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.\" $FreeBSD$ 34.\" 35.Dd May 12, 1995 36.Dt DUMPON 8 37.Os FreeBSD 2.1 38.Sh NAME 39.Nm dumpon 40.Nd "specify a device for crash dumps" 41.Sh SYNOPSIS 42.Nm dumpon 43.Op Fl v 44.Ar special_file 45.Nm dumpon 46.Op Fl v 47.Ar off 48.Sh DESCRIPTION 49.Nm Dumpon 50is used to specify a device where the kernel can save a crash dump in 51the case of a panic. 52.Pp 53Calls to 54.Nm 55normally occur from the system multi-user initialization file 56.Pa /etc/rc , 57controlled by the 58.Dq dumpdev 59variable in the boot time configuration file 60.Pa /etc/rc.conf . 61.Pp 62The size of the specified dump device must be at least 64 KB greater the 63size of physical memory. 64.Pp 65The 66.Fl v 67flag causes 68.Nm 69to be verbose about its activity. 70.Sh NOTES 71One of the system swap devices is usually chosen as the dump device, as 72swap devices are the most likely to have the required space at dump time. 73.Pp 74The 75.Nm 76program operates by setting the 77.Xr sysctl 3 78MIB variable 79.Dq kern.dumpdev 80to the device number of the designated 81.Ar special_file 82or to 83.Dv NODEV 84(meaning that no dumps are to be taken) if 85.Ar special_file 86is the text string: 87.Dq Li off . 88.Sh SEE ALSO 89.Xr sysctl 3 , 90.Xr fstab 5 , 91.Xr rc.conf 5 , 92.Xr config 8 , 93.Xr init 8 , 94.Xr rc 8 , 95.Xr savecore 8 , 96.Xr swapon 8 , 97.Xr panic 9 98.Sh FILES 99.Bl -tag -width "/dev/{wd,da}?s?b" -compact 100.It Pa /dev/{wd,da}?s?b 101standard swap areas 102.It Pa /etc/rc.conf 103boot-time system configuration 104.El 105.Sh BUGS 106Because the filesystem layer is already dead by the time a crash dump 107is taken, it is not possible to send crash dumps directly to a file. 108.Pp 109.Nm Dumpon 110currently allows only devices with minor number 1 to be used as dump 111devices. 112.Sh HISTORY 113The 114.Nm 115command appeared in 116.Fx 2.1 . 117