freebsd-dev/sbin/dumpon/dumpon.8

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.\"     From: @(#)swapon.8	8.1 (Berkeley) 6/5/93
.\" $FreeBSD$
.\"
.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
.Nm dumpon
.Op Fl v
.Ar off
.Sh DESCRIPTION
.Nm Dumpon
is used to specify a device where the kernel can save a crash dump in
the case of a panic.
.Pp
Calls to 
.Nm
normally occur from the system multi-user initialization file
.Pa /etc/rc ,
controlled by the
.Dq dumpdev
variable in the boot time configuration file 
.Pa /etc/rc.conf .
.Pp
The size of the specified dump device must be at least 64 KB greater the 
size of physical memory.
.Pp
The
.Fl v
flag causes 
.Nm
to be verbose about its activity.
.Sh NOTES
One of the system swap devices is usually chosen as the dump device, as
swap devices are the most likely to have the required space at dump time.
.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 fstab 5 ,
.Xr rc.conf 5 ,
.Xr config 8 ,
.Xr init 8 ,
.Xr rc 8 ,
.Xr savecore 8 ,
.Xr swapon 8 ,
.Xr panic 9
.Sh FILES
.Bl -tag -width "/dev/{wd,da}?s?b" -compact
.It Pa /dev/{wd,da}?s?b
standard swap areas
.It Pa /etc/rc.conf
boot-time system configuration
.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.
.Pp
.Nm Dumpon
currently allows only devices with minor number 1 to be used as dump 
devices.
.Sh HISTORY
The
.Nm
command appeared in
.Fx 2.1 .