NAME
diskpart
—
calculate default disk partition
sizes
SYNOPSIS
diskpart |
[-d ] [-p ]
[-s size]
disk-type |
DESCRIPTION
diskpart
is used to calculate the disk partition sizes
based on the default rules used at Berkeley.
Available options and operands:
-d
- An entry suitable for inclusion in the disk description file /etc/disktab is generated; for example, disktab(5).
-p
- Tables suitable for inclusion in a device driver are produced.
-s
size- The size of the disk may be limited to size with the
-s
option.
On disks that use
bad144(8) type of bad-sector forwarding, space is normally left in
the last partition on the disk for a bad sector forwarding table, although
this space is not reflected in the tables produced. The space reserved is
one track for the replicated copies of the table and sufficient tracks to
hold a pool of 126 sectors to which bad sectors are mapped. For more
information, see
bad144(8). The -s
option is intended for
other controllers which reserve some space at the end of the disk for
bad-sector replacements or other control areas, even if not a multiple of
cylinders.
The disk partition sizes are based on the total amount of space on
the disk as given in the table below (all values are supplied in units of
sectors). The ‘c
’ partition is, by
convention, used to access the entire physical disk. The device driver
tables include the space reserved for the bad sector forwarding table in the
‘c
’ partition; those used in the
disktab and default formats exclude reserved tracks. In normal operation,
either the ‘g
’ partition is used, or
the ‘d
’,
‘e
’, and
‘f
’ partitions are used. The
‘g
’ and
‘f
’ partitions are variable-sized,
occupying whatever space remains after allocation of the fixed sized
partitions. If the disk is smaller than 20 Megabytes, then
diskpart
aborts with the message
“disk too small, calculate by
hand
”.
Partition | 20-60 MB | 61-205 MB | 206-355 MB | 356+ MB |
a | 15884 | 15884 | 15884 | 15884 |
b | 10032 | 33440 | 33440 | 66880 |
d | 15884 | 15884 | 15884 | 15884 |
e | unused | 55936 | 55936 | 307200 |
h | unused | unused | 291346 | 291346 |
If an unknown disk type is specified,
diskpart
will prompt for the required disk geometry
information.
SEE ALSO
HISTORY
The diskpart
command appeared in
4.2BSD.
BUGS
Most default partition sizes are based on historical artifacts (like the RP06), and may result in unsatisfactory layouts.
When using the -d
flag, alternative disk
names are not included in the output.