Drop hurd specific dependency on libc0.3 (>= 2.3.2.ds1-12). It is
no longer needed according to Michael Bunk. Patch from Michael Biebl.
This commit is contained in:
Petter Reinholdtsen
214
man/shutdown.8
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214
man/shutdown.8
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'\" -*- coding: UTF-8 -*-
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.\" Copyright (C) 1998-2003 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 SHUTDOWN 8 "November 12, 2003" "" "Linux System Administrator's Manual"
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.\"}}}
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.\"{{{ Name
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.SH NAME
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shutdown \- bring the system down
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.\"}}}
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.\"{{{ Synopsis
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.SH SYNOPSIS
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.B /sbin/shutdown
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.RB [ \-t
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.IR sec ]
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.RB [ \-arkhncfFHP ]
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.I time
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.RI [ warning-message ]
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.\"}}}
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.\"{{{ Description
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.SH DESCRIPTION
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\fBshutdown\fP brings the system down in a secure way. All logged-in users are
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notified that the system is going down, and \fBlogin\fP(1) is blocked.
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It is possible to shut the system down immediately or after a specified delay.
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All processes are first notified that the system is going down by the
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signal \s-2SIGTERM\s0. This gives programs like \fBvi\fP(1)
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the time to save the file being edited,
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mail and news processing programs a chance to exit cleanly, etc.
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\fBshutdown\fP does its job by signalling the \fBinit\fP process,
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asking it to change the runlevel.
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Runlevel \fB0\fP is used to halt the system, runlevel \fB6\fP is used
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to reboot the system, and runlevel \fB1\fP is used to put to system into
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a state where administrative tasks can be performed; this is the default
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if neither the \fI-h\fP or \fI-r\fP flag is given to \fBshutdown\fP.
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To see which actions are taken on halt or reboot see the appropriate
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entries for these runlevels in the file \fI/etc/inittab\fP.
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.\"}}}
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.\"{{{ Options
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.SH OPTIONS
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.\"{{{ -a
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.IP "\fB\-a\fP
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Use \fB/etc/shutdown.allow\fP.
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.\"}}}
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.\"{{{ -t sec
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.IP "\fB\-t\fP \fIsec\fP"
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Tell \fBinit\fP(8) to wait \fIsec\fP seconds between sending processes the
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warning and the kill signal, before changing to another runlevel.
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.\"}}}
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.\"{{{ -k
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.IP \fB\-k\fP
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Don't really shutdown; only send the warning messages to everybody.
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.\"}}}
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.\"{{{ -r
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.IP \fB\-r\fP
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Reboot after shutdown.
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.\"}}}
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.\"{{{ -h
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.IP \fB\-h\fP
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Halt or power off after shutdown.
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.\"}}}
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.\"{{{ -H
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.IP \fB\-H\fP
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Modifier to the -h flag. Halt action is to halt or drop into boot
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monitor on systems that support it. Must be used with the -h flag.
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.\"}}}
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.\"{{{ -P
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.IP \fB\-P\fP
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Halt action is to turn off the power.
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.\"}}}
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.\"{{{ -n
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.IP \fB\-n\fP
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[DEPRECATED] Don't call \fBinit\fP(8) to do the shutdown but do it ourself.
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The use of this option is discouraged, and its results are not always what
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you'd expect.
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.\"}}}
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.\"{{{ -f
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.IP \fB\-f\fP
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Skip fsck on reboot.
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.\"}}}
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.\"{{{ -F
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.IP \fB\-F\fP
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Force fsck on reboot.
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.\"}}}
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.\"{{{ -c
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.IP \fB\-c\fP
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Cancel an already running shutdown. With this option it is of course
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not possible to give the \fBtime\fP argument, but you can enter a
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explanatory message on the command line that will be sent to all users.
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.\"}}}
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.\"{{{ time
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.IP \fItime\fP
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When to shutdown.
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.\"}}}
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.\"{{{ warning-message
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.IP \fIwarning-message\fP
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Message to send to all users.
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.\"}}}
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.PP
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The \fItime\fP argument can have different formats. First, it can be an
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absolute time in the format \fIhh:mm\fP, in which \fIhh\fP is the hour
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(1 or 2 digits) and \fImm\fP is the minute of the hour (in two digits).
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Second, it can be in the format \fB+\fP\fIm\fP, in which \fIm\fP is the
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number of minutes to wait. The word \fBnow\fP is an alias for \fB+0\fP.
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.PP
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If shutdown is called with a delay, it will create the advisory file
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.I /etc/nologin
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which causes programs such as \fIlogin(1)\fP to not allow new user
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logins. This file is created five minutes before the shutdown sequence
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starts. Shutdown removes this file if it is stopped before it
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can signal init (i.e. it is cancelled or something goes wrong).
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It also removes it before calling init to change the runlevel.
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.PP
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The \fB\-f\fP flag means `reboot fast'. This only creates an advisory
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file \fI/fastboot\fP which can be tested by the system when it comes
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up again. The boot rc file can test if this file is present, and decide not
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to run \fBfsck\fP(1) since the system has been shut down in the proper way.
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After that, the boot process should remove \fI/fastboot\fP.
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.PP
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The \fB\-F\fP flag means `force fsck'. This only creates an advisory
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file \fI/forcefsck\fP which can be tested by the system when it comes
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up again. The boot rc file can test if this file is present, and decide
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to run \fBfsck\fP(1) with a special `force' flag so that even properly
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unmounted file systems get checked.
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After that, the boot process should remove \fI/forcefsck\fP.
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.PP
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The \fB-n\fP flag causes \fBshutdown\fP not to call \fBinit\fP,
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but to kill all running processes itself.
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\fBshutdown\fP will then turn off quota, accounting, and swapping
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and unmount all file systems.
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.\"}}}
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.\"{{{ Files
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.SH ACCESS CONTROL
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\fBshutdown\fP can be called from \fBinit\fP(8) when the magic keys
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\fBCTRL-ALT-DEL\fP are pressed, by creating an appropriate entry in
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\fI/etc/inittab\fP. This means that everyone who has physical access
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to the console keyboard can shut the system down. To prevent this,
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\fBshutdown\fP can check to see if an authorized user is logged in on
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one of the virtual consoles. If \fBshutdown\fP is called with the \fB-a\fP
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argument (add this to the invocation of shutdown in /etc/inittab),
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it checks to see if the file \fI/etc/shutdown.allow\fP is present.
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It then compares the login names in that file with the list of people
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that are logged in on a virtual console (from \fI/var/run/utmp\fP). Only
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if one of those authorized users \fBor root\fP is logged in, it will
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proceed. Otherwise it will write the message
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.sp 1
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.nf
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\fBshutdown: no authorized users logged in\fP
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.fi
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.sp 1
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to the (physical) system console. The format of \fI/etc/shutdown.allow\fP
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is one user name per line. Empty lines and comment lines (prefixed by a
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\fB#\fP) are allowed. Currently there is a limit of 32 users in this file.
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.sp 1
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Note that if \fI/etc/shutdown.allow\fP is not present, the \fB-a\fP
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argument is ignored.
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.SH HALT OR POWEROFF
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The \fB-H\fP option just sets the \fIinit\fP environment variable
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\fIINIT_HALT\fP to \fIHALT\fP, and the \fB-P\fP option just sets
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that variable to \fIPOWEROFF\fP. The shutdown script that calls
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\fBhalt\fP(8) as the last thing in the shutdown sequence should
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check these environment variables and call \fBhalt\fP(8) with
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the right options for these options to actually have any effect.
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Debian 3.1 (sarge) supports this.
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.SH FILES
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.nf
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/fastboot
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/etc/inittab
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/etc/init.d/halt
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/etc/init.d/reboot
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/etc/shutdown.allow
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.fi
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.\"}}}
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.SH NOTES
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A lot of users forget to give the \fItime\fP argument
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and are then puzzled by the error message \fBshutdown\fP produces. The
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\fItime\fP argument is mandatory; in 90 percent of all cases this argument
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will be the word \fBnow\fP.
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.PP
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Init can only capture CTRL-ALT-DEL and start shutdown in console mode.
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If the system is running the X window System, the X server processes
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all key strokes. Some X11 environments make it possible to capture
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CTRL-ALT-DEL, but what exactly is done with that event depends on
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that environment.
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.PP
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Shutdown wasn't designed to be run setuid. /etc/shutdown.allow is
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not used to find out who is executing shutdown, it ONLY checks who
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is currently logged in on (one of the) console(s).
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.\"{{{ Author
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.SH AUTHOR
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Miquel van Smoorenburg, miquels@cistron.nl
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.\"}}}
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.\"{{{ See also
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.SH "SEE ALSO"
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.BR fsck (8),
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.BR init (8),
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.BR halt (8),
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.BR poweroff (8),
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.BR reboot (8)
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.\"}}}
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