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DUMPON(8)		FreeBSD	System Manager's Manual		     DUMPON(8)

NAME
     dumpon -- specify a device	for crash dumps

SYNOPSIS
     dumpon [-v] special_file
     dumpon [-v] off

DESCRIPTION
     The dumpon	utility	is used	to specify a device where the kernel can save
     a crash dump in the case of a panic.

     Calls to dumpon normally occur from the system multi-user initialization
     file /etc/rc, controlled by the ``dumpdev'' variable in the boot time
     configuration file	/etc/rc.conf.

     For most systems the size of the specified	dump device must be at least
     the size of physical memory.  Even	though an additional header is added
     to	the dump, the BIOS for a platform typically holds back some memory, so
     it	is not usually necessary to size the dump device larger	than the
     actual amount of RAM available in the machine.

     The -v flag causes	dumpon to be verbose about its activity.

IMPLEMENTATION NOTES
     Since a panic(9) condition	may occur in a situation where the kernel can-
     not trust its internal representation of the state	of any given file sys-
     tem, one of the system swap devices, and not a device containing a	file
     system, should be used as the dump	device.

     The dumpon	utility	operates by opening special_file and making a
     DIOCSKERNELDUMP ioctl(2) request on it to save kernel crash dumps.	 If
     special_file is the text string: ``off'', dumpon performs a
     DIOCSKERNELDUMP ioctl(2) on /dev/null and thus instructs the kernel not
     to	save crash dumps.

     Since dumpon cannot be used during	kernel initialization, the dumpdev
     variable of loader(8) must	be used	to enable dumps	for system panics
     which occur during	kernel initialization.

SEE ALSO
     fstab(5), rc.conf(5), config(8), init(8), loader(8), rc(8), savecore(8),
     swapon(8),	panic(9)

FILES
     /dev/{ad,da}?s?b  standard	swap areas
     /etc/rc.conf      boot-time system	configuration

BUGS
     Because the file system layer is already dead by the time a crash dump is
     taken, it is not possible to send crash dumps directly to a file.

HISTORY
     The dumpon	utility	appeared in FreeBSD 2.1.

FreeBSD	9.2			 May 12, 1995			   FreeBSD 9.2

NAME | SYNOPSIS | DESCRIPTION | IMPLEMENTATION NOTES | SEE ALSO | FILES | BUGS | HISTORY

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