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dumpsys(8)							   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	prob-
  lems 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 compres-
  sion 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 optimiza-
  tion 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