294 lines
8.9 KiB
Groff
294 lines
8.9 KiB
Groff
'\" -*- coding: UTF-8 -*-
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.\" Copyright (C) 1998-2001 Miquel van Smoorenburg.
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.\"
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.\" This program is free software; you can redistribute it and/or modify
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.\" it under the terms of the GNU General Public License as published by
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.\" the Free Software Foundation; either version 2 of the License, or
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.\" (at your option) any later version.
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.\"
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.\" This program is distributed in the hope that it will be useful,
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.\" but WITHOUT ANY WARRANTY; without even the implied warranty of
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.\" MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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.\" GNU General Public License for more details.
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.\"
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.\" You should have received a copy of the GNU General Public License
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.\" along with this program; if not, write to the Free Software
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.\" Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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.\"
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.\"{{{}}}
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.\"{{{ Title
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.TH INITTAB 5 "Dec 4, 2001" "sysvinit " "File Formats"
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.\"}}}
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.\"{{{ Name
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.SH NAME
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inittab \- format of the inittab file used by the sysv-compatible init
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process
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.\"}}}
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.\"{{{ Description
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.SH DESCRIPTION
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The \fBinittab\fP file describes which processes are started at bootup and
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during normal operation (e.g.\& /etc/init.d/boot, /etc/init.d/rc, gettys...).
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.BR init (8)
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distinguishes multiple \fIrunlevels\fP, each of which can have its own set of
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processes that are started. Valid runlevels are \fB0\fP\-\fB6\fP plus
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\fBA\fP, \fBB\fP, and \fBC\fP for \fBondemand\fP entries. An entry in the
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\fBinittab\fP file has the following format:
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.RS
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.sp
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\fIid\fP:\fIrunlevels\fP:\fIaction\fP:\fIprocess\fP
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.sp
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.RE
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Lines beginning with `#' are ignored.
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.\"{{{ id
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.IP \fIid\fP
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is a unique sequence of 1-4 characters which identifies an entry in
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.B inittab
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(for versions of sysvinit compiled with the \fIold\fP libc5 (< 5.2.18) or
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a.out libraries the limit is 2 characters).
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.sp
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Note: traditionally, for getty and other login processes, the value of the
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\fIid\fP field is kept the same as the suffix of the corresponding tty, e.g.\&
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\fB1\fP for \fBtty1\fP. Some ancient login accounting programs might
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expect this, though I can't think of any.
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.\"}}}
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.\"{{{ runlevels
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.IP \fIrunlevels\fP
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lists the runlevels for which the specified action should be taken.
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.\"}}}
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.\"{{{ action
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.IP \fIaction\fP
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describes which action should be taken.
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.\"}}}
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.\"{{{ process
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.IP \fIprocess\fP
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specifies the process to be executed. If the process field starts with
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a `+' character,
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.B init
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will not do utmp and wtmp accounting for that process. This is needed for
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gettys that insist on doing their own utmp/wtmp housekeeping. This is also
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a historic bug. The length of this field is limited to 127 characters.
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Please note that including certain characters in the process field will result
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in
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.B init
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attempting to launch a shell to interpret the command contained in the process field.
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The characters which will trigger a shell are:
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.B ~`!$^&*()=|\{}[];\"'<>?
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On systems which do not have a shell to be launched or which do not wish to
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use a shell to interpret the process field, the process field can be prefixed
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with the @ symbol. The @ will be ignored and everything followed will be treated
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as a command to be launched, literally, by the
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.B init
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service.
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In cases where both a + and @ sign are to be used (to turn off logging and shell
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interpretation), place the + sign before the @ symbol. Both flags will be handled
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and then everything following the @ will be handled by
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.B init
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.\"}}}
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.PP
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The \fIrunlevels\fP field may contain multiple characters for different
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runlevels. For example, \fB123\fP specifies that the process should be
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started in runlevels 1, 2, and 3.
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The \fIrunlevels\fP for \fBondemand\fP entries may contain an \fBA\fP,
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\fBB\fP, or \fBC\fP. The \fIrunlevels\fP field of \fBsysinit\fP,
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\fBboot\fP, and \fBbootwait\fP entries are ignored.
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.PP
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When the system runlevel is changed, any running processes that are not
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specified for the new runlevel are killed, first with \s-2SIGTERM\s0,
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then with \s-2SIGKILL\s0.
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.PP
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Valid actions for the \fIaction\fP field are:
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.\"{{{ respawn
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.IP \fBrespawn\fP
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The process will be restarted whenever it terminates (e.g.\& getty).
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.\"}}}
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.\"{{{ wait
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.IP \fBwait\fP
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The process will be started once when the specified runlevel is entered and
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.B init
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will wait for its termination.
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.\"}}}
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.\"{{{ once
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.IP \fBonce\fP
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The process will be executed once when the specified runlevel is
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entered.
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.\"}}}
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.\"{{{ boot
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.IP \fBboot\fP
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The process will be executed during system boot. The \fIrunlevels\fP
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field is ignored.
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.\"}}}
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.\"{{{ bootwait
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.IP \fBbootwait\fP
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The process will be executed during system boot, while
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.B init
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waits for its termination (e.g.\& /etc/rc).
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The \fIrunlevels\fP field is ignored.
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.\"}}}
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.\"{{{ off
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.IP \fBoff\fP
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This does nothing.
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.\"}}}
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.\"{{{ ondemand
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.IP \fBondemand\fP
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A process marked with an \fBondemand\fP runlevel will be executed
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whenever the specified \fBondemand\fP runlevel is called. However, no
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runlevel change will occur (\fBondemand\fP runlevels are `a', `b',
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and `c').
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.\"}}}
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.\"{{{ initdefault
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.IP \fBinitdefault\fP
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An \fBinitdefault\fP entry specifies the runlevel which should be
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entered after system boot. If none exists,
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.B init
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will ask for a runlevel on the console. The \fIprocess\fP field is ignored.
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.\"}}}
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.\"{{{ sysinit
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.IP \fBsysinit\fP
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The process will be executed during system boot. It will be
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executed before any \fBboot\fP or \fB bootwait\fP entries.
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The \fIrunlevels\fP field is ignored.
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.\"}}}
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.\"{{{ powerwait
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.IP \fBpowerwait\fP
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The process will be executed when the power goes down. \fBinit\fR is usually
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informed about this by a process talking to a UPS connected to the computer.
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\fBinit\fP will wait for the process to finish before continuing.
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.\"}}}
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.\"{{{ powerfail
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.IP \fBpowerfail\fP
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As for \fBpowerwait\fP, except that \fBinit\fP does not wait for the process's
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completion.
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.\"}}}
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.\"{{{ powerokwait
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.IP \fBpowerokwait\fP
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This process will be executed as soon as \fBinit\fP is informed that the
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power has been restored.
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.\"}}}
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.\"{{{ powerfailnow
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.IP \fBpowerfailnow\fP
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This process will be executed when \fBinit\fP is told that the battery of
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the external UPS is almost empty and the power is failing (provided that the
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external UPS and the monitoring process are able to detect this condition).
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.\"}}}
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.\"{{{ ctrlaltdel
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.IP \fBctrlaltdel\fP
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The process will be executed when \fBinit\fP receives the \fBSIGINT\fP signal.
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This means that someone on the system console has pressed the
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\fBCTRL\-ALT\-DEL\fP key combination. Typically one wants to execute some
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sort of \fBshutdown\fP either to get into single\-user level or to
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reboot the machine.
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.\"}}}
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.\"{{{ kbrequest
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.IP \fBkbrequest\fP
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The process will be executed when \fBinit\fP receives a signal from the
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keyboard handler that a special key combination was pressed on the
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console keyboard.
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.sp
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The documentation for this function is not complete yet; more documentation
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can be found in the kbd-x.xx packages (most recent was kbd-0.94 at
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the time of this writing). Basically you want to map some keyboard
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combination to the "KeyboardSignal" action. For example, to map Alt-Uparrow
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for this purpose use the following in your keymaps file:
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.RS
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.sp
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alt keycode 103 = KeyboardSignal
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.sp
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.RE
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.\"}}}
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.\"}}}
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.\"{{{ Examples
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.SH EXAMPLES
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This is an example of a inittab which resembles the old Linux inittab:
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.RS
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.sp
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.nf
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.ne 7
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# inittab for linux
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id:1:initdefault:
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rc::bootwait:/etc/rc
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1:1:respawn:/etc/getty 9600 tty1
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2:1:respawn:/etc/getty 9600 tty2
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3:1:respawn:/etc/getty 9600 tty3
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4:1:respawn:/etc/getty 9600 tty4
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.fi
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.sp
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.RE
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This inittab file executes \fI/etc/rc\fP during boot and starts gettys
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on tty1\-tty4.
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.PP
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A more elaborate \fBinittab\fP with different runlevels (see the comments
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inside):
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.RS
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.sp
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.nf
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.ne 19
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# Level to run in
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id:2:initdefault:
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# Boot-time system configuration/initialization script.
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si::sysinit:/etc/init.d/rcS
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# What to do in single-user mode.
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~:S:wait:/sbin/sulogin
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# /etc/init.d executes the S and K scripts upon change
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# of runlevel.
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#
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# Runlevel 0 is halt.
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# Runlevel 1 is single-user.
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# Runlevels 2-5 are multi-user.
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# Runlevel 6 is reboot.
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l0:0:wait:/etc/init.d/rc 0
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l1:1:wait:/etc/init.d/rc 1
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l2:2:wait:/etc/init.d/rc 2
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l3:3:wait:/etc/init.d/rc 3
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l4:4:wait:/etc/init.d/rc 4
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l5:5:wait:/etc/init.d/rc 5
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l6:6:wait:/etc/init.d/rc 6
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# What to do at the "3 finger salute".
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ca::ctrlaltdel:/sbin/shutdown -t1 -h now
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# Runlevel 2,3: getty on virtual consoles
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# Runlevel 3: getty on terminal (ttyS0) and modem (ttyS1)
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1:23:respawn:/sbin/getty tty1 VC linux
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2:23:respawn:/sbin/getty tty2 VC linux
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3:23:respawn:/sbin/getty tty3 VC linux
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4:23:respawn:/sbin/getty tty4 VC linux
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S0:3:respawn:/sbin/getty -L 9600 ttyS0 vt320
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S1:3:respawn:/sbin/mgetty -x0 -D ttyS1
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.fi
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.sp
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.RE
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.\"}}}
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.\"{{{ Files
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.SH FILES
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/etc/inittab
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.\"}}}
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.\"{{{ Author
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.SH AUTHOR
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\fBinit\fP was written by
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.MT miquels@\:cistron\:.nl
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Miquel van Smoorenburg
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.ME .
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This manual page was written by
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.MT lederer@\:francium\:.informatik\:.uni-bonn\:.de
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Sebastian Lederer
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.ME
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and modified by
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.MT u31b3hs@\:pool\:.informatik\:.rwth-aachen\:.de
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Michael Haardt
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.ME .
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.\"}}}
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.\"{{{ See also
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.SH "SEE ALSO"
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.BR init (8),
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.BR telinit (8)
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.\"}}}
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