1.\" Copyright (c) 1980, 1991, 1993 2.\" The Regents of the University of California. All rights reserved. 3.\" 4.\" Redistribution and use in source and binary forms, with or without 5.\" modification, are permitted provided that the following conditions 6.\" are met: 7.\" 1. Redistributions of source code must retain the above copyright 8.\" notice, this list of conditions and the following disclaimer. 9.\" 2. Redistributions in binary form must reproduce the above copyright 10.\" notice, this list of conditions and the following disclaimer in the 11.\" documentation and/or other materials provided with the distribution. 12.\" 3. All advertising materials mentioning features or use of this software 13.\" must display the following acknowledgment: 14.\" This product includes software developed by the University of 15.\" California, Berkeley and its contributors. 16.\" 4. Neither the name of the University nor the names of its contributors 17.\" may be used to endorse or promote products derived from this software 18.\" without specific prior written permission. 19.\" 20.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 21.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 22.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 23.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 24.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 25.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 26.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 27.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 28.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 29.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 30.\" SUCH DAMAGE. 31.\" 32.\" From: @(#)swapon.8 8.1 (Berkeley) 6/5/93 33.\" $FreeBSD: src/sbin/dumpon/dumpon.8,v 1.11.2.12 2003/01/26 03:12:04 keramida Exp $ 34.\" 35.Dd May 12, 1995 36.Dt DUMPON 8 37.Os 38.Sh NAME 39.Nm dumpon 40.Nd "specify a device for crash dumps" 41.Sh SYNOPSIS 42.Nm 43.Op Fl v 44.Ar special_file 45.Nm 46.Op Fl v 47.Ar off 48.Sh DESCRIPTION 49The 50.Nm 51utility is used to specify a device where the kernel can save a crash dump in 52the case of a panic. 53.Pp 54Calls to 55.Nm 56normally occur from the system multi-user initialization file 57.Pa /etc/rc , 58controlled by the 59.Dq dumpdev 60variable in the boot time configuration file 61.Pa /etc/rc.conf . 62.Pp 63For most systems the size of the specified dump device must be at least 64the size of physical memory. 65Even though an additional header is added to the dump, 66the BIOS for a platform typically holds back some memory, so it is not usually 67necessary to size the dump device larger than the actual amount of RAM 68available in the machine. 69.Pp 70The 71.Fl v 72flag causes 73.Nm 74to be verbose about its activity. 75.Sh NOTES 76Since a 77.Xr panic 9 78condition may occur in a situation 79where the kernel cannot trust its internal representation 80of the state of any given file system, 81one of the system swap devices, 82and 83.Em not 84a device containing a file system, 85should be used as the dump device. 86.Pp 87The 88.Nm 89utility operates by setting the 90.Xr sysctl 3 91MIB variable 92.Dq kern.dumpdev 93to the device number of the designated 94.Ar special_file 95or to 96.Dv NODEV 97(meaning that no dumps are to be taken) if 98.Ar special_file 99is the text string: 100.Dq Li off . 101.Pp 102Since 103.Nm 104cannot be used during kernel initialization, the 105.Va dumpdev 106variable of 107.Xr loader 8 108must be used to enable dumps for system panics which occur 109during kernel initialization. 110.Sh SEE ALSO 111.Xr sysctl 3 , 112.Xr fstab 5 , 113.Xr rc.conf 5 , 114.Xr config 8 , 115.Xr init 8 , 116.Xr loader 8 , 117.Xr rc 8 , 118.Xr savecore 8 , 119.Xr swapon 8 , 120.Xr panic 9 121.Sh FILES 122.Bl -tag -width "/dev/{ad,da}?s?b" -compact 123.It Pa /dev/{ad,da}?s?b 124standard swap areas 125.It Pa /etc/rc.conf 126boot-time system configuration 127.El 128.Sh BUGS 129Because the file system layer is already dead by the time a crash dump 130is taken, it is not possible to send crash dumps directly to a file. 131.Sh HISTORY 132The 133.Nm 134utility appeared in 135.Fx 2.1 . 136