140 lines
4.7 KiB
Groff
140 lines
4.7 KiB
Groff
.\" $NetBSD: wdogctl.8,v 1.4 2001/11/16 11:27:09 wiz Exp $
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.\"
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.\" Copyright (c) 2000 Zembu Labs, Inc.
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.\" All rights reserved.
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.\"
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.\" Author: Jason R. Thorpe <thorpej@zembu.com>
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\" 3. All advertising materials mentioning features or use of this software
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.\" must display the following acknowledgement:
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.\" This product includes software developed by Zembu Labs, Inc.
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.\" 4. Neither the name of Zembu Labs nor the names of its employees may
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.\" be used to endorse or promote products derived from this software
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.\" without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY ZEMBU LABS, INC. ``AS IS'' AND ANY EXPRESS
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.\" OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WAR-
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.\" RANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DIS-
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.\" CLAIMED. IN NO EVENT SHALL ZEMBU LABS BE LIABLE FOR ANY DIRECT, INDIRECT,
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.\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
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.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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.\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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.\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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.\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
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.\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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.\"
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.Dd October 19, 2000
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.Dt WDOGCTL 8
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.Os
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.Sh NAME
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.Nm wdogctl
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.Nd Watchdog timer control utility
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.Sh SYNOPSIS
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.Nm
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.Nm ""
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.Fl k
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.Op Fl A
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.Op Fl p Ar seconds
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.Ar timer
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.Nm ""
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.Fl u
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.Op Fl A
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.Op Fl p Ar seconds
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.Ar timer
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.Nm ""
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.Fl d
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.Sh DESCRIPTION
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.Nm
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is used to manipulate watchdog timers. Watchdog timers provide a
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means of ensuring that a system continues to make progress. This
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is accomplished by use of a timer, provided by either hardware or
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software; when the timer expires, the watchdog resets the system.
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In this case of a hardware watchdog timer, this is accomplished by
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asserting the system's hardware reset signal. In the case of a
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software watchdog timer, this is accomplished by calling the kernel's
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normal reboot path. In order to prevent the system from rebooting,
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something must refresh the timer to prevent it from expiring.
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.Pp
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The
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.Nx
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kernel provides two basic modes in which watchdog timers may
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operate: kernel tickle mode and user tickle mode. In kernel
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tickle mode, a timer in the kernel refreshes the watchdog timer.
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In user tickle mode,
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.Nm
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runs in the background and refreshes the watchdog timer. In
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kernel tickle mode, progress of the kernel is ensured. In user
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tickle mode, the ability for user programs to run within a known
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period of time is ensured. Note that user tickle mode must be
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used with caution; on a heavily loaded system, the timer may
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expire accidentally, even though user programs may be making
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(very slow) progress.
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.Pp
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In both modes, an attempt is made to refresh the watchdog timer
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in one half the timer's configured period. That is, if the
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watchdog timer has a period of 30 seconds, a refresh attempt
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is made every 15 seconds.
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.Pp
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If called without arguments,
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.Nm
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will list the timers available on the system. When arming a
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watchdog timer, the
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.Ar timer
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argument is the name of the timer to arm.
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.Pp
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Only one timer may be armed at a time; if an attempt is made
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to arm a timer when one is already armed, an error message
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will be displayed and no action will be taken.
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.Pp
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The options are as follows:
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.Bl -tag -width indent
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.It Fl k
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Arm
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.Ar timer
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in kernel tickle mode.
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.It Fl u
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Arm
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.Ar timer
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in user tickle mode.
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.It Fl A
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When arming a timer, this flag indicates that an audible alarm is
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to sound when the watchdog timer expires and resets the system.
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If the selected timer does not support an audible alarm, this
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option will be silently ignored.
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.It Fl p Ar period
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When arming a timer, this flag configures the timer period to
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.Ar period
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seconds. If the specified period it outside the timer's
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range, an error message will be displayed and no action will
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be taken.
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.It Fl d
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This flag disarms the currently active timer.
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.El
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.Sh FILES
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/dev/watchdog -- the system monitor watchdog timer device
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.Sh SEE ALSO
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.Xr envsys 4 ,
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.Xr envstat 8
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.Sh HISTORY
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The
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.Nm
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command first appeared in
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.Nx 1.5.1 .
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.Sh AUTHORS
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The
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.Nm
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command and the
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.Nx
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watchdog timer framework were written by
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.An Jason R. Thorpe
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.Aq thorpej@zembu.com ,
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and contributed by Zembu Labs, Inc.
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