fdisk(1M) fdisk(1M)
NAME
fdisk - create or modify hard disk partition table
SYNOPSIS
fdisk [argument]
DESCRIPTION
This command is used to create and modify the partition table
that is put in the first sector of the hard disk. This table
is used by the UnixWare system and other operating systems
(for example, MS-DOS) and by the first-stage bootstrap to
identify parts of the disk reserved for different operating
systems, and to identify the partition containing the second-
stage bootstrap (the active partition). The optional argument
can be used to specify the raw device associated with the hard
disk; the default value is the raw device associated with the
boot hard disk.
The program displays the partition table as it exists on the
disk, and then presents a menu allowing you to modify the
table. The menu, questions, warnings, and error messages are
intended to be self-explanatory.
If there is no partition table on the disk, you are given the
options to create a default partition or to specify the
initial table values. The default partitioning allows 100% of
the disk for the UnixWare system, and makes the UNIX system
partition active. In either case, when the initial table is
created, fdisk also writes out the first-stage bootstrap code
[see sd01(7)] along with the partition table. After the
initial table is created, only the table is changed; the
bootstrap is not modified.
Menu Options
The following are the menu options given by the fdisk program:
Create a partition
Allows you to create a new partition. The maximum
number of partitions is 4. The program will prompt for
the type of partition you want to make. You can select
from the following types:
1=UNIX System
2=pre-5.0DOS
3=post-4.0DOS
4=System
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5=other
fdisk will then ask for the size of the partition as a
percentage of the disk. For the UnixWare operating
system, the minimum UNIX system disk partition size is
60 MB for the first disk and 40 MB for the second disk.
You may also enter the letter c at this point, and the
program will ask for the starting cylinder number and
size of the partition in cylinders.
Note: If you select type 4, (System), to create a System
Configuration Partition, fdisk will not prompt you for a
starting cylinder number because the System
Configuration Partition is required to start at cylinder
0.
If a c is not entered, the program will determine the
starting cylinder number where the partition will fit.
In either case, if the partition would overlap an
existing partition, or will not fit, a message is
displayed and the program returns to the original menu.
Change Active (Boot from) partition
Allows you to specify the partition where the first-
stage bootstrap will look for the second-stage
bootstrap, otherwise known as the active partition.
Delete a partition
Allows you to delete a previously created partition.
Note that this will destroy all data in that partition.
Use this option with extreme caution.
Overwrite system master boot code
Overwrites the in-core boot code portion of the boot
sector with the UNIX system version of the master boot
code. You will need to perform an update, using fdisk's
update menu option, to have the master boot code written
to the disk. You should use the overwrite menu option
if you have had OS/2 installed on the disk previously,
because the OS/2 master boot will not boot UNIX.
However, the overwrite option is not necessary for
machines that have had MS-DOS and then OS/2 installed on
them.
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Update
Writes the new version of the table created during this
session with fdisk out to the hard disk, and exits the
program.
Exit Exits without modifying the partition table.
Errors
Most messages will be self-explanatory. The following may
appear immediately after starting the program:
fdisk: cannot open <device>
This indicates that the device name argument is not
valid.
fdisk: unable to get device parameters for device <device>
This indicates a problem with the configuration of the
hard disk, or an error in the hard disk driver.
fdisk: error reading partition table
This indicates that some error occurred when trying
initially to read the hard disk. This could be a
problem with the hard disk controller or driver, or with
the configuration of the hard disk.
This message may appear after selecting the Update option from
the menu.
fdisk: error writing boot record
This indicates that some error occurred when trying to
write the new partition table out to the hard disk.
This could be a problem with the hard disk controller,
the disk itself, the driver, or the configuration of the
hard disk.
Files
/dev/rdsk/cCbBtTdDs0
NOTICES
Cautions
Use caution when using the fdisk command. If you select the
option to delete a partition, the data on that partition is
lost and cannot be retrieved. If you delete a partition
accidentally, you will need a tape or disk backup to restore
the lost data.
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Compatibility
fdisk is compatible with MS-DOS Versions 3.2, 3.3, 4.0, and
5.0. Partitions set up using the MS-DOS 4.0 fdisk command
that are greater than 32 MB will appear in the UNIX system
display as other. Partitions can be created at sizes greater
than 32 MB for MS-DOS 5.0, and appear correctly as DOS
partitions. Partitions created with MS-DOS at any release
level that are less than 32 MB will appear correctly as DOS
partitions.
The label of a created partition will be either DOS for MS-DOS
5.0 partitions or pre-5.0DOS for any version of MS-DOS lower
than 5.0. Note, however, that the version of the partition
can be pre-5.0DOS even when the operating system in use is
MS-DOS 5.0. Therefore, do not depend on the partition label
to determine which release of MS-DOS is running.
The DOS 4.01 fdisk program assumes it can store diagnostic
information in cylinder 1020 on the hard disk. If a UNIX
system partition is created that uses cylinder 1020, DOS 4.01
fdisk will be unable to create a DOS partition. Therefore,
you must either create the UNIX system partition at the front
of the disk so that cylinder 1020 is not used, or create the
DOS partition using the UNIX System fdisk (not DOS fdisk) and
never delete it.
When setting up a DOS 4.01 partition on the hard disk to co-
reside with a UNIX partition that has already been set up, do
not allow fdisk to create the largest possible partition and
make it active (as the fdisk prompt requests). Instead, you
should manually set it up to line up against the UNIX
partition. Note that this applies to when you boots DOS 4.01
from floppy disk (not from within UNIX) and runs fdisk.
Also note that there was a previous version of the fdisk
command, intended for use with the UNIX System bkrs
(backup/restore) utility. The current version of fdisk is
used only for partitioning disks.
As noted in the section describing fdisk's menu options, you
need to use the overwrite option when installing UNIX on a
disk that has had OS/2 installed on it. The Overwrite system
master boot code option overwrites the in-core boot code
portion of the boot sector with the UNIX system master boot
code. This operation is necessary because the OS/2 boot code
will not boot UNIX. The overwrite is not necessary, however,
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on systems that had MS-DOS and then OS/2 installed on them.
To complete the overwrite, you need to use the update menu
option in fdisk.
MS-DOS and certain other operating systems do not support disk
partitions starting beyond or ending above cylinder 1023.
These operating systems may not be able to activate a
partition that starts beyond cylinder 1023. If a partition
starts before cylinder 1023 and ends after cylinder 1023, the
operating system may not be able to use the disk space above
cylinder 1023. If the partition table is updated via the DOS
fdisk command, inappropriate information may be recorded for
these partitions. If this occurs, you may not be able to boot
from these partitions again. This could also occur with
certain other operating systems.
REFERENCES
sd01(7)
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