or other) file
and the login prompt. Very useful in connection with the \-I option.
and the login prompt. This is useful with the \-\-init\-string
option.
.TP
\-\-nohints
Do not print hints about Num, Caps and Scroll Locks.
@ -232,8 +239,8 @@ no hostname at all will be shown.
.TP
\-\-long\-hostname
By default the hostname is only printed until the first dot. With
this option enabled, the fully qualified hostname by gethostname()
or (if not found) by getaddrinfo() is shown.
this option enabled, the fully qualified hostname by \fBgethostname\fR(3P)
or (if not found) by \fBgetaddrinfo\fR(3) is shown.
.TP
\-\-erase\-chars \fIstring\fP
This option specifies additional characters that should be interpreted as a
@ -284,13 +291,13 @@ For a directly connected terminal without proper carrier-detect wiring
prompt):
.RS
/sbin/agetty \-L 9600 ttyS1 vt100
/sbin/agetty \-\-local\-line 9600 ttyS1 vt100
.RE
For an old-style dial-in line with a 9600/2400/1200 baud modem:
.RS
/sbin/agetty \-mt60 ttyS1 9600,2400,1200
/sbin/agetty \-\-extract\-baud \-\-timeout 60 ttyS1 9600,2400,1200
.RE
For a Hayes modem with a fixed 115200 bps interface to the machine
@ -299,7 +306,7 @@ modem/computer DCD track modem/modem DCD, makes a DTR drop cause a
disconnection, and turns on auto-answer after 1 ring):
.RS
/sbin/agetty \-w \-I 'ATE0Q1&D2&C1S0=1\\015' 115200 ttyS1
/sbin/agetty \-\-wait\-cr \-\-init\-string 'ATE0Q1&D2&C1S0=1\\015' 115200 ttyS1
.RE
.SH SECURITY NOTICE
@ -316,7 +323,7 @@ not be interpreted as options. Use this feature if available by passing "\-\-"
before the username gets passed by \\u.
.SH ISSUE ESCAPES
The issue-file (\fI/etc/issue\fP, or the file set with the \fB\-f\fP option)
The issue-file (\fI/etc/issue\fP, or the file set with the \fB\-\-issue\-file\fP option)
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.
@ -347,7 +354,7 @@ lightmagenta, lightred, magenta, red, reset, reverse, and yellow. All unknown
names are silently ignored.
.TP
s
Insert the system name (the name of the operating system). Same as `uname \-s'.
Insert the system name (the name of the operating system). Same as 'uname \-s'.
See also the \\S escape code.
.TP
S or S{VARIABLE}
@ -362,19 +369,19 @@ l
Insert the name of the current tty line.
.TP
m
Insert the architecture identifier of the machine. Same as `uname \-m'.
Insert the architecture identifier of the machine. Same as 'uname \-m'.
.TP
n
Insert the nodename of the machine, also known as the hostname. Same as `uname \-n'.
Insert the nodename of the machine, also known as the hostname. Same as 'uname \-n'.
.TP
o
Insert the NIS domainname of the machine. Same as `hostname \-d'.
Insert the NIS domainname of the machine. Same as 'hostname \-d'.
.TP
O
Insert the DNS domainname of the machine.
.TP
r
Insert the release number of the OS. Same as `uname \-r'.
Insert the release number of the OS. Same as 'uname \-r'.
.TP
t
Insert the current time.
@ -387,7 +394,7 @@ Insert the string "1 user" or "<n> users" where <n> is the number of current
users logged in.
.TP
v
Insert the version of the OS, e.g. the build-date etc.
Insert the version of the OS, that is the build-date and such.
.PP
An example. On my system, the following \fI/etc/issue\fP file:
.sp
@ -426,22 +433,22 @@ problem reports (if syslog(3) is not used).
.SH BUGS
.ad
.fi
The baud-rate detection feature (the \fB\-m\fP option) requires that
The baud-rate detection feature (the \fB\-\-extract\-baud\fP option) requires that
\fBagetty\fP 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 \fB\-m\fP option in combination with a multiple baud
always use the \fB\-\-extract\-baud\fP option in combination with a multiple baud
rate command-line argument, so that BREAK processing is enabled.
The text in the \fI/etc/issue\fP file (or other) and the login prompt
are always output with 7-bit characters and space parity.
The baud-rate detection feature (the \fB\-m\fP option) requires that
The baud-rate detection feature (the \fB\-\-extract\-baud\fP option) requires that
the modem emits its status message \fIafter\fP raising the DCD line.
.SH DIAGNOSTICS
.ad
.fi
Depending on how the program was configured, all diagnostics are
written to the console device or reported via the syslog(3) facility.
written to the console device or reported via the \fBsyslog\fR(3) facility.
Error messages are produced if the \fIport\fP argument does not
specify a terminal device; if there is no utmp entry for the
current process (System V only); and so on.