FDISK(8) FDISK(8)
NAME
fdisk - examine or change DOS partitioning information
SYNOPSIS
/usr/sbin/fdisk <raw-device> [ inquiry ] [ action ] [
flags ]
DESCRIPTION
fdisk displays or changes the DOS partition table found in
the bootsector of i386 bootable disks. If no inquiry or
action is specified, it is run in interactive mode, allow-
ing multiple changes to the partition table to be made.
If an inquiry is specified, the result is displayed to
standard output but no changes to the partition table are
made. If an action is requested, the partition table will
usually be modified and fdisk immediately returns. When
fdisk is run in interactive mode, no changes to the parti-
tion table are effected until the user explicitly writes
the changes.
fdisk modifies only the bootsector and (unless the -boot-
sectorOnly flag is specified) the first sector of newly
allocated partitions; it does not modify other contents of
the disk in any way. However, it is used to redefine the
allocation of the disk; deleting a partition makes the
partition inaccessible and should be considered tantamount
to erasing the partition.
Flags
-useAllSectors
For compatibility with the DOS version, fdisk by
default recognizes only those sectors that are bios-
accessible. However, if fdisk is passed the -use-
AllSectors flag, it will recognize all sectors phys-
ically present. Data allocated in the extra sectors
may not be bios accessible, and certain fields in
the partition table might overflow, which might
cause problems with some operating systems. Bios
inaccessible sectors could prevent Darwin from boot-
ing, though once booted Darwin is unaffected by bios
limitations or partition table overflows.
-useBoot0
Reads in /usr/standalone/i386/boot0 to be used as
the partition boot program. If this option is not
specified, the existing boot program is retained.
-bootsectorOnly
Tells fdisk to modify only the bootsector when sav-
ing changes. Otherwise, the default behavior is to
zero the first sector of newly-created partitions to
ensure that extant data is not treated as a boot
program or meaningful partition information.
Interactive mode
When fdisk is run in interactive mode, it displays the
defined partitions and unallocated disk space, then dis-
plays a menu. Information on defined partitions includes:
Type The type of data the partition is said to contain.
rt The starting address of the partition, in megabytes.
e The size of the partition, in megabytes.
tus If the partition is marked as active, the partition
will be booted from when the selected device is the
boot device.
All unused blocks on the disk are also displayed, with
their sizes rounded to the nearest megabyte.
Interactive mode main menu options
a new partition
Allocates space on the disk for use by Darwin or
another operating system. The space is allocated
from the first adequate free block. The partition
table structure only allows for 4 partitions per
disk.
+te partition
Deallocates the space occupied by the specified par-
tition.
the active partition
Specifies which partition is to be booted from if
the selected device is the boot device.
w disk information
Displays the layout of the disk, both according to
the driver and according to the rom bios. For com-
patibility with the DOS version, fdisk by default
only recognizes those sectors that are bios-accessi-
ble. However, if fdisk is passed the -useAllSectors
flag, it will recognize all sectors physically pre-
sent.
Non-interactive mode
For the benefit of installation scripts, fdisk can be
given one inquiry or one action to effect partitioning.
Inquiries do not modify the partition table, but actions
usually do.
The following inquiries are allowed:
-isDiskPartitioned
Outputs "Yes" if the disk contains 1 or more valid
partitions, "No" otherwise.
-isThereExtendedPartition
Outputs "Yes" if the disk has a DOS extended
partition, "No" otherwise.
-isThereUFSPartition
Outputs "Yes" if the disk has a Apple UFS partition,
"No" otherwise.
-freeSpace
Outputs the size (in megabytes) of the largest free
block on the disk.
-freeWOUFS
Outputs the size (in megabytes) of the largest free
block on the disk if the Apple UFS partition were
deleted.
-freeWOUFSorExt
Outputs the size (in megabytes) of the largest free
block on the disk if the Apple UFS and extended par-
titions were deleted.
-sizeofExtended
Outputs the size (in megabytes) of the extended par-
tition.
-diskSize
Outputs the size of the disk in megabytes.
-installSize
Outputs the size that Darwin would install to on the
current disk; effectively the size of the Apple UFS
partition if the disk is partitioned, otherwise the
size of the disk.
The following actions are allowed:
-removePartitioning
Zeros out the bootsector, eliminating the partition
table and boot program. Prepares the disk so that
Darwin will install on the entire disk.
-bootPlusUFS
Partitions the disk with 8 megs reserved for the
booter (partition type 0xAB) and the remainder used
for Darwin. The booter partition is set active.
-dosPlusUFS <megsForDos>
Partitions the disk with <megsForDos> reserved for
DOS and the remainder used for Darwin.
-setAvailableToUFS
Deletes the current Apple UFS partition, then
reserves the largest free space for Darwin; doesn't
destroy other partitions.
-setExtAndAvailableToUFS
Deletes the current Apple UFS and extended parti-
tions, then reserves the largest free space for Dar-
win; doesn't destroy other partitions.
-setExtendedToUFS
Changes the current extended partition to Apple UFS.
-setUFSActive
Makes the Apple UFS partition active, but doesn't
affect the size of any partition.
SEE ALSO
disk(8)
BUGS
When creating a partition, fdisk's idea of a megabyte is
sometimes different than other versions; fdisk is not
guaranteed to locate the partition where another version
would.
fdisk knows nothing about logical partitions, which are
sub-partitions of an extended partition.
fdisk does not tolerate inconsistent partitions; a parti-
tion that overlaps another will not be included in the
partition table when it is written out, and the cylin-
der/head/sector bios values are derived from the absolute
sector numbers. Upon writing, the partition table entries
are ordered the same as the actual partitions.
Mar 30, 1998 FDISK(8)