fdisk
Hurricane Electric Internet Services
NAME
fdisk - Partition table manipulator for Linux
SYNOPSIS
fdisk [ -l ] [ -v ] [ -s partition] [ device ]
DESCRIPTION
fdisk is a menu driven program for manipulation of the
hard disk partition table. The device is usually one of
the following:
/dev/hda
/dev/hdb
/dev/sda
/dev/sdb
The partition is a device name followed by a partition
number. For example, /dev/hda1 is the first partition on
the first hard disk in the system.
If possible, fdisk will obtain the disk geometry automati-
cally. This is not necessarily the physical disk geome-
try, but is the disk geometry that MS-DOS uses for the
partition table. If fdisk warns you that you need to set
the disk geometry, please believe this statement, and set
the geometry. This should only be necessary with certain
SCSI host adapters (the drivers for which are rapidly
being modified to provide geometry information automati-
cally).
Whenever a partition table is printed out, a consistency
check is performed on the partition table entries. This
check verifies that the physical and logical start and end
points are identical, and that the partition starts and
ends on a cylinder boundary (except for the first parti-
tion).
Old versions of fdisk (all versions prior to 1.1r [includ-
ing 0.93]) incorrectly mapped the cylinder/head/sector
specification onto absolute sectors. This may result in
the first partition on a drive failing the consistency
check. If you use LILO to boot, this situation can be
ignored. However, there are reports that the OS/2 boot
manager will not boot a partition with inconsistent data.
Some versions of MS-DOS create a first partition which
does not begin on a cylinder boundary, but on sector 2 of
the first cylinder. Partitions beginning in cylinder 1
cannot begin on a cylinder boundary, but this is unlikely
to cause difficulty unless you have OS/2 on your machine.
In version 1.1r, a BLKRRPART ioctl() is performed before
exiting when the partition table is updated. This is pri-
marily to ensure that removable SCSI disks have their par-
tition table information updated. If the kernel does not
update its partition table information, fdisk warns you to
reboot. If you do not reboot your system after receiving
such a warning, you may lose or corrupt the data on the
disk. Sometimes BLKRRPART fails silently, when installing
Linux, you should always reboot after editing the parti-
tion table.
DOS 6.x WARNING
The DOS 6.x FORMAT command looks for some information in
the first sector of the data area of the partition, and
treats this information as more reliable than the informa-
tion in the partition table. DOS FORMAT expects DOS FDISK
to clear the first 512 bytes of the data area of a parti-
tion whenever a size change occurs. DOS FORMAT will look
at this extra information even if the /U flag is given --
we consider this a bug in DOS FORMAT and DOS FDISK.
The bottom line is that if you use cfdisk or fdisk to
change the size of a DOS partition table entry, then you
must also use dd to zero the first 512 bytes of that par-
tition before using DOS FORMAT to format the partition.
For example, if you were using cfdisk to make a DOS parti-
tion table entry for /dev/hda1, then (after exiting fdisk
or cfdisk and rebooting Linux so that the partition table
information is valid) you would use the command "dd
if=/dev/zero of=/dev/hda1 bs=512 count=1" to zero the
first 512 bytes of the partition. BE EXTREMELY CAREFUL if
you use the dd command, since a small typo can make all of
the data on your disk useless.
BE EXTREMELY CAREFUL if you use the dd command, since a
small typo can make all of the data on your disk useless.
For best resutls, you should always use an OS-specific
partition table program. For example, you should make DOS
partitions with the DOS FDISK program and Linux partitions
with the Linux fdisk or Linux cfdisk program.
OPTIONS
-v Prints version number of fdisk program.
-l Lists the partition tables for /dev/hda, /dev/hdb,
/dev/sda, /dev/sdb, /dev/sdc, /dev/sdd, /dev/sde,
/dev/sdf, /dev/sdg, /dev/sdh, and then exits.
-spartition
If the partition is not a DOS partition (i.e., the
partition id is greater than 10), then the size of
that partition is printed on the standard output.
This value is normally used as an argument to the
mkfs(8) program to specify the size of the parti-
tion which will be formatted.
BUGS
Although this man page (written by faith@cs.unc.edu) is
poor, there is excellent documentation in the README.fdisk
file (written by LeBlanc@mcc.ac.uk) that should always be
with the fdisk distribution. If you cannot find this file
in the util-linux-* directory or with the fdisk.c source
file, then you should write to the distributor of your
version of fdisk and complain that you do not have all of
the available documentation.
AUTHOR
A. V. Le Blanc (LeBlanc@mcc.ac.uk)
v1.0r: SCSI and extfs support added by Rik Faith
(faith@cs.unc.edu)
v1.1r: Bug fixes and enhancements by Rik Faith
(faith@cs.unc.edu), with special thanks to Michael
Bischoff (i1041905@ws.rz.tu-bs.de or mbi@mo.math.nat.tu-
bs.de).
v1.3: Latest enhancements and bug fixes by A. V. Le Blanc,
including the addition of the -s option. v2.0: Disks
larger than 2GB are now fully supported, thanks to Remy
Card's llseek support.
Hurricane Electric Internet Services
Copyright (C) 1998
Hurricane Electric.
All Rights Reserved.