Index for Section 7

Alphabetical listing for V

Bottom of page

vmzcore(7)
NAME
  vmzcore - compressed memory core dump interface

DESCRIPTION
  The vmzcore character special device file provides access to in-memory
  compressed kernel core dumps. During the boot sequence, savecore uses this
  device to recover an existing dump. (See the savecore(8) reference page for
  more information.)

  An application can determine whether a dump exists by opening and
  attempting to read a single byte from vmzcore; if no data is available, no
  dump exists.	If a dump exists, the dump header can be read from byte
  offset 1024 (2 * DEV_BSIZE); upon reading the header, an application may
  treat vmzcore like a traditional swap device dump.  A dump remains in
  memory until either an application writes to vmzcore or the memory system
  is powered down or reset.

  By default, the system attempts a memory dump only after failing the
  initial disk dump.  The dump_to_memory system attribute changes this
  behavior.  If set to `1', the system attempts to save core dumps to memory
  then attempts to save them to disk if the memory dump fails. If set to `-
  1', core dumps never are written to memory. The default value is `0'.	 (See
  sys_attrs_generic(5) for more information on system attributes.)

  This interface also supports a variation of memory dumps called "exempt
  memory dumps".  A contiguous chunk of exempt memory is first reserved at
  boot time using the Contiguous Memory Allocator. (See sysconfigdb(8).) A
  portion or all of this memory may then be handed to the kernel dump
  subsystem, which will use it in the event of a memory core dump. The system
  attribute dump_exmem_addr identifies the start of the dumpable region
  (either as a virtual or physical address).  The dump_exmem_size system
  attribute specifies the number of bytes available. By default, exempt
  memory is not included in the core dump; this can be changed by setting the
  system attribute dump_exmem_include to `1'.

RESTRICTIONS
  Regarding the exempt memory system attributes, dump_exmem_addr must be page
  aligned and dump_exmem_size a multiple of the machine word size (8 bytes).
  When combined, this range of pages must be of type M_EXEMPT.	If any of
  these conditions are not met, the system displays an error message and no
  exempt memory dump will be generated.

  Memory dumps must be compressed.  If the compressed_dump system attribute
  is not set, the system automatically will enable compression before
  attempting to write the dump.

FILES
  /dev/vmzcore

SEE ALSO
  Commands: dxkerneltuner(8), savecore(8), sysconfig(8), sysconfigdb(8)

  Files: sys_attrs_generic(5) mem(7), kmem(7)

  Kernel Debugging, System Administration

Index for Section 7

Alphabetical listing for V

Top of page