freebsd-dev/sbin/dumpon/dumpon.8
1997-02-22 14:40:44 +00:00

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.\" From: @(#)swapon.8 8.1 (Berkeley) 6/5/93
.\" $Id$
.\"
.Dd May 12, 1995
.Dt DUMPON 8
.Os FreeBSD 2.1
.Sh NAME
.Nm dumpon
.Nd "specify a device for crash dumps"
.Sh SYNOPSIS
.Nm dumpon
.Op Fl v
.Ar special_file
.Sh DESCRIPTION
.Nm Dumpon
is used to specify a device where the kernel can save a crash dump in
the case of a panic.
The system begins with no dump area configured for safety, unless a
.Dq dumps on
clause was specified in the input to
.Xr config 8 .
The dump device must be one of the swap areas
specified in the configuration file, and it must be at least the size
of physical memory.
Calls to
.Nm dumpon
normally occur in the system multi-user initialization file
.Pa /etc/rc ,
before the
.Xr savecore 8
program is run.
The
.Fl v
flag can be specified to cause the
.Nm
program to be verbose about its activity.
.Pp
The
.Nm
program operates by setting the
.Xr sysctl 3
MIB variable
.Dq kern.dumpdev
to the device number of the designated
.Ar special_file
or to
.Dv NODEV
(meaning that no dumps are to be taken) if
.Ar special_file
is the text string
.Dq Li off .
.Sh SEE ALSO
.Xr sysctl 3 ,
.Xr init 8 ,
.Xr rc 8 ,
.Xr savecore 8
.Sh FILES
.Bl -tag -width /dev/[ws]d?b -compact
.It Pa /dev/[ws]d?b
standard paging devices
.El
.Sh BUGS
Because the filesystem layer is already dead by the time a crash dump
is taken, it is not possible to send crash dumps directly to a file.
.Sh HISTORY
The
.Nm
command appeared in
.Fx 2.1 .