FreeBSD 7.0 manual page repository

FreeBSD is a free computer operating system based on BSD UNIX originally. Many IT companies, like DeployIS is using it to provide an up-to-date, stable operating system.

dumpon - specify a device for crash dumps



      dumpon - specify a device for crash dumps


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


      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 con‐
      figuration 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 64 kB header is
      added to the dump, the BIOS for a platform typically holds back some mem‐
      ory, so it is not usually necessary to size the dump device larger than
      the actual amount of RAM available in the machine.
      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) variable.
      The -v flag causes dumpon to be verbose about its activity.
      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


      /dev/{ad,da}?s?b  standard swap areas
      /etc/rc.conf      boot-time system configuration
      fstab(5), rc.conf(5), config(8), init(8), rc(8), savecore(8), swapon(8),


      The dumpon utility appeared in FreeBSD 2.1.


      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.


Based on BSD UNIX
FreeBSD is an advanced operating system for x86 compatible (including Pentium and Athlon), amd64 compatible (including Opteron, Athlon64, and EM64T), UltraSPARC, IA-64, PC-98 and ARM architectures. It is derived from BSD, the version of UNIX developed at the University of California, Berkeley. It is developed and maintained by a large team of individuals. Additional platforms are in various stages of development.