DISKMARK(8)		FreeBSD System Manager's Manual 	   DISKMARK(8)

NAME
     diskmark -- a program to mark PC disks using empty partition table
     entries

SYNOPSIS
     diskmark -w [-m magic] [-p partition] [-t type] major minor [disk]
     diskmark [-m magic] [-p partition] [-t type] [major minor] [disk]

DESCRIPTION
     The program diskmark uses an unused entry in the Master Boot Record on PC
     disks to record version information.  The author uses this information to
     determine if scratch disks should be partitioned at boot on a network
     booting compute cluster.  The information is stored in the LBA area of
     the partition table and consists of a 4 byte magic number, a 16-bit
     signed major version number and a 16-bit unsigned minor version number.

     This information is stored by creating an invalid partition table entry
     of type 0xAD or the type given by the -t option.  This entry is placed in
     entry 4 or the entry given by the -p option.

     diskmark has three modes of operation.  When called with the -w option,
     it writes an appropriate partition entry to the mbr of the specified
     disk.  The entry will only be written in the existing entry is either of
     type zero or of the type specified.  Otherwise, when called with major
     and minor, diskmark returns 0 if the magic, major, minor values in the
     partition entry match those given and 1 along with a brief error message
     if they do not.  Finally, when invoked without major and minor, the val-
     ues of magic, major, and minor stored on the disk are printed.

     Options are:

     -m magic	   Change the magic number from the default "AERO" to the
		   given value.  The entry may be in ASCII or hexadecimal and
		   must be four bytes long.

     -p partition  Change the partition to use from the default 4 to the given
		   value.  Valid values are 1-4.

     -t type	   Change the partition type from the default 0xAD to the
		   given value.  The value is one byte which may be entered in
		   unsigned decimal or hexadecimal.

     -w 	   Write the given values of major and minor along with the
		   appropriate partition type and magic number to the selected
		   partition table entry.

NOTES
     The extent to which certain operating systems or BIOSes will be compati-
     ble with this hack is unknown.  Things appear to work, but wide spread
     testing has not been done and there are no written standards to MBR par-
     tition tables.

SEE ALSO
     fdisk(8)

AUTHORS
     This manual page and the diskmark program were written by Brooks Davis
     <brooks@aero.org> for The Aerospace Corporation.

FreeBSD 5.2		       December 20, 2001		   FreeBSD 5.2