1.\" $NetBSD: wdogctl.8,v 1.4 2001/11/16 11:27:09 wiz Exp $ 2.\" 3.\" Copyright (c) 2000 Zembu Labs, Inc. 4.\" All rights reserved. 5.\" 6.\" Author: Jason R. Thorpe <thorpej@zembu.com> 7.\" 8.\" Redistribution and use in source and binary forms, with or without 9.\" modification, are permitted provided that the following conditions 10.\" are met: 11.\" 1. Redistributions of source code must retain the above copyright 12.\" notice, this list of conditions and the following disclaimer. 13.\" 2. Redistributions in binary form must reproduce the above copyright 14.\" notice, this list of conditions and the following disclaimer in the 15.\" documentation and/or other materials provided with the distribution. 16.\" 3. All advertising materials mentioning features or use of this software 17.\" must display the following acknowledgement: 18.\" This product includes software developed by Zembu Labs, Inc. 19.\" 4. Neither the name of Zembu Labs nor the names of its employees may 20.\" be used to endorse or promote products derived from this software 21.\" without specific prior written permission. 22.\" 23.\" THIS SOFTWARE IS PROVIDED BY ZEMBU LABS, INC. ``AS IS'' AND ANY EXPRESS 24.\" OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WAR- 25.\" RANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DIS- 26.\" CLAIMED. IN NO EVENT SHALL ZEMBU LABS BE LIABLE FOR ANY DIRECT, INDIRECT, 27.\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 28.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 29.\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 30.\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 31.\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 32.\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 33.\" 34.Dd October 19, 2000 35.Dt WDOGCTL 8 36.Os 37.Sh NAME 38.Nm wdogctl 39.Nd Watchdog timer control utility 40.Sh SYNOPSIS 41.Nm 42.Nm "" 43.Fl k 44.Op Fl A 45.Op Fl p Ar seconds 46.Ar timer 47.Nm "" 48.Fl u 49.Op Fl A 50.Op Fl p Ar seconds 51.Ar timer 52.Nm "" 53.Fl d 54.Sh DESCRIPTION 55.Nm 56is used to manipulate watchdog timers. Watchdog timers provide a 57means of ensuring that a system continues to make progress. This 58is accomplished by use of a timer, provided by either hardware or 59software; when the timer expires, the watchdog resets the system. 60In this case of a hardware watchdog timer, this is accomplished by 61asserting the system's hardware reset signal. In the case of a 62software watchdog timer, this is accomplished by calling the kernel's 63normal reboot path. In order to prevent the system from rebooting, 64something must refresh the timer to prevent it from expiring. 65.Pp 66The 67.Nx 68kernel provides two basic modes in which watchdog timers may 69operate: kernel tickle mode and user tickle mode. In kernel 70tickle mode, a timer in the kernel refreshes the watchdog timer. 71In user tickle mode, 72.Nm 73runs in the background and refreshes the watchdog timer. In 74kernel tickle mode, progress of the kernel is ensured. In user 75tickle mode, the ability for user programs to run within a known 76period of time is ensured. Note that user tickle mode must be 77used with caution; on a heavily loaded system, the timer may 78expire accidentally, even though user programs may be making 79(very slow) progress. 80.Pp 81In both modes, an attempt is made to refresh the watchdog timer 82in one half the timer's configured period. That is, if the 83watchdog timer has a period of 30 seconds, a refresh attempt 84is made every 15 seconds. 85.Pp 86If called without arguments, 87.Nm 88will list the timers available on the system. When arming a 89watchdog timer, the 90.Ar timer 91argument is the name of the timer to arm. 92.Pp 93Only one timer may be armed at a time; if an attempt is made 94to arm a timer when one is already armed, an error message 95will be displayed and no action will be taken. 96.Pp 97The options are as follows: 98.Bl -tag -width indent 99.It Fl k 100Arm 101.Ar timer 102in kernel tickle mode. 103.It Fl u 104Arm 105.Ar timer 106in user tickle mode. 107.It Fl A 108When arming a timer, this flag indicates that an audible alarm is 109to sound when the watchdog timer expires and resets the system. 110If the selected timer does not support an audible alarm, this 111option will be silently ignored. 112.It Fl p Ar period 113When arming a timer, this flag configures the timer period to 114.Ar period 115seconds. If the specified period it outside the timer's 116range, an error message will be displayed and no action will 117be taken. 118.It Fl d 119This flag disarms the currently active timer. 120.El 121.Sh FILES 122/dev/watchdog -- the system monitor watchdog timer device 123.Sh SEE ALSO 124.Xr envsys 4 , 125.Xr envstat 8 126.Sh HISTORY 127The 128.Nm 129command first appeared in 130.Nx 1.5.1 . 131.Sh AUTHORS 132The 133.Nm 134command and the 135.Nx 136watchdog timer framework were written by 137.An Jason R. Thorpe 138.Aq thorpej@zembu.com , 139and contributed by Zembu Labs, Inc. 140