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dumpsys(8)


NAME

  dumpsys - Copies a snapshot of memory to a dump file


SYNOPSIS

  /sbin/dumpsys [-fisuz] [-r num] directory


OPTIONS

  -f  Perform a full core dump -- the default is a partial dump.

  -i  Ignore filesystem space limit warning -- copy the dump even if there is
      insufficient filesystem space to save it.	 Only the portion of the dump
      that fits in the space available is copied.

  -r num
      Set the expected dump compression ratio, defaulting to 0.5.  A lower
      number means a better compression ratio is expected.

  -s  Print the expected size of a full and partial dump file -- no dump is
      taken.

  -u  Produce a non-compressed dump.

  -z  Disable contiguous zero suppression.


DESCRIPTION

  The dumpsys command allows you to save a snapshot of the system memory to a
  dump file.  There are times when system memory requires analysis but it may
  not be possible to halt the system and take a normal crash dump. Many
  problems can be resolved by taking a snapshot of the system memory while
  the system is running. The dumpsys command performs this function after it
  determines that there is enough file system space to save a core dump (see
  the following for information about minfree).

  Note that the system is running while dumpsys takes a snapshot of memory.
  This means that memory may be changing as it is copied.  As a result,
  analysis of the resulting dump may show inconsistencies such as  incomplete
  linked lists and partially zeroed pages.  These are features caused by the
  transitory state of memory, caused by the working system.  For this reason,
  some system problems cannot be detected by dumpsys and you must halt the
  system to take a normal crash dump.

  The dumpsys command writes information in directory. By default, directory
  is /var/adm/crash.

  The dump contains the contents of a portion of physical memory (or all of
  physical memory in the case of a full core dump) at the time of the command
  execution.  The dumpsys command saves this information in the file
  vmzcore.n, or vmcore.n if compression is supressed.  The command also
  copies the kernel executable image, usually /vmunix, to the vmunix.n file.
  You can then analyze the vmzcore.n and vmunix.n files (See the Kernel
  Debugging manual for information about analyzing core dump files.)

  The variable n indicates the number of the core file.	 For the first file,
  dumpsys creates the files vmunix.0 and vmcore.0. It then creates a file
  named directory/bounds and initializes the file with the value 1.   For
  each succeeding dump, the dumpsys command uses the value in the
  directory/bounds file and then increments that value.

  By default dumpsys produces specially compressed dump files. The
  compression scheme used is not as powerful as compress or gzip but has the
  unusual feature that any byte in the file can be extracted without
  decompressing more than about 40K (typically less), even if the dump is
  very large.  Tools such as dbx, ladebug, and kdbx, are able to read the
  compressed core files.  The expand_dump utility is provided to convert
  compressed dumps into non-compressed dumps if you want to use an analysis
  tool that does not understand the compressed format.

  A traditional non-compressed dump can be generated using the -u switch.  In
  this case the dump file will be named vmcore.n instead of vmzcore.n.

  It is possible that you may run dumpsys on a kernel that is not recent
  enough to support compressed dumps.  If this happens, dumpsys will display
  a warning that the kernel is too old, but will then produce a non-
  compressed dump.  The message is suppressed if -u is used. Conversely, if
  you try to use older versions of dumpsys with a newer kernel a non-
  compressed dump is created without a message. The older dumpsys version
  will not recognize the -u or -r options.

  The text file directory/minfree specifies the minimum number of kilobytes
  that must be left on the filesystem containing directory after dumpsys
  copies the dump. By default, this file does not exist, indicating that the
  minimum is set to zero. To specify a minimum, create the file and store the
  number of kilobytes you want reserved in it.You can override the minimum
  check of directory/minfree using the -i option.

  The -s option displays the approximate number of disk blocks that full and
  partial dumps will require.  The exact size can not be determined ahead of
  time for many reasons, such as:

  Contiguous Zero Suppression
      By default, dumpsys optimizes disk space requirements by suppressing
      the writing of contiguous zeroes.

  Working System
      System use of dynamic memory (malloc/free) changes while the system is
      in use.

  Compression Ratio
      If the dump is to be compressed, the ratio by which it will be
      compressed is not known.

  The -z option disables contiguous zero suppression.  A considerable amount
  of memory consists of contiguous zeros, that do not need to be written to
  disk.	 The dumpsys command optimizes disk space by default,  but
  optimization of disk space causes longer execution times.  If you specify
  the -z option, the run time can be 25% faster, although you will require
  more disk space.  Note that if the dump is to be compressed, zero
  supression is not usedm therefore the -z option is meaningless.

  With the exception of the -s option, execution of dumpsys requires root
  (superuser) access rights.


EXIT STATUS

  0   Success -- dump taken

  1   General error -- dump failed

  2   Insufficient file system space -- dump failed


FILES

  directory/bounds
      Specifies the number of the next dump

  directory/minfree
      Specifies the minimum number of kilobytes to be left after dump files
      are written


SEE ALSO

  Commands: dbx(1), expand_dump(8), savecore(8)

  System Administration

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