FDISK(8) UNIX Programmer's Manual FDISK(8)
NAME
fdisk - examine or change DOS partitioning information
SYNOPSIS
/usr/etc/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, allowing
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 partition table are
effected until the user explicitly writes the changes.
fdisk modifies only the bootsector and (unless the -bootsec-
torOnly flag is specified) the first sector of newly allo-
cated partitions; it does not modify other contents of the
disk in any way. However, it is used to redefine the allo-
cation 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
-useAllSectors flag, it will recognize all sectors
physically present. Data allocated in the extra sec-
tors may not be bios accessible, and certain fields in
the partition table might overflow, which might cause
problems with some operating systems. Bios inaccessi-
ble sectors could prevent NEXTSTEP from booting,
though once booted NEXTSTEP is unaffected by bios lim-
itations or partition table overflows.
-useBoot0
Reads in /usr/standalone/i386/boot0 to be used as the
partition boot program. If this option is not speci-
fied, the existing boot program is retained.
-bootsectorOnly
Tells fdisk to modify only the bootsector when saving
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 displays
a menu. Information on defined partitions includes:
Type The type of data the partition is said to contain.
Start The starting address of the partition, in megabytes.
Size The size of the partition, in megabytes.
Status
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
Create a new partition
Allocates space on the disk for use by NEXTSTEP 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.
Delete partition
Deallocates the space occupied by the specified parti-
tion.
Set the active partition
Specifies which partition is to be booted from if the
selected device is the boot device.
Show disk information
Displays the layout of the disk, both according to the
driver and accoring to the rom bios. For compatibil-
ity with the DOS verstion, fdisk by default only
recognizes those sectors that are bios-accessible.
However, if fdisk is passed the -useAllSectors flag,
it will recognize all sectors physically present.
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.
-isThereNeXTPartition
Outputs "Yes" if the disk has a NEXTSTEP partition,
"No" otherwise.
-freeSpace
Outputs the size (in megabytes) of the largest free
block on the disk.
-freeWONeXT
Outputs the size (in megabytes) of the largest free
block on the disk if the NEXTSTEP partition were
deleted.
-freeWONeXTorExt
Outputs the size (in megabytes) of the largest free
block on the disk if the NEXTSTEP and extended parti-
tions were deleted.
-sizeofExtended
Outputs the size (in megabytes) of the extended parti-
tion.
-diskSize
Outputs the size of the disk in megabytes.
-installSize
Outputs the size that NEXTSTEP would install to on the
current disk; effectively the size of the NEXTSTEP
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
NEXTSTEP will install on the entire disk.
-dosPlusNeXT <megsForDos>
Partitions the disk with <megsForDos> reserved for DOS
and the remainder used for NEXTSTEP.
-setAvailableToNeXT
Deletes the current NEXTSTEP partition, then reserves
the largest free space for NEXTSTEP; doesn't destroy
other partitions.
-setExtAndAvailableToNeXT
Deletes the current NEXTSTEP and extended partitions,
then reserves the largest free space for NEXTSTEP;
doesn't destroy other partitions.
-setExtendedToNeXT
Changes the current extended partition to NEXTSTEP.
-setNeXTActive
Makes the NEXTSTEP 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. Nor perhaps should
it, as these are gross kludges from the Evil OS Company of
the North.
fdisk does not tolerate inconsistent partitions; a partition
that overlaps another will not be included in the partition
table when it is written out, and the cylinder/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.