FDISK(ADM) UNIX System V
Name
fdisk - maintain disk partitions
Syntax
/etc/fdisk [[-p] [-ad partition] [-c partition start
size] [-f devicename]]
Description
fdisk displays information about disk partitions. fdisk
also creates and deletes disk partitions and changes the
active partition. fdisk functionality is a superset of the
MS-DOS command of the same name. fdisk is usually used
interactively from a menu.
The hard disk has at most four partitions. Only one
partition is active at any given time. It is possible to
assign a different operating system to each partition. Once
a partition is made active, the operating system resident in
that partition boots automatically once the current
operating system is halted.
The fdisk utility reports disk sizes in tracks. The number
of tracks available on a hard disk is equal to the number of
heads times the number of cylinders. The fdisk utility does
not allocate the first track or the last cylinder on the
hard disk when the ``Use Entire Disk for UNIX'' option is
used. The first track on the hard disk is reserved for
masterboot and the last cylinder is generally used when
running hard disk diagnostics. You should not allocate the
last cylinder if you plan to run diagnostics on your hard
disk.
For example, if a disk has 4 heads and 615 cylinders, it has
2460 tracks, which fdisk reports as tracks 0-2459. If you
choose the ``Use Entire Disk for UNIX'' option, fdisk will
create a XENIX partition on tracks 1-2455. Track 0 is
reserved for masterboot, and the last cylinder (tracks
2455-2459) is not assigned with the ``Use Entire Disk for
UNIX'' option.
Partitions are defined by a ``partition table'' at the end
of the master boot block. The partition table provides the
location and size of the partitions on the disk. The
partition table also defines the active partition. Each
partition can be assigned to UNIX, DOS, or some other
operating system. Once a DOS partition is set up, DOS files
and directories resident in the DOS partition may be
accessed while from the UNIX partition by means of the
dos(C) commands. DOS may be booted without the DOS
partition being active by entering ``dos'' at the boot
prompt. See boot(HW).
Arguments
-p, -a, -d, -c
These flags are used to invoke fdisk non-interactively.
The argument number, below, refers to a valid partition
number (1-4).
-p Prints out the disk partition table, one partition to a
line. For each partition, fdisk displays the following
information: partition start stop size status type.
-a number
Activates partition number.
-d number
Deletes partition number.
-c number start size
Creates a partition, number, size tracks long beginning
at track start. The -c option is used to use the
entire disk for UNIX; the appending of a dash to the
end of the command line accomplishes this, as in the
following example:
fdisk -c 1 1 -
This syntax is used only during installation. If there
are any existing partitions on the disk, this command
will fail.
-f name
Open device name and read the partition table
associated with that device's partition. The default
is /dev/rhd00.
Options
When invoked interactively (without the -p, -a, -d, or -c
options), fdisk displays a prompt and a menu of five
options. No changes are made to the partition table on the
disk until you enter ``q'' from the main menu.
1. Display Partition Table.
This option displays a table of information about each
partition on the hard disk. The PARTITION column gives
the partition number. The STATUS column tells whether
the partition is active (A) or inactive (I). TYPE
tells whether the partition is a UNIX partition, a DOS
partition, or ``other''. The option also displays the
starting track, ending track and total number of tracks
in each partition.
2. Use Entire Disk for UNIX.
fdisk creates one partition that includes all the
tracks on the disk, except the first track and the last
cylinder. This partition is assigned to the UNIX
system and is designated the active partition.
3. Use Rest of Disk for UNIX.
fdisk creates one partition that occupies the largest
available contiguous area of the disk. This partition
is assigned to UNIX and is designated the active
partition.
4. Create UNIX Partition
This option allows the creation of a partition by
altering the partition table. fdisk reports the number
of tracks available for each partition and the number
of tracks in use. fdisk prompts for the partition to
create, the starting track and size in tracks. The
change is written to the hard disk when you enter ``q''
from the main menu.
5. Activate Partition
This option activates the specified partition. Only
one partition may be active at a time. The change is
not effective until you exit. The operating system
residing in the newly activated partition boots once
the current operating system is halted.
6. Delete Partition
This option requests which partition you wish to
delete. fdisk reports the new available amount of disk
space in tracks. The change is not effective until you
exit.
Exit the fdisk program by typing a `q' at the main fdisk
menu. Your changes are now written to the hard disk.
Notes
The minimum recommended size for a UNIX partition is 40
megabytes.
Since fdisk is intended for use with DOS, it may not work
with all operating system combinations.
OS/2 partitions are displayed as UNKNOWN.
See Also
dos(C), hd(HW)
Value Added
fdisk is an extension of AT&T System V provided by the Santa
Cruz Operation.
(printed 2/15/90) FDISK(ADM)