dumpsys man page on DigitalUNIX

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dumpsys(8)							    dumpsys(8)

       dumpsys - Copies a snapshot of memory to a dump file

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

       Perform	a  full	 core  dump  -- the default is a partial dump.	Ignore
       filesystem space limit warning -- copy the dump even if there is insuf‐
       ficient filesystem space to save it.  Only the portion of the dump that
       fits in the space available is copied.  Set the expected dump  compres‐
       sion  ratio, defaulting to 0.5.	A lower number means a better compres‐
       sion ratio is expected.	Print the expected size of a full and  partial
       dump file -- no dump is taken.  Produce a non-compressed dump.  Disable
       contiguous zero suppression.

       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  mem‐
       ory.   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, direc‐
       tory 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 vmu‐
       nix.n file. You can then analyze the vmzcore.n and vmunix.n files  (See
       the  Kernel  Debugging manual for information about analyzing core dump

       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  com‐
       pression 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 analy‐
       sis 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 dis‐
       play 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	 kilo‐
       bytes  that  must  be left on the filesystem containing directory after
       dumpsys copies the dump. By default, this file does not exist, indicat‐
       ing  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: By default, dumpsys optimizes
       disk space  requirements	 by  suppressing  the  writing	of  contiguous
       zeroes.	 System	 use of dynamic memory (malloc/free) changes while the
       system is in use.  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  com‐
       pressed,	 zero supression is not usedm therefore the -z option is mean‐

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

       Success	--  dump  taken General error -- dump failed Insufficient file
       system space -- dump failed

       Specifies the number of the next dump Specifies the minimum  number  of
       kilobytes to be left after dump files are written

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

       System Administration


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