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dumpon(8) [freebsd man page]

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

NAME
dumpon -- specify a device for crash dumps SYNOPSIS
dumpon [-v] special_file dumpon [-v] off dumpon [-v] -l 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. The default type of kernel crash dump is the mini crash dump. Mini crash dumps hold only memory pages in use by the kernel. Alternatively, full memory dumps can be enabled by setting the debug.minidump sysctl(8) variable to 0. For systems using full memory dumps, the size of the specified dump device must be at least the size of physical memory. Even though an additional 64 kB 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. Also, when using full memory dumps, the dumpon utility will refuse to enable a dump device which is smaller than the total amount of physical memory as reported by the hw.physmem sysctl(8) vari- able. The -l flag causes dumpon to print the current dump device or _PATH_DEVNULL ("/dev/null") if no device is configured. 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 cannot trust its internal representation of the state of any given file system, 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. FILES
/dev/{ada,da}?s?b standard swap areas /etc/rc.conf boot-time system configuration SEE ALSO
fstab(5), rc.conf(5), config(8), init(8), loader(8), rc(8), savecore(8), swapon(8), panic(9) HISTORY
The dumpon utility appeared in FreeBSD 2.1. 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. BSD
October 8, 2014 BSD

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SAVECORE(8)						    BSD System Manager's Manual 					       SAVECORE(8)

NAME
savecore -- save a core dump of the operating system SYNOPSIS
savecore -c [-v] [device ...] savecore -C [-v] [device ...] savecore [-fkvz] [-m maxdumps] [directory [device ...]] DESCRIPTION
The savecore utility copies a core dump into directory, or the current working directory if no directory argument is given, and enters a reboot message and information about the core dump into the system log. The options are as follows: -C Check to see if a dump exists, and display a brief message to indicate the status. An exit status of 0 indicates that a dump is there, 1 indicates that none exists. This option is compatible only with the [-v] option. -c Clear the dump, so that future invocations of savecore will ignore it. -f Force a dump to be taken even if either the dump was cleared or if the dump header information is inconsistent. -k Do not clear the dump after saving it. -m maxdumps Maximum number of dumps to store. Once the number of stored dumps is equal to maxdumps the counter will restart from 0. -v Print out some additional debugging information. Specify twice for more information. -z Compress the core dump and kernel (see gzip(1)). The savecore utility looks for dumps on each device specified by the device argument(s), or on each device in /etc/fstab marked as ``dump'' or ``swap''. The savecore utility checks the core dump in various ways to make sure that it is complete. If it passes these checks, it saves the core image in directory/vmcore.# and information about the core in directory/info.#. For kernel textdumps generated with the textdump(4) facility, output will be stored in the tar(5) format and named directory/textdump.tar.#. The ``#'' is the number from the first line of the file directory/bounds, and it is incremented and stored back into the file each time savecore successfully runs. The savecore utility also checks the available disk space before attempting to make the copies. If there is insufficient disk space in the file system containing directory, or if the file directory/minfree exists and the number of free kilobytes (for non-superusers) in the file system after the copies were made would be less than the number in the first line of this file, the copies are not attempted. If savecore successfully copies the kernel and the core dump, the core dump is cleared so that future invocations of savecore will ignore it. The savecore utility is meant to be called near the end of the initialization file /etc/rc (see rc(8)). SEE ALSO
gzip(1), getbootfile(3), textdump(4), tar(5), dumpon(8), syslogd(8) HISTORY
The savecore utility appeared in 4.1BSD. Support for kernel textdumps appeared in FreeBSD 7.1. BUGS
The minfree code does not consider the effect of compression or sparse files. BSD
December 17, 2012 BSD
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