.\" Copyright 1992, 1993 Rickard E. Faith (faith@cs.unc.edu)
.\" Copyright 1998 Andries E. Brouwer (aeb@cwi.nl)
.\" May be distributed under the GNU General Public License
-.TH FDISK 8 "11 June 1998" "Linux 2.0" "Linux Programmer's Manual"
+.TH FDISK 8 "June 2010" "util-linux" "System Administration"
.SH NAME
-fdisk \- Partition table manipulator for Linux
+fdisk \- manipulate disk partition table
.SH SYNOPSIS
.B fdisk
-.RB [ \-u ]
+.RB [ \-uc ]
.RB [ \-b
.IR sectorsize ]
.RB [ \-C
.IR partition ...
.sp
.B fdisk \-v
+.sp
+.B fdisk \-h
.SH DESCRIPTION
+.B fdisk
+(in the first form of invocation)
+is a menu-driven program for creation and manipulation of
+partition tables.
+It understands DOS-type partition tables and BSD- or SUN-type disklabels.
+
+.B fdisk
+does not understand GUID partition tables (GPTs) and it is not designed
+for large partitions. In these cases, use the more advanced GNU
+.BR parted (8).
+
+.B fdisk
+does not use DOS-compatible mode and cylinders as display units by default.
+The old deprecated DOS behavior can be enabled with
+the '-c=dos -u=cylinders' command-line options.
+
Hard disks can be divided into one or more logical disks called
.IR partitions .
-This division is described in the
-.I "partition table"
+This division is recorded in the
+.IR "partition table" ,
found in sector 0 of the disk.
-
-In the BSD world one talks about `disk slices' and a `disklabel'.
+(In the BSD world one talks about `disk slices' and a `disklabel'.)
Linux needs at least one partition, namely for its root file system.
It can use swap files and/or swap partitions, but the latter are more
-efficient. So, usually one will want a second Linux partition
+efficient. So, usually one will want a second Linux partition
dedicated as swap partition.
-On Intel compatible hardware, the BIOS that boots the system
+On Intel-compatible hardware, the BIOS that boots the system
can often only access the first 1024 cylinders of the disk.
For this reason people with large disks often create a third partition,
just a few MB large, typically mounted on
There may be reasons of security, ease of administration and backup,
or testing, to use more than the minimum number of partitions.
-.B fdisk
-(in the first form of invocation)
-is a menu driven program for creation and manipulation of
-partition tables.
-It understands DOS type partition tables and BSD or SUN type disklabels.
-
-.B fdisk
-doesn't understand GUID Partition Table (GPT) and
-it is not designed for large partitions. In particular case use more advanced GNU
-.BR parted (8).
-
+.SH DEVICES
The
.I device
-is usually /dev/sda, /dev/sdb or so. A device name refers to the entire disk.
-The old systems without libata (a library used inside the Linux kernel to
+is usually /dev/sda, /dev/sdb or so. A device name refers to the entire disk.
+Old systems without libata (a library used inside the Linux kernel to
support ATA host controllers and devices) make a difference between IDE and
-SCSI disks. In such a case the device name will be /dev/hd* (IDE) or /dev/sd*
+SCSI disks. In such cases the device name will be /dev/hd* (IDE) or /dev/sd*
(SCSI).
The
.I partition
-is a
-.I device
-name followed by a partition number. For example,
-.B /dev/sda1
+is a device name followed by a partition number. For example, /dev/sda1
is the first partition on the first hard disk in the system.
See also Linux kernel documentation (the Documentation/devices.txt file).
-A BSD/SUN type disklabel can describe 8 partitions,
+.SH DISK LABELS
+A BSD/SUN-type disklabel can describe 8 partitions,
the third of which should be a `whole disk' partition.
Do not start a partition that actually uses its first sector
(like a swap partition) at cylinder 0, since that will
destroy the disklabel.
-An IRIX/SGI type disklabel can describe 16 partitions,
+An IRIX/SGI-type disklabel can describe 16 partitions,
the eleventh of which should be an entire `volume' partition,
while the ninth should be labeled `volume header'.
The volume header will also cover the partition table, i.e.,
it starts at block zero and extends by default over five cylinders.
The remaining space in the volume header may be used by header
directory entries. No partitions may overlap with the volume header.
-Also do not change its type and make some file system on it, since
+Also do not change its type or make some filesystem on it, since
you will lose the partition table. Use this type of label only when
working with Linux on IRIX/SGI machines or IRIX/SGI disks under Linux.
-A DOS type partition table can describe an unlimited number
-of partitions. In sector 0 there is room for the description
-of 4 partitions (called `primary'). One of these may be an
+A DOS-type partition table can describe an unlimited number
+of partitions. In sector 0 there is room for the description
+of 4 partitions (called `primary'). One of these may be an
extended partition; this is a box holding logical partitions,
with descriptors found in a linked list of sectors, each
preceding the corresponding logical partitions.
The four primary partitions, present or not, get numbers 1-4.
Logical partitions start numbering from 5.
-In a DOS type partition table the starting offset and the size
+In a DOS-type partition table the starting offset and the size
of each partition is stored in two ways: as an absolute number
-of sectors (given in 32 bits) and as a Cylinders/Heads/Sectors
-triple (given in 10+8+6 bits). The former is OK - with 512-byte
-sectors this will work up to 2 TB. The latter has two different
-problems. First of all, these C/H/S fields can be filled only
+of sectors (given in 32 bits), and as a Cylinders/Heads/Sectors
+triple (given in 10+8+6 bits). The former is OK -- with 512-byte
+sectors this will work up to 2 TB. The latter has two
+problems. First, these C/H/S fields can be filled only
when the number of heads and the number of sectors per track
-are known. Secondly, even if we know what these numbers should be,
+are known. And second, even if we know what these numbers should be,
the 24 bits that are available do not suffice.
DOS uses C/H/S only, Windows uses both, Linux never uses C/H/S.
necessarily the physical disk geometry (indeed, modern disks do not
really have anything like a physical geometry, certainly not something
that can be described in simplistic Cylinders/Heads/Sectors form),
-but is the disk geometry that MS-DOS uses for the partition table.
+but it is the disk geometry that MS-DOS uses for the partition table.
Usually all goes well by default, and there are no problems if
-Linux is the only system on the disk. However, if the disk has
+Linux is the only system on the disk. However, if the disk has
to be shared with other operating systems, it is often a good idea
to let an fdisk from another operating system make at least one
-partition. When Linux boots it looks at the partition table, and
+partition. When Linux boots it looks at the partition table, and
tries to deduce what (fake) geometry is required for good
cooperation with other systems.
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
+logical start and end points are identical, and that each partition starts
and ends on a cylinder boundary (except for the first partition).
Some versions of MS-DOS create a first partition which does not begin
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.
-A sync() and a BLKRRPART ioctl() (reread partition table from disk)
+A sync() and an ioctl(BLKRRPART) (reread partition table from disk)
are performed before exiting when the partition table has been updated.
Long ago it used to be necessary to reboot after the use of fdisk.
-I do not think this is the case anymore - indeed, rebooting too quickly
-might cause loss of not-yet-written data. Note that both the kernel
+I do not think this is the case anymore -- indeed, rebooting too quickly
+might cause loss of not-yet-written data. Note that both the kernel
and the disk hardware may buffer data.
.SH "DOS 6.x WARNING"
.SH OPTIONS
.TP
.BI "\-b " sectorsize
-Specify the sector size of the disk. Valid values are 512, 1024, 2048 or 4096.
-(Recent kernels know the sector size. Use this only on old kernels or
-to override the kernel's ideas.)
+Specify the sector size of the disk. Valid values are 512, 1024, 2048 or 4096.
+(Recent kernels know the sector size. Use this only on old kernels or
+to override the kernel's ideas.) Since util-linux-2.17, fdisk differentiates
+between logical and physical sector size. This option changes both sector sizes to
+.IB sectorsize .
+.TP
+.BI "\-c"[=mode]
+Specify the compatiblity mode, 'dos' or 'nondos'. The default is non-DOS
+mode. For backward compatibility, it is possible to use the option without
+the <mode> argument -- then the default is used. Note that the optional
+<mode> argument cannot be separated from the -c option by a space, the correct
+form is for example '-c=dos'.
.TP
.BI "\-C " cyls
Specify the number of cylinders of the disk.
I have no idea why anybody would want to do so.
.TP
.BI "\-H " heads
-Specify the number of heads of the disk. (Not the physical number,
+Specify the number of heads of the disk. (Not the physical number,
of course, but the number used for partition tables.)
Reasonable values are 255 and 16.
.TP
partition tables.)
A reasonable value is 63.
.TP
+.BI \-h
+Print help and then exit.
+.TP
.B \-l
List the partition tables for the specified devices and then exit.
If no devices are given, those mentioned in
.I /proc/partitions
(if that exists) are used.
.TP
-.B \-u
-When listing partition tables, give sizes in sectors instead
-of cylinders.
+.BI "\-s " partition...
+Print the size (in blocks) of each given partition.
.TP
-.BI "\-s " partition
-The
-.I size
-of the partition (in blocks) is printed on the standard output.
+.BI "\-u"[=unit]
+When listing partition tables, show sizes in 'sectors' or in 'cylinders'. The
+default is to show sizes in sectors. For backward compatibility, it is possible
+to use the option without the <units> argument -- then the default is used.
+Note that the optional <unit> argument cannot be separated from the -u option
+by a space, the correct form is for example '-u=cylinders'.
.TP
.B \-v
Print version number of
.B cfdisk
is a beautiful program that has strict requirements on
the partition tables it accepts, and produces high quality partition
-tables. Use it if you can.
+tables. Use it if you can.
.B fdisk
is a buggy program that does fuzzy things - usually it happens to
-produce reasonable results. Its single advantage is that it has
+produce reasonable results. Its single advantage is that it has
some support for BSD disk labels and other non-DOS partition tables.
Avoid it if you can.
.B sfdisk
-is for hackers only - the user interface is terrible, but it is
+is for hackers only -- the user interface is terrible, but it is
more correct than fdisk and more powerful than both fdisk and cfdisk.
Moreover, it can be used noninteractively.)
.PP
The cfdisk interface is nicer, but parted does much more: it not only
resizes partitions, but also the filesystems that live in them.
.PP
-The IRIX/SGI type disklabel is currently not supported by the kernel.
+The IRIX/SGI-type disklabel is currently not supported by the kernel.
Moreover, IRIX/SGI header directories are not fully supported yet.
.PP
The option `dump partition table to file' is missing.
.BR partprobe (8),
.BR kpartx (8)
.SH AVAILABILITY
-The fdisk command is part of the util-linux-ng package and is available from
-ftp://ftp.kernel.org/pub/linux/utils/util-linux-ng/.
+The fdisk command is part of the util-linux package and is available from
+ftp://ftp.kernel.org/pub/linux/utils/util-linux/.
projects / framework / base / util-linux-ng.git / blobdiff