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
disktab(5),
bad144(8)
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.