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From: @(#)swapon.8 8.1 (Berkeley) 6/5/93
$Id: dumpon.8,v 1.5 1997/02/22 14:32:21 peter Exp $
.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 swap_device .Sh DESCRIPTION .Nm Dumpon is used to specify a device where the kernel can save a crash dump in the case of a panic.
p The system begins with no dump area configured for safety. If a .Dq dumps on clause is specified in the kernel configuration file or if the variable .Dq Li dumpdev in the boot time configuration file
a /etc/rc.conf names a dump device, future panics will cause the kernel to save a crash dump on the specified dump device. The dump device must be one of the swap areas specified in the filesystem configuration file
a /etc/fstab , and it must be at least the size of physical memory.
p Calls to .Nm dumpon normally occur in the system multi-user initialization file
a /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. .Sh NOTES
p Hardcoding the dump device using the kernel configuration file is only useful if a kernel crashes before reaching multi-user mode. Otherwise, the use of .Nm to specify the dump device is recommended.
p 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 init 8 , .Xr config 8 , .Xr rc 8 , .Xr savecore 8 , .Xr swapon 8 , .Xr panic 9 .Sh FILES l -tag -width /dev/[ws]d?b -compact t Pa /dev/[ws]d?b standard swap areas t Pa /etc/fstab static filesystem and swap information t 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. .Sh HISTORY The .Nm command appeared in .Fx 2.1 .