NAME

memdump - memory dumper

SYNOPSIS

memdump [-kv] [-b buffer_size] [-d dump_size] [-m map_file] [-p page_size]

DESCRIPTION

This program dumps system memory to the standard output stream, skipping over holes in memory maps. By default, the program dumps the contents of physical memory (/dev/mem).

Output is in the form of a raw dump; if necessary, use the -m option to capture memory layout information.

Output should be sent off-host over the network, to avoid changing all the memory in the file system cache. Use netcat, stunnel, or openssl, depending on your requirements.

The size arguments below understand the k (kilo) m (mega) and g (giga) suffixes. Suffixes are case insensitive.

Options

-k

Attempt to dump kernel memory (/dev/kmem) rather than physical memory.

Warning: this can lock up the system to the point that you have to use the power switch (for example, Solaris 8 on 64-bit SPARC).

Warning: this produces bogus results on Linux 2.2 kernels.

Warning: this is very slow on 64-bit machines because the entire memory address range has to be searched.

Warning: kernel virtual memory mappings change frequently. Depending on the operating system, mappings smaller than page_size or buffer_size may be missed or may be reported incorrectly.

-b buffer_size (default: 0)

Number of bytes per memory read operation. By default, the program uses the page_size value.

Warning: a too large read buffer size causes memory to be missed on FreeBSD or Solaris.

-d dump-size (default: 0)

Number of memory bytes to dump. By default, the program runs until the memory device reports an end-of-file (Linux), or until it has dumped from /dev/mem as much memory as reported present by the kernel (FreeBSD, Solaris), or until pointer wrap-around happens.

Warning: a too large value causes the program to spend a lot of time skipping over non-existent memory on Solaris systems.

Warning: a too large value causes the program to copy non-existent data on FreeBSD systems.

-m map_file

Write the memory map to map_file, one entry per line. Specify -m- to write to the standard error stream. Each map entry consists of a region start address and the first address beyond that region. Addresses are separated by space, and are printed as hexadecimal numbers (0xhhhh).

-p page_size (default: 0)

Use page_size as the memory page size. By default the program uses the system page size.

Warning: a too large page size causes memory to be missed while skipping over holes in memory.

-v

Enable verbose logging for debugging purposes. Multiple -v options make the program more verbose.

BUGS

On many hardware platforms the firmware (boot PROM, BIOS, etc.) takes away some memory. This memory is not accessible through /dev/mem.

This program should produce output in a format that supports structure information such as ELF.

LICENSE

This software is distributed under the IBM Public License.

AUTHOR

Wietse Venema
IBM T.J. Watson Research
P.O. Box 704
USA